Journal articles: 'M2 protein'

1

Sansom, Mark S. P., and Ian D. Kerr. "Influenza virus M2 protein: a molecular modelling study of the ion channel." "Protein Engineering, Design and Selection" 6, no. 1 (1993): 65–74. http://dx.doi.org/10.1093/protein/6.1.65.

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Gabbard, J., N. Velappan, R. Di Niro, J. Schmidt, C. A. Jones, S. M. Tompkins, and A. R. M. Bradbury. "A humanized anti-M2 scFv shows protective in vitro activity against influenza." Protein Engineering Design and Selection 22, no. 3 (October 16, 2008): 189–98. http://dx.doi.org/10.1093/protein/gzn070.

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Li, Dongsheng, David A. Jans, Phillip G. Bardin, Jayesh Meanger, John Mills, and Reena Ghildyal. "Association of Respiratory Syncytial Virus M Protein with Viral Nucleocapsids Is Mediated by the M2-1 Protein." Journal of Virology 82, no. 17 (June 25, 2008): 8863–70. http://dx.doi.org/10.1128/jvi.00343-08.

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ABSTRACT Cytoplasmic inclusions in respiratory syncytial virus-infected cells comprising viral nucleocapsid proteins (L, N, P, and M2-1) and the viral genome are sites of viral transcription. Although not believed to be necessary for transcription, the matrix (M) protein is also present in these inclusions, and we have previously shown that M inhibits viral transcription. In this study, we have investigated the mechanisms for the association of the M protein with cytoplasmic inclusions. Our data demonstrate for the first time that the M protein associates with cytoplasmic inclusions via an interaction with the M2-1 protein. The M protein colocalizes with M2-1 in the cytoplasm of cells expressing only the M and M2-1 proteins and directly interacts with M2-1 in a cell-free binding assay. Using a cotransfection system, we confirmed that the N and P proteins are sufficient to form cytoplasmic inclusions and that M2-1 localizes to these inclusions; additionally, we show that M associates with cytoplasmic inclusions only in the presence of the M2-1 protein. Using truncated mutants, we show that the N-terminal 110 amino acids of M mediate the interaction with M2-1 and the subsequent association with nucleocapsids. The interaction of M2-1 with M and, in particular, the N-terminal region of M may represent a target for novel antivirals that block the association of M with nucleocapsids, thereby inhibiting virus assembly.

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Gupta, Vibhor, and Rameshwar N. K. Bamezai. "Human pyruvate kinase M2: A multifunctional protein." Protein Science 19, no. 11 (October 26, 2010): 2031–44. http://dx.doi.org/10.1002/pro.505.

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Parks, G. D., J. D. Hull, and R. A. Lamb. "Transposition of domains between the M2 and HN viral membrane proteins results in polypeptides which can adopt more than one membrane orientation." Journal of Cell Biology 109, no. 5 (November 1, 1989): 2023–32. http://dx.doi.org/10.1083/jcb.109.5.2023.

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The influenza A virus M2 polypeptide is a small integral membrane protein that does not contain a cleaved signal sequence, but is unusual in that it assumes the membrane orientation of a class I integral membrane protein with an NH2-terminal ectodomain and a COOH-terminal cytoplasmic tail. To determine the domains of M2 involved in specifying membrane orientation, hybrid genes were constructed and expressed in which regions of the M2 protein were linked to portions of the paramyxovirus HN and SH proteins, two class II integral membrane proteins that adopt the opposite orientation in membranes from M2. A hybrid protein (MgMH) consisting of the M2 NH2-terminal and membrane-spanning domains linked precisely to the HN COOH-terminal ectodomain was found in cells in two forms: integrated into membranes in the M2 topology or completely translocated across the endoplasmic reticulum membrane and ultimately secreted from the cell. The finding of a soluble form suggested that in this hybrid protein the anchor function of the M2 signal/anchor domain can be overridden. A second hybrid which contained the M2 NH2 terminus linked to the HN signal anchor and ectodomain (MgHH) was found in both the M2 and the HN orientation, suggesting that the M2 NH2 terminus was capable of reversing the topology of a class II membrane protein. The exchange of the M2 signal/anchor domain with that of SH resulted in a hybrid protein which assumed only the M2 topology. Thus, all these data suggest that the NH2-terminal 24 residues to M2 are important for directing the unusual membrane topology of the M2 protein. These data are discussed in relationship to the loop model for insertion of proteins into membranes and the role of charged residues as a factor in determining orientation.

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Wang, J. F., and K. C. Chou. "Insights from studying the mutation-induced allostery in the M2 proton channel by molecular dynamics." Protein Engineering Design and Selection 23, no. 8 (June 22, 2010): 663–66. http://dx.doi.org/10.1093/protein/gzq040.

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Mintaev, Ramil R., Andrei V. Alexeevski, and Larisa V. Kordyukova. "Co-evolution analysis to predict protein–protein interactions within influenza virus envelope." Journal of Bioinformatics and Computational Biology 12, no. 02 (April 2014): 1441008. http://dx.doi.org/10.1142/s021972001441008x.

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Interactions between integral membrane proteins hemagglutinin (HA), neuraminidase (NA), M2 and membrane-associated matrix protein M1 of influenza A virus are thought to be crucial for assembly of functionally competent virions. We hypothesized that the amino acid residues located at the interface of two different proteins are under physical constraints and thus probably co-evolve. To predict co-evolving residue pairs, the EvFold ( http://evfold.org ) program searching the (nontransitive) Direct Information scores was applied for large samplings of amino acid sequences from Influenza Research Database ( http://www.fludb.org/ ). Having focused on the HA, NA, and M2 cytoplasmic tails as well as C-terminal domain of M1 (being the less conserved among the protein domains) we captured six pairs of correlated positions. Among them, there were one, two, and three position pairs for HA–M2, HA–M1, and M2–M1 protein pairs, respectively. As expected, no co-varying positions were found for NA–HA, NA–M1, and NA–M2 pairs obviously due to high conservation of the NA cytoplasmic tail. The sum of frequencies calculated for two major amino acid patterns observed in pairs of correlated positions was up to 0.99 meaning their high to extreme evolutionary sustainability. Based on the predictions a hypothetical model of pair-wise protein interactions within the viral envelope was proposed.

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Chen, Benjamin J., George P. Leser, David Jackson, and Robert A. Lamb. "The Influenza Virus M2 Protein Cytoplasmic Tail Interacts with the M1 Protein and Influences Virus Assembly at the Site of Virus Budding." Journal of Virology 82, no. 20 (August 13, 2008): 10059–70. http://dx.doi.org/10.1128/jvi.01184-08.

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ABSTRACT The cytoplasmic tail of the influenza A virus M2 proton-selective ion channel has been shown to be important for virus replication. Previous analysis of M2 cytoplasmic tail truncation mutants demonstrated a defect in incorporation of viral RNA (vRNA) into virions, suggesting a role for M2 in the recruitment of M1-vRNA complexes. To further characterize the effect of the M2 cytoplasmic tail mutations on virus assembly and budding, we constructed a series of alanine substitution mutants of M2 with mutations in the cytoplasmic tail, from residues 71 to 97. Mutant proteins M2-Mut1 and M2-Mut2, with mutations of residues 71 to 73 and 74 to 76, respectively, appeared to have the greatest effect on virus-like particle and virus budding, showing a defect in M1 incorporation. Mutant viruses containing M2-Mut1 and M2-Mut2 failed to replicate in multistep growth analyses on wild-type (wt) MDCK cells and were able to form plaques only on MDCK cells stably expressing wt M2 protein. Compared to wt M2 protein, M2-Mut1 and M2-Mut2 were unable to efficiently coimmunoprecipitate with M1. Furthermore, statistical analysis of planar sheets of membrane from cells infected by virus containing M2-Mut1 revealed a reduction in M1-hemagglutinin (HA) and M2-HA clustering as well as a severe loss of clustering between M1 and M2. These results suggest an essential, direct interaction between the cytoplasmic tail of M2 and M1 that promotes the recruitment of the internal viral proteins and vRNA to the plasma membrane for efficient virus assembly to occur.

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Rossman, Jeremy S., Xianghong Jing, George P. Leser, Victoria Balannik, Lawrence H. Pinto, and Robert A. Lamb. "Influenza Virus M2 Ion Channel Protein Is Necessary for Filamentous Virion Formation." Journal of Virology 84, no. 10 (March 10, 2010): 5078–88. http://dx.doi.org/10.1128/jvi.00119-10.

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ABSTRACT Influenza A virus buds from cells as spherical (∼100-nm diameter) and filamentous (∼100 nm × 2 to 20 μm) virions. Previous work has determined that the matrix protein (M1) confers the ability of the virus to form filaments; however, additional work has suggested that the influenza virus M2 integral membrane protein also plays a role in viral filament formation. In examining the role of the M2 protein in filament formation, we observed that the cytoplasmic tail of M2 contains several sites that are essential for filament formation. Additionally, whereas M2 is a nonraft protein, expression of other viral proteins in the context of influenza virus infection leads to the colocalization of M2 with sites of virus budding and lipid raft domains. We found that an amphipathic helix located within the M2 cytoplasmic tail is able to bind cholesterol, and we speculate that M2 cholesterol binding is essential for both filament formation and the stability of existing viral filaments.

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10

Santiago, Luis, and Ravinder Abrol. "Understanding G Protein Selectivity of Muscarinic Acetylcholine Receptors Using Computational Methods." International Journal of Molecular Sciences 20, no. 21 (October 24, 2019): 5290. http://dx.doi.org/10.3390/ijms20215290.

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The neurotransmitter molecule acetylcholine is capable of activating five muscarinic acetylcholine receptors, M1 through M5, which belong to the superfamily of G-protein-coupled receptors (GPCRs). These five receptors share high sequence and structure homology; however, the M1, M3, and M5 receptor subtypes signal preferentially through the Gαq/11 subset of G proteins, whereas the M2 and M4 receptor subtypes signal through the Gαi/o subset of G proteins, resulting in very different intracellular signaling cascades and physiological effects. The structural basis for this innate ability of the M1/M3/M5 set of receptors and the highly homologous M2/M4 set of receptors to couple to different G proteins is poorly understood. In this study, we used molecular dynamics (MD) simulations coupled with thermodynamic analyses of M1 and M2 receptors coupled to both Gαi and Gαq to understand the structural basis of the M1 receptor’s preference for the Gαq protein and the M2 receptor’s preference for the Gαi protein. The MD studies showed that the M1 and M2 receptors can couple to both Gα proteins such that the M1 receptor engages with the two Gα proteins in slightly different orientations and the M2 receptor engages with the two Gα proteins in the same orientation. Thermodynamic studies of the free energy of binding of the receptors to the Gα proteins showed that the M1 and M2 receptors bind more strongly to their cognate Gα proteins compared to their non-cognate ones, which is in line with previous experimental studies on the M3 receptor. A detailed analysis of receptor–G protein interactions showed some cognate-complex-specific interactions for the M2:Gαi complex; however, G protein selectivity determinants are spread over a large overlapping subset of residues. Conserved interaction between transmembrane helices 5 and 6 far away from the G-protein-binding receptor interface was found only in the two cognate complexes and not in the non-cognate complexes. An analysis of residues implicated previously in G protein selectivity, in light of the cognate and non-cognate structures, shaded a more nuanced role of those residues in affecting G protein selectivity. The simulation of both cognate and non-cognate receptor–G protein complexes fills a structural gap due to difficulties in determining non-cognate complex structures and provides an enhanced framework to probe the mechanisms of G protein selectivity exhibited by most GPCRs.

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Rossman, Jeremy S., and Robert A. Lamb. "Autophagy, Apoptosis, and the Influenza Virus M2 Protein." Cell Host & Microbe 6, no. 4 (October 2009): 299–300. http://dx.doi.org/10.1016/j.chom.2009.09.009.

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12

Christofk, Heather R., Matthew G. Vander Heiden, Ning Wu, John M. Asara, and Lewis C. Cantley. "Pyruvate kinase M2 is a phosphotyrosine-binding protein." Nature 452, no. 7184 (March 2008): 181–86. http://dx.doi.org/10.1038/nature06667.

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13

Mendez-Villuendas, Eduardo, and D. Peter Tieleman. "Membrane Curvature Induced via Influenza M2 Protein Clusters." Biophysical Journal 108, no. 2 (January 2015): 468a—469a. http://dx.doi.org/10.1016/j.bpj.2014.11.2561.

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14

Pinto, Lawrence H., Leslie J. Holsinger, and Robert A. Lamb. "Influenza virus M2 protein has ion channel activity." Cell 69, no. 3 (May 1992): 517–28. http://dx.doi.org/10.1016/0092-8674(92)90452-i.

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15

Sugrue, R. J., R. B. Belshe, and A. J. Hay. "Palmitoylation of the influenza a virus M2 protein." Virology 179, no. 1 (November 1990): 51–56. http://dx.doi.org/10.1016/0042-6822(90)90272-s.

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16

Mason, Stephen W., Erika Aberg, Carol Lawetz, Rachel DeLong, Paul Whitehead, and Michel Liuzzi. "Interaction between Human Respiratory Syncytial Virus (RSV) M2-1 and P Proteins Is Required for Reconstitution of M2-1-Dependent RSV Minigenome Activity." Journal of Virology 77, no. 19 (October 1, 2003): 10670–76. http://dx.doi.org/10.1128/jvi.77.19.10670-10676.2003.

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ABSTRACT We have investigated protein-protein interactions among the respiratory syncytial virus (RSV) RNA polymerase subunits using affinity chromatography. Here we demonstrate a novel interaction of P and M2-1 proteins. Phosphorylation of either M2-1 or P appears to be dispensable for this interaction. Internal deletions within P mapped the M2-1-binding domain to a region between residues 100 and 120. Alanine-scanning mutagenesis within this region of P revealed that substitution of any one of the three residues, L101, Y102, and F109, prevented both M2-1 and P binding and expression of an M2-1-dependent luciferase reporter gene. However, these same mutations did not prevent the activity of an M2-1-independent chloramphenicol acetyltransferase minigenome, suggesting that these residues of P specifically affect M2-1-P interaction. On the basis of these observations, it is possible that the interaction between RSV M2-1 and P proteins is important for viral replication.

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Cartee, Tara L., and Gail W. Wertz. "Respiratory Syncytial Virus M2-1 Protein Requires Phosphorylation for Efficient Function and Binds Viral RNA during Infection." Journal of Virology 75, no. 24 (December 15, 2001): 12188–97. http://dx.doi.org/10.1128/jvi.75.24.12188-12197.2001.

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ABSTRACT The M2-1 protein of respiratory syncytial (RS) virus is a transcriptional processivity and antitermination factor. The M2-1 protein has a Cys3His1 zinc binding motif which is essential for function, is phosphorylated, and has been shown to interact with the RS virus nucleocapsid (N) protein. In the work reported here, we determined the sites at which the M2-1 protein was phosphorylated and investigated the importance of these phosphorylated residues for M2-1 function in transcription. By combining protease digestion, matrix-assisted laser desorption ionization–time of flight mass spectrometry, and site-directed mutagenesis, we identified the phosphorylated residues as serines 58 and 61, not threonine 56 and serine 58 as previously reported. Serines 58 and 61 and the surrounding amino acids are in a consensus sequence for phosphorylation by casein kinase I. Consistent with this, we showed that the unphosphorylated M2-1 protein synthesized in Escherichia coli could be phosphorylated in vitro by casein kinase I. The effect of eliminating phosphorylation by site-specific mutagenesis of serines 58 and 61 on the function of the M2-1 protein in transcription of RS virus subgenomic replicons was assayed. The activities of the M2-1 protein phosphorylation mutants in transcriptional antitermination were tested over a range of concentrations and were found to be substantially inhibited at all concentrations. The data show that phosphorylation is important for the M2-1 protein function in transcription. However, mutation of the M2-1 phosphorylation sites did not interfere with the ability of the M2-1 protein to interact with the N protein in transfected cells. The interaction of the M2-1 and N proteins in cotransfected cells was found to be sensitive to RNase A, indicating that the M2-1–N protein interaction was mediated via RNA. Furthermore, the M2-1 protein was shown to bind monocistronic and polycistronic RS virus mRNAs during infection.

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Rangaswamy, Udaya S., Brigid M. O’Flaherty, and Samuel H. Speck. "Tyrosine 129 of the Murine Gammaherpesvirus M2 Protein Is Critical for M2 Function In Vivo." PLoS ONE 9, no. 8 (August 14, 2014): e105197. http://dx.doi.org/10.1371/journal.pone.0105197.

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Maeda, Shoji, Qianhui Qu, Michael J. Robertson, Georgios Skiniotis, and Brian K. Kobilka. "Structures of the M1 and M2 muscarinic acetylcholine receptor/G-protein complexes." Science 364, no. 6440 (May 9, 2019): 552–57. http://dx.doi.org/10.1126/science.aaw5188.

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Muscarinic acetylcholine receptors are G protein–coupled receptors that respond to acetylcholine and play important signaling roles in the nervous system. There are five muscarinic receptor subtypes (M1R to M5R), which, despite sharing a high degree of sequence identity in the transmembrane region, couple to different heterotrimeric GTP-binding proteins (G proteins) to transmit signals. M1R, M3R, and M5R couple to the Gq/11 family, whereas M2R and M4R couple to the Gi/o family. Here, we present and compare the cryo–electron microscopy structures of M1R in complex with G11 and M2R in complex with GoA. The M1R-G11 complex exhibits distinct features, including an extended transmembrane helix 5 and carboxyl-terminal receptor tail that interacts with G protein. Detailed analysis of these structures provides a framework for understanding the molecular determinants of G-protein coupling selectivity.

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Zhou, Helen, Xing Cheng, and Hong Jin. "Identification of Amino Acids That Are Critical to the Processivity Function of Respiratory Syncytial Virus M2-1 Protein." Journal of Virology 77, no. 9 (May 1, 2003): 5046–53. http://dx.doi.org/10.1128/jvi.77.9.5046-5053.2003.

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ABSTRACT The M2-1 protein of respiratory syncytial virus (RSV) is a transcription processivity factor that is essential for virus replication. The function of RSV M2-1 protein can be examined by using an RSVlacZ minigenome assay in vitro since the expression of the lacZ gene is dependent on M2-1. The M2-1 protein of pneumonia virus of mice (PVM), also a member of the Pneumovirus genus, functions poorly in the RSVlacZ minigenome assay despite conservation of the Cys3-His1 motif at its N terminus and an overall 40% amino acid identity with RSV M2-1. To identify the amino acids responsible for the differences between these two proteins, two chimeric proteins were constructed. The RSV/PVM (RP) M2-1 chimera that contains the N-terminal 30 amino acids from RSV and the remaining C-terminal 148 amino acids from PVM maintained a level of activity at an ca. 36% of RSV M2-1. However, the PVM/RSV (PR) M2-1 chimera with the N-terminal 29 amino acids from PVM and 164 amino acids from RSV had an activity of <5% of RSV M2-1, indicating that the functional determinants are mainly located in the N terminus of M2-1. Mutagenesis of the N terminus of PR M2-1 and RSV M2-1 identified that Leu-16 and Asn-17 of RSV M2-1 are critical to the M2-1 function. In addition, several charged residues in the N terminus of RSV M2-1 also contributed to the functional integrity of M2-1.

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Lee, W. H., C. Y. Loo, K. L. Van, A. V. Zavgorodniy, and R. Rohanizadeh. "Regulating Protein Adsorption onto Hydroxyapatite: Amino Acid Treatment." Key Engineering Materials 493-494 (October 2011): 666–71. http://dx.doi.org/10.4028/www.scientific.net/kem.493-494.666.

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Hydroxyapatite (HA) has been widely used as bone grafts due to its chemical and structural similarities to the mineral phase of hard tissues. Applying the combination of osteogenic proteins with HA materials can accelerate bone regeneration in defective areas. The aim of the study was investigating the treatment of HA particles with different amino acids such as serine (Ser), asparagine (Asn), aspartic acid (Asp) and arginine (Arg) to enhance the adsorption ability of HA carrier for delivering therapeutic proteins in body. Results: The crystallinity of HA reduced when amino acids were added during HA preparation. Depending on the types of amino acid, the specific surface area of the amino acid-functionalized HA particles varied from 105 to 149 m2/g. Bovine serum albumin (BSA) and lysozyme were used as model proteins for adsorption study. The protein adsorption onto the surface of amino acid-functionalized HA depended on the polarities of HA particles, whereby positively charged Arg-HA had higher affinity towards BSA (0.269 mg/m2) compared to lysozyme (0.133 mg/m2). Alternatively, the binding affinity of lysozyme (0.2 mg/m2) onto the negatively charged Asp-HA was higher compared to BSA (0.129 mg/m2). The amino acids functionalized-HA particles that had higher proteins adsorption demonstrated a lower protein release rate.

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Jin, Hong, Xing Cheng, Helen Z. Y. Zhou, Shengqiang Li, and Adam Seddiqui. "Respiratory Syncytial Virus That Lacks Open Reading Frame 2 of the M2 Gene (M2-2) Has Altered Growth Characteristics and Is Attenuated in Rodents." Journal of Virology 74, no. 1 (January 1, 2000): 74–82. http://dx.doi.org/10.1128/jvi.74.1.74-82.2000.

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ABSTRACT The M2 gene of respiratory syncytial virus (RSV) encodes two putative proteins: M2-1 and M2-2; both are believed to be involved in the RNA transcription or replication process. To understand the function of the M2-2 protein in virus replication, we deleted the majority of the M2-2 open reading frame from an infectious cDNA clone derived from the human RSV A2 strain. Transfection of HEp-2 cells with the cDNA clone containing the M2-2 deletion, together with plasmids that encoded the RSV N, P, and L proteins, produced a recombinant RSV that lacked the M2-2 protein (rA2ΔM2-2). Recombinant virus rA2ΔM2-2 was recovered and characterized. The levels of viral mRNA expression for 10 RSV genes examined were unchanged in cells infected with rA2ΔM2-2, except that a shorter M2 mRNA was detected. However, the ratio of viral genomic or antigenomic RNA to mRNA was reduced in rA2ΔM2-2-infected cells. By use of an antibody directed against the bacterially expressed M2-2 protein, the putative M2-2 protein was detected in cells infected with wild-type RSV but not in cells infected with rA2ΔM2-2. rA2ΔM2-2 displayed a small-plaque morphology and grew much more slowly than wild-type RSV in HEp-2 cells. In infected Vero cells, rA2ΔM2-2 exhibited very large syncytium formation compared to that of wild-type recombinant RSV. rA2ΔM2-2 appeared to be a host range mutant, since it replicated poorly in HEp-2, HeLa, and MRC5 cells but replicated efficiently in Vero and LLC-MK2 cells. Replication of rA2ΔM2-2 in the upper and lower respiratory tracts of mice and cotton rats was highly restricted. Despite its attenuated replication in rodents, rA2ΔM2-2 was able to provide protection against challenge with wild-type RSV A2. The genotype and phenotype of the M2-2 deletion mutant were stably maintained after extensive in vitro passages. The attenuated phenotype of rA2ΔM2-2 suggested that rA2ΔM2-2 may be a potential candidate for use as a live attenuated vaccine.

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Ahmadian, G., P. Chambers, and A. J. Easton. "Detection and characterization of proteins encoded by the second ORF of the M2 gene of pneumoviruses." Journal of General Virology 80, no. 8 (August 1, 1999): 2011–16. http://dx.doi.org/10.1099/0022-1317-80-8-2011.

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The nucleotide sequence of the M2 gene of pneumonia virus of mice (PVM) was determined. The sequence showed that the gene encoded a protein of 176 amino acids with a predicted molecular mass of 20165 Da from a major ORF, which is smaller than the equivalent proteins encoded by human, bovine and ovine respiratory syncytial (RS) viruses. The PVM M2 protein is conserved, having 41% similarity to the equivalent human RS virus protein. In common with the M2 genes of the RS viruses and avian pneumovirus (APV), the PVM mRNA also contained a second ORF (ORF2) that partially overlaps the first ORF and which is capable of encoding a 98 residue polypeptide. No significant sequence identity could be detected between the putative M2 ORF2 proteins of PVM, APV and the RS viruses. The expression of the M2 ORF2 proteins of the pneumoviruses was investigated by using monospecific antisera raised against GST fusion proteins. Western blot analysis demonstrated the presence of polypeptides encoded by M2 ORF2 of PVM and RS virus corresponding with those predicted by in vitro translation studies, but this was not the case for APV. The PVM polypeptide was present as three distinct products in vivo. The PVM and RS virus polypeptides were also detected in cells by immunofluorescence, which showed that both were present in the cytoplasm with a degree of localization in inclusion bodies. No APV M2 ORF2 protein could be detected in vivo. The RS virus M2 ORF2 polypeptide was shown to accumulate during infection and the potential implications of this are discussed.

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Hardy, Richard W., and Gail W. Wertz. "The Cys3-His1 Motif of the Respiratory Syncytial Virus M2-1 Protein Is Essential for Protein Function." Journal of Virology 74, no. 13 (July 1, 2000): 5880–85. http://dx.doi.org/10.1128/jvi.74.13.5880-5885.2000.

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ABSTRACT The M2 gene of respiratory syncytial (RS) virus has two open reading frames (ORFs). ORF1 encodes a 22-kDa protein termed M2-1. The M2-1 protein contains a Cys3-His1 motif (C-X7-C-X5-C-X3-H) near the amino terminus. This motif is conserved in all human, bovine, and ovine strains of RS virus. A similar motif found in the mammalian transcription factor Nup475 has been shown to bind zinc. The M2-1 protein of human RS virus functions as a transcription factor which increases polymerase processivity, and it enhances readthrough of intergenic junctions during RS virus transcription, thereby acting as a transcription antiterminator. The M2-1 protein also interacts with the nucleocapsid protein. We examined the effects of mutations of cysteine and histidine residues predicted to coordinate zinc in the Cys3-His1 motif on transcription antitermination and N protein binding. We found that mutating the predicted zinc-coordinating residues, the cysteine residues at amino acid positions 7 and 15 and the histidine residue at position 25, prevented M2-1 from enhancing transcriptional readthrough. In contrast, mutations of amino acids within this motif not predicted to coordinate zinc had no effect. Mutations of the predicted zinc-coordinating residues in the Cys3-His1 motif also prevented M2-1 from interacting with the nucleocapsid protein. One mutation of a noncoordinating residue in the motif which did not affect readthrough during transcription, E10G, prevented interaction with the nucleocapsid protein. This suggests that M2-1 does not require interaction with the nucleocapsid protein in order to function during transcription. Analysis of the M2-1 protein in reducing sodium dodecyl sulfate-polyacrylamide gels revealed two major forms distinguished by their mobilities. The slower migrating form was shown to be phosphorylated, whereas the faster migrating form was not. Mutations in the Cys3-His1 motif caused a change in distribution of the M2-1 protein from the slower to the faster migrating form. The data presented here show that the Cys3-His1 motif of M2-1 is essential for maintaining the functional integrity of the protein.

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Veit, M., H. D. Klenk, A. Kendal, and R. Rott. "The M2 protein of influenza A virus is acylated." Journal of General Virology 72, no. 6 (June 1, 1991): 1461–65. http://dx.doi.org/10.1099/0022-1317-72-6-1461.

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26

Betakova, Tatiana. "M2 Protein-A Proton Channel of Influenza A Virus." Current Pharmaceutical Design 13, no. 31 (November 1, 2007): 3231–35. http://dx.doi.org/10.2174/138161207782341295.

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27

Guinea, Rosario, and Luis Carrasco. "Influenza virus M2 protein modifies membrane permeability inE. colicells." FEBS Letters 343, no. 3 (May 2, 1994): 242–46. http://dx.doi.org/10.1016/0014-5793(94)80564-4.

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28

Rossman, Jeremy S., Xianghong Jing, George P. Leser, and Robert A. Lamb. "Influenza Virus M2 Protein Mediates ESCRT-Independent Membrane Scission." Cell 142, no. 6 (September 2010): 902–13. http://dx.doi.org/10.1016/j.cell.2010.08.029.

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29

Park, Eun K., Maria R. Castrucci, Allen Portner, and Yoshihiro Kawaoka. "The M2 Ectodomain Is Important for Its Incorporation into Influenza A Virions." Journal of Virology 72, no. 3 (March 1, 1998): 2449–55. http://dx.doi.org/10.1128/jvi.72.3.2449-2455.1998.

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ABSTRACT M2 is an integral protein of influenza A virus that functions as an ion channel. The ratio of M2 to HA in influenza A virions differs from that found on the cell surface, suggesting selective incorporation of M2 and HA into influenza virions. To examine the sequences that are important for M2 incorporation into virions, we used an incorporation assay that involves expressing M2 from a plasmid, transfecting the plasmid into recipient cells, and then infecting those cells with influenza virus. To test the importance of the different regions of the protein (extracellular, transmembrane, and cytoplasmic) in determining M2 incorporation, we created chimeric mutants of M2 and Sendai virus F proteins, exchanging corresponding extracellular, transmembrane, and cytoplasmic domains. Of the six possible chimeric mutants, only three were expressed on the cell surface. Of these three chimeric proteins, only one mutant (with the extracellular domain from M2 and the rest from F) was incorporated into influenza virions. These results suggest that the extracellular domain of M2 is important for its incorporation into virions.

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Shao, Xia, Boting Wu, Pu Chen, Yanxia Zhan, Feng Li, Fanli Hua, Lihua Sun, and Yunfeng Cheng. "The Role of M2 Macrophage in Primary Immune Thrombocytopenia." Blood 134, Supplement_1 (November 13, 2019): 2355. http://dx.doi.org/10.1182/blood-2019-129667.

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Background: Primary immune thrombocytopenia (ITP) is an acquired autoimmune hemorrhagic disorder, characterized by immune-mediated platelet destruction and impaired megakaryocyte maturation. Although impaired T cells have been implicated to participate in the pathogenesis of ITP, another immune cell signified as M2 macrophages has not been investigated properly in ITP patients. This study aimed to investigate the role of M2 macrophage subsets in primary immune thrombocytopenia (ITP). Methods: Peripheral blood mononuclear cells (PBMC) from newly diagnosed ITP patients and healthy controls (HC) were isolated. M2-like macrophages (CD68+CD163+) and M2 macrophages (CX3CR1+CD163+) were measured by flow cytometry. The correlation between CD68+CD163+ cells and CX3CR1+CD163+ cells was also analyzed. The CX3CR1+cells were sorted by magnetic bead, CD68+CD163+ in PBMC of ITP patients and healthy controls were then isolated, and the proportion of m2-like macrophages before and after the sorting was analyzed. The PPAR gamma and arg-1 levels of mRNAs and proteins of CX3CR1+ M2 macrophages were examined by Real-time PCR and Western Blot, respectively. Results: CX3CR1+CD163+M2 macrophages were positively correlated with CD68+ CD163+ M2-like macrophages in ITP patients (r = 0.54, p < 0.01). After magnetic bead separation, the proportion of CD68+CD163+ cells in CX3CR1+ cells was significantly increased (p = 0.02). Compared with HC, both the mRNA and protein levels of arg-1 of CX3CR1+ M2 macrophages were significantly increased in patients with ITP. The expression level of PPAR gamma protein was significantly increased in ITP than that of HC. However no statistical difference was detected at mRNA expression level, although it was numerically higher in ITP patients than in HC ( p = 0.19). Conclusion: The peripheral CX3CR1+ M2 macrophage exercises similar phenotypes and functions of M2 macrophage. The remarkably increased expression of arg-1 at both transcription and protein levels and PPAR gamma at protein level of CX3CR1+M2 macrophages in ITP patients suggests potential immunomodulatory functions of these macrophage subsets during ITP pathogenesis. However, no significant change at mRNA level of PPAR gamma indicating that the increased PPAR gamma protein level might be caused by other mechanisms, such as after transcription abnormalities, which warrants further investigation. Disclosures No relevant conflicts of interest to declare.

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Dang, C. V., and W. M. Lee. "Identification of the human c-myc protein nuclear translocation signal." Molecular and Cellular Biology 8, no. 10 (October 1988): 4048–54. http://dx.doi.org/10.1128/mcb.8.10.4048.

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We identified and characterized two regions of the human c-myc protein that target proteins into the nucleus. Using mutant c-myc proteins and proteins that fuse portions of c-myc to chicken muscle pyruvate kinase, we found that residues 320 to 328 (PAAKRVKLD; peptide M1) induced complete nuclear localization, and their removal from c-myc resulted in mutant proteins that distributed in both the nucleus and cytoplasm but retained rat embryo cell cotransforming activity. Residues 364 to 374 (RQRRNELKRSP; peptide M2) induced only partial nuclear targeting, and their removal from c-myc resulted in mutant proteins that remained nuclear but were cotransformationally inactive. We conjugated synthetic peptides containing M1 or M2 to human serum albumin and microinjected the conjugate into the cytoplasm of Vero cells. The peptide containing M1 caused rapid and complete nuclear accumulation, whereas that containing M2 caused slower and only partial nuclear localization. Thus, M1 functions as the nuclear localization signal of c-myc, and M2 serves some other and essential function.

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Dang, C. V., and W. M. Lee. "Identification of the human c-myc protein nuclear translocation signal." Molecular and Cellular Biology 8, no. 10 (October 1988): 4048–54. http://dx.doi.org/10.1128/mcb.8.10.4048-4054.1988.

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We identified and characterized two regions of the human c-myc protein that target proteins into the nucleus. Using mutant c-myc proteins and proteins that fuse portions of c-myc to chicken muscle pyruvate kinase, we found that residues 320 to 328 (PAAKRVKLD; peptide M1) induced complete nuclear localization, and their removal from c-myc resulted in mutant proteins that distributed in both the nucleus and cytoplasm but retained rat embryo cell cotransforming activity. Residues 364 to 374 (RQRRNELKRSP; peptide M2) induced only partial nuclear targeting, and their removal from c-myc resulted in mutant proteins that remained nuclear but were cotransformationally inactive. We conjugated synthetic peptides containing M1 or M2 to human serum albumin and microinjected the conjugate into the cytoplasm of Vero cells. The peptide containing M1 caused rapid and complete nuclear accumulation, whereas that containing M2 caused slower and only partial nuclear localization. Thus, M1 functions as the nuclear localization signal of c-myc, and M2 serves some other and essential function.

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Alvarado-Facundo, Esmeralda, Yamei Gao, Rosa María Ribas-Aparicio, Alicia Jiménez-Alberto, Carol D. Weiss, and Wei Wang. "Influenza Virus M2 Protein Ion Channel Activity Helps To Maintain Pandemic 2009 H1N1 Virus Hemagglutinin Fusion Competence during Transport to the Cell Surface." Journal of Virology 89, no. 4 (December 3, 2014): 1975–85. http://dx.doi.org/10.1128/jvi.03253-14.

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ABSTRACTThe influenza virus hemagglutinin (HA) envelope protein mediates virus entry by first binding to cell surface receptors and then fusing viral and endosomal membranes during endocytosis. Cleavage of the HA precursor (HA0) into a surface receptor-binding subunit (HA1) and a fusion-inducing transmembrane subunit (HA2) by host cell enzymes primes HA for fusion competence by repositioning the fusion peptide to the newly created N terminus of HA2. We previously reported that the influenza virus M2 protein enhances pandemic 2009 influenza A virus [(H1N1)pdm09] HA-pseudovirus infectivity, but the mechanism was unclear. In this study, using cell-cell fusion and HA-pseudovirus infectivity assays, we found that the ion channel function of M2 was required for enhancement of HA fusion and HA-pseudovirus infectivity. The M2 activity was needed only during HA biosynthesis, and proteolysis experiments indicated that M2 proton channel activity helped to protect (H1N1)pdm09 HA from premature conformational changes as it traversed low-pH compartments during transport to the cell surface. While M2 has previously been shown to protect avian influenza virus HA proteins of the H5 and H7 subtypes that have polybasic cleavage motifs, this study demonstrates that M2 can protect HA proteins from human H1N1 strains that lack a polybasic cleavage motif. This finding suggests that M2 proton channel activity may play a wider role in preserving HA fusion competence among a variety of HA subtypes, including HA proteins from emerging strains that may have reduced HA stability.IMPORTANCEInfluenza virus infects cells when the hemagglutinin (HA) surface protein undergoes irreversible pH-induced conformational changes after the virus is taken into the cell by endocytosis. HA fusion competence is primed when host cell enzymes cleave the HA precursor. The proton channel function of influenza virus M2 protein has previously been shown to protect avian influenza virus HA proteins that contain a polybasic cleavage site from pH-induced conformational changes during biosynthesis, but this effect is less well understood for human influenza virus HA proteins that lack polybasic cleavage sites. Using assays that focus on HA entry and fusion, we found that the M2 protein also protects (H1N1)pdm09 influenza A virus HA from premature conformational changes as it transits low-pH compartments during biosynthesis. This work suggests that M2 may play a wider role in preserving HA function in a variety of influenza virus subtypes that infect humans and may be especially important for HA proteins that are less stable.

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Hull, J. D., R. Gilmore, and R. A. Lamb. "Integration of a small integral membrane protein, M2, of influenza virus into the endoplasmic reticulum: analysis of the internal signal-anchor domain of a protein with an ectoplasmic NH2 terminus." Journal of Cell Biology 106, no. 5 (May 1, 1988): 1489–98. http://dx.doi.org/10.1083/jcb.106.5.1489.

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The M2 protein of influenza A virus is a small integral membrane protein of 97 residues that is expressed on the surface of virus-infected cells. M2 has an unusual structure as it lacks a cleavable signal sequence yet contains an ectoplasmic amino-terminal domain of 23 residues, a 19 residue hydrophobic transmembrane spanning segment, and a cytoplasmic carboxyl-terminal domain of 55 residues. Oligonucleotide-mediated deletion mutagenesis was used to construct a series of M2 mutants lacking portions of the hydrophobic segment. Membrane integration of the M2 protein was examined by in vitro translation of synthetic mRNA transcripts prepared using bacteriophage T7 RNA polymerase. After membrane integration, M2 was resistant to alkaline extraction and was converted to an Mr approximately equal to 7,000 membrane-protected fragment after digestion with trypsin. In vitro integration of M2 requires the cotranslational presence of the signal recognition particle. Deletion of as few as two residues from the hydrophobic segment of M2 markedly decreases the efficiency of membrane integration, whereas deletion of six residues completely eliminates integration. M2 proteins containing deletions that eliminate stable membrane anchoring are apparently not recognized by signal recognition particles, as these polypeptides remain sensitive to protease digestion, indicating that in addition they do not have a functional signal sequence. These data thus indicate that the signal sequence that initiates membrane integration of M2 resides within the transmembrane spanning segment of the polypeptide.

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Choi, Hae-Seul, Chang-Zhu Pei, Jun-Hyeok Park, Soo-Yeon Kim, Seung-Yeon Song, Gyeong-Jin Shin, and Kwang-Hyun Baek. "Protein Stability of Pyruvate Kinase Isozyme M2 Is Mediated by HAUSP." Cancers 12, no. 6 (June 12, 2020): 1548. http://dx.doi.org/10.3390/cancers12061548.

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The ubiquitin–proteasome system (UPS) is responsible for proteasomal degradation, regulating the half-life of the protein. Deubiquitinating enzymes (DUBs) are components of the UPS and inhibit degradation by removing ubiquitins from protein substrates. Herpesvirus-associated ubiquitin-specific protease (HAUSP) is one such deubiquitinating enzyme and has been closely associated with tumor development. In a previous study, we isolated putative HAUSP binding substrates by two-dimensional electrophoresis (2-DE) and identified them by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF/MS) analysis. The analysis showed that pyruvate kinase isoenzyme M2 (PKM2) was likely to be one of the substrates for HAUSP. Further study revealed that PKM2 binds to HAUSP, confirming the interaction between these proteins, and that PKM2 possesses the putative HAUSP binding motif, E or P/AXXS. Therefore, we generated mutant forms of PKM2 S57A, S97A, and S346A, and found that S57A had less binding affinity. In a previous study, we demonstrated that PKM2 is regulated by the UPS, and that HAUSP- as a DUB-acted on PKM2, thus siRNA for HAUSP increases PKM2 ubiquitination. Our present study newly highlights the direct interaction between HAUSP and PKM2.

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Iwatsuki-Horimoto, Kiyoko, Taisuke Horimoto, Takeshi Noda, Maki Kiso, Junko Maeda, Shinji Watanabe, Yukiko Muramoto, Ken Fujii, and Yoshihiro Kawaoka. "The Cytoplasmic Tail of the Influenza A Virus M2 Protein Plays a Role in Viral Assembly." Journal of Virology 80, no. 11 (June 1, 2006): 5233–40. http://dx.doi.org/10.1128/jvi.00049-06.

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ABSTRACT The viral replication cycle concludes with the assembly of viral components to form progeny virions. For influenza A viruses, the matrix M1 protein and two membrane integral glycoproteins, hemagglutinin and neuraminidase, function cooperatively in this process. Here, we asked whether another membrane protein, the M2 protein, plays a role in virus assembly. The M2 protein, comprising 97 amino acids, possesses the longest cytoplasmic tail (54 residues) of the three transmembrane proteins of influenza A viruses. We therefore generated a series of deletion mutants of the M2 cytoplasmic tail by reverse genetics. We found that mutants in which more than 22 amino acids were deleted from the carboxyl terminus of the M2 tail were viable but grew less efficiently than did the wild-type virus. An analysis of the virions suggested that viruses with M2 tail deletions of more than 22 carboxy-terminal residues apparently contained less viral ribonucleoprotein complex than did the wild-type virus. These M2 tail mutants also differ from the wild-type virus in their morphology: while the wild-type virus is spherical, some of the mutants were filamentous. Alanine-scanning experiments further indicated that amino acids at positions 74 to 79 of the M2 tail play a role in virion morphogenesis and affect viral infectivity. We conclude that the M2 cytoplasmic domain of influenza A viruses plays an important role in viral assembly and morphogenesis.

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Thelander, M., A. Gräslund, and L. Thelander. "Subunit M2 of mammalian ribonucleotide reductase. Characterization of a homogeneous protein isolated from M2-overproducing mouse cells." Journal of Biological Chemistry 260, no. 5 (March 1985): 2737–41. http://dx.doi.org/10.1016/s0021-9258(18)89423-6.

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Zebedee, S. L., and R. A. Lamb. "Influenza A virus M2 protein: monoclonal antibody restriction of virus growth and detection of M2 in virions." Journal of Virology 62, no. 8 (1988): 2762–72. http://dx.doi.org/10.1128/jvi.62.8.2762-2772.1988.

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Hughey, Patsy G., Paul C. Roberts, Leslie J. Holsinger, Suzanne L. Zebedee, Robert A. Lamb, and Richard W. Compans. "Effects of Antibody to the Influenza A Virus M2 Protein on M2 Surface Expression and Virus Assembly." Virology 212, no. 2 (October 1995): 411–21. http://dx.doi.org/10.1006/viro.1995.1498.

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McCown, Matthew F., and Andrew Pekosz. "The Influenza A Virus M2 Cytoplasmic Tail Is Required for Infectious Virus Production and Efficient Genome Packaging." Journal of Virology 79, no. 6 (March 15, 2005): 3595–605. http://dx.doi.org/10.1128/jvi.79.6.3595-3605.2005.

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ABSTRACT The M2 integral membrane protein encoded by influenza A virus possesses an ion channel activity that is required for efficient virus entry into host cells. The role of the M2 protein cytoplasmic tail in virus replication was examined by generating influenza A viruses encoding M2 proteins with truncated C termini. Deletion of 28 amino acids (M2Stop70) resulted in a virus that produced fourfold-fewer particles but >1,000-fold-fewer infectious particles than wild-type virus. Expression of the full-length M2 protein in trans restored the replication of the M2 truncated virus. Although the M2Stop70 virus particles were similar to wild-type virus in morphology, the M2Stop70 virions contained reduced amounts of viral nucleoprotein and genomic RNA, indicating a defect in vRNP packaging. The data presented indicate the M2 cytoplasmic tail plays a role in infectious virus production by coordinating the efficient packaging of genome segments into influenza virus particles.

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Shi, Xuan-Zheng, and Sushil K. Sarna. "G protein-mediated dysfunction of excitation-contraction coupling in ileal inflammation." American Journal of Physiology-Gastrointestinal and Liver Physiology 286, no. 6 (June 2004): G899—G905. http://dx.doi.org/10.1152/ajpgi.00408.2003.

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Inflammation impairs the circular muscle contractile response to muscarinic (M) receptor activation. The aim of this study was to investigate whether the expression of muscarinic receptors, their binding affinity, and the expression and activation of receptor-coupled G proteins contribute to the suppression of contractility in inflammation. The studies were performed on freshly dissociated single smooth muscle cells from normal and inflamed canine ileum. Northern blotting indicated the presence of only M2 and M3 receptors on canine ileal circular muscle cells. Inflammation did not alter the mRNA or protein expression of M2 and M3 receptors. The maximal binding and Kd values also did not differ between normal and inflamed cells. However, the contractile response to ACh in M3 receptor-protected cells was suppressed, whereas that in M2 receptor-protected cells was enhanced. Further experiments indicated that the expression and binding activity of Gαq/11 protein, which couples to M3 receptors, were downregulated, whereas those of Gαi3, which couples to M2 receptors, were upregulated in inflamed cells. We concluded that inflammation depresses M3 receptor function, but it enhances M2 receptor function in ileum. These effects are mediated by the differentially altered expression and binding activity of their respective coupled Gαq/11 and Gαi3 proteins.

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Tang, Roderick S., Nick Nguyen, Xing Cheng, and Hong Jin. "Requirement of Cysteines and Length of the Human Respiratory Syncytial Virus M2-1 Protein for Protein Function and Virus Viability." Journal of Virology 75, no. 23 (December 1, 2001): 11328–35. http://dx.doi.org/10.1128/jvi.75.23.11328-11335.2001.

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ABSTRACT The M2-1 protein of human respiratory syncytial virus (hRSV) promotes processive RNA synthesis and readthrough at RSV gene junctions. It contains four highly conserved cysteines, three of which are located in the Cys3-His1motif at the N terminus of M2-1. Each of the four cysteines, at positions 7, 15, 21, and 96, in the M2-1 protein of hRSV A2 strain was individually replaced by glycines. When tested in an RSV minigenome replicon system using β-galactosidase as a reporter gene, C7G, C15G, and C21G located in the Cys3-His1motif showed a significant reduction in processive RNA synthesis compared to wild-type (wt) M2-1. C96G, which lies outside the Cys3-His1 motif, was fully functional in supporting processive RNA synthesis in vitro. Each of these cysteine substitutions was introduced into an infectious antigenomic cDNA clone derived from hRSV A2 strain. Except for C96G, which resulted in a viable virus, no viruses were recovered with mutations in the Cys3-His1 motif. This indicates that the Cys3-His1 motif is critical for M2-1 function and for RSV replication. The functional requirement of the C terminus of the M2-1 protein was examined by engineering premature stop codons that caused truncations of 17, 46, or 67 amino acids from the C terminus. A deletion of 46 or 67 amino acids abolished the synthesis of full-length β-galactosidase mRNA and did not result in the recovery of viable viruses. However, a deletion of 17 amino acids from the C terminus of M2-1 reduced processive RNA synthesis in vitro and was well tolerated by RSV. Relocation of the M2-1 termination codon upstream of the M2-2 initiation codons did not significantly affect the expression of the M2-2 protein. Both rA2-Tr17 and rA2-C96G did not replicate as efficiently as wt rA2 in HEp-2 cells and was restricted in replication in the respiratory tracts of cotton rats.

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Watanabe, Tokiko, Shinji Watanabe, Hiroshi Ito, Hiroshi Kida, and Yoshihiro Kawaoka. "Influenza A Virus Can Undergo Multiple Cycles of Replication without M2 Ion Channel Activity." Journal of Virology 75, no. 12 (June 15, 2001): 5656–62. http://dx.doi.org/10.1128/jvi.75.12.5656-5662.2001.

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ABSTRACT Ion channel proteins are common constituents of cells and have even been identified in some viruses. For example, the M2 protein of influenza A virus has proton ion channel activity that is thought to play an important role in viral replication. Because direct support for this function is lacking, we attempted to generate viruses with defective M2 ion channel activity. Unexpectedly, mutants with apparent loss of M2 ion channel activity by an in vitro assay replicated as efficiently as the wild-type virus in cell culture. We also generated a chimeric mutant containing an M2 protein whose transmembrane domain was replaced with that from the hemagglutinin glycoprotein. This virus replicated reasonably well in cell culture but showed no growth in mice. Finally, a mutant lacking both the transmembrane and cytoplasmic domains of M2 protein grew poorly in cell culture and showed no growth in mice. Thus, influenza A virus can undergo multiple cycles of replication without the M2 transmembrane domain responsible for ion channel activity, although this activity promotes efficient viral replication.

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Herskowitz, Jeremy H., Andrea M. Siegel, Meagan A. Jacoby, and Samuel H. Speck. "Systematic Mutagenesis of the Murine Gammaherpesvirus 68 M2 Protein Identifies Domains Important for Chronic Infection." Journal of Virology 82, no. 7 (January 30, 2008): 3295–310. http://dx.doi.org/10.1128/jvi.02234-07.

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ABSTRACT Murine gammaherpesvirus 68 (MHV68) infection of inbred mice represents a genetically tractable small-animal model for assessing the requirements for the establishment of latency, as well as reactivation from latency, within the lymphoid compartment. By day 16 postinfection, MHV68 latency in the spleen is found in B cells, dendritic cells, and macrophages. However, as with Epstein-Barr virus, by 3 months postinfection MHV68 latency is predominantly found in isotype-switched memory B cells. The MHV68 M2 gene product is a latency-associated antigen with no discernible homology to any known cellular or viral proteins. However, depending on experimental conditions, the M2 protein has been shown to play a critical role in both the efficient establishment of latency in splenic B cells and reactivation from latently infected splenic B cells. Inspection of the sequence of the M2 protein reveals several hallmarks of a signaling molecule, including multiple PXXP motifs and two potential tyrosine phosphorylation sites. Here, we report the generation of a panel of recombinant MHV68 viruses harboring mutations in the M2 gene that disrupt putative functional motifs. Subsequent analyses of the panel of M2 mutant viruses revealed a functionally important cluster of PXXP motifs in the C-terminal region of M2, which have previously been implicated in binding Vav proteins (P. A. Madureira, P. Matos, I. Soeiro, L. K. Dixon, J. P. Simas, and E. W. Lam, J. Biol. Chem. 280:37310-37318, 2005; L. Rodrigues, M. Pires de Miranda, M. J. Caloca, X. R. Bustelo, and J. P. Simas, J. Virol. 80:6123-6135, 2006). Further characterization of two adjacent PXXP motifs in the C terminus of the M2 protein revealed differences in the functions of these domains in M2-driven expansion of primary murine B cells in culture. Finally, we show that tyrosine residues 120 and 129 play a critical role in both the establishment of splenic latency and reactivation from latency upon explant of splenocytes into tissue culture. Taken together, these analyses will aide future studies for identifying M2 interacting partners and B-cell signaling pathways that are manipulated by the M2 protein.

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Cheng, Xing, HyunJung Park, Helen Zhou, and Hong Jin. "Overexpression of the M2-2 Protein of Respiratory Syncytial Virus Inhibits Viral Replication." Journal of Virology 79, no. 22 (November 15, 2005): 13943–52. http://dx.doi.org/10.1128/jvi.79.22.13943-13952.2005.

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ABSTRACT The M2-2 protein of respiratory syncytial virus (RSV) is involved in regulation of viral RNA transcription and replication. Encoded by the next-to-last gene of RSV, the M2-2 open reading frame (ORF) overlaps with the upstream M2-1 ORF, suggesting that the production of the M2-2 protein might be tightly regulated during virus replication. To evaluate the effect of M2-2 overexpression on RSV replication, the M2-2 gene was separated from M2-1 by leaving it at the position prior to the M2-1 or moving it to the promoter proximal position as an independent transcriptional unit in the RSV A2 genome. Although recombinant viruses bearing the shuffled M2-2 gene were recovered and expressed higher levels of M2-2, most of these viruses grew poorly in HEp-2 cells. Sequence analysis revealed that various mutations (substitution, insertion, and deletion) occurred in the M2-2 gene, resulting in reduced M2-2 activity as measured by the RSV minigenome system. Further examination of the M2-2 sequence and its function showed that either one of the first two AUG codons located at the 5′ end of M2-2 could be used to produce a functional M2-2 protein and that deletion of the first six amino acids from its N terminus or four amino acids from its C terminus greatly reduced its function. The effect of M2-2 protein on RSV replication was also studied by examining RSV replication in cells transiently expressing M2-2. The M2-2 protein expressed at a high level completely inhibited RSV replication. These results strongly suggested that the level of the M2-2 protein produced in the infected cells is critical to RSV replication.

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Manzoor, Rashid, Manabu Igarashi, and Ayato Takada. "Influenza A Virus M2 Protein: Roles from Ingress to Egress." International Journal of Molecular Sciences 18, no. 12 (December 7, 2017): 2649. http://dx.doi.org/10.3390/ijms18122649.

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Drakopoulos, Antonios, Christina Tzitzoglaki, Chulong Ma, Kathrin Freudenberger, Anja Hoffmann, Yanmei Hu, Günter Gauglitz, Michaela Schmidtke, Jun Wang, and Antonios Kolocouris. "Affinity of Rimantadine Enantiomers against Influenza A/M2 Protein Revisited." ACS Medicinal Chemistry Letters 8, no. 2 (January 27, 2017): 145–50. http://dx.doi.org/10.1021/acsmedchemlett.6b00311.

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Alavi-Esfahani, MA, F. Fotouhi-Chahooki, M. Saleh, R. Tavakoli, B. Farahmand, A. Ghaemi, and M. Tavassoti-Kheiri. "Over Expression of Influenza Virus M2 Protein in Prokaryotic System." Iranian Journal of Virology 6, no. 4 (November 1, 2012): 13–19. http://dx.doi.org/10.21859/isv.6.4.13.

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Kitagawa, Yoshinori, Min Zhou, Mayu Yamaguchi, Takayuki Komatsu, Kenji Takeuchi, Masae Itoh, and Bin Gotoh. "Human metapneumovirus M2-2 protein inhibits viral transcription and replication." Microbes and Infection 12, no. 2 (February 2010): 135–45. http://dx.doi.org/10.1016/j.micinf.2009.11.002.

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Bettaieb, Ahmed, Jesse Bakke, Naoto Nagata, Kosuke Matsuo, Yannan Xi, Siming Liu, Daniel AbouBechara, et al. "Protein Tyrosine Phosphatase 1B Regulates Pyruvate Kinase M2 Tyrosine Phosphorylation." Journal of Biological Chemistry 288, no. 24 (May 2, 2013): 17360–71. http://dx.doi.org/10.1074/jbc.m112.441469.

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Journal articles on the topic 'M2 protein'

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