12-O-Tetradecanoylphorbol-13-acetate-induced Dephosphorylation of Protein Kinase Cα Correlates with the Presence of a Membrane-associated Protein Phosphatase 2A Heterotrimer*
- From the Imperial Cancer Research Fund, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom
- § Friedrich Miescher Institute, P. O. Box 2543, CH 4002, Basel, Switzerland
- ¶To whom correspondence should be addressed.
Abstract
Protein kinase C signaling is desensitized through a combination of dephosphorylation and proteolysis in intact cells. The process of dephosphorylation is analyzed here, as well as its relationship to degradation. It is established for protein kinase Cα that dephosphorylation occurs in a membrane compartment following activation and temporally preceding significant degradation. The phosphatase responsible for the dephosphorylation appears to be a heterotrimeric type 2A phosphatase, which is shown to be in part constitutively membrane associated. Consistent with a role for this activity, okadaic acid is shown to inhibit the phorbol ester-induced dephosphorylation of protein kinase C that occurs in intact cells. Furthermore, phorbol ester-induced down-regulation of protein kinase Cα is shown not to be dependent on the rate of dephosphorylation, indicating that these desensitizing pathways may operate in parallel.
Footnotes
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↵* This work was suported in part by a fellowship from the European Commission (to F. B.) and as part of a European Commission Biomed Program (to P. J. P.). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- PKC
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protein kinase C
- TPA
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12-O-tetradecanoylphorbol-13-acetate
- PAGE
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polyacrylamide gel electrophoresis
- OA
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okadaic acid.
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↵2 P. J. Parker, unpublished observations.
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↵3 F. Bornancin and P. J. Parker, unpublished observations.
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- Received September 8, 1996.
- Revision received October 4, 1996.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
