Proteasome-mediated degradation of RNase L in response to phorbol-12-myristate-13-acetate (PMA) treatment of mouse L929 cells.
2'-5' Oligoadenylate (2-5A)-dependent RNase L is one of the key enzymes involved in the molecular mechanisms of interferon (IFN) function. Although the regulation of RNase L by 2-5A has been studied extensively, relatively little is known about how RNase L is controlled by posttranslational processes. Here, we report that phorbol-12-myristate-13-acetate (PMA) treatment of mouse L929 fibroblasts caused rapid degradation of RNase L in a dose-dependent and time-dependent manner. RNase L levels were decreased to 40% of control levels after only 5 min exposure of cells to PMA, suggesting the involvement of protein kinase C (PKC). After PMA treatment for 1 h, RNase L levels decreased to 18% of the pretreatment levels. Decay of RNase L was measured by 2-5A binding assay, ribonuclease activity, and protein levels in Western blots probed with antibody to murine RNase L. PMA treatment caused decreases in the levels of RNase L in both cytoplasm and nucleus. To explore the mechanism of RNase L degradation, we treated cells with the selective proteasome inhibitors, ALLN, MG132, and PSI, prior to PMA treatment. These inhibitors completely blocked the degradation of RNase L caused by PMA. Our results show a novel regulatory pathway for RNase L that could have an impact on its antitumor and antiviral functions.
Chase
Barbara I
BI
Department of Chemistry, Cleveland State University, Cleveland, OH 44115, USA.
Zhou
Yan
Y
Xiang
Ying
Y
Silverman
Robert H
RH
Zhou
Aimin
A
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004722:Endoribonucleases / Q000378:metabolism*; D016898:Interferon-alpha / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology; D051379:Mice; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D021381:Protein Transport / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D016898:Interferon-alpha; D007976:Leupeptins; D009097:Multienzyme Complexes; D009842:Oligopeptides; C090535:benzyloxycarbonyl-isoleucyl-glutamyl(O-tert-butyl)-alanyl-leucinal; C063261:acetylleucyl-leucyl-norleucinal; C016658:phorbolol myristate acetate; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D013755:Tetradecanoylphorbol Acetate; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde