Journal articles: 'Secretory granula'

1

von Zglinicki, Thomas, and Godfried M. Roomans. "X-Ray Microanalysis of the Intestine: Identification of Electrolyte Secreting Cells." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 2 (August 12, 1990): 342–43. http://dx.doi.org/10.1017/s0424820100135319.

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Frozen dried cryosections of mouse jejunum were investigated. Besides Paneth and Goblet cells, two different types of crypt enterocytes could be distinguished according to clearly different electrolyte concentrations and to the presence (type A) or absence (type B) of small secretion granula in the cytoplasm.Secretion was stimulated by an intraperitoneal injection of either isoproterenol or pilocarpine. In some experiments, isoproterenol stimulation was blocked by alloxan, a potent inhibitor of the adenylate cyclase. Changes of cytoplasmic element concentrations were measured in frozen dried cryosections. In addition, the water content of the cells was measured by fully quantitative bulk specimen x-ray microanalysis.It was expected that actively secreting cells should display a decrease of Cl concentrations. This behaviour was confirmed in crypt A cells exclusively (Fig. 1). Therefore, it was concluded that crypt A cells are the main secretory cells in the intestinal epithelium.The water content of all epithelial cells in the intestine was found to increase under pilocarpine stimulation and to decrease under isoproterenol stimulation (Fig. 2).

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Cossu, M., M. S. Lantini, and R. Puxeddu. "Immunocytochemical localization of Lewis blood group antigens in human salivary glands." Journal of Histochemistry & Cytochemistry 42, no. 8 (August 1994): 1135–42. http://dx.doi.org/10.1177/42.8.8027532.

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We demonstrated the immunohistochemical distribution of Le-a and Le-b blood group antigens in human major and minor salivary glands at the ultrastructural level by applying a post-embedding immunogold staining method. In secretors' glands, a faint Le-a reactivity was found only in mucous droplets, whereas Le-b antigen was intensely stained in secretory granules of most mucous cells, in those of intercalated duct cells, in the pale granular matrix of some serous cells, and, when osmication was omitted, in cytoplasmatic vesicles and cell surfaces of striated ducts. In the submandibular gland of a non-secretor, Le-a antigen was considerably stained in mucous droplets, whereas Le-b reactivity was restricted to the striated duct cells. These results indicate that the secretor status affects the secretion of Lewis antigens by mucous, serous, and intercalated duct cells but not the presence of Le-b as a surface antigen in striated duct cells.

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Skott, O. "Do osmotic forces play a role in renin secretion?" American Journal of Physiology-Renal Physiology 255, no. 1 (July 1, 1988): F1—F10. http://dx.doi.org/10.1152/ajprenal.1988.255.1.f1.

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Secretory granules swell during exocytosis. Swelling may follow fusion and assist in extrusion of the granular content, or swelling may cause granular fusion with the plasmalemma. A granular proton gradient has been suggested to be involved in such preexocytic granular swelling. Exocytosis of renin from juxtaglomerular cells of isolated preparations is very sensitive to changes in the extracellular osmolality. Extracellular hyposmolality causes swelling of secretory granules, fusions between peripherally located granules and plasmalemma, and an increased number of release episodes. Induction of granule swelling at constant extracellular osmolality also stimulates renin release. Newly recruited renin granules are osmosensitive, and a high extracellular osmolality blocks secretion induced by other means (low calcium). Dissipation of granular proton gradients inhibits renin release without affecting the osmosensitivity. Thus, in renin release in vitro, a granular swelling precedes fusion and exocytosis, and a granular proton gradient may contribute to preexocytic swelling when extracellular osmolality is constant. The osmosensitivity may be important for macula densamediated renin release.

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Barg, Sebastian, Ping Huang, Lena Eliasson, Deborah J. Nelson, Stefanie Obermüller, Patrik Rorsman, Frank Thévenod, and Erik Renström. "Priming of insulin granules for exocytosis by granular Cl− uptake and acidification." Journal of Cell Science 114, no. 11 (June 1, 2001): 2145–54. http://dx.doi.org/10.1242/jcs.114.11.2145.

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ATP-dependent priming of the secretory granules precedes Ca2+-regulated neuroendocrine secretion, but the exact nature of this reaction is not fully established in all secretory cell types. We have further investigated this reaction in the insulin-secreting pancreatic B-cell and demonstrate that granular acidification driven by a V-type H+-ATPase in the granular membrane is a decisive step in priming. This requires simultaneous Cl− uptake through granular ClC-3 Cl− channels. Accordingly, granule acidification and priming are inhibited by agents that prevent transgranular Cl− fluxes, such as 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS) and an antibody against the ClC-3 channels, but accelerated by increases in the intracellular ATP:ADP ratio or addition of hypoglycemic sulfonylureas. We suggest that this might represent an important mechanism for metabolic regulation of Ca2+-dependent exocytosis that is also likely to be operational in other secretory cell types.

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Kemter, Elisabeth, Andreas Müller, Martin Neukam, Anna Ivanova, Nikolai Klymiuk, Simone Renner, Kaiyuan Yang, et al. "Sequential in vivo labeling of insulin secretory granule pools in INS-SNAP transgenic pigs." Proceedings of the National Academy of Sciences 118, no. 37 (September 10, 2021): e2107665118. http://dx.doi.org/10.1073/pnas.2107665118.

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β cells produce, store, and secrete insulin upon elevated blood glucose levels. Insulin secretion is a highly regulated process. The probability for insulin secretory granules to undergo fusion with the plasma membrane or being degraded is correlated with their age. However, the molecular features and stimuli connected to this behavior have not yet been fully understood. Furthermore, our understanding of β cell function is mostly derived from studies of ex vivo isolated islets in rodent models. To overcome this translational gap and study insulin secretory granule turnover in vivo, we have generated a transgenic pig model with the SNAP-tag fused to insulin. We demonstrate the correct targeting and processing of the tagged insulin and normal glycemic control of the pig model. Furthermore, we show specific single- and dual-color granular labeling of in vivo–labeled pig pancreas. This model may provide unprecedented insights into the in vivo insulin secretory granule behavior in an animal close to humans.

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Burgoyne, Robert D., and Alan Morgan. "Secretory Granule Exocytosis." Physiological Reviews 83, no. 2 (April 1, 2003): 581–632. http://dx.doi.org/10.1152/physrev.00031.2002.

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Regulated exocytosis of secretory granules or dense-core granules has been examined in many well-characterized cell types including neurons, neuroendocrine, endocrine, exocrine, and hemopoietic cells and also in other less well-studied cell types. Secretory granule exocytosis occurs through mechanisms with many aspects in common with synaptic vesicle exocytosis and most likely uses the same basic protein components. Despite the widespread expression and conservation of a core exocytotic machinery, many variations occur in the control of secretory granule exocytosis that are related to the specialized physiological role of particular cell types. In this review we describe the wide range of cell types in which regulated secretory granule exocytosis occurs and assess the evidence for the expression of the conserved fusion machinery in these cells. The signals that trigger and regulate exocytosis are reviewed. Aspects of the control of exocytosis that are specific for secretory granules compared with synaptic vesicles or for particular cell types are described and compared to define the range of accessory control mechanisms that exert their effects on the core exocytotic machinery.

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7

Tooze, John. "Secretory granule formation." Cell Biophysics 19, no. 1 (October 1991): 117–30. http://dx.doi.org/10.1007/bf02989885.

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Möhn, H., V. Le Cabec, S. Fischer, and I. Maridonneau-Parini. "The src-family protein-tyrosine kinase p59hck is located on the secretory granules in human neutrophils and translocates towards the phagosome during cell activation." Biochemical Journal 309, no. 2 (July 15, 1995): 657–65. http://dx.doi.org/10.1042/bj3090657.

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The src-family protein-tyrosine kinase p59hck is mainly expressed in neutrophils; however, its functional role in these cells is unknown. Several other src-family members are localized on secretory vesicles and have been proposed to regulate intracellular traffic. We have established here the subcellular localization of p59hck in human neutrophils. Immunoblotting of subcellular fractions showed that approx. 60% of the p59hck per cell is localized on the secretory granules; the other 40% is distributed equally between non-granular membranes and the cytosol. Immunofluorescence of neutrophils and HL60 cells suggests that the p59hck-positive granules are azurophil granules. Granular p59hck is highly susceptible to degradation by an azurophil-granule proteinase. Different forms of p59hck occur in the three subcellular compartments: a 61 kDa form is mainly found in the granules, a 59 kDa form is predominant in the non-granular membranes, whereas cytosolic p59hck migrates as a doublet at 63 kDa. During the process of phagocytosis-linked degranulation, induced by serum-opsonized zymosan in neutrophils or HL60 cells, granular p59hck translocates towards the phagosome. The subcellular localization of p59hck suggests that the enzyme could be involved in the regulation of the degranulation process.

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Alvarez de Toledo, G., and J. M. Fernandez. "Patch-clamp measurements reveal multimodal distribution of granule sizes in rat mast cells." Journal of Cell Biology 110, no. 4 (April 1, 1990): 1033–39. http://dx.doi.org/10.1083/jcb.110.4.1033.

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Using patch-clamp techniques, we have followed the attributes of the secretory granules of peritoneal mast cells obtained from rats of different ages. The granule attributes were determined by following the step increases in the cell surface membrane area caused by the exocytosis of the granules in GTP gamma S stimulated mast cells. Our data show that the amount of granule membrane available for exocytosis depends exponentially on the weight (age) of the donor rat, reaching a maximum at approximately 300 g. The data are consistent with an exponential growth in the number of granules contained by mast cells of maturing animals. Histograms of the sizes of the step increases in surface area caused by exocytosis of the granules showed at least four equally spaced peaks of similar variance where the position of the first peak and the spacing between peaks averaged 1.3 +/- 0.4 micron2. In all cells recorded, no more than seven peaks could be found, the higher order peaks having a lower probability of occurrence. The distribution of granule sizes did not change measurably between young and adult animals. This study suggests that at least two separate steps may determine the size of a secretory granule: granule to granule fusion that may account for the subunit composition of granule sizes and traffic of microvesicles through the maturing granules that may account for the variance observed in the granule sizes. This study also demonstrates a novel way to study granulo-genesis in living cells.

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Sano, K., S. Waguri, N. Sato, E. Kominami, and Y. Uchiyama. "Coexistence of renin and cathepsin B in secretory granules of granular duct cells in male mouse submandibular gland." Journal of Histochemistry & Cytochemistry 41, no. 3 (March 1993): 433–38. http://dx.doi.org/10.1177/41.3.8429206.

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Cathepsin B, a representative lysosomal cysteine proteinase, has been demonstrated to coexist with renin in secretary granules of rat pituitary LH/FSH cells and renal juxtaglomerular cells. We investigated immunocytochemically the localization of cathepsins B, H, and L in the submandibular gland of male mice, in which active renin is also produced. By light microscopy, granular immunodeposits for cathepsin B were detected in epithelial cells of the gland, particularly in granular duct cells and interstitial cells. Immunoreactivity for cathepsins H and L was mainly found in interstitial cells, although that for cathepsin H was weakly seen in acinar cells. By electron microscopy, immunogold particles indicating cathepsin B intensely labeled small granules near the Golgi complex of granular duct cells and weakly labeled large secretory granules, whereas those showing renin labeled both granules. Double immunostaining co-localized immunogold particles showing renin and cathepsin B in small perinuclear granules near the Golgi complex. Some immunopositive granules seemed to be closely associated with the Golgi elements. These results indicate that the co-localization of renin and cathepsin B is also seen in secretory granules of granular duct cells in the mouse submandibular gland, as seen in rat juxtaglomerular and LH/FSH cells. This suggests that cathepsin B is one of the possible candidates for the renin-processing enzyme.

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11

Peng Loh, Y., and Taeyoon Kim. "Neuropeptide secretory granule biogenesis." Neuropeptides 40, no. 6 (December 2006): 426–27. http://dx.doi.org/10.1016/j.npep.2006.09.011.

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12

Hutton, J. C. "The insulin secretory granule." Diabetologia 32, no. 5 (May 1989): 271–81. http://dx.doi.org/10.1007/bf00265542.

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13

Datta, Yvonne H., Hagop Youssoufian, Peter W. Marks, and Bruce M. Ewenstein. "Targeting of a Heterologous Protein to a Regulated Secretion Pathway in Cultured Endothelial Cells." Blood 94, no. 8 (October 15, 1999): 2696–703. http://dx.doi.org/10.1182/blood.v94.8.2696.420k29_2696_2703.

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The stimulation of regulated exocytosis in vascular endothelial cells (EC) by a variety of naturally occurring agonists contributes to the interrelated processes of inflammation, thrombosis, and fibrinolysis. The Weibel-Palade body (WPB) is a well-described secretory granule in EC that contains both von Willebrand factor (vWF) and P-selectin, but the mechanisms responsible for the targeting of these proteins into this organelle remain poorly understood. Through adenoviral transduction, we have expressed human growth hormone (GH) as a model of regulated secretory protein sorting in EC. Immunofluorescence microscopy of EC infected with GH-containing recombinant adenovirus (GHrAd) demonstrated a granular distribution of GH that colocalized with vWF. In contrast, EC infected with an rAd expressing the IgG1 heavy chain (IG), a constitutively secreted protein, did not demonstrate colocalization of IG and vWF. In response to phorbol ester, GH as well as endogenously synthesized vWF were rapidly released from GHrAd-infected EC. By immunofluorescence microscopy, granular colocalization of GH with endogenous tissue-type plasminogen activator (tPA) was also demonstrated, and most of the tPA colocalized with vWF. These data indicate that EC are capable of selectively targeting heterologous proteins, such as GH, to the regulated secretory pathway, which suggests that EC and neuroendocrine cells share common protein targeting recognition signals or receptors.

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14

Tooze, S. A., T. Flatmark, J. Tooze, and W. B. Huttner. "Characterization of the immature secretory granule, an intermediate in granule biogenesis." Journal of Cell Biology 115, no. 6 (December 15, 1991): 1491–503. http://dx.doi.org/10.1083/jcb.115.6.1491.

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The events in the biogenesis of secretory granules after the budding of a dense-cored vesicle from the trans-Golgi network (TGN) were investigated in the neuroendocrine cell line PC12, using sulfate-labeled secretogranin II as a marker. The TGN-derived dense-cored vesicles, which we refer to as immature secretory granules, were found to be obligatory organellar intermediates in the biogenesis of the mature secretory granules which accumulate in the cell. Immature secretory granules were converted to mature secretory granules with a half-time of approximately 45 min. This conversion entailed an increase in their size, implying that the maturation of secretory granules includes a fusion event involving immature secretory granules. Pulse-chase labelling of PC12 cells followed by stimulation with high K+, which causes the release of secretogranin II, showed that not only mature, but also immature secretory granules were capable of undergoing regulated exocytosis. The kinetics of secretion of secretogranin II, as well as those of a constitutively secreted heparan sulfate proteoglycan, were reduced by treatment of PC12 cells with nocodazole, suggesting that both secretory granules and constitutive secretory vesicles are transported to the plasma membrane along microtubules. Our results imply that certain membrane proteins, e.g., those involved in the fusion of post-TGN vesicles with the plasma membrane, are sorted upon exit from the TGN, whereas other membrane proteins, e.g., those involved in the interaction of post-TGN vesicles with the cytoskeleton, may not be sorted.

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Dahlgren, C., S. R. Carlsson, A. Karlsson, H. Lundqvist, and C. Sjölin. "The lysosomal membrane glycoproteins Lamp-1 and Lamp-2 are present in mobilizable organelles, but are absent from the azurophil granules of human neutrophils." Biochemical Journal 311, no. 2 (October 15, 1995): 667–74. http://dx.doi.org/10.1042/bj3110667.

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The subcellular localization of two members of a highly glycosylated protein group present in lysosomal membranes in most cells, the lysosome-associated membrane proteins 1 and 2 (Lamp-1 and Lamp-2), was examined in human neutrophil granulocytes. Antibodies that were raised against purified Lamp-1 adn Lamp-2 gave a distinct granular staining of the cytoplasm upon immunostaining of neutrophils. Subcellular fractionation was used to separate the azurophil and specific granules from a light-membrane fraction containing plasma membranes and secretory vesicles, and Western blotting was used to determine the presence of the Lamps in these fractions. The results show that Lamp-1 and Lamp-2 are present in the specific-granule-enriched fraction and in the light-membrane fraction, but not in the azurophil granules. Separation of secretory vesicles from plasma membranes disclosed that the light-membrane Lamps were present primarily in the secretory-vesicle-enriched fraction. During phagocytosis both Lamp-1 and Lamp-2 became markedly concentrated around the ingested particle and they both appear on the cell surface when the secretory organelles are mobilized.

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Bonnemaison, Mathilde, Nils Bäck, Yimo Lin, Juan S. Bonifacino, Richard Mains, and Betty Eipper. "AP-1A Controls Secretory Granule Biogenesis and Trafficking of Membrane Secretory Granule Proteins." Traffic 15, no. 10 (August 15, 2014): 1099–121. http://dx.doi.org/10.1111/tra.12194.

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Elias, Peter M., Theodora Mauro, Ulrich Rassner, Laszlo Kömüves, Barbara E. Brown, Gopinathan K. Menon, and Christopher Cullander. "The Secretory Granular Cell: The Outermost Granular Cell as a Specialized Secretory Cell." Journal of Investigative Dermatology Symposium Proceedings 3, no. 2 (August 1998): 87–100. http://dx.doi.org/10.1038/jidsymp.1998.20.

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LU, JINLING, NATALIA GUSTAVSSON, QIMING LI, GEORGE K. RADDA, THOMAS C. SÜDHOF, and WEIPING HAN. "GENERATION OF TRANSGENIC MICE FOR IN VIVO DETECTION OF INSULIN-CONTAINING GRANULE EXOCYTOSIS AND QUANTIFICATION OF INSULIN SECRETION." Journal of Innovative Optical Health Sciences 02, no. 04 (October 2009): 397–405. http://dx.doi.org/10.1142/s1793545809000711.

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Insulin secretion is a complex and highly regulated process. Although much progress has been made in understanding the cellular mechanisms of insulin secretion and regulation, it remains unclear how conclusions from these studies apply to living animals. That few studies have been done to address these issues is largely due to the lack of suitable tools in detecting secretory events at high spatial and temporal resolution in vivo. When combined with genetically encoded biosensor, optical imaging is a powerful tool for visualization of molecular events in vivo. In this study, we generated a DNA construct encoding a secretory granule resident protein that is linked with two spectrally separate fluorescent proteins, a highly pH-sensitive green pHluorin on the intra-granular side and a red mCherry in the cytosol. Upon exocytosis of secretory granules, the dim pHluorin inside the acidic secretory granules became highly fluorescent outside the cells at neutral pH, while mCherry fluorescence remained constant in the process, thus allowing ratiometric quantification of insulin secretory events. Furthermore, mCherry fluorescence enabled tracking the movement of secretory granules in living cells. We validated this approach in insulin-secreting cells, and generated a transgenic mouse line expressing the optical sensor specifically in pancreatic β-cells. The transgenic mice will be a useful tool for future investigations of molecular mechanism of insulin secretion in vitro and in vivo.

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Thévenod, Frank. "Ion channels in secretory granules of the pancreas and their role in exocytosis and release of secretory proteins." American Journal of Physiology-Cell Physiology 283, no. 3 (September 1, 2002): C651—C672. http://dx.doi.org/10.1152/ajpcell.00600.2001.

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Regulated secretion in exocrine and neuroendocrine cells occurs through exocytosis of secretory granules and the subsequent release of stored small molecules and proteins. The introduction of biophysical techniques with high temporal and spatial resolution, and the identification of Ca2+-dependent and -independent “docking” and “fusion” proteins, has greatly enhanced our understanding of exocytosis. The cloning of families of ion channel proteins, including intracellular ion channels, has also revived interest in the role of secretory granule ion channels in exocytotic secretion. Thus secretory granules of pancreatic acinar cell express a ClC-2 Cl−channel, a HCO[Formula: see text]-permeable member of the CLCA Ca2+-dependent anion channel family, and a KCNQ1 K+channel. Evidence suggests that these channels may facilitate the release of digestive enzymes and/or prevent exocytosed granules from collapsing during “kiss and run” recycling. In pancreatic β-cells, a granular ClC-3 Cl−channel provides a shunt pathway for a vacuolar-type H+-ATPase. Acidification “primes” the granules for Ca2+-dependent exocytosis and release of insulin. In summary, secretory granules are equipped with specific sets of ion channels, which modulate regulated exocytosis and the release of macromolecules. These channels could represent excellent targets for therapeutic interventions to control exocytotic secretion in relevant diseases, such as pancreatitis, cystic fibrosis, or diabetes mellitus.

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Tranah, Thomas H., Godhev K. Manakkat Vijay, Jennifer M. Ryan, R. Daniel Abeles, Paul K. Middleton, and Debbie L. Shawcross. "Dysfunctional neutrophil effector organelle mobilization and microbicidal protein release in alcohol-related cirrhosis." American Journal of Physiology-Gastrointestinal and Liver Physiology 313, no. 3 (September 1, 2017): G203—G211. http://dx.doi.org/10.1152/ajpgi.00112.2016.

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Patients with alcohol-related cirrhosis (ALD) are prone to infection. Circulating neutrophils in ALD are dysfunctional and predict development of sepsis, organ dysfunction, and survival. Neutrophil granules are important effector organelles containing a toxic array of microbicidal proteins, whose controlled release is required to kill microorganisms while minimizing inflammation and damage to host tissue. We investigated the role of these granular responses in contributing to immune disarray in ALD. Neutrophil granular content and mobilization were measured by flow cytometric quantitation of cell-surface/intracellular markers, [secretory vesicles (CD11b), secondary granules (CD66b), and primary granules (CD63; myeloperoxidase)] before and after bacterial stimulation in 29 patients with ALD cirrhosis (15 abstinent; 14 actively drinking) compared with healthy controls (HC). ImageStream Flow Cytometry characterized localization of granule subsets within the intracellular and cell-surface compartments. The plasma cytokine environment was analyzed using ELISA/cytokine bead array. Circulating neutrophils were primed in the resting state with upregulated surface expression of CD11b ( P = 0.0001) in a cytokine milieu rich in IL-8 ( P < 0.001) and lactoferrin ( P = 0.035). Neutrophils showed exaggerated mobilization to the cell surface of primary granules at baseline ( P = 0.001) and in response to N-formyl-l-methionyl-l-leucyl-l-phenylalanine ( P = 0.009) and Escherichia coli ( P = 0.0003) in ALD. There was no deficit in granule content or mobilization to the cell membrane in any granule subset observed. Paradoxically, active alcohol consumption abrogated the hyperresponsive neutrophil granular responses compared with their abstinent counterparts. Neutrophils are preprimed at baseline with augmented effector organelle mobilization in response to bacterial stimulation; neutrophil degranulation is not a mechanism leading to innate immunoparesis in ALD.NEW & NOTEWORTHY Neutrophil granule release is dysregulated in patients with alcohol-related cirrhosis (ALD) with augmented effector organelle mobilization and microbiocidal protein release. Neutrophil granules are upregulated in ALD at baseline and demonstrate augmented responses to bacterial challenge. The granular responses in ALD did not contribute to the observed functional deficit in innate immunity but rather were dysregulated and hyperresponsive, which may induce bystander damage to host tissue. Paradoxically, active alcohol consumption abrogated the excessive neutrophil granular responses to bacterial stimulus compared with their abstinent counterparts.

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Yoshiyuki Osamura, R., M. Chrétien, and M. Marcinkiewicz. "Ultrastructural localization of secretory granule." Pathology - Research and Practice 183, no. 5 (September 1988): 617–19. http://dx.doi.org/10.1016/s0344-0338(88)80024-4.

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Rajagopal, Chitra, Kathryn L. Stone, Victor P. Francone, Richard E. Mains, and Betty A. Eipper. "Secretory Granule to the Nucleus." Journal of Biological Chemistry 284, no. 38 (July 27, 2009): 25723–34. http://dx.doi.org/10.1074/jbc.m109.035782.

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Kim, Taeyoon, Marjorie C. Gondré-Lewis, Irina Arnaoutova, and Y. Peng Loh. "Dense-Core Secretory Granule Biogenesis." Physiology 21, no. 2 (April 2006): 124–33. http://dx.doi.org/10.1152/physiol.00043.2005.

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The dense-core secretory granule is a key organelle for secretion of hormones and neuropeptides in endocrine cells and neurons, in response to stimulation. Cholesterol and granins are critical for the assembly of these organelles at the trans-Golgi network, and their biogenesis is regulated quantitatively by posttranscriptional and posttranslational mechanisms.

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Germanos, Mark, Andy Gao, Matthew Taper, Belinda Yau, and Melkam A. Kebede. "Inside the Insulin Secretory Granule." Metabolites 11, no. 8 (August 5, 2021): 515. http://dx.doi.org/10.3390/metabo11080515.

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The pancreatic β-cell is purpose-built for the production and secretion of insulin, the only hormone that can remove glucose from the bloodstream. Insulin is kept inside miniature membrane-bound storage compartments known as secretory granules (SGs), and these specialized organelles can readily fuse with the plasma membrane upon cellular stimulation to release insulin. Insulin is synthesized in the endoplasmic reticulum (ER) as a biologically inactive precursor, proinsulin, along with several other proteins that will also become members of the insulin SG. Their coordinated synthesis enables synchronized transit through the ER and Golgi apparatus for congregation at the trans-Golgi network, the initiating site of SG biogenesis. Here, proinsulin and its constituents enter the SG where conditions are optimized for proinsulin processing into insulin and subsequent insulin storage. A healthy β-cell is continually generating SGs to supply insulin in vast excess to what is secreted. Conversely, in type 2 diabetes (T2D), the inability of failing β-cells to secrete may be due to the limited biosynthesis of new insulin. Factors that drive the formation and maturation of SGs and thus the production of insulin are therefore critical for systemic glucose control. Here, we detail the formative hours of the insulin SG from the luminal perspective. We do this by mapping the journey of individual members of the SG as they contribute to its genesis.

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Watson, E. L., D. DiJulio, D. Kauffman, J. Iversen, M. R. Robinovitch, and K. T. Izutsu. "Evidence for G proteins in rat parotid plasma membranes and secretory granule membranes." Biochemical Journal 285, no. 2 (July 15, 1992): 441–49. http://dx.doi.org/10.1042/bj2850441.

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G proteins were identified in rat parotid plasma membrane-enriched fractions and in two populations of isolated secretory granule membrane fractions. Both [32P]ADP-ribosylation analysis with bacterial toxins and immunoblot analysis with crude and affinity-purified antisera specific for alpha subunits of G proteins were utilized. Pertussis toxin catalysed the ADP-ribosylation of a 41 kDa substrate in the plasma membrane fraction and both secretory granule membrane fractions. Cholera toxin catalysed the ADP-ribosylation of two substrates with molecular masses of 44 kDa and 48 kDa in the plasma membrane fraction but not in the secretory granule fractions. However, these substrates were detected in the secretory granule fractions when recombinant ADP-ribosylating factor was present in the assay medium. Immunoblot analysis of rat parotid membrane fractions using both affinity-purified and crude antisera revealed strong immunoreactivity of these membranes with anti-Gs alpha, -Gi alpha 1/alpha 2 and -Gi alpha 3 sera. In contrast Gs alpha was the major substrate found in both of the secretory granule fractions. Granule membrane fractions also reacted moderately with anti-Gi alpha 3 antiserum, and weakly with anti-Gi alpha 1/alpha 2 and -G(o) alpha sera. The results demonstrate that the parotid gland membranes express a number of G proteins. The presence of G proteins in secretory granule membranes suggests that they may play a direct role in regulating exocytosis in exocrine glands.

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Smelova, I. V., E. S. Golovneva, T. G. Kravchenko, and V. I. Petukhova. "On the Regulatory Capabilities of Thyroid Mast Cells in Thiamazole Model of Hypothyroidism and Infrared Laser Exposure." Journal of Ural Medical Academic Science 18, no. 1 (2021): 20–28. http://dx.doi.org/10.22138/2500-0918-2021-18-1-20-28.

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The regulatory effect of mast cells on the state of thyroid gland in hypothyroidism and laser therapy remains unclear. Aim: to study the secretory processes of mast cells in relationship with the indicators of functional activity of thyroid gland. Materials and methods. Experimental groups: (55 rats) 1) intact rats, 2) hypothyroidism (thiamazole 25mg/kg) 3) hypothyroidism and 0.5W laser exposure, 4) hypothyroidism and 2.0W laser exposure. Histological samples of the thyroid gland were removed on the 1, 7, and 30 days. Histological sections were stained with toluidine blue. Morphometric data analysis included descriptive statistics and non-parametric tests (Mann Whitney, Spearman correlation coefficient). Results. The increase in the granular saturation of mast cells and the average histochemical coefficient was observed in the hypothyroidism group, the degranulation index increased by day 30. After 0.5 W laser exposure, there was a decrease in the granular content in mast cells and an increase in the degranulation index; the granular saturation increased by day 30. After 2.0 W laser exposure, the content of granules in mast cells decreased on day 1, and on days 7 and 30 it was higher than in the hypothyroidism group; the degranulation index decreased by day 30. The correlation was revealed between the indicators of granule accumulation in a mast cell, the index of mast cell degranulation, the thyroid epithelium height, and relative vascular area. Conclusions. The synthesis processes prevailed over secretion for mastocytes in thiamazole hypothyroidism. 0.5 W laser exposure was more effective for stimulation of the secretory processes in mast cells compared to 2.0 W exposure. The secretory activity of mast cells was associated with the functional activity of thyroid gland, which confirms their regulatory role in tissue repair after thiamazole induced hypothyroidism modeling.

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Johnson, Jennifer L., Jlenia Monfregola, Gennaro Napolitano, William B. Kiosses, and Sergio D. Catz. "Vesicular trafficking through cortical actin during exocytosis is regulated by the Rab27a effector JFC1/Slp1 and the RhoA-GTPase–activating protein Gem-interacting protein." Molecular Biology of the Cell 23, no. 10 (May 15, 2012): 1902–16. http://dx.doi.org/10.1091/mbc.e11-12-1001.

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Cytoskeleton remodeling is important for the regulation of vesicular transport associated with exocytosis, but a direct association between granular secretory proteins and actin-remodeling molecules has not been shown, and this mechanism remains obscure. Using a proteomic approach, we identified the RhoA-GTPase–activating protein Gem-interacting protein (GMIP) as a factor that associates with the Rab27a effector JFC1 and modulates vesicular transport and exocytosis. GMIP down-regulation induced RhoA activation and actin polymerization. Importantly, GMIP-down-regulated cells showed impaired vesicular transport and exocytosis, while inhibition of the RhoA-signaling pathway induced actin depolymerization and facilitated exocytosis. We show that RhoA activity polarizes around JFC1-containing secretory granules, suggesting that it may control directionality of granule movement. Using quantitative live-cell microscopy, we show that JFC1-containing secretory organelles move in areas near the plasma membrane deprived of polymerized actin and that dynamic vesicles maintain an actin-free environment in their surroundings. Supporting a role for JFC1 in RhoA inactivation and actin remodeling during exocytosis, JFC1 knockout neutrophils showed increased RhoA activity, and azurophilic granules were unable to traverse cortical actin in cells lacking JFC1. We propose that during exocytosis, actin depolymerization commences near the secretory organelle, not the plasma membrane, and that secretory granules use a JFC1- and GMIP-dependent molecular mechanism to traverse cortical actin.

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Farias, Maria De Fatima Diniz Baptista, and Simone Chinicz Cohen. "Estudos ultraestruturais da glândula de Mehlis de Metamicrocotyla macracantha (Monogenea, Microcotylidae) parasito de Mugil liza (Teleostei)." Brazilian Journal of Veterinary Research and Animal Science 42, no. 5 (October 1, 2005): 367. http://dx.doi.org/10.11606/issn.1678-4456.bjvras.2005.26413.

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A ultraestrutura da glândula de Mehlis de Metamicrocotyla macracantha, parasita de brânquia coletado de Mugil liza do Rio de Janeiro, Brasil, foi estudado através da microscopia eletrônica de transmissão. A glândula de Mehlis consiste de dois tipos de células secretoras, S1 e S2, cada uma produzindo um corpo secretor diferente. Os corpos S1 são esféricos, em forma de lamelas e observados em diferentes estágios de desenvolvimentos no citoplasma dessas células. Os corpos S2 são esféricos a ovais com conteúdos densos, apresentando uma estrutura cristalina. O citoplasma das células da glândula de Mehlis apresenta também ribossmas livres, retículo endoplasmático granular e complexo de Golgi, organelas características de células secretoras.

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Beuret, Nicole, Hansruedi Stettler, Anja Renold, Jonas Rutishauser, and Martin Spiess. "Expression of Regulated Secretory Proteins Is Sufficient to Generate Granule-like Structures in Constitutively Secreting Cells." Journal of Biological Chemistry 279, no. 19 (March 2, 2004): 20242–49. http://dx.doi.org/10.1074/jbc.m310613200.

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The formation of secretory granules and regulated secretion are generally assumed to occur only in specialized endocrine, neuronal, or exocrine cells. We discovered that regulated secretory proteins such as the hormone precursors pro-vasopressin, pro-oxytocin, and pro-opiomelanocortin, as well as the granins secretogranin II and chromogranin B but not the constitutive secretory protein α1-protease inhibitor, accumulate in granular structures at the Golgi and in the cell periphery in transfected COS-1 fibroblast cells. The accumulations were observed in 30–70% of the transfected cells expressing the pro-hormones and for virtually all of the cells expressing the granins. Similar structures were also generated in other cell lines believed to be lacking a regulated secretory pathway. The accumulations resembled secretory granules morphologically in immunofluorescence and electron microscopy. They were devoid of markers of the endoplasmic reticulum, endosomes, and lysosomes but in part stained positive for the trans-Golgi network marker TGN46, consistent with their formation at the trans-Golgi network. When different regulated proteins were coexpressed, they were frequently found in the same granules, whereas α1-protease inhibitor could not be detected in accumulations formed by secretogranin II, demonstrating segregation of regulated from constitutive secretory proteins. In pulse-chase experiments, significant intracellular storage of secretogranin II and chromogranin B was observed and secretion of retained secretogranin II was stimulated with the calcium ionophore A23187. The results suggest that expression of regulated cargo proteins is sufficient to generate structures that resemble secretory granules in the background of constitutively secreting cells, supporting earlier proposals on the mechanism of granule formation.

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Turgeon, J. L., and R. H. Cooper. "Protein kinase C and an endogenous substrate associated with adenohypophyseal secretory granules." Biochemical Journal 237, no. 1 (July 1, 1986): 53–61. http://dx.doi.org/10.1042/bj2370053.

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Secretory granules isolated from anterior pituitary glands were examined for Ca2+/phospholipid-dependent protein kinase (protein kinase C) activity as well as the occurrence of granule-associated substrate proteins. Sheep adenohypophyses were fractionated by differential and sucrose-density-gradient centrifugation to yield a granule fraction enriched for luteinizing-hormone (lutropin)-containing secretory granules. Marker-enzyme analysis showed no detectable cytosolic contamination, although there were small amounts of plasma membranes (2-4%) and lysosomes (4-6%) associated with the preparation. As determined by histone-H1 phosphorylation after DEAE-cellulose DE-52 chromatography, protein kinase C activity with a marked dependence on Ca2+ and lipid (4-fold increase in their presence) was evident in the secretory-granule fraction. Phosphorylation in vitro of the secretory-granule fraction by endogenous and exogenous protein kinase C revealed a protein of Mr 36,000, which by two-dimensional SDS/polyacrylamide-gel electrophoresis showed multiple sites of phosphorylation. The Mr-36,000 protein was not found in cytosolic or plasma-membrane fractions and was not phosphorylated by the catalytic subunit of cyclic AMP-dependent protein kinase. Several secretory-granule proteins served as substrates for the catalytic subunit, the most prominent of which were of Mr 63,000, 23,000 and 21,000. From these data, we suggest that phosphorylation of secretory-granule-associated proteins by protein kinase C and by cyclic AMP-dependent protein kinase may be important in secretion regulation in the anterior pituitary gland.

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Bruinsma, Stephen, Declan J. James, Melanie Quintana Serrano, Joseph Esquibel, Sang Su Woo, Elle Kielar-Grevstad, Ellen Crummy, Rehan Qurashi, Judy A. Kowalchyk, and Thomas F. J. Martin. "Small molecules that inhibit the late stage of Munc13-4–dependent secretory granule exocytosis in mast cells." Journal of Biological Chemistry 293, no. 21 (April 3, 2018): 8217–29. http://dx.doi.org/10.1074/jbc.ra117.001547.

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Ca2+-dependent secretory granule fusion with the plasma membrane is the final step for the exocytic release of inflammatory mediators, neuropeptides, and peptide hormones. Secretory cells use a similar protein machinery at late steps in the regulated secretory pathway, employing protein isoforms from the Rab, Sec1/Munc18, Munc13/CAPS, SNARE, and synaptotagmin protein families. However, no small-molecule inhibitors of secretory granule exocytosis that target these proteins are currently available but could have clinical utility. Here we utilized a high-throughput screen of a 25,000-compound library that identified 129 small-molecule inhibitors of Ca2+-triggered secretory granule exocytosis in RBL-2H3 mast cells. These inhibitors broadly fell into six different chemical classes, and follow-up permeable cell and liposome fusion assays identified the target for one class of these inhibitors. A family of 2-aminobenzothiazoles (termed benzothiazole exocytosis inhibitors or bexins) was found to inhibit mast cell secretory granule fusion by acting on a Ca2+-dependent, C2 domain–containing priming factor, Munc13-4. Our findings further indicated that bexins interfere with Munc13-4–membrane interactions and thereby inhibit Munc13-4–dependent membrane fusion. We conclude that bexins represent a class of specific secretory pathway inhibitors with potential as therapeutic agents.

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ARVAN, Peter, and David CASTLE. "Sorting and storage during secretory granule biogenesis: looking backward and looking forward." Biochemical Journal 332, no. 3 (June 15, 1998): 593–610. http://dx.doi.org/10.1042/bj3320593.

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Secretory granules are specialized intracellular organelles that serve as a storage pool for selected secretory products. The exocytosis of secretory granules is markedly amplified under physiologically stimulated conditions. While granules have been recognized as post-Golgi carriers for almost 40 years, the molecular mechanisms involved in their formation from the trans-Golgi network are only beginning to be defined. This review summarizes and evaluates current information about how secretory proteins are thought to be sorted for the regulated secretory pathway and how these activities are positioned with respect to other post-Golgi sorting events that must occur in parallel. In the first half of the review, the emerging role of immature secretory granules in protein sorting is highlighted. The second half of the review summarizes what is known about the composition of granule membranes. The numerous similarities and relatively limited differences identified between granule membranes and other vesicular carriers that convey products to and from the plasmalemma, serve as a basis for examining how granule membrane composition might be established and how its unique functions interface with general post-Golgi membrane traffic. Studies of granule formation in vitro offer additional new insights, but also important challenges for future efforts to understand how regulated secretory pathways are constructed and maintained.

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Williams, John A., Xuequn Chen, and Maria E. Sabbatini. "Small G proteins as key regulators of pancreatic digestive enzyme secretion." American Journal of Physiology-Endocrinology and Metabolism 296, no. 3 (March 2009): E405—E414. http://dx.doi.org/10.1152/ajpendo.90874.2008.

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Small GTP-binding (G) proteins act as molecular switches to regulate a number of cellular processes, including vesicular transport. Emerging evidence indicates that small G proteins regulate a number of steps in the secretion of pancreatic acinar cells. Diverse small G proteins have been localized at discrete compartments along the secretory pathway and particularly on the secretory granule. Rab3D, Rab27B, and Rap1 are present on the granule membrane and play a role in the steps leading up to exocytosis. Whether the function of these G proteins is simply to ensure appropriate targeting or if they are involved as regulatory molecules is discussed. Most evidence suggests that Rab3D and Rab27B play a role in tethering the secretory granule to its target membrane. Other Rabs have been identified on the secretory granule that are associated with different steps in the secretory pathway. The Rho family small G proteins RhoA and Rac1 also regulate secretion through remodeling of the actin cytoskeleton. Possible mechanisms for regulation of these G proteins and their effector molecules are considered.

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Castle, J. D., P. Arvan, and R. Cameron. "Protein Production and Secretion in Exocrine Cells." Journal of Dental Research 66, no. 1_suppl (February 1987): 633–37. http://dx.doi.org/10.1177/00220345870660s105.

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Acinar cells of exocrine glands are highly specialized for producing, storing, and discharging secretory proteins for use on surfaces that represent interfaces between the organism and the surrounding environment. These functions are achieved through the secretory pathway that includes a series of functionally distinct intracellular compartments — The endoplasmic reticulum, subcompartmenls of the Go/gi complex, and the secretion granule in which exportable macromolecules are stored at high concentrations. Most secretion occurs by granule exocytosis in response to external hormonal or neural stimuli. Although these processes have been traced in a variety of morphological and biochemical studies, very little is known about the mechanisms involved in facilitating and maintaining secretory storage, orchestrating discharge at the apical cell surface, and in ensuring conservation and re-internalization of the granule membrane. Recent studies initiated on cell fractions obtained from the rat parotid gland have provided significant insight into the protein storage conditions that prevail in the granule interior and the components of the granule membrane that are likely to be involved in general secretory function such as exocytosis.

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Castle, J. D., P. Arvan, and R. Cameron. "Protein Production and Secretion in Exocrine Cells." Journal of Dental Research 66, no. 2_suppl (February 1987): 633–37. http://dx.doi.org/10.1177/00220345870660s205.

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Acinar cells of exocrine glands are highly specialized for producing, storing, and discharging secretory proteins for use on surfaces that represent interfaces between the organism and the surrounding environment. These functions are achieved through the secretory pathway that includes a series of functionally distinct intracellular compartments — the endoplasmic reticulum, subcompartments of the Golgi complex, and the secretion granule in which exportable macromolecules are stored at high concentrations. Most secretion occurs by granule exocytosis in response to external hormonal or neural stimuli. Although these processes have been traced in a variety of morphological and biochemical studies, very Utile is known about the mechanisms involved in facilitating and maintaining secretory storage, orchestrating discharge at the apical cell surface, and in ensuring conservation and re-internalization of the granule membrane. Recent studies initiated on cell fractions obtained from the rat parotid gland have provided significant insight into the protein storage conditions that prevail in the granule interior and the components of the granule membrane that are likely to be involved in general secretory function such as exocytosis.

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Barbeck, Mike, Marie-Luise Schröder, Said Alkildani, Ole Jung, and Ronald E. Unger. "Exploring the Biomaterial-Induced Secretome: Physical Bone Substitute Characteristics Influence the Cytokine Expression of Macrophages." International Journal of Molecular Sciences 22, no. 9 (April 24, 2021): 4442. http://dx.doi.org/10.3390/ijms22094442.

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In addition to their chemical composition various physical properties of synthetic bone substitute materials have been shown to influence their regenerative potential and to influence the expression of cytokines produced by monocytes, the key cell-type responsible for tissue reaction to biomaterials in vivo. In the present study both the regenerative potential and the inflammatory response to five bone substitute materials all based on β-tricalcium phosphate (β-TCP), but which differed in their physical characteristics (i.e., granule size, granule shape and porosity) were analyzed for their effects on monocyte cytokine expression. To determine the effects of the physical characteristics of the different materials, the proliferation of primary human osteoblasts growing on the materials was analyzed. To determine the immunogenic effects of the different materials on human peripheral blood monocytes, cells cultured on the materials were evaluated for the expression of 14 pro- and anti-inflammatory cytokines, i.e., IL-6, IL-10, IL-1β, VEGF, RANTES, IL-12p40, I-CAM, IL-4, V-CAM, TNF-α, GM-CSF, MIP-1α, Il-8 and MCP-1 using a Bio-Plex® Multiplex System. The granular shape of bone substitutes showed a significant influence on the osteoblast proliferation. Moreover, smaller pore sizes, round granular shape and larger granule size increased the expression of GM-CSF, RANTES, IL-10 and IL-12 by monocytes, while polygonal shape and the larger pore sizes increased the expression of V-CAM. The physical characteristics of a bone biomaterial can influence the proliferation rate of osteoblasts and has an influence on the cytokine gene expression of monocytes in vitro. These results indicate that the physical structure of a biomaterial has a significant effect of how cells interact with the material. Thus, specific characteristics of a material may strongly affect the regenerative potential in vivo.

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Sobota, Jacqueline A., Francesco Ferraro, Nils Bäck, Betty A. Eipper, and Richard E. Mains. "Not All Secretory Granules Are Created Equal: Partitioning of Soluble Content Proteins." Molecular Biology of the Cell 17, no. 12 (December 2006): 5038–52. http://dx.doi.org/10.1091/mbc.e06-07-0626.

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Secretory granules carrying fluorescent cargo proteins are widely used to study granule biogenesis, maturation, and regulated exocytosis. We fused the soluble secretory protein peptidylglycine α-hydroxylating monooxygenase (PHM) to green fluorescent protein (GFP) to study granule formation. When expressed in AtT-20 or GH3 cells, the PHM-GFP fusion protein partitioned from endogenous hormone (adrenocorticotropic hormone, growth hormone) into separate secretory granule pools. Both exogenous and endogenous granule proteins were stored and released in response to secretagogue. Importantly, we found that segregation of content proteins is not an artifact of overexpression nor peculiar to GFP-tagged proteins. Neither luminal acidification nor cholesterol-rich membrane microdomains play essential roles in soluble content protein segregation. Our data suggest that intrinsic biophysical properties of cargo proteins govern their differential sorting, with segregation occurring during the process of granule maturation. Proteins that can self-aggregate are likely to partition into separate granules, which can accommodate only a few thousand copies of any content protein; proteins that lack tertiary structure are more likely to distribute homogeneously into secretory granules. Therefore, a simple “self-aggregation default” theory may explain the little acknowledged, but commonly observed, tendency for both naturally occurring and exogenous content proteins to segregate from each other into distinct secretory granules.

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Hashimoto, S., G. Fumagalli, A. Zanini, and J. Meldolesi. "Sorting of three secretory proteins to distinct secretory granules in acidophilic cells of cow anterior pituitary." Journal of Cell Biology 105, no. 4 (October 1, 1987): 1579–86. http://dx.doi.org/10.1083/jcb.105.4.1579.

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The distribution of three proteins discharged by regulated exocytosis--growth hormone (GH), prolactin (PRL), and secretogranin II (SgII)--was investigated by double immunolabeling of ultrathin frozen sections in the acidophilic cells of the bovine pituitary. In mammotrophs, heavy PRL labeling was observed over secretory granule matrices (including the immature matrices at the trans Golgi surface) and also over Golgi cisternae. In contrast, in somatotrophs heavy GH labeling was restricted to the granule matrices; vesicles and tubules at the trans Golgi region showed some and the Golgi cisternae only sparse labeling. All somatotrophs and mammotrophs were heavily positive for GH and PRL, respectively, and were found to contain small amounts of the other hormone as well, which, however, was almost completely absent from granules, and was more concentrated in the Golgi complex, admixed with the predominant hormone. Mixed somatomammotrophs (approximately 26% of the acidophilic cells) were heavily positive for both GH and PRL. Although admixed within Golgi cisternae, the two hormones were stored separately within distinct granule types. A third type of granule was found to contain SgII. Spillage of small amounts of each of the three secretory proteins into granules containing predominantly another protein was common, but true intermixing (i.e., coexistence within single granules of comparable amounts of two proteins) was very rare. It is concluded that in the regulated pathway of acidophilic pituitary, cell mechanisms exist that cause sorting of the three secretory proteins investigated. Such mechanisms operate beyond the Golgi cisternae, possibly at the sites where condensation of secretion products into granule matrices takes place.

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Leblond, F. A., G. Viau, J. Lainé, and D. Lebel. "Reconstitution in vitro of the pH-dependent aggregation of pancreatic zymogens en route to the secretory granule: implication of GP-2." Biochemical Journal 291, no. 1 (April 1, 1993): 289–96. http://dx.doi.org/10.1042/bj2910289.

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Regulated secretory proteins are thought to be sorted in the trans-Golgi network (TGN) via selective aggregation. To elucidate the biogenesis of the secretory granule in the exocrine pancreas, we reconstituted in vitro the conditions of pH and ions believed to exist in the TGN using the end product of this sorting process, the zymogen granule contents. Protein aggregation was dependent on pH (acidic) and on the presence of cations (10 mM Ca2+, 150 mM K+) to reproduce the pattern of proteins found in the granule. The constitutive secretory protein IgG was excluded from these aggregates. Zymogen aggregation correlated with the relative proportion of the major granule membrane protein GP-2 in the assay. These results show that the glycosylphosphatidylinositol-anchored protein GP-2 co-aggregates with zymogens in the acidic environment believed to exist in the pancreatic TGN, and thus suggest that GP-2 would function as a membrane anchor for zymogen aggregates, facilitating their entrapment in budding vesicles directed towards the regulated secretory pathway.

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Henningsson, Frida, Sonja Hergeth, Robert Cortelius, Magnus Åbrink, and Gunnar Pejler. "A role for serglycin proteoglycan in granular retention and processing of mast cell secretory granule components." FEBS Journal 273, no. 21 (November 2006): 4901–12. http://dx.doi.org/10.1111/j.1742-4658.2006.05489.x.

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Wong, J. G., K. T. Izutsu, M. R. Robinovitch, J. M. Iversen, M. E. Cantino, and D. E. Johnson. "Microprobe analysis of maturation-related elemental changes in rat parotid secretory granules." American Journal of Physiology-Cell Physiology 261, no. 6 (December 1, 1991): C1033—C1041. http://dx.doi.org/10.1152/ajpcell.1991.261.6.c1033.

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Electron probe X-ray microanalysis was use to quantitate the elemental and mass changes that take place during the secretory granule maturation process. A single injection of isoproterenol stimulated the depletion of secretory granules from rat parotid acinar cells. Granules at different stages of maturation were analyzed as they reaccumulated within the cells over time. Dry mass measurements revealed that secretory material becomes concentrated about twofold within maturing granules. Nearly all of the increase in mass concentration could be attributed to a reduction in water space. Data are presented that indicate that Na, K, Cl, and water all efflux from secretory granules during maturation. In contrast, granule S content is positively correlated with maturation. Hence, significant changes in granule elemental and water contents occur during the maturation process.

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Venkatesh, S. G., and S. U. Gorr. "A sulfated proteoglycan is necessary for storage of exocrine secretory proteins in the rat parotid gland." American Journal of Physiology-Cell Physiology 283, no. 2 (August 1, 2002): C438—C445. http://dx.doi.org/10.1152/ajpcell.00552.2001.

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Sulfated proteoglycans have been proposed to play a role in the sorting and storage of secretory proteins in exocrine secretory granules. Rat parotid acinar cells expressed a 40- to 60-kDa proteoglycan that was stored in secretory granules. Treatment of the tissue with the proteoglycan synthesis inhibitor paranitrophenyl xyloside resulted in the complete abrogation of the sulfated proteoglycan. Pulse-chase experiments in the presence of the xyloside analog showed a significant reduction in the stimulated secretion and granule storage of the newly synthesized regulated secretory proteins amylase and parotid secretory protein. Inhibition of proteoglycan sulfation by chlorate did not affect the sorting of these proteins. The effect of proteoglycan synthesis inhibition on protein sorting was completely reversed upon treatment with a weak acid. These results suggest that the sulfated proteoglycan is necessary for sorting and storage of regulated secretory proteins in the exocrine parotid gland. Preliminary evidence suggests that the mechanism involves the modulation of granule pH by the proteoglycan rather than a direct interaction with other granule components.

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Courel, Maïté, Carrie Rodemer, Susan T. Nguyen, Alena Pance, Antony P. Jackson, Daniel T. O'Connor, and Laurent Taupenot. "Secretory Granule Biogenesis in Sympathoadrenal Cells." Journal of Biological Chemistry 281, no. 49 (October 10, 2006): 38038–51. http://dx.doi.org/10.1074/jbc.m604037200.

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Huh, Yang Hoon, Soung Hoo Jeon, and Seung Hyun Yoo. "Chromogranin B-induced Secretory Granule Biogenesis." Journal of Biological Chemistry 278, no. 42 (August 5, 2003): 40581–89. http://dx.doi.org/10.1074/jbc.m304942200.

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45

Austin, C., R. Demaimay, I. Hinners, C. Panaretou, F. Wendler, and S. Tooze. "Molecular dissection of secretory granule biogenesis." Biochemical Society Transactions 29, no. 3 (June 1, 2001): A62. http://dx.doi.org/10.1042/bst029a062.

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Kelly, Regis B. "Secretory granule and synaptic vesicle formation." Current Opinion in Cell Biology 3, no. 4 (August 1991): 654–60. http://dx.doi.org/10.1016/0955-0674(91)90037-y.

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47

Marino, C. R., J. D. Castle, and F. S. Gorelick. "Regulated phosphorylation of secretory granule membrane proteins of the rat parotid gland." American Journal of Physiology-Gastrointestinal and Liver Physiology 259, no. 1 (July 1, 1990): G70—G77. http://dx.doi.org/10.1152/ajpgi.1990.259.1.g70.

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An antiserum raised against purified rat parotid secretory granule membrane proteins has been used to identify organelle-specific protein phosphorylation events following stimulation of intact cells from the rat parotid gland. After lobules were prelabeled with [32P]orthophosphate and exposed to secretagogues, phosphoproteins were immunoprecipitated with the granule membrane protein antiserum, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and visualized by autoradiography. Parallel studies of stimulated amylase release were performed. Isoproterenol treatment of parotid lobules resulted in an increase in the phosphate content of immunoprecipitable 60- and 72-kDa proteins that correlated with amylase release in a time-dependent manner. Forskolin addition mimicked these effects, but only the isoproterenol effects were reversed by propranolol treatment. To confirm the specificity of the antiserum to the secretory granule membrane fraction, subcellular isolation techniques were employed following in situ phosphorylation. The 60- and 72-kDa phosphoproteins were immunoprecipitated from both a particulate fraction and a purified secretory granule fraction. Furthermore, the extraction properties of both species suggest that they are integral membrane proteins. These findings support the possibility that stimulus-regulated secretion may involve phosphorylation of integral membrane proteins of the exocrine secretory granule.

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POULI, Aristea E., Evaggelia EMMANOUILIDOU, Chao ZHAO, Christina WASMEIER, John C. HUTTON, and Guy A. RUTTER. "Secretory-granule dynamics visualized in vivo with a phogrin–green fluorescent protein chimaera." Biochemical Journal 333, no. 1 (July 1, 1998): 193–99. http://dx.doi.org/10.1042/bj3330193.

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To image the behaviour in real time of single secretory granules in neuroendocrine cells we have expressed cDNA encoding a fusion construct between the dense-core secretory-granule-membrane glycoprotein, phogrin (phosphatase on the granule of insulinoma cells), and enhanced green fluorescent protein (EGFP). Expressed in INS-1 β-cells and pheochromocytoma PC12 cells, the chimaera was localized efficiently (up to 95%) to dense-core secretory granules (diameter 200–1000 nm), identified by co-immunolocalization with anti-(pro-)insulin antibodies in INS-1 cells and dopamine β-hydroxylase in PC12 cells. Using laser-scanning confocal microscopy and digital image analysis, we have used this chimaera to monitor the effects of secretagogues on the dynamics of secretory granules in single living cells. In unstimulated INS-1 β-cells, granule movement was confined to oscillatory movement (dithering) with period of oscillation 5–10 s and mean displacement < 1 µm. Both elevated glucose concentrations (30 mM), and depolarization of the plasma membrane with K+, provoked large (5–10 µm) saltatory excursions of granules across the cell, which were never observed in cells maintained at low glucose concentration. By contrast, long excursions of granules occurred in PC12 cells without stimulation, and occurred predominantly from the cell body towards the cell periphery and neurite extensions. Purinergic-receptor activation with ATP provoked granule movement towards the membrane of PC12 cells, resulting in the transfer of fluorescence to the plasma membrane consistent with fusion of the granule and diffusion of the chimaera in the plasma membrane. These results illustrate the potential use of phogrin–EGFP chimeras in the study of secretory-granule dynamics, the regulation of granule–cytoskeletal interactions and the trafficking of a granule-specific transmembrane protein during the cycle of exocytosis and endocytosis.

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Tompkins, Linda S., Kevin D. Nullmeyer, Sean M. Murphy, Craig S. Weber, and Ronald M. Lynch. "Regulation of secretory granule pH in insulin-secreting cells." American Journal of Physiology-Cell Physiology 283, no. 2 (August 1, 2002): C429—C437. http://dx.doi.org/10.1152/ajpcell.01066.2000.

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Luminal acidification is important for the maturation of secretory granules, yet little is known regarding the regulation of pH within them. A pH-sensitive green fluorescent protein (EGFP) was targeted to secretory granules in RIN1046-38 insulinoma cells by using a construct in which the EGFP gene was preceded by the nucleotide sequence for human growth hormone. Stimulatory levels of glucose doubled EGFP secretion from cell cultures, and potentiators of glucose-induced insulin secretion enhanced EGFP release. Thus this targeted EGFP is useful for population measurements of secretion. However, less than ∼4% of total cell EGFP was released after 1.5 h of stimulation. Consequently, when analyzed in single cells, fluorescence of the targeted EGFP acts as an indicator of pH within secretory granules. Glucose elicited a decrease in granule pH, whereas inhibitors of the V-type H+-ATPase increased pH and blocked the glucose effect. Granule pH also was modified by effectors of the protein kinase A pathway, with activation eliciting granule alkalinization, suggesting that potentiation of peptide release by cAMP may involve regulated changes in secretory granule pH.

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Chock, S. P., E. A. Schmauder-Chock, E. Cordella-Miele, L. Miele, and A. B. Mukherjee. "The localization of phospholipase A2 in the secretory granule." Biochemical Journal 300, no. 3 (June 15, 1994): 619–22. http://dx.doi.org/10.1042/bj3000619.

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A heat-resistant phospholipase A2 has been detected in the secretory granules of the mast cell [Chock, Rhee, Tang and Schmauder-Chock (1991) Eur. J. Biochem. 195, 707-713]. By using ultrastructural immunocytochemical techniques, we have now localized this enzyme to the matrix of the secretory granule. Like the cyclo-oxygenase [Schmauder-Chock and Chock (1989) J. Histochem. Cytochem. 37, 1319-1328], this enzyme also adheres tightly to the ribbon-like granule matrix components. The results from Western-blot analysis suggest that it has a molecular mass of about 14 kDa. The localization of the phospholipase A2, the presence of a phospholipid store with millimolar concentrations of calcium and the localization of the enzymes of the arachidonic acid cascade make the secretory granule a natural site for lipid-mediator synthesis. The packaging of phospholipase A2, together with its substrate and the components of the arachidonic acid cascade, in the secretory granule represents a physical arrangement by which the initiation of the cascade and the release of mediators can be directly linked to the stimulation of cell-surface receptors.

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Journal articles on the topic 'Secretory granula'

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