Identification of a G-protein in depolarizing rod bipolar cells.
Synaptic transmission from photoreceptors to depolarizing bipolar cells is mediated by the APB glutamate receptor. This receptor apparently is coupled to a G-protein which activates cGMP-phosphodiesterase to modulate cGMP levels and thus a cGMP-gated cation channel. We attempted to localize this system immunocytochemically using antibodies to various components of the rod phototransduction cascade, including Gt (transducin), phosphodiesterase, the cGMP-gated channel, and arrestin. All of these antibodies reacted strongly with rods, but none reacted with bipolar cells. Antibodies to a different G-protein, G(o), reacted strongly with rod bipolar cells of three mammalian species (which are depolarizing and APB-sensitive). Also stained were subpopulations of cone bipolar cells but not the major depolarizing type in cat (b1). G(o) antibody also stained certain salamander bipolar cells. Thus, across a wide range of species, G(o) is present in retinal bipolar cells, and at least some of these are depolarizing and APB-sensitive.
Vardi
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N
Department of Anatomy, University of Pennsylvania, Philadelphia 19104-6058.
Matesic
D F
DF
Manning
D R
DR
Liebman
P A
PA
Sterling
P
P
D000595:Amino Acid Sequence; D000818:Animals; D000941:Antigens / Q000032:analysis; D019393:Arrestin; D002415:Cats; D002417:Cattle; D054815:Cyclic Nucleotide-Gated Cation Channels; D005136:Eye Proteins / Q000032:analysis; D005455:Fluorescent Antibody Technique; D019204:GTP-Binding Proteins / Q000032:analysis*; D007395:Interneurons / Q000737:chemistry*; D007473:Ion Channels; D008253:Macaca mulatta; D008969:Molecular Sequence Data; D010726:Phosphodiesterase Inhibitors / Q000032:analysis; D010727:Phosphoric Diester Hydrolases / Q000032:analysis; D051381:Rats; D012374:Rod Cell Outer Segment / Q000737:chemistry*; D015293:Transducin / Q000032:analysis; D014562:Caudata
D000941:Antigens; D019393:Arrestin; D054815:Cyclic Nucleotide-Gated Cation Channels; D005136:Eye Proteins; D007473:Ion Channels; D010726:Phosphodiesterase Inhibitors; D010727:Phosphoric Diester Hydrolases; D019204:GTP-Binding Proteins; D015293:Transducin