Activity and regulation of the centrosome-associated proteasome.
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.
Fabunmi
R P
RP
Department of Physiology, The University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
Wigley
W C
WC
Thomas
P J
PJ
DeMartino
G N
GN
D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002458:Cell Fractionation; D018385:Centrosome / Q000201:enzymology*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D010450:Endopeptidases / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006367:HeLa Cells; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism*; D015739:Nocodazole / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D014452:Ubiquitins / Q000378:metabolism
D015853:Cysteine Proteinase Inhibitors; D009097:Multienzyme Complexes; D014452:Ubiquitins; D000255:Adenosine Triphosphate; D013762:Tetrahydrofolate Dehydrogenase; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C091939:ubiquitin isopeptidase; D015739:Nocodazole