RACK1-mediated integration of adhesion and insulin-like growth factor I (IGF-I) signaling and cell migration are defective in cells expressing an IGF-I receptor mutated at tyrosines 1250 and 1251
RACK1-mediated integration of adhesion and insulin-like growth factor I (IGF-I) signaling and cell migration are defective in cells expressing an IGF-I receptor mutated at tyrosines 1250 and 1251
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DOI：
10.1074/jbc.m412889200
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发表时间：
2005-03-04
影响因子：
4.8
通讯作者：
O'Connor, R
中科院分区：
文献类型：
--
作者：
Kiely, PA;Leahy, M;O'Connor, R
活化C激酶支架蛋白受体(RACK1)被认为是介导胰岛素样生长因子I受体(IGF-IR)和黏附信号整合的分子。在这里，我们利用一个缺乏抗凋亡和转化功能的IGF-IR突变体(Y1250F/Y1251F)来研究这种信号整合的机制。RACK1仅在贴壁细胞中与IGF-IR相关，而在非贴壁细胞、淋巴细胞或表达Y1250F/Y1251F突变体的细胞中不与IGF-IR相关。在瞬时表达Y1250F/Y1251F突变体的R细胞中，RACK1与Beta1整合素发生结构性关联，而不与Shc、Src或Shp2关联。伴随而来的是含有IGF-IR、RACK1和Beta1整合素的复合体的丧失；迁移能力的丧失；Src和FAK活性的增强；Akt的磷酸化增强；以及p38丝裂原激活的蛋白激酶活性的降低。在表达Y1250F/Y1251F突变体的细胞中，SHC不受IGF-IR的影响而被磷酸化，并且仍然与蛋白磷酸酶2A有关。在非贴壁培养中，用IGF-IR刺激的细胞中也观察到了类似的信号变化。我们的数据表明，表达Y1250F/Y1251F突变的细胞中RACK1支架功能的破坏会导致调节Akt活性和促进焦点黏附的周转和细胞迁移所必需的黏附信号的丢失。
The scaffolding protein receptor for activated C kinase (RACK1) has been proposed to mediate the integration of insulin-like growth factor I receptor (IGF-IR) and adhesion signaling. Here we investigated the mechanism of this integration of signaling, by using an IGF-IR mutant (Y1250F/Y1251F) that is deficient in anti-apoptotic and transforming function. RACK1 was found to associate with the IGF-IR only in adherent cells and did not associate with the IGF-IR in nonadherent cells, lymphocytic cells, or cells expressing the Y1250F/Y1251F mutant. In R-cells transiently expressing the Y1250F/Y1251F mutant RACK1 became constitutively associated with beta1 integrin and did not associate with Shc, Src, or Shp2. This was accompanied by the loss of formation of a complex containing the IGF-IR, RACK1, and beta1 integrin; loss of migratory capacity; enhanced Src and FAK activity; enhanced Akt phosphorylation; and decreased p38 mitogen-activated protein kinase activity. Shc was not phosphorylated in response to IGF-IR in cells expressing the Y1250F/Y1251F mutant and remained associated with protein phosphatase 2A. Similar alterations in signaling were observed in cells that were stimulated with IGF-IR in nonadherent cultures. Our data suggest that disruption of RACK1 scaffolding function in cells expressing the Y1250F/Y1251F mutant results in the loss of adhesion signals that are necessary to regulate Akt activity and to promote turnover of focal adhesions and cell migration.