The integrin specificity of human recombinant osteopontin

The ability of full-length human recombinant osteopontin (OPN) to support t he adhesion of various cr, integrin-expressing cell lines was determined in order to characterize its integrin selectivity. The identity of this prote in was assessed by cDNA sequence and mass spectroscopic analysis, and confi rmed as full-length OPN. Neither the human embryonic kidney 293 cell line, which expresses the alpha(V)beta(1) integrin, nor the human colonic adenoca rcinoma 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 d ependent manner. In addition, this OPN-mediated cellular adhesion was compl etely blocked with an anti-alpha(V)beta(3) integrin antibody (LM609), confi rming that only the alpha(V)beta(3) integrin mediated this cellular adhesio n. 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. T his finding may have implications for the design of therapeutics targeting OPN-integrin interactions. (C) 1999 Elsevier Science Inc.