title: Direct activation of cGMP-dependent channels of retinal rods by the cGMP phosphodiesterase.
abstract: The cationic conductances of purified bovine retinal rod membranes were studied by incorporation of vesicles into planar lipid bilayers. When the membranes were stripped of all peripheral proteins [guanine nucleotide-binding protein (G protein) and cGMP phosphodiesterase (3',5'-cyclic-GMP 5'-nucleotidohydrolase), EC 3.1.4.35], sodium and calcium fluxes were almost only observed in the presence of cGMP. Reconstitution experiments in which purified cGMP phosphodiesterase alone or with G protein were reassociated to the vesicles in proportions similar to those found in the native rod provide evidence for a direct interaction between the cGMP-dependent channel protein and the phosphodiesterase. (i) In its inhibited state, phosphodiesterase markedly stimulates the activity of the channels in the presence of cGMP (situation in the dark-adapted rod) but is not capable of activating the channels in the absence of cGMP. (ii) In the absence of cGMP, activation of the phosphodiesterase by G protein with GTP bound (equivalent to photoexcitation) induces the opening of cation channels that have the same conductance for sodium ions as cGMP-activated channels (20-22 pS, with two sublevels of about 7 pS and 13 pS).
authors: Centre National de la Recherche Scentifique, URA 520, Centre d'Etudes Nucléaires de Grenoble, France.
authors: N
authors: N
authors: Bennett
authors: M
authors: M
authors: Ildefonse
authors: S
authors: S
authors: Crouzy
authors: Y
authors: Y
authors: Chapron
authors: A
authors: A
authors: Clerc
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000502:physiology*; D000818:Animals; D002417:Cattle; D006152:Cyclic GMP / Q000502:physiology*; D004110:Diltiazem / Q000494:pharmacology; D004553:Electric Conductivity; D019204:GTP-Binding Proteins / Q000502:physiology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials; D008970:Molecular Weight; D010786:Photoreceptor Cells / Q000502:physiology*; D012964:Sodium / Q000502:physiology
chemical_list: D007473:Ion Channels; D012964:Sodium; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D019204:GTP-Binding Proteins; D004110:Diltiazem; D006152:Cyclic GMP