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

Patrick A Kiely,Madeline Leahy,Denise O'Gorman,Rosemary O'Connor

doi:10.1074/jbc.m412889200

Patrick A Kiely, Madeline Leahy + Show 2 more

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https://doi.org/10.1074/jbc.m412889200

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Abstract

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-I 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-I 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.

Highlights

The IGF-IR1 is widely expressed and, activated by the ligands IGF-I or IGF-II, is essential for normal growth during development as well as for cell survival, differentiation, and migration in fibroblasts, muscle cells, lymphocytes, and neuronal cells
Association of RACK1 with the insulin-like growth factor I receptor (IGF-IR) Is Dependent on Cell Adhesion—The regulatory adapter protein RACK1 has previously been shown to associate with the IGF-IR in a ligandindependent manner in fibroblasts and MCF-7 cells [22]
When Rϩ cells were stimulated with IGF-I for up to 60 min, the amount of RACK1 that co-precipitated with the IGF-IR remained constant regardless of the degree of tyrosine phosphorylation of the IGF-IR (Fig. 1A)

Summary

Introduction

The IGF-IR1 is widely expressed and, activated by the ligands IGF-I or IGF-II, is essential for normal growth during development as well as for cell survival, differentiation, and migration in fibroblasts, muscle cells, lymphocytes, and neuronal cells. The data demonstrate that the lack of RACK1-mediated integration of adhesion and IGF-IR signaling that is necessary for cell migration is deficient in cells expressing the Y1250F/Y1251F mutant.

Results

Conclusion