Binding of SGTA to Rpn13 selectively modulates protein quality control

Pawel Leznicki, Jelena Korac Prlic, Katarzyna Kliza, Koraljka Husnjak, Yvonne Nyathi, Ivan Dikic, Stephen High

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Rpn13 is an intrinsic proteasomal ubiquitin receptor that facilitates substrate capture prior to degradation. Here we show that the C-terminal region of Rpn13 binds to the tetratricopeptide repeat (TPR) domain of SGTA, a cytosolic factor implicated in the quality control of mislocalised membrane proteins (MLPs). The overexpression of SGTA results in a substantial increase in steady state MLP levels, consistent with an effect on proteasomal degradation. However, this effect is strongly dependent upon the interaction of SGTA with the proteasomal component Rpn13. Hence, overexpression of the SGTA binding region of Rpn13, or point mutations within the SGTA TPR domain, both inhibit SGTA binding to the proteasome and substantially reduce MLP levels. These findings suggest that SGTA can regulate the access of MLPs to the proteolytic core of the proteasome, implying that a protein quality control cycle involving SGTA and the BAG6 complex can operate at the 19S regulatory particle. We speculate that the binding of SGTA to Rpn13 may enable specific polypeptides to escape proteasomal degradation and/or selectively modulate substrate degradation.
Original languageEnglish
Pages (from-to)3187-3196
Number of pages9
JournalJournal of Cell Science
Issue number17
Publication statusPublished - 1 Sept 2015


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