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Abram Akopian

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Abram Akopian, Ph.D.

Associate Professor;
Department of Physiology and Neuroscience (Bloomfield Research)

Contact Info

Address
550 First Ave
Dept. Physiology & Neuroscience Floor 1 Room 149
Medical Science Building
New York, NY 10016

Phone: 212-263-0561
Email: Abram.Akopian@nyumc.org

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Research Summary

Our recent studies indicate that activation of ionotropic GluRs induce clathrin-mediated internalization of Cav1.3 subtype of LTCC in retinal ganglion cells (RGC). The internalization depends on Ca2+ entry and F-actin reorganization, and correlated well with glutamate-induced downregulation of Ca2+ channel activity. We currently testing the hypothesis that glutamate-induced internalization of LTCCs may serve as a negative-feedback mechanism to protect retinal neurons against excitotoxic damage. Our findings are likely to point at a universal mechanism that underlies neuroprotection in degenerative diseases in the retina and across the CNS.

Research Interests

The main focus of our research is understanding the neuromodulatory mechanisms that regulate the functioning of retinal ganglion cells (RGC) with emphasis on glutamate receptors (GluR) and voltage-gated Ca2+ channels. In the vertebrate retina, Ca2+ entry through voltage-gated L-type Ca2+ channels (LTCC) triggers an array of physiological events, including neurotransmitter release, activation of intracellular signaling, cellular excitability and gene expression. Excess Ca2+ entry into neurons, e.g. by overstimulation of GluRs, however, may cause cell death. To maintain physiologically important processes and at the same time to avoid an elevation of intracellular Ca2+ to pathological levels, neurons have evolved multiple regulatory mechanisms. One possible mechanism controlling the activity of Ca2+ channels is changes in the number of channels by trafficking into and out of the plasma membrane. Using electrophysiological, immunocytochemical and imaging techniques we currently study the regulated internalization of LTCCs in retinal amacrine and ganglion cells.

Research Documents

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All data from NYU Health Sciences Library Faculty Bibliography — -

Contact:
http://hsl.med.nyu.edu/faculty-bibliography-search#about

Trafficking of presynaptic PMCA signaling complexes in mouse photoreceptors requires Cav1.4 alpha1 subunits
Xing, Wei; Akopian, Abram; Krizaj, David
2012 ;723:739-744, Advances in experimental medicine & biology
— id: 160271, year: 2012, vol: 723, page: 739, stat: Journal Article,

Masked excitatory crosstalk between the ON and OFF visual pathways in the mammalian retina
Farajian, Reza; Pan, Feng; Akopian, Abram; Volgyi, Bela; Bloomfield, Stewart A
2011 Sep 15;589(Pt 18):4473-4489, Journal of physiology
— id: 137837, year: 2011, vol: 589, page: 4473, stat: Journal Article,

CaV1.3 L-type Ca2+ channels modulate depression-like behaviour in mice independent of deaf phenotype
Busquet, Perrine; Nguyen, Ngoc Khoi; Schmid, Eduard; Tanimoto, Naoyuki; Seeliger, Mathias W; Ben-Yosef, Tamar; Mizuno, Fengxia; Akopian, Abram; Striessnig, Jorg; Singewald, Nicolas
2010 May;13(4):499-513, International journal of neuropsychopharmacology
— id: 163309, year: 2010, vol: 13, page: 499, stat: Journal Article,

Glutamate-induced internalization of Cav1.3 L-type Ca2+ channels protects retinal neurons against excitotoxicity
Mizuno, Fengxia; Barabas, Peter; Krizaj, David; Akopian, Abram
2010 Mar 15;588(Pt 6):953-966, Journal of physiology
— id: 108428, year: 2010, vol: 588, page: 953, stat: Journal Article,

CaV1.3 L-type calcium channels modulate depression-like behavior in mice independent of deaf phenotype
Busquet P.; Nguyen N.K.; Schmid E.; Tanimoto N.; Seeliger M.W.; Ben-Yosef T.; Mizuno F.; Akopian A.; Singewald N.; Striessnig J.
2009 ;9:?-?, BMC pharmacology
— id: 122705, year: 2009, vol: 9, page: ?, stat: Journal Article,

Calcium homeostasis and cone signaling are regulated by interactions between calcium stores and plasma membrane ion channels
Szikra, Tamas; Barabas, Peter; Bartoletti, Theodore M; Huang, Wei; Akopian, Abram; Thoreson, Wallace B; Krizaj, David
2009 ;4(8):e6723-e6723 e6723, PLoS ONE
— id: 163310, year: 2009, vol: 4, page: e6723, stat: Journal Article,

Disruption of actin cytoskeleton causes internalization of Ca(v)1.3 (alpha 1D) L-type calcium channels in salamander retinal neurons
Cristofanilli, Massimiliano; Mizuno, Fengxia; Akopian, Abram
2007 ;13:1496-1507, Molecular vision
— id: 74463, year: 2007, vol: 13, page: 1496, stat: Journal Article,

Glutamate-induced Ca2+ influx in third-order neurons of salamander retina is regulated by the actin cytoskeleton
Akopian, A; Szikra, T; Cristofanilli, M; Krizaj, D
2006 ;138(1):17-24, Neuroscience
— id: 64196, year: 2006, vol: 138, page: 17, stat: Journal Article,

Calcium channel and glutamate receptor activities regulate actin organization in salamander retinal neurons
Cristofanilli, Massimiliano; Akopian, Abram
2006 Sep 1;575(Pt 2):543-554, Journal of physiology
— id: 68980, year: 2006, vol: 575, page: 543, stat: Journal Article,

Actin filaments regulate voltage-gated ion channels in salamander retinal ganglion cells
Schubert, T; Akopian, A
2004 ;125(3):583-590, Neuroscience
— id: 163311, year: 2004, vol: 125, page: 583, stat: Journal Article,

Activity-dependent phosphorylation of tyrosine hydroxylase in dopaminergic neurons of the rat retina
Witkovsky, Paul; Veisenberger, Eleonora; Haycock, John W; Akopian, Abram; Garcia-Espana, Antonio; Meller, Emanuel
2004 May 28;24(17):4242-4249, Journal of neuroscience
— id: 45999, year: 2004, vol: 24, page: 4242, stat: Journal Article,

Role of actin Microfilaments in the regulation of voltage-gated ion channels in salamander retinal neurons
Akopian, A; Schubert, T
2003 MAY ;44(19):U734-U734, Investigative ophthalmology & visual science. IOVS
— id: 55470, year: 2003, vol: 44, page: U734, stat: Journal Article,

Differential modulation of light-evoked on- and off-EPSCs by paired-pulse stimulation in salamander retinal ganglion cells
Akopian, Abram
2003 Mar 28;967(1-2):235-246, Brain research
— id: 39264, year: 2003, vol: 967, page: 235, stat: Journal Article,

Effect of hypothalamic proline-rich-polypeptide on voltage-gated Ca2+ currents in retinal ganglion cells
Akopian, Abram; Galoyan, Armen
2003 Dec;28(12):1867-1871, Neurochemical research
— id: 46291, year: 2003, vol: 28, page: 1867, stat: Journal Article,

Paired-pulse modulation of On- and Off-EPSCs in retinal ganglion cells
Akopian, A
2002 MAY ;43(19):U1343-U1343, Investigative ophthalmology & visual science. IOVS
— id: 55464, year: 2002, vol: 43, page: U1343, stat: Journal Article,

Calcium and retinal function
Akopian, Abram; Witkovsky, Paul
2002 Apr;25(2):113-132, Molecular neurobiology
— id: 39683, year: 2002, vol: 25, page: 113, stat: Journal Article,

Intracellular calcium reduces light-induced excitatory post-synaptic responses in salamander retinal ganglion cells
Akopian A; Witkovsky P
2001 Apr 1;532(Pt 1):43-53, Journal of physiology
— id: 26758, year: 2001, vol: 532, page: 43, stat: Journal Article,

Glutamate-induced calcium accumulation in salamander retinal neurons
Akopian, A; Schubert, T; Weiler, R
2001 MAR 15 ;42(4):S677-S677, Investigative ophthalmology & visual science. IOVS
— id: 54983, year: 2001, vol: 42, page: S677, stat: Journal Article,

Neuromodulation of ligand- and voltage-gated channels in the amphibian retina
Akopian A
2000 Sep 1;50(5):403-410, Microscopy research & technique
— id: 11551, year: 2000, vol: 50, page: 403, stat: Journal Article,

Somatostatin modulates voltage-gated K(+) and Ca(2+) currents in rod and cone photoreceptors of the salamander retina
Akopian A; Johnson J; Gabriel R; Brecha N; Witkovsky P
2000 Feb 1;20(3):929-936, Journal of neuroscience
— id: 11856, year: 2000, vol: 20, page: 929, stat: Journal Article,

Relationship between intracellular Ca2+ and light-evoked EPSCs in retinal ganglion cells
Akopian, A; Witkovsky, P
2000 MAR 15 ;41(4):S935-S935, Investigative ophthalmology & visual science. IOVS
— id: 54625, year: 2000, vol: 41, page: S935, stat: Journal Article,

Effects of glutamate-related ligands on the electroretinogram (ERG) of the Xenopus retina
Szikra, T; Akopian, A; Witkovsky, P
2000 NOV ;12(11):486-486, European journal of neuroscience
— id: 54454, year: 2000, vol: 12, page: 486, stat: Journal Article,

Calcium released from intracellular stores inhibits GABAA-mediated currents in ganglion cells of the turtle retina
Akopian A; Gabriel R; Witkovsky P
1998 Sep;80(3):1105-1115, Journal of neurophysiology
— id: 12072, year: 1998, vol: 80, page: 1105, stat: Journal Article,

Both high- and low voltage-activated calcium currents contribute to the light-evoked responses of luminosity horizontal cells in the Xenopus retina
Akopian A; Krizaj D; Witkovsky P
1997 Jul 11;762(1-2):121-130, Brain research
— id: 56919, year: 1997, vol: 762, page: 121, stat: Journal Article,

Intracellular calcium induces inactivation of A-current in fish retinal horizontal cells
Akopian, A; Witkovsky, P
1997 MAR 15 ;38(4):2875-2875, Investigative ophthalmology & visual science. IOVS
— id: 53238, year: 1997, vol: 38, page: 2875, stat: Journal Article,

Gain of rod to horizontal cell synaptic transfer: relation to glutamate release and a dihydropyridine-sensitive calcium current
Witkovsky P; Schmitz Y; Akopian A; Krizaj D; Tranchina D
1997 Oct 1;17(19):7297-7306, Journal of neuroscience
— id: 7283, year: 1997, vol: 17, page: 7297, stat: Journal Article,

Activation of metabotropic glutamate receptors decreases a high-threshold calcium current in spiking neurons of the Xenopus retina
Akopian A; Witkovsky P
1996 May-Jun;13(3):549-557, Visual neuroscience
— id: 12605, year: 1996, vol: 13, page: 549, stat: Journal Article,

D2 dopamine receptor-mediated inhibition of a hyperpolarization-activated current in rod photoreceptors
Akopian A; Witkovsky P
1996 Sep;76(3):1828-1835, Journal of neurophysiology
— id: 12548, year: 1996, vol: 76, page: 1828, stat: Journal Article,

D2 dopamine receptor modulates hyperpolarization activated current in xenopus rods: A role for [Ca]
Akopian, A; Witkovsky, P
1996 FEB 15 ;37(3):24-24, Investigative ophthalmology & visual science. IOVS
— id: 53018, year: 1996, vol: 37, page: 24, stat: Journal Article,

DOPAMINE MODULATES DISTINCT HYPERPOLARIZATION-ACTIVATED CURRENTS IN RODS AND GLIAL-CELLS
AKOPIAN, A; WITKOVSKY, P
1995 MAR 15 ;36(4):S289-S289, Investigative ophthalmology & visual science. IOVS
— id: 87332, year: 1995, vol: 36, page: S289, stat: Journal Article,

Feedback from luminosity horizontal cells mediates depolarizing responses of chromaticity horizontal cells in the Xenopus retina
Witkovsky P; Gabriel R; Krizaj D; Akopian A
1995 Apr 11;92(8):3556-3560, Proceedings of the National Academy of Sciences of the United States of America
— id: 56728, year: 1995, vol: 92, page: 3556, stat: Journal Article,

Modulation of transient outward potassium current by GTP, calcium, and glutamate in horizontal cells of the Xenopus retina
Akopian A; Witkovsky P
1994 May;71(5):1661-1671, Journal of neurophysiology
— id: 12975, year: 1994, vol: 71, page: 1661, stat: Journal Article,

The effects of L-glutamate, AMPA, quisqualate, and kainate on retinal horizontal cells depend on adaptational state: implications for rod-cone interactions
Krizaj D; Akopian A; Witkovsky P
1994 Sep;14(9):5661-5671, Journal of neuroscience
— id: 8332, year: 1994, vol: 14, page: 5661, stat: Journal Article,

Activation of Protein Kinase C Modulates Light Responses in Horizontal Cells of the Turtle Retina
Akopian A; McReynolds J; Weiler R
1992 ;4(8):745-749, European journal of neuroscience
— id: 66504, year: 1992, vol: 4, page: 745, stat: Journal Article,

BACKGROUND ILLUMINATION MODULATES DOPAMINERGIC ACTIVITY AND THE RECEPTIVE-FIELD SIZE OF HORIZONTAL CELLS IN THE TURTLE RETINA
AKOPIAN, A; WEILER, R; KOLBINGER, W
1992 MAR 15 ;33(4):1406-1406, Investigative ophthalmology & visual science. IOVS
— id: 52058, year: 1992, vol: 33, page: 1406, stat: Journal Article,

Effects of background illuminations on the receptive field size of horizontal cells in the turtle retina are mediated by dopamine
Weiler R; Akopian A
1992 Jun 8;140(1):121-124, Neuroscience letters
— id: 66503, year: 1992, vol: 140, page: 121, stat: Journal Article,

Short-term potentiation of off-responses in turtle horizontal cells
Akopian A; McReynolds J; Weiler R
1991 Apr 12;546(1):132-138, Brain research
— id: 66505, year: 1991, vol: 546, page: 132, stat: Journal Article,