Osmotic stress inhibits proteasome by p38 MAPK-dependent phosphorylation.
Osmotic stress causes profound perturbations of cell functions. Although the adaptive responses required for cell survival upon osmotic stress are being unraveled, little is known about the effects of osmotic stress on ubiquitin-dependent proteolysis. We now report that hyperosmotic stress inhibits proteasome activity by activating p38 MAPK. Osmotic stress increased the level of polyubiquitinated proteins in the cell. The selective p38 inhibitor SB202190 decreased osmotic stress-associated accumulation of polyubiquitinated proteins, indicating that p38 MAPK plays an inhibitory role in the ubiquitin proteasome system. Activated p38 MAPK stabilized various substrates of the proteasome and increased polyubiquitinated proteins. Proteasome preparations purified from cells expressing activated p38 MAPK had substantially lower peptidase activities than control proteasome samples. Proteasome phosphorylation sites dependent on p38 were identified by measuring changes in the extent of proteasome phosphorylation in response to p38 MAPK activation. The residue Thr-273 of Rpn2 is the major phosphorylation site affected by p38 MAPK. The mutation T273A in Rpn2 blocked the proteasome inhibition that is mediated by p38 MAPK. These results suggest that p38 MAPK negatively regulates the proteasome activity by phosphorylating Thr-273 of Rpn2.
Department of Biochemistry and Translational Research Center for Protein Function Control, Yonsei University, Seoul 120-749, Korea.
Seung-Hoon
SH
Lee
Yoon
Y
Park
Sungjoo Kim
SK
Yoon
Jong-Bok
JB
Yoon
D000255:Adenosine Triphosphate / Q000737:chemistry*; D001665:Binding Sites; D006367:HeLa Cells; D006602:Hexosyltransferases; D006801:Humans; D020935:MAP Kinase Signaling System; D013058:Mass Spectrometry / Q000379:methods; D009995:Osmosis; D010455:Peptides / Q000737:chemistry; D010748:Phosphopeptides / Q000737:chemistry; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism; D061988:Proteasome Inhibitors; D011485:Protein Binding; D025801:Ubiquitin / Q000737:chemistry*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D010455:Peptides; D010748:Phosphopeptides; D061988:Proteasome Inhibitors; D025801:Ubiquitin; D000255:Adenosine Triphosphate; D006602:Hexosyltransferases; C517590:RPN2 protein, human; D048051:p38 Mitogen-Activated Protein Kinases; D046988:Proteasome Endopeptidase Complex