THE PROTEIN-KINASE-C ACTIVATOR TPA MODULATES CELLULAR-LEVELS AND DISTRIBUTION OF E-CADHERIN IN HT-29 HUMAN INTESTINAL EPITHELIAL-CELLS

The importance of E-cadherin protein in the establishment and maintena nce of homotypic contacts in epithelial cells has already been determi ned. We report here that the association of E-cadherin to cytoskeleton , required for the functionality of this protein, increases progressiv ely after seeding; in HT-29 M6 cells 4-5 days mere required for detect ing most of E-cadherin in the Triton X-100-insoluble (cytoskeleton-ass ociated) fraction. The phorbol ester TPA differently affected E-cadher in levels in HT-29 M6 cells; at day 2-3, when most E-cadherin was foun d not-associated to the cytoskeleton, very important decreases (90%) i n the total levels of this protein were detected as soon as 6 h after the addition of this compound. However, on later days (day 5), the pre dominant effect by 6 h was a translocation from the Triton-insoluble t o the soluble fraction. The E-cadherin-associated proteins alpha-caten in and beta-catenin were not significantly affected by treatment with TPA.