title: Characterization of an L-type calcium channel expressed by human retinal Müller (glial) cells.
abstract: The traditional notion that glial cells are permeable only to potassium has been revised. For example, glia from various parts of the nervous system have calcium-permeable ion channels. Since characterization of the calcium channels in glia is limited, the purpose of this study was to determine the molecular identity and examine the functional properties of a voltage-gated calcium channel expressed by Müller cells, the predominant glia of the retina. Whole-cell and perforated-patch recordings of human Müller cells in culture revealed a high threshold voltage-activated calcium current that is blocked by dihydropyridines, but not by omega-conotoxin GVIA or omega-conotoxin MVIIC. RT-PCR of cultured human Müller cells using primers specific for the calcium channel subunits demonstrated the expression of an L-type channel composed of the alpha 1D, alpha 2 and beta 3 subunits. The alpha 2 subunit of the Müller cell calcium channel is a splice variant which is distinct from either the skeletal muscle alpha 2s or the brain alpha 2b. Our electrophysiological experiments indicate that the alpha 1D/alpha 2/beta 3 calcium channel is functionally linked with the activation of a potassium channel that may serve as one of the pathways for the redistribution by Müller cells of excess retinal potassium.
authors: Department of Ophthalmology, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor 48105, USA.
authors: D G
authors: DG
authors: Puro
authors: J J
authors: JJ
authors: Hwang
authors: O J
authors: OJ
authors: Kwon
authors: H
authors: H
authors: Chin
mesh_terms: D000595:Amino Acid Sequence; D015220:Calcium Channels / Q000502:physiology*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects*; D008969:Molecular Sequence Data; D009457:Neuroglia / Q000378:metabolism*; D009553:Nimodipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D012333:RNA, Messenger / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D012333:RNA, Messenger; D009553:Nimodipine