Titre du document / Document title

αvβ3 integrins and Pyk2 mediate insulin-like growth factor I activation of src and mitogen- activated protein kinase in 3T3-L1 cells

Auteur(s) / Author(s)

SEKIMOTO Hiroko ; EIPPER-MAINS Jodi ; POND-TOR Sunthorn ; BONEY Charlotte M. ;

Résumé / Abstract

IGF-I stimulates cell growth through interaction of the IGF receptor with multiprotein signaling complexes. However, the mechanisms of IGF-I receptor-mediated signaling are not completely understood. We have previously shown that IGF-I-stimulated 3T3-L1 cell proliferation is dependent on Src activation of the ERK-½ MAPK pathway. We hypothesized that IGF-I activation of the MAPK pathway is mediated through integrin activation of Src-containing signaling complexes. The disintegrin echistatin decreased IGF-I phosphorylation of Src and MAPK, and blocking antibodies to αv and β3 integrin subunits inhibited IGF-I activation of MAPK, suggesting that αvβ3 integrins mediate IGF-I mitogenic signaling. IGF-I increased ligand binding to av(33 as detected by immunofluorescent staining of ligand-induced binding site antibody and stimulated phosphorylation of the (33 subunit, consistent with inside-out activation of αvβ3 integrins. IGF-I increased tyrosine phosphorylation of the focal adhesion kinase (FAK) Pyk2 (calcium-dependent proline-rich tyrosine kinase-2) to a much greater extent than FAK, and increased association of Src with Pyk2 but not FAK. The intracellular calcium chelator BAPTA prevented IGF-I phosphorylation of Pyk2, Src, and MAPK, suggesting that IGF-I activation of Pyk2 is calcium dependent. Transient transfection with a dominant-negative Pyk2, which lacks the autophosphorylation and Src binding site, decreased IGF-I activation of MAPK, but no inhibition was seen with transfected wild-type Pyk2. These results indicate that IGF-I signaling to MAPK is dependent on inside-out activation of αvβ3 integrins and integrin-facilitated multiprotein complex formation involving Pyk2 activation and association with Src.

Revue / Journal Title

Molecular endocrinology   ISSN 0888-8809   CODEN MOENEN 

Source / Source

2005, vol. 19, n^o7, pp. 1859-1867 [9 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Endocrine Society, Bethesda, MD, ETATS-UNIS  (1987) (Revue)

Localisation / Location

INIST-CNRS, Cote INIST : 21131, 35400013852513.0160