AMSH, an ESCRT-III associated enzyme, deubiquitinates cargo on MVB/late endosomes.
The appropriate sorting of vesicular cargo, including cell-surface proteins, is critical for many cellular functions. Ubiquitinated cargo is targeted to endosomes and digested by lysosomal enzymes. We previously identified AMSH, a deubiquitination enzyme (DUB), to be involved in vesicular transport. Here, we purified an AMSH-binding protein, CHMP3, which is an ESCRT-III subunit. ESCRT-III functions on maturing endosomes, indicating AMSH might also play a role in MVB/late endosomes. Expression of an AMSH mutant lacking CHMP3-binding ability resulted in aberrant endosomes with accumulations of ubiquitinated cargo. Nevertheless, CHMP3-binding capability was not essential for AMSH's in vitro DUB activity or its endosomal localization, suggesting that, in vivo, the deubiquitination of endosomal cargo is CHMP3-dependent. Ubiquitinated cargo also accumulated on endosomes when catalytically inactive AMSH was expressed or AMSH was depleted. These results suggest that both the DUB activity of AMSH and its CHMP3-binding ability are required to clear ubiquitinated cargo from endosomes.
Kyuuma
Masanao
M
Department of Microbiology and Immunology, Tohoku University Graduate School of Medicine, Seiryo-machi, Sendai, 980-8575 Japan.
Kikuchi
Kazu
K
Kojima
Katsuhiko
K
Sugawara
Yuriko
Y
Sato
Mariko
M
Mano
Nariyasu
N
Goto
Junichi
J
Takeshita
Toshikazu
T
Yamamoto
Akitsugu
A
Sugamura
Kazuo
K
Tanaka
Nobuyuki
N
D002384:Catalysis; D002460:Cell Line; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding; D025801:Ubiquitin / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase
C498543:CHMP3 protein, human; D056827:Endosomal Sorting Complexes Required for Transport; D009419:Nerve Tissue Proteins; C486696:STAMBP protein, human; D025801:Ubiquitin; D010450:Endopeptidases; D043222:Ubiquitin Thiolesterase