Ubiquitination of protein kinase C-α and degradation by the proteasome

Hyeon Woo Lee, Lucinda Smith, George Pettit, Alexander Vinitsky, Jeffrey Bingham Smith

Research output: Contribution to journalArticlepeer-review

145 Scopus citations


Bryostatins and phorbol esters acutely activate and subsequently down- regulate protein kinase C (PKC) by inducing its proteolysis via an unknown pathway. Here we show that treatment of renal epithelial cells with bryostatin 1 (Bryo) produced novel PKC-α species, which were larger than the native protein (80 kDa). The >80 kDa PKC-α species contained Ubi as indicated by immunostaining and accumulated in the presence of lactacystin, a selective inhibitor of proteolysis by the proteasome. In vitro experiments with 125I-ubiquitin and membranes from Bryo-treated cells showed that PKC- α became ubiquitinated by a reaction that depended on ATP and a cytosolic fraction. Lactacystin or a peptidyl aldehyde, Bz-Gly-Leu-Ala-leucinal, which inhibits certain proteinase activities of the proteasome, inhibited Bryo- evoked disappearance of PKC-α protein from the cells. Lacta preserved Bryo- induced 32P-labeled PKC-α indicating that the proteasome inhibitor spared activated enzyme from down-regulation in vivo. These findings show that Bryo induces the degradation of PKC-α by the ubiquitin-proteasome complex.

Original languageEnglish (US)
Pages (from-to)20973-20976
Number of pages4
JournalJournal of Biological Chemistry
Issue number35
StatePublished - 1996

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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