The Pattern of Enhancement of Src Kinase Activity on Platelet-derived Growth Factor Stimulation of Glioblastoma Cells Is Affected by the Integrin Engaged*
- ‡Department of Pathology, Division of Neuropathology and the §Department of Medicine, Division of Pulmonary and Critical Care Medicine, The University of Alabama at Birmingham, Birmingham, Alabama 35294
- ¶ To whom correspondence should be addressed: University of Alabama at Birmingham, LHRB 567, 701 South 19th St., Birmingham, AL 35294. Tel.: 205-975-7847; Fax: 205-934-7346; E-mail: gladson{at}uab.edu.
Abstract
Enhanced expression of both integrin αvβ3 and platelet-derived growth factor receptor (PDGFr) has been described in glioblastoma tumors. We therefore explored the possibility that integrin αvβ3 cooperates with PDGFr to promote cell migration in glioblastoma cells, and extended the study to identify the Src family members that are activated on PDGF stimulation. Glioblastoma cells utilize integrins αvβ3 and αvβ5 to mediate vitronectin attachment. We found that physiologic PDGF stimulation (83 pm, 10 min) of vitronectin-adherent cells promoted the specific recruitment of integrin αvβ3-containing focal adhesions to the cell cortex and αvβ3-mediated cell motility. Analysis of PDGFr immunoprecipitates indicated an association of the PDGFr β with integrin αvβ3, but not integrin αvβ5. Cells plated onto collagen or laminin, which engage different integrins, exhibited significantly less migration on PDGF stimulation, indicating a cooperation of αvβ3 and the PDGFr β in glioblastoma cells that promotes migration. Further analysis of the cells plated onto vitronectin indicated that PDGF stimulation caused an increase in Src kinase activity, which was associated with integrin αvβ3. In the vitronectin-adherent cells, Lyn was associated preferentially with αvβ3 both in the presence and absence of PDGF stimulation. In contrast, Fyn was associated with both αvβ3 and αvβ5. Moreover, PDGF stimulation increased the activity of Lyn, but not Fyn, in vitronectin-adherent cells, and the activity of Fyn, but not Lyn, in laminin-adherent cells. Using cells attached to mAb anti-αvβ3 or mAb anti-integrin α6, we confirmed the activation of specific members of the Src kinase family with PDGF stimulation. Down-regulation of Lyn expression by siRNA significantly inhibited the cell migration mediated by integrin αvβ3 in PDGF-stimulated cells, demonstrating the PDGFr β cooperates with integrin αvβ3 in promoting the motility of vitronectin-adherent glioblastoma cells through a Lyn kinase-mediated pathway. Notably, the data indicate that engagement of different integrins alters the identity of the Src family members that are activated on stimulation with PDGF.
Footnotes
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↵1 The abbreviations used are: PDGF, platelet-derived growth factor; PDGFr, PDGF receptor; BSA, bovine serum albumin; mAb, monoclonal antibody; PBS, phosphate-buffered saline; FAK, focal adhesion kinase.
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↵* This work was supported by Grants CA59958 and CA97110 from the NCI, National Institutes of Health (to C. L. G.) and by Grant HL58655 from the HLB, National Institutes of Health and the Veterans Administration Merit Review Board (to M. A. O.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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- Received May 5, 2003.
- Revision received July 18, 2003.
- The American Society for Biochemistry and Molecular Biology, Inc.
