THE MAJOR MYRISTOYLATED PKC SUBSTRATE (MARCKS) IS INVOLVED IN CELL SPREADING, TYROSINE PHOSPHORYLATION OF PAXILLIN, AND FOCAL CONTACT FORMATION

The expression of the myristoylated PKC substrate MARCKS is reduced in tumor-derived choroidal melanoma cells (OCM-1), We transfected the OC M-1 cells with MARCKS cDNA and we selected clones with stable overexpr ession of the protein, Tyrosine phosphorylation of paxillin, a biochem ical marker of focal contact formation, was conserved upon serum starv ation when MARCKS was overexpressed, while it was almost abolished in the control cells. Immunofluorescent labelling of paxillin and vinculi n, another component of focal contact, revealed that these structures were conserved upon serum starvation when MARCKS was overexpressed but not in the control cells, Furthermore, the cell morphology was affect ed by the ectopic expression of MARCKS, leading to increased spreading and formation of membrane processes, These data suggest the involveme nt of MARCKS in cell spreading and focal contact formation. (C) 1997 F ederation of European Biochemical Societies.