The long term goals of this research are to 1) characterize each member of the VLA family of five heterodimers with regard to cell matrix adhesion functions and 2) obtain genetic sequence information essential for the long term understanding of VLA proteins. Already it is known that antisera to the VLA Beta subunit (common to all VLA structures) blocks cell adhesion to fibronectin and laminan, and two VLA structures (VLA-3 nd VLA- 5) resemble known receptors for fibronectin. The availability of both a panel of monoclonal antibodies recognizing different VLA subunits, and an abundant supply of purified VLA proteins now makes it feasible to carry out the following specific aims. (1) The matrix-adherence capabilities for each VLA heterodimer will be determined against a panel of cell matric components (e.g. fibronectin, laminan, collagens). Native VLA structures on whole cells, and purified VLA in liposomes will be tested for adherence, and results will be confirmed using specific anti-VLA antibodies in blocking and cell surface modulation studies. (2) To determine the importance of arg-gly-asp (R-G-D) recognition in VLA- mediated adhesion, a) the inhibitory capacities or R-G-D- containing peptides will be tested, b) anti-alpha and anti-beta sera as well as alpha and/or beta liposomes will be used to evaluate the relative contributions of VLA subunits to R-G-D recognition, and c) peptides containing the R-G-D sequence will be specifically crosslinked to VLA proteins to identify the alpha or beta subunit(s) involved in R-G-D recognition. (3) To obtain basic structural information, genes for VLA subunits will be cloned and sequenced. Antisera to purified alpha subunits will be used to screen lamda gt11 cDNA libraries, and if necessary, probes based on known protein sequence will be used to screen lambda gt10 cDNA libraries. This information will a) allow detailed comparisons of VLA subunit structures and b) allow further comparisons within a broader """"""""super family"""""""" of more distantly related cell surface recognition structures such as LFA-1 and Mac-1 proteins. Specific cell adhesion to extracellular matrix proteins is a phenomenon of fundamental importance to tissue organization, cell migration, embryogenesis, neoplastic transformation and tumor cell metastasis. Thus structural information from detailed biochemical analyses of the VLA protein family now can provide a significant framework for organizing, comparing, and understanding the many diverse cell surface glycoproteins which have been implicated in cell matrix adhesion.
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