The role of soluble GTP binding proteins in the differentiation of adipocytes

研究了ST-13前脂肪细胞分化为地塞米松/异丁基甲基黄嘌呤敏感表型前后细胞膜组分和胞浆组分中gtp结合蛋白的丰度和亚细胞分布。分化后，特异性抗血清免疫印迹法检测到的Gialpha和Gsalpha的丰度在按膜蛋白归一化时没有变化。与此相反，用免疫印迹法检测到膜上的Goalpha蛋白在分化后增加了约5倍。ST-13细胞质中含有α，但不含Gialpha和Gsalpha，分化后细胞质中α含量也增加了4倍。抗Goalpha（22-35）和Goalpha（345-354）肽的血清识别出细胞膜部分和细胞质部分的Goalpha增加。此外，百日咳毒素催化的膜和细胞质中添加外源性β - γ亚基的adp核糖基化在分化后都有所增加，这可能反映了分化细胞中α - γ的产生增加。抗糖尿病药AD4743对ST-13细胞的脂肪细胞分化也有促进作用，分化后膜和细胞质部分的α α含量也增加。另一方面，经维甲酸抑制分化的ST-13细胞的细胞膜和胞质中α α含量没有升高。这些结果表明Goalpha可能参与小鼠前脂肪细胞ST-13细胞的分化。

The abundance and the subcellular distribution of GTP-binding proteins was studied in membrance fraction and cytosolic fraction from ST-13 preadipocyte cells before and after differentiation to dexamethazone/isobutylmethylxanthine-sensitive phenotype. After differentiation, the abundance of Gialpha and Gsalpha as detected by immunoblotting with specific antisera was not changed when normalized as per membrane protein. In contrast, Goalpha in membrane as detected by immunoblotting with a specific antiserum against whole Goalpha protein was increased about five-fold after differentiation. ST-13 contains Goalpha, but not Gialpha or Gsalpha in cytosolic fraction and Goalpha in cytosolic fraction also increased to four-fold after differentiation.Antisera against the peptides of Goalpha (22-35) and Goalpha (345-354) recognized the increase of Goalpha in the membrane fraction and cytosolic fraction. Furthermore, pertussis toxin-catalyzed ADP-ribosylation of both membrane and cytosolic fractions in which exogenous betagamma subunits were added was shown to be increased after differentiation, possibly reflecting the increased production of Goalpha in differentiated cells. Antidiabetic agent AD4743 also enhanced adipocyte differentiation of ST-13 cell and Goalpha in membrane and cytosolic fractions was also increased after differentiation. On the other hand, Goalpha in membrane and cytosolic fractions of ST-13 cells which were suppressed to differentiated by retinoic acid was not increased. These results indicate that Goalpha may involve the differentiation of murine preadipocyte ST-13 cells.