Enzymatic blockade of the ubiquitin-proteasome pathway.
Enzymatic blockade of the ubiquitin-proteasome pathway.
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DOI：
10.1371/journal.pbio.1000605
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发表时间：
2011-03
期刊：
影响因子：
9.8
通讯作者：
Ploegh HL
中科院分区：
文献类型：
--
作者：
Ernst R;Claessen JH;Mueller B;Sanyal S;Spooner E;van der Veen AG;Kirak O;Schlieker CD;Weihofen WA;Ploegh HL
A viral ubiquitin-specific protease domain blocks cellular protein turnover by preemptive removal of ubiquitin chains and establishes an essential role for deubiquitylation in the removal of unfolded proteins from the endoplasmic reticulum. Ubiquitin-dependent processes control much of cellular physiology. We show that expression of a highly active, Epstein-Barr virus-derived deubiquitylating enzyme (EBV-DUB) blocks proteasomal degradation of cytosolic and ER-derived proteins by preemptive removal of ubiquitin from proteasome substrates, a treatment less toxic than the use of proteasome inhibitors. Recognition of misfolded proteins in the ER lumen, their dislocation to the cytosol, and degradation are usually tightly coupled but can be uncoupled by the EBV-DUB: a misfolded glycoprotein that originates in the ER accumulates in association with cytosolic chaperones as a deglycosylated intermediate. Our data underscore the necessity of a DUB activity for completion of the dislocation reaction and provide a new means of inhibition of proteasomal proteolysis with reduced cytotoxicity. Constant turnover of proteins is part of normal cellular physiology. Newly synthesized proteins that fail to fold are recognized by dedicated receptors and tagged for immediate degradation. The tag usually consists of a chain of a small protein, ubiquitin, and is recognized by the proteasome. We introduce a new tool to interfere with proteasomal degradation: a ubiquitin-specific protease domain (EBV-DUB) derived from Epstein-Barr Virus. This EBV-DUB, when expressed in mammalian cells, preemptively removes ubiquitin chains (deubiquitylation) and so frustrates substrate recognition and engagement by the proteasome. The natural history of misfolded, secretory proteins is poorly understood because of the strict coupling of recognition, tagging for degradation, and proteolysis. The EBV-DUB uncouples these processes and stabilizes short-lived intermediates, an activity that helped us to address the question of how such misfolded proteins are extracted from the relevant cellular compartments. Our data are consistent with the idea that unfolded substrates targeted for degradation are threaded through a narrow pore of the chaperone protein known as p97. In order to pass through the pore, the protein must first have any already attached ubiquitin chains removed; a second cycle of ubiquitylation is then required to allow engagement of the proteasome. Entry of substrate into the proteolytic chamber again requires removal of ubiquitin. We thus propose two rounds of ubiquitin attachment and removal in the course of the extraction and degradation of misfolded proteins.
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影响因子：
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通讯作者：
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