Phosphorylation is required for PMA- and cell-cycle-induced degradation of protein kinase Cdelta.
Classical and novel protein kinase C (PKC) isoforms are down-regulated as a result of chronic activation by certain tumour promoters and physiological stimuli; however, the mechanisms leading to down-regulation are not fully understood. In the present study, we have studied the PMA ('TPA')-induced degradation of PKCdelta in NIH 3T3 cells under culture conditions where PKCdelta displays cell-cycle-dependent down-regulation. In contrast with previous studies, a hyperphosphorylated form of this PKC isoform, promoted by calyculin A, was rapidly degraded in PMA-treated cells. Similarly, the presence of calyculin A enhanced the down-regulation of PKCdelta observed on G(1)/S-phase progression through the cell cycle. Analysis of phosphorylation-site mutants indicated that the T-loop Thr(505) phosphorylation site was critical for induced degradation.
Protein Phosphorylation Laboratory, Cancer Research UK London Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, U.K.
Jyoti
J
Srivastava
Katarzyna J
KJ
Procyk
Xavier
X
Iturrioz
Peter J
PJ
Parker
D016475:3T3 Cells; D000818:Animals; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D015536:Down-Regulation; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism*; D008387:Marine Toxins; D051379:Mice; D010080:Oxazoles / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D051745:Protein Kinase C-delta; D016196:S Phase / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013912:Threonine / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism
D007527:Isoenzymes; D008387:Marine Toxins; D010080:Oxazoles; D025801:Ubiquitin; D013912:Threonine; C059041:calyculin A; C497259:Prkcd protein, mouse; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D013755:Tetradecanoylphorbol Acetate