Transformation-sensitive localization of alpha-protein kinase C at cell-cell contacts in rat renal proximal tubule epithelial cells.

Immunocytofluorescence studies were used to compare alpha-protein kinase C (PKC) localization in primary cultures of renal proximal tubule epithelial cells (RPTE) with E1A-immortalized and SV40-transformed derivatives. Both cytosolic and nuclear staining were apparent in all of the RPTE. In primary RPTE, Triton X-100-insoluble alpha-PKC was also apparent and was concentrated in cell junctions. Cell junction alpha-PKC was diminished in E1A-immortalized and absent from SV40-transformed RPTE, even though total cellular content was not decreased. These results emphasize that subcellular location may play an important role in regulating signal transduction through PKC-dependent pathways. Phorbol ester treatment induced cell membrane ruffling in primary RPTE, and alpha-PKC was redistributed to membrane ruffles. However, the redistributed alpha-PKC was Triton soluble and, therefore, was distinct from cell junction alpha-PKC. The loss of alpha-PKC from cell junctions in phorbol ester-treated and oncogene-altered cells suggests that there are cellular determinants regulating alpha-PKC association with junctional complexes.