Activity and Regulation of the Centrosome-associated Proteasome

doi:10.1074/jbc.275.1.409

Activity and Regulation of the Centrosome-associated Proteasome*

From the Department of Physiology, The University of Texas Southwestern Medical Center, Dallas, Texas 75235

Abstract

Regulated proteolysis is important for maintaining appropriate cellular levels of many proteins. The bulk of intracellular protein degradation is catalyzed by the proteasome. Recently, the centrosome was identified as a novel site for concentration of the proteasome and associated regulatory proteins (Wigley, W. C., Fabunmi, R. P., Lee, M. G., Marino, C. R., Muallem, S., DeMartino, G. N., and Thomas, P. J. (1999) J. Cell Biol. 145, 481–490). Here we provide evidence that centrosomes contain the active 26 S proteasome that degrades ubiquitinated-protein and proteasome-specific peptide substrates. Moreover, the centrosomes contain an ubiquitin isopeptidase activity. The proteolytic activity is ATP-dependent and is inhibited by proteasome inhibitors. Notably, treatment of cells with inhibitors of proteasome activity promotes redistribution of the proteasome and associated regulatory proteins to the centrosome independent of an intact microtubule system. These data provide biochemical evidence for active proteasomal complexes at the centrosome, highlighting a novel function for this organizing structure.

Footnotes

↵* This work was supported by research Grants DK46181 (to G. N. D.) and DK49835 (to P. J. T.) from the NIDDK, National Institutes of Health, the Muscular Dystrophy Association (to G. N. D.), and Grant 9740033N from the American Heart Association (to P. J. T.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ Contributed equally to this work and are listed alphabetically.
↵§ Established Investigator of the American Heart Association.
↵¶ To whom correspondence may be addressed: Dept. of Physiology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75235. Tel.: (214) 648-3308; Fax: (214) 648-4771; E-mail: gdemar@mednet.swmed.edu.
↵‖ To whom correspondence may be addressed: Dept. of Physiology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75235. Tel.: (214) 648-8723; Fax: (214) 648-9268; E-mail: thomas07@utsw.swmed.edu.
↵2 Thrower, J. S., Hoffman, L., Rechsteiner, M., and Pickart, C. M. (2000) EMBO J., in press.
↵3 R. P. Fabunmi, W. C. Wigley, P. J. Thomas, and G. N. DeMartino, unpublished observations.
Abbreviations:

ER

endoplasmic reticulum

PCM

pericentriolar matrix

CFTR

cystic fibrosis transmembrane regulator

Ubal

ubiquitin aldehyde

Ub₅-DHFR

polyubiquitin-conjugated dihydrofolate reductase
- Received July 30, 1999.
- Revision received October 21, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.