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Gregory B. Melikian
Ph.D.
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| Academic Title:
Professor |
| Primary Appointment:
Microbiology and Immunology |
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gmelikian@ihv.umaryland.edu |
| Location:
MRB,
N656 |
| Phone:
(410) 706-4781 |
| Fax:
(410) 706-4694 |
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Personal History
1980-1984: Ph.D. (Biophysics), Moscow Institute of Information Transition Problems Acad. Sci. USSR and Institute of Electrochemistry Acad. Sci. USSR.
1984-1988: Postdoctoral Fellow, Laboratory of Biophysics, Yerevan hysics Institute (Armenia).
1990-1994: Instructor, Department of Molecular Biophysics and Physiology, Rush University, Chicago.
1994-1998: Assistant Professor, Department of Molecular Biophysics and Physiology, Rush University, Chicago.
1998-2005: Associate Professor, Department of Molecular Biophysics and Physiology, Rush University, Chicago.
2005-2007: Associate Professor, Institute of Human Virology, UMBI, Baltimore.
2007-2009: Associate Professor, Department of Microbiology and Immunology, UMB, Baltimore.
2009-present: Professor, Department of Microbiology and Immunology, UMB, Baltimore.
Research Interests
Our laboratory is interested in understanding the mechanisms of entry and fusion of enveloped viruses. Current focus is on human, avian and murine retroviruses, as well as on the fusion reaction mediated by the Hepatitis C E1/E2 glycorptoeins. Our main strategy is to capture and characterize intermediate stages of fusion through testing their resistance to neutralizing antibodies and to specific inhibitors. This approach led to demonstration that HIV Env completes folding into its final six-helix bundle structure after, but not before, fusion pore formation.
Our strategic goal is to elucidate structure-function relationships of diverse viral glycoproteins and to identify the critical steps of virus entry by imaging single virus entry into to host cells. This is accomplished by labeling pseudoviral particles with fluorescent dyes and time-resolved imaging of their entry and fusion by confocal microscopy. By combining sensitive functional techniques with fluorescence microscopy, we have shown that, contrary to a common perception, HIV-1 enters cells via endocytosis as opposed to the direct fusion with the plasma membrane.
Lab Techniques and Equipment
* Fluorescence microscopy
* Confocal microscopy
* Total Internal Reflection microscopy
* Virus-cell fusion and infectivity assays Electrophysiology
Publications
Selected Publications
MelikyanG.B., Niles W.D., Peeples M.E., and Cohen F.S. 1993. Influenza hemagglutinin-mediated fusion pores connecting cells to planar membranes: flickering to final expansion. J. Gen. Physiol. 102:1131-1149.
Melikyan G.B., Niles W.D., and Cohen F.S.. 1993. Influenza virus hemagglutinin-induced cell-planar bilayer fusion: Quantitative dissection of fusion pore kinetics into stages. J. Gen. Physiol. 102:1151-1170.
Melikyan G.B., Niles W.D., Cohen F.S. 1995. The fusion kinetics of influenza hemagglutinin expressing cells to planar bilayer membranes is affected by HA density and host cell surface. J. Gen. Physiol. 106:783-802.
Melikyan G.B., Niles W.D., Ratinov V., Karhanek M., Zimmerberg J., and Cohen F.S.. 1995. Comparison of transient and successful fusion pores connecting influenza hemagglutinin expressing cells to planar membranes. J. Gen. Physiol. 106:803-819.
Melikyan G.B., White J.M., and Cohen F.S.. 1995. GPI-anchored influenza hemagglutinin induces hemifusion to both red blood cell and planar bilayer membranes. J. Cell Biol. 131:679-691.
Melikyan G.B., Deriy B.N., Ok D.C., and Cohen F.S.. 1996. Voltage-dependent translocation of R18 and DiI across lipid bilayers leads to fluorescence changes. Biophys. J. 71:2680-2691.
Melikyan G.B., Brener S.A., Ok D.C., and Cohen F.S.. 1997. Inner but not outer membrane leaflets control the transition from glycosylphosphatidylinositol-anchored influenza hemagglutinin-induced hemifusion to full fusion. J. Cell Biol. 136:995-1005.
Melikyan G.B., Jin H., Lamb R.A., and Cohen F.S.. 1997. The role of the cytoplasmic tail region of influenza virus hemagglutinin in formation and growth of fusion pores. Virology. 235:118-128.
Razinkov V.I., Melikyan G.B., Epand R.M., Epand R.F., and Cohen F.S. 1998. Effects of spontaneous bilayer curvature on influenza virus-mediated fusion pores. J. Gen. Physiol. 112:409-422.
Melikyan G.B., Lin S., Roth M.G., and Cohen F.S. 1999. Amino acid sequence requirements of the transmembrane and cytoplasmic domains of influenza virus hemagglutinin for viable membrane fusion. Mol. Biol. Cell. 10:1821-1836.
Markosyan R.M., Melikyan G.B., and Cohen F.S. 1999. Tension of membranes expressing hemagglutinin of influenza virus inhibits fusion. Biophys. J. 77:943-952.
Qiao H., Armstrong R.T., Melikyan G.B., Cohen F.S., and White J.M. 1999. A specific point mutant at position 1 of the influenza hemagglutinin fusion peptide displays a hemifusion phenotype. Mol. Biol. Cell. 17:2559-2569.
Razinkov V.I., Melikyan G.B., and Cohen F.S. 1999. Hemifusion between cells expressing hemagglutinin of influenza virus and planar membranes can precede the formation of fusion pores that subsequently fully enlarge. Biophys. J. 77:3144-3151.
Melikyan G.B., Markosyan R.M., Brener S.A., Rozenberg Y., and Cohen F.S. 2000. Role of the cytoplasmic tail of ecotropic Moloney Murine leukemia virus Env protein in fusion pore formation. J. Virol. 74:447-455.
Markosyan R.M., Cohen F.S., and Melikyan G.B. 2000. The lipid-anchored ectodomain of influenza virus hemagglutinin (GPI-HA) is capable of inducing nonenlarging fusion pores. Mol. Biol. Cell. 11: 1143-1152.
Melikyan G.B., Markosyan R.M., Roth M.G., and Cohen F.S. 2000. A point mutation in the transmembrane domain of the hemagglutinin of influenza virus stabilizes a hemifusion intermediate that can transit to fusion. Mol. Biol. Cell. 11:3765-3775.
Melikyan G.B., Markosyan R.M., Hemmati H., Delmedico M.K., Lambert D.M., and Cohen F.S. 2000. Evidence that the transition of HIV-1 gp41 into a six-helix bundle, not the bundle configuration, induces membrane fusion. J. Cell Biol. 151:413-423.
Cohen F.S. and Melikyan G.B. Implications of a fusion peptide structure. 2001. Nature Struct. Biol. 8:653-655.
Markosyan R.M., Melikyan G.B., and Cohen F.S. 2001. Evolution of intermediates of influenza virus hemagglutinin-mediated fusion revealed by kinetic measurements of pore formation. Biophys. J. 80:812-821.
Markosyan R.M., Ma X., Lu M., Cohen F.S., and Melikyan G.B. 2002. The mechanism of inhibition of HIV-1 Env-mediated cell-cell fusion by recombinant gp41 ectodomain cores. Virology. 302:174-184.
Markosyan R.M., Cohen F.S., and Melikyan G.B. 2003. HIV-1 envelope proteins complete their folding into six-helix bundles immediately after fusion pore formation. Mol. Biol. Cell. 14:926-938.
Abrahamyan L.G., Markosyan R.M., Moore J.P., Cohen F.S., and Melikyan G.B. 2003. HIV-1 Env with an intersubunit disulfide bond engages coreceptors, but requires bond reduction after engagement to induce fusion. J. Virol. 77:5829-5836.
Borrego-Diaz E., Peeples M.E., Markosyan R.M., Melikyan G.B., and Cohen F.S.. 2003. Completion of trimeric hairpin formation of influenza virus hemagglutinin promotes fusion pore opening and enlargement. Virology. 316:234-244.
Saez-Cirion A., Arrondo J.L.R., Gomara M.J., Lorizate M., Lloro I., Melikyan G.B., and Nieva J.L.. 2003. Structural and functional roles of HIV-1 gp41 pre-transmembrane sequence segmentation. Biophys. J. 85:3769-3780.
Egelhofer M., Brandenburg G., Martinius H., Schult-Dietrich P., Melikyan G.B., Kunert R., Baum C., Choi I., Alexandrov A., and von Laer D.. 2003. Inhibition of HIV-1 entry in cells expressing gp41-derived peptides. J. Virol. 78:568-575.
Melikyan G.B., Barnard R.J.O., Markosyan R.M., Young J.A.T., and Cohen F.S.. 2004. Low pH is required for ASLV Env-induced hemifusion and fusion pore formation, but not for pore growth. J. Virol. 78:3753-3762.
Markosyan R.M., Bates P., Cohen F.S., and Melikyan G.B. 2004. A study of low pH-induced refolding of Env of Avian Sarcoma and Leukosis Virus into a six-helix bundle. Biophys. J. 87:3291-3298.
Abrahamyan L.G., Mkrtchyan S. R., Binley J., Lu M., Melikyan G.B., and Cohen F.S.. 2005. Presence of the cytoplasmic tail slows the folding of HIV-1 Env into six-helix bundles. J. Virol. 79:106-115.
Melikyan G.B., Barnard R.J.O., Abrahamyan L.G., Mothes W., and Young J.A.T. 2005. Imaging individual retroviral fusion events: from hemifusion to pore formation and growth. Proc. Natl. Acad. Sci. USA, 102:8728-8733.
Mkrtchyan S.R., Markosyan R.M., Eadon M, Moore J.P., Melikyan G.B., and Cohen F.S. Ternary complex formation of Human Immunodeficiency Virus type 1 Env, CD4, and coreceptor captured as an intermediate of membrane fusion. J. Virol., 2005, 79:11161-11169.
Markosyan R.M., Cohen F.S., and Melikyan G.B. Time-resolved imaging of HIV-1 Env-mediated lipid and content mixing between a single virion and cell membrane. Mol. Biol. Cell, 2005, 16:5502-5513.
Melikyan G.B., Egelhofer M., von Laer D. Membrane-anchored inhibitory peptides capture HIV-1 gp41 conformations that engage the target membrane prior to fusion. J. Virol., 2006, 80:3249-3258.
Heredia, A., B. Gilliam, O. Latinovic, N. Le, D. Bamba, A. DeVico, G.B. Melikyan, R.C. Gallo, R.R. Redfield. 2007. Rapamycin reduces CCR5 density levels on CD4 T cells and this effect results in potentiation of Enfuvirtide (T-20) against R5 HIV-1 in vitro. Antimicrob. Agents Chemother. 2007, 51:2489-2496.
Melikyan G.B., Platt E.J., Kabat D. The role of the N-terminal segment of CCR5 in HIV-1 Env-mediated membrane fusion and the mechanism of virus adaptation to CCR5 lacking this segment. Retrovirology, 2007, 4:55.
Melikyan G.B. Common principles and intermediates of viral protein-mediated fusion: the HIV-1 paradigm. Retrovirology 2008, 5:111.
Miyauchi K., Kim Y., Latinovic O., Morozov V., and Melikyan G.B. HIV Enters Cells via Endocytosis and Dynamin-Dependent Fusion with Endosomes. Cell, 2009, 137:433-444.
Miyauchi K., Kozlov M.M. and Melikyan G.B. Early steps of HIV-1 fusion define the sensitivity to inhibitory peptides that block 6-helix bundle formation. PLoS Pathogens, 2009 (in press).
Faculty members:
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