Characterization of mammalian Ecm29, a 26 S proteasome-associated protein that localizes to the nucleus and membrane vesicles.
In addition to its thirty or so core subunits, a number of accessory proteins associate with the 26 S proteasome presumably to assist in substrate degradation or to localize the enzyme within cells. Among these proteins is ecm29p, a 200-kDa yeast protein that contains numerous HEAT repeats as well as a putative VHS domain. Higher eukaryotes possess a well conserved homolog of yeast ecm29p, and we produced antibodies to three peptides in the human Ecm29 sequence. The antibodies show that Ecm29 is present exclusively on 26 S proteasomes in HeLa cells and that Ecm29 levels vary markedly among mouse organs. Confocal immunofluorescence microscopy localizes Ecm29 to the centrosome and a subset of secretory compartments including endosomes, the ER and the ERGIC. Ecm29 is up-regulated 2-3-fold in toxinresistant mutant CHO cells exhibiting increased rates of ER-associated degradation. Based on these results we propose that Ecm29 serves to couple the 26 S proteasome to secretory compartments engaged in quality control and to other sites of enhanced proteolysis.
Gorbea
Carlos
C
Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA.
Goellner
Geoffrey M
GM
Teter
Ken
K
Holmes
Randall K
RK
Rechsteiner
Martin
M
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D001923:Brain Chemistry; D016466:CHO Cells; D002417:Cattle; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry*; D018385:Centrosome / Q000737:chemistry; D006224:Cricetinae; D003412:Cricetulus; D003593:Cytoplasm / Q000737:chemistry; D022162:Cytoplasmic Vesicles / Q000737:chemistry*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D011992:Endosomes / Q000737:chemistry; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000032:analysis* / Q000737:chemistry / Q000502:physiology; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D011467:Prostate; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000378:metabolism*
D000906:Antibodies; C497362:ECPAS protein, human; D009687:Nuclear Proteins; D010446:Peptide Fragments; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease