A phorbol ester and phospholipid-activated, calcium-unresponsive protein kinase in mouse epidermis: Characterization and separation from protein kinase C
✍ Scribed by M. Gschwendt; W. Kittstein; F. Horn; H. Leibersperger; F. Marks
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 748 KB
- Volume
- 40
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
The phosphorylation of an Mr 82,000 protein (p82) in the Triton X-100 extract of the particulate fraction of mouse epidermis is dependent on the phorbol ester 1 2-O-tetradecanoylphorbol-13-acetate (TPA) or diacylglycerol and phospholipid and, contrary to protein kinase C (PKC)-catalyzed phosphorylation, cannot be activated by calcium plus phospholipid. The novel p82 kinase differs also from PKC in many other respects, such as substrate specificity, turnover rate, and sensitivity to inhibitors. The p82 kinase can be separated from PKC by chromatography on phenyl sepharose and does not react with a polyclonal PKC antiserum. Like PKC, the novel kinase phosphorylates its substrate on threonine and serine, but not on tyrosine. Similar to PKC, the epidermal p82-kinase system is downmodulated after TPA treatment of mouse skin, with a half-life of around 5 h. Down-modulation is also accomplished by the phorbol ester RPA, but not by the CaZ ' ionophore A23 187, and it is inhibited by the immunosuppressive agent cyclosporin A. In addition to down-modulation, TPA treatment of the animals activates a phosphatase that dephosphorylates phosphorylated p82 in the extract of the particulate fraction.