Regulation of both PDK1 and the phosphorylation of PKC-zeta and -delta by a C-terminal PRK2 fragment

Hodgkinson, Conrad P. and Sale, Graham J. (2002) Regulation of both PDK1 and the phosphorylation of PKC-zeta and -delta by a C-terminal PRK2 fragment. Biochemistry, 41 (2), 561-569. (doi:10.1021/bi010719z).

Abstract

The mechanism by which PDK1 regulates AGC kinases remains unclear. To further understand this process, we performed a yeast two-hybrid screen using PDK1 as bait. PKC-, PKC-, and PRK2 were identified as interactors of PDK1. A combination of yeast two-hybrid binding assays and coprecipitation from mammalian cells was used to characterize the nature of the PDK1-PKC interaction. The presence of the PH domain of PDK1 inhibited the interaction of PDK1 with the PKCs. A contact region of PDK1 was mapped between residues 314 and 408. The interaction of PDK1 with the PKCs required the full-length PKC- and - proteins apart from their C-terminal tails. PDK1 was able to phosphorylate full-length PKC- and - but not PKC- and - constructs containing the PDK1 phosphorylation site but lacking the C-terminal tails. A C-terminal PRK2 fragment, normally produced by caspase-3 cleavage during apoptosis, inhibited PDK1 autophosphorylation by >90%. The ability of PDK1 to phosphorylate PKC- and - in vitro was also markedly inhibited by the PRK2 fragment. Additionally, generation of the PRK2 fragment in vivo inhibited by >90% the phosphorylation of endogenous PKC- by PDK1. In conclusion, these results show that the C-terminal tail of PKC is a critical determinant for PKC- and - phosphorylation by PDK1. Moreover, the C-terminal PRK2 fragment acts as a potent negative regulator of PDK1 autophosphorylation and PDK1 kinase activity against PKC- and -. As the C-terminal PRK2 fragment is naturally generated during apoptosis, this may provide a mechanism of restraining prosurvival signals during apoptosis.

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