Liu Yong, Buck David C, Neve Kim A
Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon, USA.
Mol Pharmacol. 2008 Aug;74(2):371-8. doi: 10.1124/mol.108.044925. Epub 2008 Apr 29.
S100B is a calcium-binding protein with both extracellular and intracellular regulatory activities in the mammalian brain. We have identified a novel interaction between S100B and the dopamine D(2) receptor. Our results also suggest that the binding of S100B to the dopamine D(2) receptor enhances receptor signaling. This conclusion is based on the following observations: 1) S100B and the third cytoplasmic loop of the dopamine D(2) receptor interact in a bacterial two-hybrid system and in a poly-histidine pull-down assay; 2) immunoprecipitation of the D(2) receptor also precipitates FLAG-S100B from human embryonic kidney 293 cell homogenates and endogenous S100B from rat neostriatal homogenates; 3) S100B immunoreactivity was detected in cultured neostriatal neurons expressing the D(2) receptor; 4) a putative S100B binding motif is located at residues 233 to 240 of the D(2) receptor, toward the amino terminus of the third cytoplasmic loop. D(3)-IC3, which does not bind S100B, does not contain this motif; and 5) coexpression of S100B in D(2) receptor-expressing 293 cells selectively increased D(2) receptor stimulation of extracellular signal-regulated kinases and inhibition of adenylate cyclase.
S100B是一种钙结合蛋白，在哺乳动物大脑中具有细胞外和细胞内调节活性。我们发现了S100B与多巴胺D(2)受体之间的新型相互作用。我们的结果还表明，S100B与多巴胺D(2)受体的结合增强了受体信号传导。这一结论基于以下观察结果：1）S100B与多巴胺D(2)受体的第三个细胞质环在细菌双杂交系统和多组氨酸下拉试验中相互作用；2）对D(2)受体进行免疫沉淀时，也能从人胚肾293细胞匀浆中沉淀出FLAG-S100B，并从大鼠新纹状体匀浆中沉淀出内源性S100B；3）在表达D(2)受体的培养新纹状体神经元中检测到S100B免疫反应性；4）一个假定的S100B结合基序位于D(2)受体的第233至240位残基处，朝向第三个细胞质环的氨基末端。不与S100B结合的D(3)-IC3不包含该基序；5）在表达D(2)受体的293细胞中共表达S100B可选择性增加D(2)受体对细胞外信号调节激酶的刺激以及对腺苷酸环化酶的抑制。
