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Ataxin3 Deubiquitination Activity is Stimulated by Association with Specific Binding Partners
Author(s) -
Rao Maya V.,
Loll Patrick J.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.816.1
Subject(s) - endoplasmic reticulum , ubiquitin , microbiology and biotechnology , protease , cytosol , chemistry , ubiquitin ligase , protein degradation , biochemistry , enzyme , biology , gene
Ataxin3 is a cysteine protease that carries out deubiquitination (DUB) and contributes to protein quality control in the cell. It specifically interacts with the molecular motor protein p97 to extract misfolded protein substrates from the endoplasmic reticulum to the cytosol, and thus plays a crucial role in endoplasmic ‐reticulum‐associated degradation. The extraction depends on the ubiquitination of the substrate, which helps recruit p97 and also tags the substrate for degradation. We believe this tag is trimmed or cleaved by ataxin3 to facilitate entry of the substrate into the extraction or degradation apparatus. Furthermore, ataxin3 also directly recognizes and binds both mono‐ubiquitin and poly‐ubiquitin chains. We propose that ataxin3 interacts with both p97 and the ubiquitinated substrate, forming an active complex enabling cleavage of the ubiquitin chain and handoff of the substrate to the degradation machinery. Using surface plasmon resonance, we have characterized the affinity of p97 for ataxin3, and assessed the effect of p97's nucleotide‐binding state on its association with ataxin3. We also propose that ataxin3's DUB activity is regulated by its interaction with these binding partners. By use of a fluorogenic enzyme assay, we have shown that ataxin3 activity is enhanced in the presence of ubiquitin and is further increased by p97. Such robust stimulation of DUB activity has not been described previously.