Frizzo Juliana Karl, Tramontina Francine, Bortoli Erica, Gottfried Carmen, Leal Rodrigo B, Lengyel Imre, Donato Rosario, Dunkley Peter R, Gonçalves Carlos-Alberto
Departamento de Bioquímica, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
Neurochem Res. 2004 Apr;29(4):735-40. doi: 10.1023/b:nere.0000018844.51009.40.
S100B belongs to a family of calcium-binding proteins involved in cell cycle and cytoskeleton regulation. We observed an inhibitory effect of S100B on glial fibrillary acidic protein (GFAP) phosphorylation, when stimulated by cAMP or Ca2+/calmodulin, in a cytoskeletal fraction from primary astrocyte cultures. We found that S100B has no direct effect on CaM KII activity, the major kinase in this cytoskeletal fraction able to phosphorylate GFAP. The inhibition of GFAP phosphorylation is most likely due to the binding of S100B to the phosphorylation sites on this protein and blocking the access of these sites to the protein kinases. This inhibition was dependent on Ca2+. However, Zn2+ could substitute for Ca2+. The inhibitory effect of S100B was prevented by TRTK-12, a peptide that blocks S100B interaction with several target proteins including glial fibrillary acidic protein. These data suggest a role for S100B in the assembly of intermediate filaments in astrocytes.
S100B属于参与细胞周期和细胞骨架调节的钙结合蛋白家族。我们观察到，在原代星形胶质细胞培养物的细胞骨架组分中，当受到cAMP或Ca2+/钙调蛋白刺激时，S100B对胶质纤维酸性蛋白（GFAP）磷酸化具有抑制作用。我们发现S100B对CaM KII活性没有直接影响，CaM KII是该细胞骨架组分中能够磷酸化GFAP的主要激酶。GFAP磷酸化的抑制很可能是由于S100B与该蛋白上的磷酸化位点结合，并阻止这些位点与蛋白激酶接触。这种抑制作用依赖于Ca2+。然而，Zn2+可以替代Ca2+。TRTK-12可阻止S100B与包括胶质纤维酸性蛋白在内的几种靶蛋白相互作用，它可消除S100B的抑制作用。这些数据表明S100B在星形胶质细胞中间丝组装中发挥作用。
