Biomaterial Database

Growth of human melanocyte cultures supported by 12-O-tetradecanoylphorbol-13-acetate is mediated through protein kinase C activation. 1992

Y Arita, and K R O'Driscoll, and I B Weinstein

Comprehensive Cancer Center, Columbia University, New York, New York 10032.

To investigate the role of protein kinase C (PKC) in the 12-O-tetradecanoylphorbol-13-acetate (TPA)-dependent growth of human melanocytes, we analyzed the effects of phorbol ester treatment on both PKC expression and growth control in these cells. We found that established cultures of normal melanocytes contain the PKC alpha, PKC beta, and PKC epsilon isoforms. The abilities of various phorbol ester compounds to stimulate DNA synthesis in these cultured melanocytes correlated with their known potencies for activation of PKC and tumor promotion. Dose-response studies revealed that the most effective TPA concentration for stimulation of DNA synthesis and growth of melanocytes (10 ng/ml TPA) also supported a relatively high level of PKC enzyme activity, increased membrane association of the PKC alpha and PKC epsilon isoforms, and led to a high level of phosphorylation of a major PKC substrate, the myristoylated alanine-rich C kinase substrate (MARCKS) protein. Melanocytes incubated for 48 h with TPA at a higher concentration (100 ng/ml TPA) exhibited suboptimal TPA-stimulated DNA synthesis (28% of maximal) and decreased phosphorylation of the MARCKS substrate protein (50% of maximal). Furthermore, treatment of melanocytes with 100 ng/ml TPA for 48 h resulted in a marked decrease in total PKC enzyme activity and the loss of expression of the PKC alpha and PKC epsilon isoforms in both the cytosol and membrane-bound fractions, when examined by immunoblot analysis. These results, taken together, suggest that continuous activation of PKC by TPA, rather than the loss of PKC due to TPA-induced down-regulation, is responsible for the growth-stimulatory effects of phorbol esters on normal human melanocytes. Additionally, the conditioned medium from TPA-treated human melanocytes stimulated DNA synthesis in quiescent melanocytes and human melanoma cells, thus suggesting that activation of the PKC signaling pathway in melanocytes leads to the production of an autocrine growth factor. These findings may be relevant to the autonomous growth of malignant melanomas.

UI	MeSH Term	Description	Entries
D007527	Isoenzymes	Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.	Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D008544	Melanocytes	Mammalian pigment cells that produce MELANINS, pigments found mainly in the EPIDERMIS, but also in the eyes and the hair, by a process called melanogenesis. Coloration can be altered by the number of melanocytes or the amount of pigment produced and stored in the organelles called MELANOSOMES. The large non-mammalian melanin-containing cells are called MELANOPHORES.	Melanocyte
D008565	Membrane Proteins	Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.	Cell Membrane Protein,Cell Membrane Proteins,Cell Surface Protein,Cell Surface Proteins,Integral Membrane Proteins,Membrane-Associated Protein,Surface Protein,Surface Proteins,Integral Membrane Protein,Membrane Protein,Membrane-Associated Proteins,Membrane Associated Protein,Membrane Associated Proteins,Membrane Protein, Cell,Membrane Protein, Integral,Membrane Proteins, Integral,Protein, Cell Membrane,Protein, Cell Surface,Protein, Integral Membrane,Protein, Membrane,Protein, Membrane-Associated,Protein, Surface,Proteins, Cell Membrane,Proteins, Cell Surface,Proteins, Integral Membrane,Proteins, Membrane,Proteins, Membrane-Associated,Proteins, Surface,Surface Protein, Cell
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D010766	Phosphorylation	The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.	Phosphorylations
D011493	Protein Kinase C	An serine-threonine protein kinase that requires the presence of physiological concentrations of CALCIUM and membrane PHOSPHOLIPIDS. The additional presence of DIACYLGLYCEROLS markedly increases its sensitivity to both calcium and phospholipids. The sensitivity of the enzyme can also be increased by PHORBOL ESTERS and it is believed that protein kinase C is the receptor protein of tumor-promoting phorbol esters.	Calcium Phospholipid-Dependent Protein Kinase,Calcium-Activated Phospholipid-Dependent Kinase,PKC Serine-Threonine Kinase,Phospholipid-Sensitive Calcium-Dependent Protein Kinase,Protein Kinase M,Calcium Activated Phospholipid Dependent Kinase,Calcium Phospholipid Dependent Protein Kinase,PKC Serine Threonine Kinase,Phospholipid Sensitive Calcium Dependent Protein Kinase,Phospholipid-Dependent Kinase, Calcium-Activated,Serine-Threonine Kinase, PKC
D011506	Proteins	Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.	Gene Products, Protein,Gene Proteins,Protein,Protein Gene Products,Proteins, Gene
D002455	Cell Division	The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.	M Phase,Cell Division Phase,Cell Divisions,Division Phase, Cell,Division, Cell,Divisions, Cell,M Phases,Phase, Cell Division,Phase, M,Phases, M
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D004247	DNA	A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).	DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA