Salceda Rocío, Aguirre-Ramirez Marisela
Instituto de Fisiologia Celular, Universidad Nacional Autónoma de Mexico Apdo. Postal 70-253, 04510 México, DF México.
Neurochem Res. 2005 Mar;30(3):411-6. doi: 10.1007/s11064-005-2616-1.
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.
我们研究了完整分离的蛙视网膜中3H-甘氨酸和3H-士的宁与甘氨酸受体（GlyR）的特异性结合。为避免甘氨酸与甘氨酸摄取位点结合，实验在无钠培养基中的低配体浓度下进行。两种放射性标记配体的结合均达到饱和。对结合的甘氨酸和士的宁进行Scatchard分析显示，KD分别为2.5和2.0微摩尔。甘氨酸的特异性结合被β-丙氨酸、肌氨酸和士的宁取代。甘氨酸和肌氨酸使士的宁结合被取代50%。肌氨酸改变了GlyR中士的宁结合位点的特性。抑制或激活腺苷酸环化酶并提高cAMP水平的化合物可显著降低两种放射性配体的结合。蛋白激酶C的佛波酯激活剂显著降低甘氨酸和士的宁结合。这些结果表明，视网膜中甘氨酸受体可响应蛋白激酶A和C的内源性激活以及蛋白磷酸化对甘氨酸受体功能的调节而发生调节。
