The first overall goal of this proposal is to characterize two newly discovered heterodimers in the VLA adhesion receptor family. Functions are not known for the newly discovered VLA-G and VLA-7, but it is strongly suspected that they both may mediate cell attachment to extracallular matrix. The second overall goal of the proposal is to characterize a novel alternate beta"""""""" subunit which sometimes may replace the alpha6 subunit of VLA-6. The association of a6 with this """"""""alternate beta"""""""" subunit (here called alpha6BP) represents an important exception to the customary alpha- beta subunit association pattern seen for all of the other known members of the integrin superfamily of cell adhesion molecules. To accomplish these two goals, the following specific aims will be carried out: (1) Monoclonal and polyclonal antibodies will be prepared against alpha6BP, VLA6 and VLA-7 subunits. (2) Antibodies recognizing VLA-6, VLA-7 and alpha6BP will be used to determine the cell surface distribution of these structures on a panel of normal and transformed cell, and also their subcellular locative relative to adhesion plaque proteins will be analyzed by fluorescence microscopy. (3) Biochemical analyses of VLA-6, VLA-7 and alpha6BP structures will include i) subunit processing and association as studied in metabolic labeling experiments, ii) two dimension O'Farrell gels and peptide maps, and iii) studies of the proteolytic interconversior of different forms of alpha6BP. (4) antibodies directed against VLA-6, VLA-7 and alpha6BP will be tested for ability to block cell adherence extracellular matrix components. (5) The alpha subunit of VLA-6 and that alpha6BP protein will be cloned from lambda gt11 expression libraries, and the cDNA will be sequenced. (6) The synthesis and phosphorylation of VLA-6, VLA-7 and alpha6BP will be studied in comparison to other VLA heterodimers in response to stimuli such as TGFbeta and vitamin D. The VLA proteins serve as a vital transmembrane link between the extracullular matrix and cytoskeleton. In that capacity, that are of fundamental importance to tissue organization, cell migration and differentiation, embryogenesis, and cell transformation and metastasis. The detailed knowledge gained from this proposal will greatly aid in the understanding of these processes.
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