Boisclair Y R, Yang Y W, Stewart J M, Rechler M M
Growth and Development Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Growth Regul. 1994 Sep;4(3):136-46.
Insulin and insulin-like growth factor (IGF)-I are thought to be major metabolic regulators of IGF-binding protein-2 (IGFBP-2). We have examined the regulation of IGFBP-2 expression by IGF-I and insulin in 293 cells, a cell line derived from human embryonic kidney. The predominant 34 kDa IGFBP in media conditioned by unstimulated 293 cells was identified as IGFBP-2 by immunoprecipitation. IGFBP-2 levels were increased 6 to 7-fold following incubation with IGF-I, IGF-II or insulin for 48 h. A corresponding increase in IGFBP-2 mRNA was not observed, suggesting that regulation occurred at the translational or post-translational level. The stimulation of IGFBP-2 by IGF-I and insulin was reversibly abolished by incubation with protein synthesis inhibitors such as cycloheximide. Biosynthetic labeling of quiescent 293 cells using [35S]cysteine indicated that incubation with insulin or IGF-I for 24 h increased the synthesis of total cell proteins (predominantly intracellular) and IGFBP-2 (predominantly secreted) to a similar extent (2- to 4-fold). These results suggest that the increase in IGFBP-2 secreted by 293 cells after incubation with IGF-I or insulin largely results from a general stimulation of protein synthesis.
胰岛素和胰岛素样生长因子（IGF）-I被认为是IGF结合蛋白-2（IGFBP-2）的主要代谢调节因子。我们研究了IGF-I和胰岛素对源自人胚胎肾的293细胞中IGFBP-2表达的调节。通过免疫沉淀法确定，未刺激的293细胞条件培养基中主要的34 kDa IGFBP为IGFBP-2。用IGF-I、IGF-II或胰岛素孵育48小时后，IGFBP-2水平增加了6至7倍。未观察到IGFBP-2 mRNA相应增加，这表明调节发生在翻译或翻译后水平。用蛋白质合成抑制剂如放线菌酮孵育可逆转IGF-I和胰岛素对IGFBP-2的刺激作用。用[35S]半胱氨酸对静止的293细胞进行生物合成标记表明，用胰岛素或IGF-I孵育24小时可使总细胞蛋白（主要是细胞内蛋白）和IGFBP-2（主要是分泌蛋白）的合成增加到相似程度（2至4倍）。这些结果表明，293细胞在与IGF-I或胰岛素孵育后分泌的IGFBP-2增加主要是由于蛋白质合成的普遍刺激。
