Protein kinase C activity and light sensitivity of single amphibian rods.
Biochemical experiments by others have indicated that protein kinase C activity is present in the rod outer segment, with potential or demonstrated targets including rhodopsin, transducin, cGMP-phosphodiesterase (PDE), guanylate cyclase, and arrestin, all of which are components of the phototransduction cascade. In particular, PKC phosphorylations of rhodopsin and the inhibitory subunit of PDE (PDE ) have been studied in some detail, and suggested to have roles in downregulating the sensitivity of rod photoreceptors to light during illumination. We have examined this question under physiological conditions by recording from a single, dissociated salamander rod with a suction pipette while exposing its outer segment to the PKC activators phorbol-12-myristate,13-acetate (PMA) or phorbol-12,13-dibutyrate (PDBu), or to the PKC-inhibitor GF109203X. No significant effect of any of these agents on rod sensitivity was detected, whether in the absence or presence of a background light, or after a low bleach. These results suggest that PKC probably does not produce any acute downregulation of rod sensitivity as a mechanism of light adaptation, at least for isolated amphibian rods.
Xiong
W
W
Howard Hughes Medical Institute, Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Nakatani
K
K
Ye
B
B
Yau
K
K
D000557:Ambystoma; D000818:Animals; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010477:Perfusion; D010775:Photic Stimulation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects; D014785:Vision, Ocular / Q000187:drug effects / Q000502:physiology*
D004791:Enzyme Inhibitors; D011493:Protein Kinase C