title: A protein interaction network for Ecm29 links the 26 S proteasome to molecular motors and endosomal components.
abstract: 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.
authors.affiliation: Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84112, USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Gorbea
authors.forename: Gregory
authors.initials: G
authors.lastname: Pratt
authors.forename: Vicença
authors.initials: V
authors.lastname: Ustrell
authors.forename: Russell
authors.initials: R
authors.lastname: Bell
authors.forename: Sudhir
authors.initials: S
authors.lastname: Sahasrabudhe
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hughes
authors.forename: Martin
authors.initials: M
authors.lastname: Rechsteiner
mesh_terms: 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
chemical_list: 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