A protein interaction network for Ecm29 links the 26 S proteasome to molecular motors and endosomal components.
Ecm29 is a 200-kDa HEAT repeat protein that binds the 26 S proteasome. Genome-wide two-hybrid screens and mass spectrometry have identified molecular motors, endosomal components, and ubiquitin-proteasome factors as Ecm29-interacting proteins. The C-terminal half of human Ecm29 binds myosins and kinesins; its N-terminal region binds the endocytic proteins, Vps11, Rab11-FIP4, and rabaptin. Whereas full-length FLAG-Ecm29, its C-terminal half, and a small central fragment of Ecm29 remain bound to glycerol-gradient-separated 26 S proteasomes, the N-terminal half of Ecm29 does not. Confocal microscopy showed that Ecm-26 S proteasomes are present on flotillin-positive endosomes, but they are virtually absent from caveolin- and clathrin-decorated endosomes. Expression of the small central fragment of Ecm29 markedly reduces proteasome association with flotillin-positive endosomes. Identification of regions within Ecm29 capable of binding molecular motors, endosomal proteins, and the 26 S proteasome supports the hypothesis that Ecm29 serves as an adaptor for coupling 26 S proteasomes to specific cellular compartments.
Gorbea
Carlos
C
Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112, USA.
Pratt
Gregory
G
Ustrell
Vicença
V
Bell
Russell
R
Sahasrabudhe
Sudhir
S
Hughes
Robert E
RE
Rechsteiner
Martin
M
D000818:Animals; D011992:Endosomes / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D020409:Molecular Motor Proteins / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
D020409:Molecular Motor Proteins; D046988:Proteasome Endopeptidase Complex; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C497362:ECPAS protein, human; C424438:VPS11 protein, human; C061553:ATP dependent 26S protease