title: Biphasic effects of 12-O-tetradecanoylphorbol-13-acetate on the cell morphology of low calcium-grown human epidermal carcinoma cells: involvement of translocation and down regulation of protein kinase C.
abstract: The present study was performed to investigate involvement of protein kinase C in the biphasic effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on cell morphology in low calcium (0.07 mM)-grown cells of a human epidermal squamous cell carcinoma cell line. The low calcium-grown cells formed no desmosomal cell-cell contact and showed roughly circular arrangements of keratin intermediate filaments around the nucleus. Treatment with 10 ng/ml of TPA induced a rapid formation (within 15 min) of cell-cell contact and reorganization of keratin intermediate filaments from a circular organization to a radial arrangement in these low calcium-grown cells. These structural phenomena were associated with a transient increase in membrane-bound protein kinase C activity. However, the prolonged treatment longer than 24 h led to a prominent decrease in the number of cell-cell contacts, that had been once formed, and caused fibroblastic changes of cell morphology in association with a decrease in the membrane-bound protein kinase C activity. Addition of 20 microM 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride, a potential inhibitor of protein kinase C, to the medium with TPA blocked the formation of cell-cell contact. Addition of 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride alone to normal calcium-grown cell cultures exhibiting cell-cell contact resulted in a decrease in the number of cell-cell contacts and in the fibroblastic morphological changes after 24-h incubation. These results suggest that the effects of TPA are biphasic as follows: the initial stage, inducing cell-cell contact formation associated with the translocation of protein kinase C activity from the cytosol to the membrane; and the late stage, exhibiting a fibroblastic morphological change with a decrease in the number of cell-cell contacts associated with the down regulation of this enzyme activity by TPA.
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000201:enzymology / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003470:Culture Media; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D007633:Keratins / Q000032:analysis; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity*
chemical_list: D002121:Calcium Channel Blockers; D003470:Culture Media; D007546:Isoquinolines; D010879:Piperazines; D007633:Keratins; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium