Bernasconi R, Galli C, Calanca V, Nakajima T, Molinari M. Stringent requirement for HRD1, SEL1L, and OS-9/XTP3-B for disposal of ERAD-LS substrates.
ACTA ACUST UNITED AC 2010;
188:223-35. [PMID:
20100910 PMCID:
PMC2812524 DOI:
10.1083/jcb.200910042]
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Abstract
Soluble ERAD substrates require the Hrd1 E3 ligase for degradation compared with membrane-anchored peptides that use GP78.
Sophisticated quality control mechanisms prolong retention of protein-folding intermediates in the endoplasmic reticulum (ER) until maturation while sorting out terminally misfolded polypeptides for ER-associated degradation (ERAD). The presence of structural lesions in the luminal, transmembrane, or cytosolic domains determines the classification of misfolded polypeptides as ERAD-L, -M, or -C substrates and results in selection of distinct degradation pathways. In this study, we show that disposal of soluble (nontransmembrane) polypeptides with luminal lesions (ERAD-LS substrates) is strictly dependent on the E3 ubiquitin ligase HRD1, the associated cargo receptor SEL1L, and two interchangeable ERAD lectins, OS-9 and XTP3-B. These ERAD factors become dispensable for degradation of the same polypeptides when membrane tethered (ERAD-LM substrates). Our data reveal that, in contrast to budding yeast, tethering of mammalian ERAD-L substrates to the membrane changes selection of the degradation pathway.
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