title: cAMP-induced phosphorylation of 26S proteasomes on Rpn6/PSMD11 enhances their activity and the degradation of misfolded proteins.
abstract: Although rates of protein degradation by the ubiquitin-proteasome pathway (UPS) are determined by their rates of ubiquitination, we show here that the proteasome's capacity to degrade ubiquitinated proteins is also tightly regulated. We studied the effects of cAMP-dependent protein kinase (PKA) on proteolysis by the UPS in several mammalian cell lines. Various agents that raise intracellular cAMP and activate PKA (activators of adenylate cyclase or inhibitors of phosphodiesterase 4) promoted degradation of short-lived (but not long-lived) cell proteins generally, model UPS substrates having different degrons, and aggregation-prone proteins associated with major neurodegenerative diseases, including mutant FUS (Fused in sarcoma), SOD1 (superoxide dismutase 1), TDP43 (TAR DNA-binding protein 43), and tau. 26S proteasomes purified from these treated cells or from control cells and treated with PKA degraded ubiquitinated proteins, small peptides, and ATP more rapidly than controls, but not when treated with protein phosphatase. Raising cAMP levels also increased amounts of doubly capped 26S proteasomes. Activated PKA phosphorylates the 19S subunit, Rpn6/PSMD11 (regulatory particle non-ATPase 6/proteasome subunit D11) at Ser14. Overexpression of a phosphomimetic Rpn6 mutant activated proteasomes similarly, whereas a nonphosphorylatable mutant decreased activity. Thus, proteasome function and protein degradation are regulated by cAMP through PKA and Rpn6, and activation of proteasomes by this mechanism may be useful in treating proteotoxic diseases.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115.
authors.forename: Sudarsanareddy
authors.initials: S
authors.lastname: Lokireddy
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115.
authors.forename: Nikolay Vadimovich
authors.initials: NV
authors.lastname: Kukushkin
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115 Alfred_Goldberg@hms.harvard.edu.
authors.forename: Alfred Lewis
authors.initials: AL
authors.lastname: Goldberg
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D015151:Immunoblotting; D009154:Mutation; D058988:Phosphodiesterase 4 Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D059748:Proteolysis / Q000187:drug effects; D020889:Rolipram / Q000494:pharmacology; D012694:Serine / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D058988:Phosphodiesterase 4 Inhibitors; D014665:Vasodilator Agents; D005576:Colforsin; D012694:Serine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C549955:PSMD11 protein, human; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D020889:Rolipram
keywords: Rpn6/PSMD11; cAMP; cAMP-dependent protein kinase; proteasomes; protein degradation