DIFFERENTIAL TRANSLOCATION OF PROTEIN-KINASE-C-EPSILON DURING HELA-CELL ADHESION TO A GELATIN SUBSTRATUM

The spreading of HeLa cells, following attachment to a collagen or gel atin substratum, requires the activation of protein kinase C (PKC). Me mbrane-bound PKC was previously shown to be activated during cell atta chment and in response to the activation of a series of lipid second m essengers turned on by the ligation of beta 1-integrin collagen recept ors. HeLa cells express the alpha, gamma, epsilon, zeta, lambda, and i ota isozymes of PKC as determined by Western blotting with specific an tibodies. Only PKC epsilon redistributed from the cytosol to the membr ane during cell adhesion. Most of the PKC epsilon in cells that were i n suspension was in the cytosolic fraction. During cell attachment to a gelatin matrix, all of the PKC epsilon moved out of the cytosol, wit h most going to the membrane fraction. After the cells became fully sp read, PKC epsilon began to reappear in the cytosol. Translocation of P KC epsilon was not observed during the adhesion of cells to culture di shes where cells nonspecifically attach but do not spread, The convent ional PKC alpha and -gamma isozymes were translocated from the cytosol to the membrane only when phorbol ester was present at a concentratio n that increases the rate and extent of cell spreading. Under normal c onditions, i.e. in the absence of phorbol ester, PKC epsilon appears t o be the PKC isozyme responsible for the regulation of HeLa cell adhes ion to the extracellular matrix.