Enhanced expression of both
integrin alpha v beta 3 and
platelet-derived growth factor receptor (PDGFr) has been described in
glioblastoma tumors. We therefore explored the possibility that
integrin alpha v beta 3 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 alpha v beta 3 and alpha v beta 5 to mediate
vitronectin attachment. We found that physiologic PDGF stimulation (83 pm, 10 min) of
vitronectin-adherent cells promoted the specific recruitment of
integrin alpha v beta 3-containing focal adhesions to the cell cortex and alpha v beta 3-mediated cell motility. Analysis of PDGFr immunoprecipitates indicated an association of the
PDGFr beta with
integrin alpha v beta 3, but not
integrin alpha v beta 5. Cells plated onto
collagen or
laminin, which engage different
integrins, exhibited significantly less migration on PDGF stimulation, indicating a cooperation of alpha v beta 3 and the
PDGFr beta 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 alpha v beta 3. In the
vitronectin-adherent cells, Lyn was associated preferentially with alpha v beta 3 both in the presence and absence of PDGF stimulation. In contrast, Fyn was associated with both alpha v beta 3 and alpha v beta 5. 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-alpha v beta 3 or mAb anti-
integrin alpha 6, 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 alpha v beta 3 in PDGF-stimulated cells, demonstrating the
PDGFr beta cooperates with
integrin alpha v beta 3 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.