Takenaka I M, Hightower L E
Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269-3044.
J Cell Physiol. 1992 Sep;152(3):568-77. doi: 10.1002/jcp.1041520317.
In this report we show that: (1) molecular chaperones in the heat shock protein (hsp) family are a new class of cellular proteins induced by Transforming Growth Factor-beta 1 (TGF beta), a cytokine present in serum, (2) rapid induction of Hsc70 precedes a general increase in protein synthesis and may be a preparatory event, (3) TGF beta is a potent regulator of overall protein synthesis in chicken embryo cells (CEC), and (4) isoforms of Hsp90 with different biochemical properties exist, raising the possibility that they may have different functions. TGF beta can substitute for serum in stimulating synthesis of members of the Hsp90 and Hsp70 families of stress proteins, whereas other cytokines, including PDGF, FGF, and EGF, were not effective nor did they enhance the stimulatory effect of TGF beta on the hsp's. Analysis of the induction of hsp's using one- and two-dimensional polyacrylamide gel electrophoresis indicated that members of the Hsp70 family of molecular chaperones were induced rapidly by TGF beta, reaching maximum rates of accumulation by 5 hours of treatment. Total protein synthesis increased more slowly, undergoing an approximately twofold increase in 24 hours. Using a modified protocol for two-dimensional gel electrophoresis, the Hsp90 protein family was separated into four isoelectric forms, two of which were phosphorylated (Hsp90-2 and -4). These phosphorylated isoforms turned over faster than the unphosphorylated forms of Hsp90. All four isoforms were heat inducible, but only Hsp90-2 and -3 were induced rapidly by TGF beta, again within 5 hours of treatment. The effects of serum on these protein families were similar to those of TGF beta, suggesting that this cytokine may be the serum component primarily responsible for up-regulating members of the Hsp90 and Hsp70 families. We hypothesize that cells rapidly increase their chaperoning capacity for newly synthesized polypeptides in preparation for an increase in the rate of synthesis of proteins up-regulated by TGF beta.
在本报告中，我们表明：（1）热休克蛋白（hsp）家族中的分子伴侣是一类新的细胞蛋白，由血清中存在的细胞因子转化生长因子-β1（TGF-β）诱导产生；（2）Hsc70的快速诱导先于蛋白质合成的普遍增加，可能是一个准备事件；（3）TGF-β是鸡胚细胞（CEC）中整体蛋白质合成的有效调节剂；（4）存在具有不同生化特性的Hsp90同工型，这增加了它们可能具有不同功能的可能性。TGF-β可以替代血清刺激应激蛋白Hsp90和Hsp70家族成员的合成，而其他细胞因子，包括血小板衍生生长因子（PDGF）、成纤维细胞生长因子（FGF）和表皮生长因子（EGF），均无效，也不能增强TGF-β对热休克蛋白的刺激作用。使用一维和二维聚丙烯酰胺凝胶电泳分析热休克蛋白的诱导情况表明，分子伴侣Hsp70家族成员被TGF-β快速诱导，在处理5小时时达到最大积累速率。总蛋白质合成增加得更慢，在24小时内增加约两倍。使用改良的二维凝胶电泳方案，Hsp90蛋白家族被分离为四种等电形式，其中两种被磷酸化（Hsp90-2和-4）。这些磷酸化的同工型比未磷酸化的Hsp90形式周转更快。所有四种同工型都可被热诱导，但只有Hsp90-2和-3在TGF-β处理后5小时内快速诱导产生。血清对这些蛋白质家族的影响与TGF-β相似，表明这种细胞因子可能是血清中主要负责上调Hsp90和Hsp70家族成员的成分。我们推测，细胞会迅速提高其对新合成多肽的伴侣能力，为TGF-β上调的蛋白质合成速率增加做准备。
