The integrin specificity of human recombinant osteopontin

The ability of full-length human recombinant osteopontin (OPN) to support the adhesion of various cr, integrin-expressing cell lines was determined in order to characterize its integrin selectivity. The identity of this protein was assessed by cDNA sequence and mass spectroscopic analysis, and confirmed as full-length OPN. Neither the human embryonic kidney 293 cell line, which expresses the alpha(V)beta(1) integrin, nor the human colonic adenocarcinoma HT-29 cell line, which expresses the alpha(V)beta(5) integrin, were able to adhere to OPN; both of these cell lines are deficient in the beta(3) subunit. In contrast, an alpha(V)beta(3) integrin-expressing cell line, SK-MEL-24, was able to adhere to OPN in an arginine-glycine-aspartic acid dependent manner. In addition, this OPN-mediated cellular adhesion was completely blocked with an anti-alpha(V)beta(3) integrin antibody (LM609), confirming that only the alpha(V)beta(3) integrin mediated this cellular adhesion. These data demonstrate that, at least among the alpha(V) integrins, only the alpha(V)beta(3) is able to support cellular adhesion to osteopontin. This finding may have implications for the design of therapeutics targeting OPN-integrin interactions. (C) 1999 Elsevier Science Inc.