Protein kinase C V3 domain mutants with differential sensitivities to m-calpain are not resistant to phorbol-ester-induced down-regulation.
Distinct linker sequences were introduced into the protease-sensitive V3 domain of protein kinase C-alpha and the mutant proteins were expressed in COS-1 cells. Partially purified preparations of these mutants were functionally similar to wild-type protein kinase C-alpha, however their susceptibility to m-calpain was quite distinct, with one mutant being insensitive to cleavage. The three mutants, after expression in COS-1 cells, were found to behave in a manner indistinguishable from wild-type protein kinase C-alpha with respect to subcellular distribution, acute responses to 12-O-tetradecanoyl-phorbol 13-acetate and 12-O-tetradecanoyl-phorbol-13-acetate-induced down-regulation. The data imply that down-regulation of protein kinase C-alpha is likely to involve a general degradative process rather than cleavage by a site-specific protease.
Protein Phosphorylation Laboratory, Imperial Cancer Research Fund, London, England.
M
M
Junco
C
C
Webster
C
C
Crawford
L
L
Bosca
P J
PJ
Parker
D000595:Amino Acid Sequence; D000818:Animals; D002154:Calpain / Q000494:pharmacology*; D002417:Cattle; D002478:Cells, Cultured; D015536:Down-Regulation; D006868:Hydrolysis; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011493:Protein Kinase C / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D011493:Protein Kinase C; D002154:Calpain; D013755:Tetradecanoylphorbol Acetate