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 D2 receptor. Our results also suggest that the binding of S100B to the dopamine D2 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 D2 receptor also precipitates FLAG-S100B from human embryonic kidney 293 cell homogenates and endogenous S100B from rat neostriatal homogenates; 3) S100B immuno-reactivity was detected in cultured neostriatal neurons expressing the D2 receptor; 4) a putative S100B binding motif is located at residues 233 to 240 of the D2 receptor, toward the amino terminus of the third cytoplasmic loop. D3-IC3, which does not bind S100B, does not contain this motif; and 5) coexpression of S100B in D2 receptor-expressing 293 cells selectively increased D2 receptor stimulation of extracellular signal-regulated kinases and inhibition of adenylate cyclase.
ASJC Scopus subject areas
- Molecular Medicine