Recoverin regulates light-dependent phosphodiesterase activity in retinal rods.
The Ca2+-binding protein recoverin may regulate visual transduction in retinal rods and cones, but its functional role and mechanism of action remain controversial. We compared the photoresponses of rods from control mice and from mice in which the recoverin gene was knocked out. Our analysis indicates that Ca2+-recoverin prolongs the dark-adapted flash response and increases the rod's sensitivity to dim steady light. Knockout rods had faster Ca2+ dynamics, indicating that recoverin is a significant Ca2+ buffer in the outer segment, but incorporation of exogenous buffer did not restore wild-type behavior. We infer that Ca2+-recoverin potentiates light-triggered phosphodiesterase activity, probably by effectively prolonging the catalytic activity of photoexcited rhodopsin.
Makino
Clint L
CL
Department of Ophthalmology, Harvard Medical School and the Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA. cmakino@meei.harvard.edu
Dodd
R L
RL
Chen
J
J
Burns
M E
ME
Roca
A
A
Simon
M I
MI
Baylor
D A
DA
D000222:Adaptation, Physiological / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology* / Q000528:radiation effects; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D004789:Enzyme Activation / Q000528:radiation effects; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D008027:Light; D008074:Lipoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D051603:Recoverin; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology* / Q000528:radiation effects*
D002135:Calcium-Binding Proteins; D005136:Eye Proteins; D008074:Lipoproteins; C496732:Rcvrn protein, mouse; D011994:Recombinant Proteins; D051603:Recoverin; D010727:Phosphoric Diester Hydrolases