The met receptor degradation pathway: requirement for Lys48-linked polyubiquitin independent of proteasome activity.
Acute stimulation of the receptor for the hepatocyte growth factor/scatter factor Met leads to receptor monoubiquitination and down-regulation through the lysosomal degradation pathway. We have determined that the Met receptor undergoes multiple monoubiquitination as opposed to the appendage of polyubiquitin chains. Nevertheless, overexpression of ubiquitin in HEK293T cells enhances the rate of Met receptor degradation, in contrast to a point mutant of ubiquitin (K48R) that cannot form Lys(48)-linked polyubiquitin chains. Furthermore, an enhancement of Met degradation is also seen under conditions where the proteasome is inhibited by lactacystin. We propose that this reflects polyubiquitin-dependent sorting of Met, as the overexpression of ubiquitin but not K48R ubiquitin also restores hepatocyte growth factor-dependent phosphorylation of the endosomal coat protein Hrs from inhibition by lactacystin. Our data indicate a requirement for K48R-linked polyubiquitin for Met endosomal trafficking independent of its canonical function of targeting for proteasomal degradation.
Physiological Laboratory, University of Liverpool, Crown St. Liverpool L69 3BX, UK.
Stephanie
S
Carter
Sylvie
S
Urbé
Michael J
MJ
Clague
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D015536:Down-Regulation; D011992:Endosomes / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D017228:Hepatocyte Growth Factor / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008239:Lysine / Q000737:chemistry*; D008247:Lysosomes / Q000378:metabolism; D010766:Phosphorylation; D017354:Point Mutation; D025821:Polyubiquitin / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism; D051176:beta Catenin
C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D015534:Trans-Activators; D025801:Ubiquitin; D051176:beta Catenin; D025821:Polyubiquitin; C067713:lactacystin; D049452:Green Fluorescent Proteins; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; D046988:Proteasome Endopeptidase Complex; D008239:Lysine; D000111:Acetylcysteine