Pei Yee Tey,Almut Dufner,Klaus-Peter Knobeloch,Jonathan N Pruneda,Michael J Clague,Sylvie Urbé
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Rapid turnover of CTLA4 is associated with a complex architecture of reversible ubiquitylation.
The immune checkpoint regulator CTLA4 is an unusually short-lived membrane protein. Here, we show that its lysosomal degradation is dependent on ubiquitylation at lysine residues 203 and 213. Inhibition of the v-ATPase partially restores CTLA4 levels following cycloheximide treatment, but also reveals a fraction that is secreted in exosomes. The endosomal deubiquitylase, USP8, interacts with CTLA4, and its loss enhances CTLA4 ubiquitylation in cancer cells, mouse CD4+ T cells, and cancer cell-derived exosomes. Depletion of the USP8 adapter protein, HD-PTP, but not ESCRT-0 recapitulates this cellular phenotype but shows distinct properties vis-à-vis exosome incorporation. Re-expression of wild-type USP8, but neither a catalytically inactive nor a localization-compromised ΔMIT domain mutant can rescue delayed degradation of CTLA4 or counteract its accumulation in clustered endosomes. UbiCRest analysis of CTLA4-associated ubiquitin chain linkages identifies a complex mixture of conventional Lys63- and more unusual Lys27- and Lys29-linked polyubiquitin chains that may underly the rapidity of protein turnover.
期刊介绍:
The Journal of Cell Biology (JCB) is a comprehensive journal dedicated to publishing original discoveries across all realms of cell biology. We invite papers presenting novel cellular or molecular advancements in various domains of basic cell biology, along with applied cell biology research in diverse systems such as immunology, neurobiology, metabolism, virology, developmental biology, and plant biology. We enthusiastically welcome submissions showcasing significant findings of interest to cell biologists, irrespective of the experimental approach.