Alpha-V-dependent outside-in signaling is required for the regulation of CD44 surface expression, MMP-2 secretion, and cell migration by osteopontin in human melanoma cells

The level of integrin alpha v beta 3 and its ligand osteopontin (OPN) has been directly correlated to tumorigenicity of melanoma and other cancer cells. We have previously shown an increase in pp(60c-Src) kinase activity associated with integrin alpha v beta 3 in melanoma cells (M21) treated with soluble OPN. pp(60c-Src) kinase activity was not observed in melanoma cells expressing alpha v that lacks the cytoplasmic domain (alpha v995). Results of the current study demonstrate that the amino acid sequence '995RPPQEEQERE1004' in the beta-turn of alpha v chain is required for the interaction of pp(60c-Src). our results suggest that the beta-turn of alpha v chain may be indispensable for av-associated signaling complex formation and outside-in signaling. To further analyze the av133 signaling in melanoma cells, we over expressed OPN in M21 cells (M21/OPN). CD44 surface expression and MMP-2 activity in the conditioned medium were increased to a greater extent in M21/OPN cells as compared with M21 or av995 cells. Also, M21/OPN cells exhibit increased motility, which is markedly reduced upon treatment with inhibitors to av and MMP-2. Our findings suggest that the increase in MMP-2 activity is integrin-dependent as MMP-2 activity is reduced in cells treated with an inhibitor to av or in av995 cells expressing mutant alpha v. (c) 2006 Elsevier Inc. All rights reserved.