TY - JOUR
T1 - Ubiquitination of protein kinase C-α and degradation by the proteasome
AU - Lee, Hyeon Woo
AU - Smith, Lucinda
AU - Pettit, George
AU - Vinitsky, Alexander
AU - Smith, Jeffrey Bingham
PY - 1996
Y1 - 1996
N2 - 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.
AB - 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.
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U2 - 10.1074/jbc.271.35.20973
DO - 10.1074/jbc.271.35.20973
M3 - Article
C2 - 8702857
AN - SCOPUS:0029812896
SN - 0021-9258
VL - 271
SP - 20973
EP - 20976
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 35
ER -