Добірка наукової літератури з теми "Immunophilin molecules"

The immunophilin FKBP51 forms heterocomplexes with molecular chaperones, protein-kinases, protein-phosphatases, autophagy-related factors, and transcription factors. Like most scaffold proteins, FKBP51 can use a simple tethering mechanism to favor the efficiency of interactions with partner molecules, but it can also exert more complex allosteric controls over client factors, the immunophilin itself being a putative regulation target. One of the simplest strategies for regulating pathways and subcellular localization of proteins is phosphorylation. In this study, it is shown that scaffold immunophilin FKBP51 is resolved by resolutive electrophoresis in various phosphorylated isoforms. This was evidenced by their reactivity with specific anti-phosphoamino acid antibodies and their fade-out by treatment with alkaline phosphatase. Interestingly, stress situations such as exposure to oxidants or in vivo fasting favors FKBP51 translocation from mitochondria to the nucleus. While fasting involves phosphothreonine residues, oxidative stress involves tyrosine residues. Molecular modeling predicts the existence of potential targets located at the FK1 domain of the immunophilin. Thus, oxidative stress favors FKBP51 dephosphorylation and protein degradation by the proteasome, whereas FK506 binding protects the persistence of the post-translational modification in tyrosine, leading to FKBP51 stability under oxidative conditions. Therefore, FKBP51 is revealed as a phosphoprotein that undergoes differential phosphorylations according to the stimulus.

The identification of new factors that may function as cancer markers and become eventual pharmacologic targets is a challenge that may influence the management of tumor development and management. Recent discoveries connecting Hsp90-binding immunophilins with the regulation of signalling events that can modulate cancer progression transform this family of proteins in potential unconventional factors that may impact on the screening and diagnosis of malignant diseases. Immunophilins are molecular chaperones that group a family of intracellular receptors for immunosuppressive compounds. A subfamily of the immunophilin family is characterized by showing structural tetratricopeptide repeats, protein domains that are able to interact with the C-terminal end of the molecular chaperone Hsp90, and via the proper Hsp90-immunophilin complex, the biological properties of a number of client-proteins involved in cancer biology are modulated. Recent discoveries have demonstrated that two of the most studied members of this Hsp90- binding subfamily of immunophilins, FKBP51 and FKBP52, participate in several cellular processes such as apoptosis, carcinogenesis progression, and chemoresistance. While the expression levels of some members of the immunophilin family are affected in both cancer cell lines and human cancer tissues compared to normal samples, novel regulatory mechanisms have emerged during the last few years for several client-factors of immunophilins that are major players in cancer development and progression, among them steroid receptors, the transctiption factor NF-κB and the catalytic subunit of telomerase, hTERT. In this review, recent findings related to the biological properties of both iconic Hsp90-binding immunophilins, FKBP51 and FKBP52, are reviewed within the context of their interactions with those chaperoned client-factors. The potential roles of both immunophilins as potential cancer biomarkers and non-conventional pharmacologic targets for cancer treatment are discussed.

The pathophysiology of vascular disease in diabetes involves abnormalities in endothelial cells, vascular smooth muscle cells, and monocytes. The metabolic abnormalities that characterize diabetes, such as hyperglycemia, increased free fatty acids, and insulin resistance, each provoke molecular mechanisms that contribute to vascular dysfunction. Several molecules have been identified as risk markers, and have been studied to prevent progression of disease and long-term complications. Markers such as C-reactive protein and monocyte chemoattractant protein-1 are used to assess risk for adverse cardiac events, but elevated levels are possible due to the presence of other risk factors as part of the natural physiological defense mechanism. In this review we discuss potential of cyclophilin-A, a secreted oxidative-stress-induced immunophilin with diverse functions. We present evidence for a significant role of cyclophilin-A in the pathogenesis of atherosclerosis in diabetes, and its potential as a marker for vascular disease in type-2 diabetes.

Immunophilins are members of a highly conserved family of proteins all of which are cis-trans peptidyl-prolyl isomerases. The prototypic members of the immunophilin family, cyclophilin A and FKPB12, were discovered on the basis of their ability to bind and mediate the immunosuppressive effects of the drugs cyclosporin, FK506, and rapamycin. However, the prolyl isomerase activity of these proteins is not involved in any of the immunosuppressive effects. Indeed, despite the fact that all members of the family are prolyl isomerases, the cellular role of this enzymatic function has not been clearly defined. In many cases, immunophilins are widely expressed and are present at high levels in some tissues. Moreover, while the number of proteins that belong to the immunophilin family continues to grow, the natural cellular functions of all but a few remain obscure. An example where immunophilins do appear to have a defined cellular role, in the absence of immunosuppressive ligands, is the modulation of intracellular calcium release channel function by FKBP12 and FKBP12.6. In this case, FKBPs are integral parts of three types of calcium release channel complexes, skeletal and cardiac ryanodine receptors and the inositol 1,4,5-trisphosphate receptor. In each case, FKBPs modulate channel function possibly by enhancing the cooperativity between subunits.

A cDNA for human FKBP51 has been cloned and sequenced, and protein products have been expressed in both in vitro and bacterial systems. The deduced amino acid sequence for human FKBP51 is 90% identical to sequences of recently described murine proteins and is 55% identical to the sequence of human FKBP52. Human FKBP51 mRNA is expressed in a wide range of tissues, and the protein has peptidylprolyl isomerase activity that is inhibited by FK506 but not cyclosporine. FKBP51 is the same as a previously described progesterone receptor-associated immunophilin that, similar to FKBP52 and cyclophilin 40, is an Hsp90-binding protein and appears in functionally mature steroid receptor complexes along with Hsp90 and p23. Each of the three receptor-associated immunophilins displays interactions with progesterone receptor that are more dynamic than Hsp90-receptor interactions. Whereas FKBP52 and FKBP51 compete about equally well for binding to Hsp90 in a purified system, FKBP51 accumulates preferentially in progesterone receptor complexes assembled in a cell-free system. This observation provides a precedent for differential interactions between Hsp90-associated immunophilins and target proteins such as steroid receptors.

FK506 binding proteins (FKBPs) in cells are known as immunophilins. We have identifi ed and characterized a cDNA encoding an endoplasmic reticulum (ER) immunophilin, FKBP23, from pig liver by nested PCR. The predicted amino acid sequence of pig FKBP23 shows high identity to those of human FKBP23 and mouse FKBP23. It possesses a conserved FKBP-type peptidylprolyl cis-trans isomerase (PPIase) domain and EF-hand domain. We constructed a plasmid to express pFKBP23. Furthermore, we proved that the recombinant pFKBP23 can specifi cally bind to natural BiP, the main protein of the molecular chaperone Hsp70 in ER lumen; the binding is interrelated with the Ca2+ concentration just as the FKBP23 from mice.

The specific regulation of inflammatory processes by steroid hormones has been actively studied in recent years, especially by progesterone (P4) and progestins. The mechanisms of the anti-inflammatory and immunomodulatory P4 action are not fully clear. The anti-inflammatory effects of P4 can be defined as nonspecific, associated with the inhibition of NF-κB and COX, as well as the inhibition of prostaglandin synthesis, or as specific, associated with the regulation of T-cell activation, the regulation of the production of pro- and anti-inflammatory cytokines, and the phenomenon of immune tolerance. The specific anti-inflammatory effects of P4 and its derivatives (progestins) can also include the inhibition of proliferative signaling pathways and the antagonistic action against estrogen receptor beta-mediated signaling as a proinflammatory and mitogenic factor. The anti-inflammatory action of P4 is accomplished through the participation of progesterone receptor (PR) chaperones HSP90, as well as immunophilins FKBP51 and FKBP52, which are the validated targets of clinically approved immunosuppressive drugs. The immunomodulatory and anti-inflammatory effects of HSP90 inhibitors, tacrolimus and cyclosporine, are manifested, among other factors, due to their participation in the formation of an active ligand–receptor complex of P4 and their interaction with its constituent immunophilins. Pharmacological agents such as HSP90 inhibitors can restore the lost anti-inflammatory effect of glucocorticoids and P4 in chronic inflammatory and autoimmune diseases. By regulating the activity of FKBP51 and FKBP52, it is possible to increase or decrease hormonal signaling, as well as restore it during the development of hormone resistance. The combined action of immunophilin suppressors with steroid hormones may be a promising strategy in the treatment of chronic inflammatory and autoimmune diseases, including endometriosis, stress-related disorders, rheumatoid arthritis, and miscarriages. Presumably, the hormone receptor- and immunophilin-targeted drugs may act synergistically, allowing for a lower dose of each.

The immunosuppressants cyclosporin A (CsA) and FK506 appear to block T-cell function by inhibiting the calcium-regulated phosphatase calcineurin. While multiple distinct intracellular receptors for these drugs (cyclophilins and FKBPs, collectively immunophilins) have been characterized, the functionally active ones have not been discerned. We found that overexpression of cyclophilin A or B or FKBP12 increased T-cell sensitivity to CsA or FK506, respectively, demonstrating that they are able to mediate the inhibitory effects of their respective immunosuppressants in vivo. In contrast, cyclophilin C, FKBP13, and FKBP25 had no effect. Direct comparison of the Ki of each drug-immunophilin complex for calcineurin in vitro revealed that although calcineurin binding was clearly necessary, it was not sufficient to explain the in vivo activity of the immunophilin. Subcellular localization was shown also to play a role, since gene deletions of cyclophilins B and C which changed their intracellular locations altered their activities significantly. Cyclophilin B has been shown previously to be located within calcium-containing intracellular vesicles; its ability to mediate CsA inhibition implies that certain components of the signal transduction machinery are also spatially restricted within the cell.

Mips (macrophage infectivity potentiators) are a subset of immunophilins associated with virulence in a range of micro-organisms. These proteins possess peptidylprolyl isomerase activity and are inhibited by drugs including rapamycin and tacrolimus. We determined the structure of the Mip homologue [BpML1 (Burkholderia pseudomallei Mip-like protein 1)] from the human pathogen and biowarfare threat B. pseudomallei by NMR and X-ray crystallography. The crystal structure suggests that key catalytic residues in the BpML1 active site have unexpected conformational flexibility consistent with a role in catalysis. The structure further revealed BpML1 binding to a helical peptide, in a manner resembling the physiological interaction of human TGFβRI (transforming growth factor β receptor I) with the human immunophilin FKBP12 (FK506-binding protein 12). Furthermore, the structure of BpML1 bound to the class inhibitor cycloheximide N-ethylethanoate showed that this inhibitor mimics such a helical peptide, in contrast with the extended prolyl-peptide mimicking shown by inhibitors such as tacrolimus. We suggest that Mips, and potentially other bacterial immunophilins, participate in protein–protein interactions in addition to their peptidylprolyl isomerase activity, and that some roles of Mip proteins in virulence are independent of their peptidylprolyl isomerase activity.

Oilseed rape is largely infected by several phytopathogens and two most economical important diseases are blackleg caused by fungus species complex Leptosphaeria maculans and L. biglobosa and clubroot caused by protist P. brassicae. The sequenced genomes of these phytopathogens provide opportunity to uncover various aspects related to disease infection, host pathogen interactions, plant disease resistance, and evolution of pathogens. Considering these we focused on one of the most conserved family called immunophilins (IMMs) in these genomes. IMMs are comprised of three structurally unrelated sub-families including cyclophilins (CYPs), FK506-binding proteins (FKBPs), and parvulin-like proteins (PARs). We identified putative members of IMMs in each phytopathogen using bioinformatics approaches. We further characterized the IMMs based on domain architecture, subcellular localization, exon-intron organization, transcriptomic expression patterns, gene ontology terms, conserved motifs presents and evolutionary analyses. IMMs are performing several vital roles in plants, animals and fungi. However, in phytopathogens their roles are not well established except for cyclophilin that implicates in pathogenicity in some phytopathogens. Therefore, we exploited the role of cyclophilin in L. maculans and L. biglobosa using expression profiles and in P. brassicae using Magnaporthe oryzae cyclophilin deletion mutant. Overall, we concluded that the cyclophilin acts as a virulence determinant in our studied phytopathogens. However, delineating the precise role of other IMMs would also be imperative. Taken together, our findings for the first time shed light on the highly conserved IMM family in the oilseed rape pathogens.

Peptidyl prolyl isomerases (PPIase) are a class of enzymes that are required to catalyse the conversion of proline residues from cis to trans conformation. There are several classes of PPIase molecules, including parvulins, cyclophilins, and FK506 binding proteins (FKBPs). Among these PPIase molecules each class contains a conserved PPIase domain that facilitates protein to protein interactions. These PPIase molecules have diverse functions in cellular function and disease progression. FKBPs are a group of immunophilin molecules that are known to interact with immunosuppressant molecules FK506 and rapamycin to stop the immune response and inhibit mTOR, respectively. The structure and function of FKBPs is diverse, these proteins act to facilitate protein to protein interactions, act as co-chaperones, translocate throughout the cell in response to stress events, and bind to DNA. Importantly, FKBPs have been implicated in the pathogenesis of cancer, largely through their roles in co-chaperoning hormone receptors in hormone responsive cancers i.e. breast and prostate cancers. Of particular interest, FKBP25, a 25kDa protein that consists of two functional domains, an N terminal basic helix–loop–helix and C terminal PPIase domain. FKBP25 is known to be involved in protein folding, cytoskeletal dynamics, DNA damage repair, double stranded RNA binding, interacting with the pre-ribosome, and cellular stress responses. Despite the variety of roles that FKBP25 is known to play, there is limited research regarding FKBP25 role in disease and cell differentiation. To address this, initial studies investigated the role of FKBP25 in breast cancer progression and epithelial to mesenchymal transition (EMT). Here it was found that FKBP25 protein expression is reduced in both mesenchymal breast cancer cell types, including BT-549, Hs578t, MDA-MB-231. To further understand the potential role of FKBP25 in breast cancer pathogenesis, a variety of mutations that contribute to malignant transformation were examined. Here it was found that the oncogenic mutations, that are associated with growth pathways in fact increased FKBP25 expression. However, in an epidermal growth factor mediated model EMT in MDA- MB-468 breast cancer cells, it was identified that FKBP25 protein expression was reduced. This implies that the loss of FKBP25 protein expression may be required for de-differentiation and progression of cancer cells. As such, it was hypothesised that FKBP25 protein expression was correlated with the level of cellular differentiation. To examine this hypothesis, next a model of mesenchymal to epithelial transition (MET) was analysed. The C2C12 model of myogenesis to study the role of FKBP25 in an MET-like example of cell differentiation. Previous studies have identified that FKBP25 is the most highly expressed FKBP in skeletal muscle and is expressed in the top 10% of the skeletal muscle proteome. Here it was identified that in proliferative myoblasts there is a higher level of FKBP25 protein expression compared to that of post mitotic myotubes. This was further demonstrated in a model of C2C12 quiescence where it was demonstrated that upon removal from the cell cycle, myoblasts accumulate greater levels of FKBP25 protein expression, which is then reduced upon re-entry to the cell cycle. Interestingly, this trend was not observed in human primary myoblasts, however, was identified in human rhabdomyosarcoma cells which may be due to the presence of p53 and MyoD mutations. Furthermore, in vivo models of muscle plasticity were examined to assess the impact of FKBP25 on skeletal muscle regeneration considering FKBP25 is the most highly expressed FKBP in mature skeletal muscle. Here it was discovered that FKBP25 protein expression is increased in models of regeneration including, chronic mechanical loading, murine muscular dystrophy (mdx), and denervation. It is hypothesised that this was observed due to extensive cytoskeletal remodelling to repair structural damage caused by hypertrophy and atrophy of fibres. Next, we examined the impact of FKBP25 knockdown (25KD) on cell biology and function of MDA-MB-468 and C2C12 cells. 25KD cells were developed using doxycycline inducible SMARTvector (Dharmacon, CO, USA) short hairpin RNA technology. After confirming adequate 25KD, it was observed that in both cell lines 25KD resulted in an increase in proliferation compared to respective non-targeting (NT) cells. Furthermore, in MDA-MB-468 cells, it was observed that there were no changes to invasion outgrowth or migration in vitro. However, it was demonstrated that 25KD resulted in decreased anchorage dependent growth, which could be explained by alterations to cytoskeletal stability. Conversely, in C2C12 myoblasts it was found that 25KD resulted in a significant increase in wound healing migration. Upon investigation of myogenic regulatory factor expression in differentiated 25KD myotubes it was revealed that there were no changes in protein expression. Furthermore, upon measurement of fibre diameter and fusion index it was found that there were no discernible changes to myotube formation. Finally, the influence of 25KD on tubulin regulation and dynamics was assessed. Initially, the presence of microtubule (MT) post-translational modifications was assessed, including detyrosination and acetylation which are associated with MT stability. Both C2C12 and MDA-MB-468 25KD cells showed no changes to stabilising modifications. Similarly, upon examination of MT stabilising protein stathmin, both C2C12 and MDA-MB-468 25KD showed no change to stathmin expression. After this, the impact of 25KD on tubulin polymerisation under control and paclitaxel treated (induction of maximal polymerisation) conditions was explored. However, here no differences in MT polymer content was found in either 25KD in either C2C12 or MDA- MB-468 cells. In conclusion, this thesis has examined the potential role of FKBP25 in cell differentiation and de-differentiation in EMT and MET-like models. It was found that FKBP25 is required for some cell processed including proliferation, anchorage dependent growth, and migration. It was hypothesised that this was a result of cytoskeletal reorganisation and altered MT dynamics, however, this was unable to be demonstrated. Further studies should further examine the impact of 25KD on MT dynamics using methods less prone to error. Nonetheless, FKBP25 was demonstrated to have a role in cell proliferation and differentiation. Maintenance of FKBP25 protein in both cancers and skeletal muscle could help to preserve epithelial-like phenotype and maintain structural integrity, respectively.

La réplication et l’assemblage du virus de l’hépatite C (VHC) sont régulés finement dans le temps et l’espace par les interactions protéiques entre le virus avec l’hôte. La compréhension de la biologie du virus ainsi que sa pathogénicité passe par les connaissances relatives aux interactions virus/hôte. Afin d’identifier ces interactions, nous avons exploité une approche d’immunoprécipitation (IP) couplée à une détection par spectrométrie de masse (MS), pour ensuite évaluer le rôle des protéines identifiées dans le cycle viral par une technique de silençage génique. Les protéines virales Core, NS2, NS3/4A, NS4B, NS5A et NS5B ont été exprimées individuellement dans les cellules humaines 293T et immunoprécipitées afin d’isoler des complexes protéiques qui ont été soumis à l’analyse MS. Ainsi, 98 protéines de l’hôte ont été identifiées avec un enrichissement significatif et illustrant une spécificité d’interaction. L’enrichissement de protéines connues dans la littérature a démontré la force de l’approche, ainsi que la validation de 6 nouvelles interactions virus/hôte. Enfin, le rôle de ces interactants sur la réplication virale a été évalué dans un criblage génomique par ARN interférant (ARNi). Deux systèmes rapporteurs de la réplication virale ont été utilisés : le système de réplicon sous-génomique (Huh7-Con1-Fluc) et le système infectieux (J6/JFH-1/p7Rluc2a), ainsi qu’un essai de toxicité cellulaire (Alamar Blue). Parmi les protéines de l’hôte interagissant avec le VHC, 28 protéines ont démontré un effet significatif sans effet de toxicité cellulaire, suggérant fortement un rôle dans la réplication du VHC. Globalement, l’étude a mené à l’identification de nouvelles interactions virus/hôte et l’identification de nouvelles cibles thérapeutiques potentielles.
Hepatitis C virus (HCV) replication and assembly are tightly regulated in time and space within the cell, most likely due to protein interactions between virus and host. In order to better understand HCV biology and its pathogenesis, there is a need to unravel virus/host interaction network. We extended our knowledge of virus/host interactions by the identification of cellular proteins associated to HCV proteins using an immunoprecipitation (IP) technique coupled to mass spectrometry (MS), and further evaluate the role of retrieved interactors using gene knockdown. FLAG-tagged viral proteins Core, NS2, NS3/4A, NS4B, NS5A and NS5B have been expressed individually in 293T human cells, and immunoprecipitated protein complexes have been submitted to MS analysis for identification of host proteins. In this study, 98 proteins were significantly enriched and showed specific interaction to a viral protein. Retrieval of previously characterized interacting proteins proved the strength of the method. Six newly identified interactors by MS were individually confirmed using IP of viral proteins. We evaluated the role of identified interactors in HCV replication by performing a functional lentivirus-based RNA interference (RNAi) screen. Two reporter systems were used: the sub- genomic replicon (Huh7-Con1-Fluc) and a full length infectious clone (J6/JFH-1/p7Rluc2a), as well as the cellular toxicity assay Alamar blue. Of the identified host interactors, 28 proteins showed a significant effect on HCV replication upon gene knockdown and without cellular toxicity. Overall, the study led to the identification of novel virus/host interactions essential in HCV life cycle and provides novel potential drug targets.