STUDIES ON SIGNAL TRANSDUCTION AND CELLULAR FUNCTION OF ANTI-ADHESIVE MATRIX MOLECULES.

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Several extracellular matrix molecules with anti-adhesive activity have been reported but the mechanisms are yet unknown. Proteoglycan, PG-M/versican shows such an activity in Ca^<2+>-dependent manner through its chondroitin sulfate chain. We have firstly identified annexin VI as a cell surface receptor possibly involved in the signal transduction of the anti-adhesive activity. Transfection of annexin VI cDNA into A431 cells resulted in the localization of some of the expressed annexin VI on the cell surfaces shown by the FACS analysis and the cell attachment activity to chondroitin sulfate-coated dishes which the original cells never showed. Further, the gained cell attachment activity was specific to the chondroitin sulfate but not to other glycosaminoglycans and the unique structure of annexin VI was required for the activity. However, the newly developed magnetic bead assay for the elucidation of clustering signaling molecules revealed no detection of the molecules associating with the cell surface annexin VI.Curiously, there was the association of cytoplasmic annexin VI with fibronectin-coated beads. In addition, no significant inhibition to the anti-adhesive activity of PG-M/versican was observed with various reagents known to have inhibitory activities to signal transduction such as HA 1004. Furthermore, a line of evidences for no involvement of newly found Pyk2 family molecule, CAK were obtained. We are now taking different ways for the purpose by performing the experiments where the mutants of PG-M/versican or the spliced variants without chondroitin sulfate are being expressed in cells, tissues or animals to evaluate the anti-adhesive effects in situ.