IOVS AJP: Endocrinology and Metabolism
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(Investigative Ophthalmology and Visual Science. 2002;43:2097-2104.)
© 2002 by The Association for Research in Vision and Ophthalmology, Inc.

Retinal Voltage-Dependent Anion Channel: Characterization and Cellular Localization

Dan Gincel1, Noga Vardi2 and Varda Shoshan-Barmatz1

1 From the Department of Life Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel; and the 2 Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania.

PURPOSE. To characterize and localize retinal voltage-dependent anion channel (VDAC) and to understand its possible contribution to mitochondrial function and dysfunction.

METHODS. VDAC was characterized by a method involving purification from isolated mitochondria and reconstitution into a planar lipid bilayer (PLB). The permeability transition pore (PTP) was monitored by Ca2+ accumulation in isolated mitochondria and swelling of mitochondria. Localization was studied by immunocytochemistry and in situ hybridization.

RESULTS. Retinal VDACs exhibited the electrophysiological fingerprint of the VDAC superfamily. It had a maximal chord conductance of 3.7 ± 0.1 nanosiemens (nS) in 1 M NaCl, and a voltage-dependent conductance that was highest at transmembrane potential close to zero. It was modulated by glutamate, which decreased the channel’s open probability, and by La3+ and ruthenium amine binuclear complex (Ru360), which closed the channel. Energized and freshly prepared retinal mitochondria accumulated Ca2+ that is inhibited by La3+ ruthenium red and Ru360. Subsequent to Ca2+ accumulation, mitochondria released the accumulated Ca2+, probably through activation of the PTP. Ru360 inhibited Ca2+ release and mitochondrial swelling. VDAC was present in mitochondria of all retinal cell types: photoreceptor, bipolar, horizontal, amacrine, and ganglion cells. Most cells primarily expressed VDAC-1, but they also expressed VDAC-2 and -3.

CONCLUSIONS. These results suggest that VDAC is involved in PTP activity and/or regulation and thus is an important player in retinal degeneration associated with PTP-mediated mitochondrial dysfunction.






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Copyright © 2002 by the Association for Research in Vision and Ophthalmology