Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.25.1 (proteasome)
 28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane and secretory proteins that fail to pass quality control in the endoplasmic reticulum are discharged into the cytosol and degraded by the proteasome. Many of the mammalian components involved in this process remain to be identified. We performed a biochemical search for proteins that interact with SEL1L, a protein that is part of the mammalian HRD1 ligase complex and involved in substrate recognition. SEL1L is crucial for dislocation of Class I major histocompatibility complex heavy chains by the human cytomegalovirus US11 protein. We identified AUP1, UBXD8, UBC6e, and OS9 as functionally important components of this degradation complex in mammalian cells, as confirmed by mutagenesis and dominant negative versions of these proteins.
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PMID:SEL1L nucleates a protein complex required for dislocation of misfolded glycoproteins. 1871 Nov 32

Terminally misfolded proteins that accumulate in the endoplasmic reticulum (ER) are dislocated and targeted for ubiquitin-dependent destruction by the proteasome. UBC6e is a tail-anchored E2 ubiquitin-conjugating enzyme that is part of a dislocation complex nucleated by the ER-resident protein SEL1L. Little is known about the turnover of tail-anchored ER proteins. We constructed a set of UBC6e transmembrane domain replacement mutants and found that the tail anchor of UBC6e is vital for its function, its stability, and its mode of membrane integration, the last step dependent on the ASNA1/TRC40 chaperone. We constructed a tail-anchored UBC6e variant that requires for its removal from the ER membrane not only YOD1 and p97, two cytosolic proteins involved in the extraction of ER transmembrane or luminal proteins, but also UBXD8, AUP1 and members of the Derlin family. Degradation of tail-anchored proteins thus relies on components that are also used in other aspects of protein quality control in the ER.
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PMID:The transmembrane segment of a tail-anchored protein determines its degradative fate through dislocation from the endoplasmic reticulum. 2043 96

Quality control of endoplasmic reticulum proteins involves the identification and engagement of misfolded proteins, dislocation of the misfolded protein across the endoplasmic reticulum (ER) membrane, and ubiquitin-mediated targeting to the proteasome for degradation. Ancient ubiquitous protein 1 (AUP1) physically associates with the mammalian HRD1-SEL1L complex, and AUP1 depletion impairs degradation of misfolded ER proteins. One of the functions of AUP1 in ER quality control is to recruit the soluble E2 ubiquitin-conjugating enzyme UBE2G2. We further show that the CUE domain of AUP1 regulates polyubiquitylation and facilitates the interaction of AUP1 with the HRD1 complex and with dislocation substrates. AUP1 localizes both to the ER and to lipid droplets. The AUP1 expression level affects the abundance of cellular lipid droplets and as such represents the first protein with lipid droplet regulatory activity to be linked to ER quality control. These findings indicate a possible connection between ER protein quality control and lipid droplets.
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PMID:Dual role of ancient ubiquitous protein 1 (AUP1) in lipid droplet accumulation and endoplasmic reticulum (ER) protein quality control. 2185 22