title: Phorbol ester binding and protein kinase C activity in normal and transformed human keratinocytes.
abstract: Normal keratinocytes, SV40-transformed keratinocytes (SVK14), and various squamous carcinoma cell (SCC) lines have been used as an in vitro model system to study the properties of phorbol ester receptor and protein kinase C expression during keratinocyte differentiation. The cell lines used exhibit a decreasing capacity to differentiate in the order of keratinocytes approximately SVK14 greater than SCC-12F2 greater than SCC-15 greater than SCC-4; moreover, all cell lines respond to a low external Ca2+ concentration by a decreased capacity to differentiate. Normal keratinocytes exhibited the highest number of phorbol ester receptors as compared to the other cell lines, while each individual cell line exhibited a higher number of phorbol ester receptors during growth under normal Ca2+ conditions as compared to cells grown under low Ca2+ conditions. The apparent dissociation constant (Kd) demonstrated only small variations in the various cell lines. In contrast, the cytoplasmic protein kinase C activity, was found to be higher in cells grown under low Ca2+ conditions than in cells grown under normal Ca2+ conditions, indicating the absence of a causal relationship between cytoplasmic protein kinase C activity and phorbol ester receptor expression. Therefore the properties of protein kinase C have been determined in more detail in normal keratinocytes and SCC-15 cells. These studies revealed differences between protein kinase C properties from the two cell lines grown under normal and low Ca2+ conditions. The differences included the effect of phorbol 12-myristate 13-acetate (PMA) on the redistribution pattern of protein kinase C between the cytoplasmic and particulate fractions as well as the activating effect of diolein in vitro on protein kinase C activity, partly purified from particulate or cytoplasmic fractions. These observations demonstrate that the functional protein kinase C activity of keratinocytes is determined by various endogenous and exogenous activators and that these activators are modulated differently in various cell lines, under various growth conditions (low Ca2+ versus normal Ca2+).
mesh_terms: D029742:Caenorhabditis elegans Proteins; D002273:Carcinogens / Q000378:metabolism; D002352:Carrier Proteins; D002460:Cell Line; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D000078404:Epidermal Cells; D004817:Epidermis / Q000201:enzymology / Q000276:immunology; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007633:Keratins / Q000378:metabolism; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011955:Receptors, Drug; D013539:Simian virus 40 / Q000235:genetics*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D029742:Caenorhabditis elegans Proteins; D002273:Carcinogens; D002352:Carrier Proteins; D010703:Phorbol Esters; D011955:Receptors, Drug; C083141:phorbol ester binding protein; C027776:phorbol ester receptor; D015240:Phorbol 12,13-Dibutyrate; D007633:Keratins; D066246:ErbB Receptors; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate