Serine phosphorylation facilitates protein degradation by the human mitochondrial ClpXP protease
Abstract
ClpXP is a two-component mitochondrial matrix protease. The caseinolytic mitochondrial matrix peptidase chaperone subunit X (ClpX) recognizes and translocates protein substrates into the degradation chamber of the caseinolytic protease P (ClpP) for proteolysis. ClpXP degrades damaged respiratory chain proteins and is necessary for cancer cell survival. Despite the critical role of ClpXP in mitochondrial protein quality control, the specific degrons, or modifications that tag substrate proteins for degradation by human ClpXP, are still unknown. We demonstrated that phosphorylated serine (pSer) targets substrates to ClpX and facilitates their degradation by ClpXP in biochemical assays. In contrast, ClpP hyperactivated by the small-molecule drug ONC201 lost the preference for phosphorylated substrates. Hydrogen deuterium exchange mass spectrometry combined with biochemical assays showed that pSer binds the RKL loop of ClpX. ClpX variants with substitutions in the RKL loop failed to recognize phosphorylated substrates. In intact cells, ClpXP also preferentially degraded substrates with pSer. Moreover, ClpX substrates with the pSer were selectively found in aggregated mitochondrial proteins. Our work uncovers a mechanism for substrate recognition by ClpXP, with implications for targeting acute myeloid leukemia and other disorders involving ClpXP dysfunction.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (28)
Yue Feng
Monica M. Goncalves
Yulia Jitkova
Alexander F. A. Keszei
Princess Margaret Cancer Center
Yongran Yan
Princess Margaret Cancer Centre, University Health Network
Chaitra Sarathy
Princess Margaret Cancer Centre, University Health Network
Jonathan St-Germain
Princess Margaret Cancer Centre, University Health Network
Tristan M. G. Kenney
Princess Margaret Cancer Centre, University Health Network
Matthew Tcheng
Vincent Trudel
Department of Chemistry, University of Toronto
Ross S. Mancini
Krembil Brain Institute, University Health Network
Rahul Upadhyay
Krembil Brain Institute, University Health Network
Rose Hurren
Princess Margaret Cancer Centre, University Health Network
Marcela Gronda
Princess Margaret Cancer Centre, University Health Network
Matthew Schultz
Princess Margaret Cancer Centre, University Health Network
Kaylen Soriano
Princess Margaret Cancer Centre, University Health Network
Kaitlin Lees
Princess Margaret Cancer Centre, University Health Network
Neil C. Pomroy
Princess Margaret Cancer Centre, University Health Network
S. Quinn W. Currie
Gilbert G. Privé
Princess Margaret Cancer Centre, University Health Network
Mark A. Reed
Department of Chemistry, University of Toronto
Andrei K. Yudin
Davenport Research Laboratories, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
Linda Z. Penn
Princess Margaret Cancer Centre, University Health Network
Cheryl H. Arrowsmith
Brian Raught
Mohammad T. Mazhab-Jafari
Princess Margaret Cancer Center
Siavash Vahidi
Aaron D. Schimmer