The cytosolic tail of class I MHC heavy chain is required for its dislocation by the human cytomegalovirus US2 and US11 gene products

Story, Craig M.; Furman, Margo H.; Ploegh, Hidde L.

doi:10.1073/pnas.96.15.8516

Cited by 75 publications

(74 citation statements)

References 37 publications

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“…3c) was longer than that of endogenous heavy chain, which has been reported to bẽ 3-5 min (Wiertz et al, 1996b). The observation that the chimeric class I molecules were degraded with slower kinetics than endogenous heavy chains (Fiebiger et al, 2002;Story et al, 1999;Tirosh et al, 2003). Nevertheless, these results imply that chimeric HC-CTAP molecules were targeted for the proteasomal degradation in US2-expressing cells.…”

Section: Hc-ctap Is Degraded In a Gpus2-dependent Mannercontrasting

confidence: 47%

Endoplasmic reticulum chaperones participate in human cytomegalovirus US2-mediated degradation of class I major histocompatibility complex molecules

Orešić

Tortorella

2008

Journal of General Virology

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Inhibition of cell-surface expression of major histocompatibility complex class I molecules by human cytomegalovirus (HCMV, a b-herpesvirus) promotes escape from recognition by CD8 + cytotoxic T cells. The HCMV US2 and US11 gene products induce class I downregulation during the early phase of HCMV infection by facilitating the degradation of class I heavy chains. The HCMV proteins promote the transport of the class I heavy chains across the endoplasmic reticulum (ER) membrane into the cytosol by a process referred to as 'dislocation', which is then followed by proteasome degradation. This process has striking similarities to the degradation of misfolded ER proteins mediated by ER quality control. Even though the major steps of the dislocation reaction have been characterized, the cellular proteins, specifically the ER chaperones involved in targeting class I for dislocation, have not been fully delineated. To elucidate the chaperones involved in HCMV-mediated class I dislocation, we utilized a chimeric class I heavy chain with an affinity tag at its carboxy terminus. Interestingly, US2 but not US11 continued to target the class I chimera for destruction, suggesting a structural limitation for US11-mediated degradation. Association studies in US2 cells and in cells that express a US2 mutant, US2-186HA, revealed that class I specifically interacts with calnexin, BiP and calreticulin. These findings demonstrate that US2-mediated class I destruction utilizes specific chaperones to facilitate class I dislocation. The data suggest a more general model in which the chaperones that mediate protein folding may also function during ER quality control to eliminate aberrant ER proteins.

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Section: Hc-ctap Is Degraded In a Gpus2-dependent Mannercontrasting

confidence: 47%

Endoplasmic reticulum chaperones participate in human cytomegalovirus US2-mediated degradation of class I major histocompatibility complex molecules

Orešić

Tortorella

2008

Journal of General Virology

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“…Our findings suggest the cellular mechanism of MHC I dislocation is different from that used by these viral proteins. In contrast to HRD1-mediated dislocation, the MHC I cytosolic tail is essential for US11-mediated dislocation and tailless HLA-A2 is stabilized in US11-expressing cells, despite the interaction with US11 being preserved (22). US11-mediated MHC I dislocation does not require lysine residues (23,24), so ubiquitination may be targeted to nonlysine residues in the MHC I tail.…”

Section: Discussionmentioning

confidence: 99%

“…Similar to HRD1-mediated MHC I dislocation, lysineless MHC I HCs are dislocated in US11-expressing cells with delayed kinetics of degradation (24). US2 interacts with the luminal domain of conformational, β2m-associated MHC I HC, but requires the MHC I transmembrane domain, and possibly tail residues, to mediate dislocation (22,25). Mutation of cytosolic tail lysines results in a marked loss of US2-induced ubiquitination of membrane-associated MHC I HCs, implying that TRC8 preferentially targets lysine residues in the MHC I tail (26).…”

Section: Discussionmentioning

confidence: 99%

MHC class I molecules are preferentially ubiquitinated on endoplasmic reticulum luminal residues during HRD1 ubiquitin E3 ligase-mediated dislocation

Burr

Boomen

Bye

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Misfolded MHC class I heavy chains (MHC I HCs) are targeted for endoplasmic reticulum (ER)-associated degradation (ERAD) by the ubiquitin E3 ligase HRD1, and E2 ubiquitin conjugating enzyme UBE2J1, and represent one of the few known endogenous ERAD substrates. The mechanism by which misfolded proteins are dislocated across the ER membrane into the cytosol is unclear. Here, we investigate the requirements for MHC I ubiquitination and degradation and show that endogenous misfolded MHC I HCs are recognized in the ER lumen by EDEM1 in a glycan-dependent manner and targeted to the core SEL1L/HRD1/UBE2J1 complex. A soluble MHC I HC lacking its transmembrane domain and cytosolic tail uses the same ERAD components and is degraded as efficiently as wildtype MHC I. Unexpectedly, HRD1-dependent polyubiquitination is preferentially targeted to the ER luminal domain of full-length MHC I HCs, despite the presence of an exposed cytosolic C-terminal tail. MHC I luminal domain ubiquitination occurs before p97 ATPase-mediated extraction from the ER membrane and can be targeted to nonlysine, as well as lysine, residues. A subset of integral membrane proteins, therefore, requires an early dislocation event to expose part of their luminal domain to the cytosol, before HRD1-mediated polyubiquitination and dislocation.T he assembly and regulated expression of plasma membrane and secreted proteins is fundamentally reliant on effective endoplasmic reticulum quality control (ERQC). Endoplasmic reticulum (ER)-associated degradation (ERAD) is central to ERQC, selectively disposing of misfolded or surplus proteins to maintain ER homeostasis. ERAD involves recognition, ubiquitination, and retrotranslocation of substrates from the ER to the cytosol for proteasome-mediated degradation (1). Polyubiquitination of the substrate is critical, both for facilitating ER membrane extraction by the p97 ATPase-ubiquitin fusion degradation 1 (Ufd1)-nuclear protein localization 4 (Npl4) complex (2-4) and for delivery to the proteasome. However, the precise role of ubiquitin in the actual dislocation event is unclear.The cellular ERAD machinery consists of multiprotein complexes, typically comprising a membrane-embedded ubiquitin E3 ligase, which engages substrates directly or via ER luminal adaptors (1). Different substrates degraded by the same E3 may use distinct ERAD cofactors that facilitate substrate delivery to the ligase and E2-conjugating enzyme for ubiquitination.Attempts to delineate distinct degradation pathways according to the site of the defect in a misfolded protein have been made in yeast. Proteins with cytosolic defects (ERAD-C) require Doa10p, whereas proteins with transmembrane (ERAD-M) or luminal (ERAD-L) lesions use Hrd1p (5, 6). The expanded repertoire of ERAD E3s in mammalian cells makes developing analogous rules more challenging. 3-hydroxy-3-methylglutaryl-CoA reductase degradation protein 1 (HRD1) and its homolog gp78/autocrine motility factor receptor (AMFR) are the best-characterized mammalian ERAD ligases. The association of HR...

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“…US11 and US2 are small (Ͻ30 kDa), transmembrane glycoproteins that are localized to the ER. Both bind to class I heavy chains (Wiertz et al, 1996a;Story et al, 1999), but the mechanism by which they act to effect heavy chain dislocation is unknown.…”

Section: Introductionmentioning

confidence: 99%

Polyubiquitination Is Required for US11-dependent Movement of MHC Class I Heavy Chain from Endoplasmic Reticulum into Cytosol

Shamu

Flierman

Ploegh

et al. 2001

MBoC

Self Cite

119

113

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The human cytomegalovirus protein US11 induces the dislocation of MHC class I heavy chains from the endoplasmic reticulum (ER) into the cytosol for degradation by the proteasome. With the use of a fractionated, permeabilized cell system, we find that US11 activity is needed only in the cell membranes and that additional cytosolic factors are required for heavy chain dislocation. We identify ubiquitin as one of the required cytosolic factors. Cytosol depleted of ubiquitin does not support heavy chain dislocation from the ER, and activity can be restored by adding back purified ubiquitin. Methylated-ubiquitin or a ubiquitin mutant lacking all lysine residues does not substitute for wild-type ubiquitin, suggesting that polyubiquitination is required for US11-dependent dislocation. We propose a new function for ubiquitin in which polyubiquitination prevents the lumenal domain of the MHC class I heavy chain from moving back into the ER lumen. A similar mechanism may be operating in the dislocation of misfolded proteins from the ER in the cellular quality control pathway.

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The cytosolic tail of class I MHC heavy chain is required for its dislocation by the human cytomegalovirus US2 and US11 gene products

Cited by 75 publications

References 37 publications

Endoplasmic reticulum chaperones participate in human cytomegalovirus US2-mediated degradation of class I major histocompatibility complex molecules

Endoplasmic reticulum chaperones participate in human cytomegalovirus US2-mediated degradation of class I major histocompatibility complex molecules

MHC class I molecules are preferentially ubiquitinated on endoplasmic reticulum luminal residues during HRD1 ubiquitin E3 ligase-mediated dislocation

Polyubiquitination Is Required for US11-dependent Movement of MHC Class I Heavy Chain from Endoplasmic Reticulum into Cytosol

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