AMSH is an endosome-associated ubiquitin isopeptidase.
The JAMM (JAB1/MPN/Mov34 metalloenzyme) motif has been proposed to provide the active site for isopeptidase activity associated with the Rpn11/POH1 subunit of the 19S-proteasome and the Csn5-subunit of the signalosome. We have looked for similar activity in associated molecule with the SH3 domain of STAM (AMSH), a JAMM domain-containing protein that associates with the SH3-domain of STAM, a protein, which regulates receptor sorting at the endosome. We demonstrate isopeptidase activity against K48-linked tetraubiquitin and K63-linked polyubiquitin chains to generate di-ubiquitin and free ubiquitin, respectively. An inactivating mutation (D348A) in AMSH leads to accumulation of ubiquitin on endosomes and the concomitant stabilization of a ubiquitinated form of STAM, which requires an intact ubiquitin interaction motif (UIM) within STAM. Short interfering RNA knockdown of AMSH enhances the degradation rate of EGF receptor (EGFR) following acute stimulation and ubiquitinated EGFR provides a substrate for AMSH in vitro. We propose that AMSH is a deubiquitinating enzyme with functions at the endosome, which oppose the ubiquitin-dependent sorting of receptors to lysosomes.
Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX, UK.
John
J
McCullough
Michael J
MJ
Clague
Sylvie
S
Urbé
D020816:Amino Acid Motifs; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002384:Catalysis; D015536:Down-Regulation; D010450:Endopeptidases; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008164:Luminescent Proteins / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D013997:Time Factors; D025801:Ubiquitin / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D018909:src Homology Domains
D002352:Carrier Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D008164:Luminescent Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; C486696:STAMBP protein, human; D025801:Ubiquitin; D049452:Green Fluorescent Proteins; D044767:Ubiquitin-Protein Ligases; D005982:Glutathione Transferase; D066246:ErbB Receptors; D010450:Endopeptidases; D043222:Ubiquitin Thiolesterase