c-Crk, a substrate of the insulin-like growth factor-1 receptor tyrosine kinase, functions as an early signal mediator in the adipocyte differentiation process
c-Crk, a substrate of the insulin-like growth factor-1 receptor tyrosine kinase, functions as an early signal mediator in the adipocyte differentiation process
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DOI：
10.1074/jbc.m004927200
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发表时间：
2000-11-03
影响因子：
4.8
通讯作者：
Liao, K
中科院分区：
文献类型：
--
作者：
Jin, SH;Zhai, B;Liao, K
3T3-L1前脂肪细胞向脂肪细胞的分化是由一系列诱导剂诱导的，包括糖皮质激素、一种升高细胞cAMP的药物和胰岛素样生长因子-1受体的配体。先前的研究表明，蛋白酪氨酸磷酸酶（PTPase） HA2是PTPase 1B的同源物，参与分化诱导剂启动的信号级联反应。钒酸盐是一种有效的PTPase抑制剂，在程序的早期阶段阻止脂肪细胞分化，但对分化所需的有丝分裂克隆扩增没有影响。前脂肪细胞暴露于钒酸盐和诱导剂导致pp35的积累，pp35是一种磷酸酪氨酸蛋白，是PTPase HA2的底物。通过氨基酸序列和色氨酸肽的质量分析，pp35被纯化为c-Crk，一种已知的胰岛素样生长因子-1受体酪氨酸激酶的细胞质靶点。用c-Crk反义RNA表达载体转染3T3-L1前脂肪细胞可显著降低c-Crk水平，阻止向脂肪细胞分化。C3G是一种结合c-Crk中SH3结构域的蛋白，对C3G的研究表明，c-Crk的磷酸化使C3G无法进入SH3结构域。综上所述，这些发现表明，用钒酸盐将c-Crk锁定在磷酸化状态可以阻止其参与启动脂肪细胞分化的信号系统。
Differentiation of 3T3-L1 preadipocytes into adipocytes is induced by a combination of inducers, including a glucocorticoid, an agent that elevates cellular cAMP, and a ligand of the insulin-like growth factor-1 receptor. Previous studies have implicated protein-tyrosine phosphatase (PTPase) HA2, a homologue of PTPase 1B, in the signaling cascade initiated by the differentiation inducers. Vanadate, a potent PTPase inhibitor, blocks adipocyte differentiation at an early stage in the program, but has no effect on the mitotic clonal expansion required for differentiation. Exposure of preadipocytes to vanadate along with the inducing agents led to the accumulation of pp35, a phosphotyrosyl protein that is a substrate for PTPase HA2. pp35 was purified to homogeneity and shown by amino acid sequence and mass analyses of tryptic peptides to be c-Crk, a known cytoplasmic target of the insulin-like growth factor-1 receptor tyrosine kinase. Transfection of 3T3-L1 preadipocytes with a c-Crk antisense RNA expression vector markedly reduced c-Crk levels and prevented differentiation into adipocytes. Studies with C3G, a protein that binds to the SH3 domain in c-Crk, showed that phosphorylation of c-Crk rendered the SH3 domain inaccessible to C3G. Taken together, these findings indicate that locking c-Crk in the phosphorylated state with vanadate prevents its participation in the signaling system that initiates adipocyte differentiation.