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- Title
Differential Down-Regulation of Protein Kinase C Subspecies in Normal Human Melanocytes: Possible Involvement of the ζ Subspecies in Growth Regulation.
- Authors
Oka, Masahiro; Ogita, Kouji; Ando, Hideya; Kikkawa, Ushio; Ichihashi, Masamitsu
- Abstract
Normal human melanocytes are often grown <em>in vitro</em> in the continuous presence of 12-O-tetradecanoylphorbol-13-acetate (TPA) for growth <em>in vitro</em>. The expression of protein kinase C (PKC) subspecies, which are the major cellular receptors for phorbol esters, was examined in melanocytes after long-term treatment with TPA to investigate the role of PKC subspecies in TPA-dependent cell growth. The PKC enzyme activity detected in quiescent melanocytes was almost completely depleted in cells after incubation with 85 nM TPA for 48 h. Immunoblot analysis indicated that, among the PKC subspecies α, β, δ, ε, and ζ expressed in quiescent cells, α-, β-, δ-, and ε-PKC were significantly down-regulated, whereas ζ-PKC remained at detectable levels in TPA-treated cells. TPA did not significantly affect the expression or subcellular distribution of ζ-PKC in melanocytes. Immunoprecipitation assay revealed that the enzyme activity of ζ-PKC was increased in both the cytosol and particulate cell fractions, but the increase was much greater in the latter. The activation of ζ-PKC lasted for 24 to 48 h after the addition of TPA; thereafter, ζ-PKC activity returned to basal levels. DNA synthesis was shown to change concomitantly with the activation of ζ-PKC in TPA-treated cells. These results indicate that TPA induces not only the down-regulation of α-, β-, δ-, and ε-PKC, but also long-term activation of ζ-PKC in melanocytes, and that activation of ζ-PKC parallels the growth of normal human melanocytes.
- Subjects
PROTEIN kinase C; PROTEIN kinases; MELANOCYTES; EPITHELIAL cells; GROWTH regulators; GENES
- Publication
Journal of Investigative Dermatology, 1995, Vol 105, Issue 4, p567
- ISSN
0022-202X
- Publication type
Article
- DOI
10.1111/1523-1747.ep12323485