Characterization of strychnine-sensitive glycine receptor in the intact frog retina: modulation by protein kinases.
We studied 3H-glycine and 3H-strychnine specific binding to glycine receptor (GlyR) in intact isolated frog retinas. To avoid glycine binding to glycine uptake sites, experiments were performed at low ligand concentrations in a sodium-free medium. The binding of both radiolabeled ligands was saturated. Scatchard analysis of bound glycine and strychnine revealed a KD of 2.5 and 2.0 microM, respectively. Specific binding of glycine was displaced by beta-alanine, sarcosine, and strychnine. Strychnine binding was displaced 50% by glycine, and sarcosine. Properties of the strychnine-binding site in the GlyR were modified by sarcosine. Binding of both radioligands was considerably reduced by compounds that inhibit or activate adenylate cyclase and increased cAMP levels. A phorbol ester activator of PKC remarkably decreased glycine and strychnine binding. These results suggest modulation of GlyR in response to endogenous activation of protein kinases A and C, as well as protein phosphorylation modulating GlyR function in retina.
Salceda
Rocío
R
Instituto de Fisiologia Celular, Universidad Nacional Autónoma de Mexico Apdo. Postal 70-253, 04510 México, DF México. rsalceda@ifc.unam.mx
Aguirre-Ramirez
Marisela
M
D000262:Adenylyl Cyclases / Q000378:metabolism; D000409:Alanine / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D066298:In Vitro Techniques; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D011894:Rana pipiens; D018009:Receptors, Glycine / Q000187:drug effects* / Q000378:metabolism; D012160:Retina / Q000187:drug effects* / Q000201:enzymology*; D012521:Sarcosine / Q000494:pharmacology; D013331:Strychnine / Q000378:metabolism / Q000494:pharmacology*
D018009:Receptors, Glycine; D000242:Cyclic AMP; D011494:Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000262:Adenylyl Cyclases; D006152:Cyclic GMP; D013331:Strychnine; D000409:Alanine; D005998:Glycine; D012521:Sarcosine