An intramolecular salt bridge drives the soluble domain of GTP-bound atlastin into the postfusion conformation

Morin-Leisk, Jeanne; Saini, Simran G.; Meng, Xin; Makhov, Alexander M.; Zhang, Peijun; Lee, Tina H.

doi:10.1083/jcb.201105006

Cited by 35 publications

(72 citation statements)

References 22 publications

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“…On the other hand, another feature of the ERGIC, the lectin ERGIC-53, was excluded from the assembly compartment. As observed in TEM, the latter directly brought together membranes from the ER and the Golgi apparatus, which was consistent with an enrichment of this compartment in, respectively, Atlastin 1 [50][51][52] and GM130/GOLGA2 [41] , both reported to reorganize and/or maintain membranes of their organelle. In addition, an enrichment in both RAB1 and its GDI, like what was observed in the assembly compartment, has been reported to initiate a cascade of events involving GBF1, ARF1 and phosphatidylinositol 4-kinase Ⅲ alpha (PI4KⅢα) [43] , which may increase the local proportion of phosphatidylinositol 4-phosphate [63] and subvert endocytic trafficking [64] .…”

Section: Discussionsupporting

confidence: 61%

“…Interestingly, in these cells, the expression of RAB1 GDP dissociation inhibitor (GDI) [49] was enhanced and co-localized with HCV proteins in a pattern reminiscent of RAB1's ( Figure 8). In addition, the expression of Atlastin 1, a high molecular weight GTPase that is involved in maintenance of the ER compartment [50] and fusion of ER tubules [51] , as well as in ERto-Golgi trafficking [52] , was up-regulated in BHK-WNV cells compared to parental BHK-21 cells (Figure 9). We detected its presence within the CANX-enriched compartment formed in BHK-WNV cells (Figure 10), as well as that of p115/USO1 [53] , required for membrane fusion of ERGIC vesicles with the Golgi apparatus.…”

Section: Rab1 and Conformational Hcv Protein Subspecies Colocalize Wimentioning

confidence: 98%

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Assembly and release of infectious hepatitis C virus involving unusual organization of the secretory pathway

Triyatni

Berger

Saunier

2016

WJH

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Institutional review board statement: Approved the use of serum IgG of a patient cured from an HCV infection for in vitro studies (Hôpital and Institut Cochin, Paris).Institutional animal care and use committee statement: Not applicable.Conflict-of-interest statement: Saunier B, Triyatni M and Berger EA are co-inventors on NIH-owned patent #US 9052321 B2 on the HCV particle production system. Triyatni M et al . Unusual secretory pathway of hepatitis C virus in thin section transmission electron microscopy. These findings were compared with the JFH-1 strain/Huh-7.5 cell model. RESULTS:We found that CANX was necessary for the production of HCV particles by BHK-WNV cells. This process involved the recruitment of a subset of HCV proteins, detected by immunoglobulin of an HCV-cured patient, in a compartment of rearranged membranes bypassing the endoplasmic reticulum-Golgi intermediary compartment and surrounded by mitochondria. It also involved the maturation of N-linked glycans on HCV envelope proteins, which was required for assembly and/or secretion of HCV particles. The formation of this specialized compartment required RAB1; upon expression of HCV structural genes, this compartment developed large vesicles with viral particles. RAB1 and alpha-tubulin were required for the release of HCV particles. These cellular factors were also involved in the production of HCVcc in the JFH-1 strain/Huh-7.5 cell system, which involves HCV RNA replication. The secretion of HCV particles by BHK-WNV cells presents similarities with a pathway involving caspase-1; a caspase-1 inhibitor was found to suppress the production of HCV particles from a full-length genome. CONCLUSION:Prior activity of the WNV subgenomic replicon in BHK-21 cells promoted re-wiring of host factors for the assembly and release of infectious HCV in a caspase-1-dependent mechanism. Core tip: Our system for production of authentic infectious hepatitis C virus (HCV) in non-humanized, nonhepatic cells involves the rearrangement of inner cellular membranes triggered by the replication of flaviviruses. The present results suggest that this feature relies on the re-wiring of host factors that usually contribute to the secretion of glycoproteins to generate an unusual secretory pathway. This model offers a new way to study the properties of free HCV particles, i.e. , independently from lipoproteins.Triyatni M, Berger EA, Saunier B. Assembly and release of infectious hepatitis C virus involving unusual organization of the secretory pathway.

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Section: Discussionsupporting

confidence: 61%

Section: Rab1 and Conformational Hcv Protein Subspecies Colocalize Wimentioning

confidence: 98%

Assembly and release of infectious hepatitis C virus involving unusual organization of the secretory pathway

Triyatni

Berger

Saunier

2016

WJH

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“…It has been proposed that GTP hydrolysis occurs after fusion, although this is difficult to reconcile with in vitro experiments showing that GTP hydrolysis is required for membrane fusion (21). Other models postulate that GTP binding is sufficient for the tethering of the two membranes through dimerization of ATL molecules sitting in opposing membranes (trans dimer) (9,13,22), or that GTP binding and hydrolysis occur in a monomer before trans dimerization (19).…”

Section: Significancementioning

confidence: 99%

Cis and trans interactions between atlastin molecules during membrane fusion

Liu

Bian

Romano

et al. 2015

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

115

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Atlastin (ATL), a membrane-anchored GTPase that mediates homotypic fusion of endoplasmic reticulum (ER) membranes, is required for formation of the tubular network of the peripheral ER. How exactly ATL mediates membrane fusion is only poorly understood. Here we show that fusion is preceded by the transient tethering of ATL-containing vesicles caused by the dimerization of ATL molecules in opposing membranes. Tethering requires GTP hydrolysis, not just GTP binding, because the two ATL molecules are pulled together most strongly in the transition state of GTP hydrolysis. Most tethering events are futile, so that multiple rounds of GTP hydrolysis are required for successful fusion. Supported lipid bilayer experiments show that ATL molecules sitting on the same (cis) membrane can also undergo nucleotide-dependent dimerization. These results suggest that GTP hydrolysis is required to dissociate cis dimers, generating a pool of ATL monomers that can dimerize with molecules on a different (trans) membrane. In addition, tethering and fusion require the cooperation of multiple ATL molecules in each membrane. We propose a comprehensive model for ATL-mediated fusion that takes into account futile tethering and competition between cis and trans interactions. T he endoplasmic reticulum (ER) consists of tubules and sheets connected into a characteristic network by membrane fusion (1-3). In contrast to heterotypic fusion between viral and cellular membranes or between intracellular transport vesicles and target membranes, the fusing ER membranes are identical (i.e., homotypic fusion). The mechanism of heterotypic fusion has been studied extensively, leading to the concept that a conformational change of a viral fusion protein or the assembly of SNARE proteins pulls two opposing membranes together so that they can fuse (4-7). Recently, some insight has been obtained into homotypic ER fusion as well. This process is mediated by the atlastins (ATLs) in metazoans and by Sey1p/ROOT HAIR DEFECTIVE3 (RHD3)-related proteins in yeast and plants (8,9).The ATLs and Sey1p/RHD3 are membrane-bound GTPases that belong to the dynamin family (reviewed in refs. 10, 11). They contain cytosolic N-terminal GTPase (G) and helical bundle domains, followed by two closely spaced transmembrane (TM) segments and a cytosolic C-terminal tail (12)(13)(14). A role for the GTPases in ER fusion is suggested by the observation that their depletion or mutational inactivation leads to long, nonbranched tubules or fragmented ER (8, 9). Nonbranched ER tubules are also observed on expression of dominant-negative ATL mutants (8,12). In addition, the fusion of ER vesicles in Xenopus laevis egg extracts is prevented by ATL antibodies or a cytosolic fragment of ATL (8,15), and the fusion of the ER in mating yeast cells is delayed on SEY1 deletion (16). Most convincingly, proteoliposomes containing purified ATL, Sey1p, or RHD3 undergo GTP-dependent fusion in vitro (9,13,16,17). Defects in ATL-mediated ER fusion can cause hereditary spastic paraplegia, a neurodegenerativ...

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“…5a: a N-terminal domain (amino acids 1-338), a middle domain (347-432) which is followed by the hydrophobic, membrane spanning part (446-488) and a C-terminal domain (497-558). The main function of atlastin is the fusion of the ER membranes which is mediated by the N-terminal domain exerting GTPase functions [17]- [20]. The C-terminal (CT) contains an amphiphatic helix-forming segment which plays a key role for the fusion of ER membranes as shown in the last section.…”

Section: Atlastin-3 An Er Homofusion Mediating Proteinmentioning

confidence: 99%

“…5). Both domains have been shown to play a key role for the fusion process [18]- [20]. The fusion process is driven by the formation of a tight complex between two atlastins anchored in the juxtaposed membranes [19] resulting in their strong adhesion.…”

Section: Analogies Between Atlastin-mediated Homotype Fusion and Snarmentioning

confidence: 99%

Endoplasmatic reticulum shaping by generic mechanisms and protein-induced spontaneous curvature

Sackmann

2014

Advances in Colloid and Interface Science

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An intramolecular salt bridge drives the soluble domain of GTP-bound atlastin into the postfusion conformation

Abstract: Before ER tubule fusion, the atlastin GTPase undergoes a “prefusion” to “postfusion” conformational change that is mediated by an intramolecular salt bridge.

Cited by 35 publications

References 22 publications

Assembly and release of infectious hepatitis C virus involving unusual organization of the secretory pathway

Assembly and release of infectious hepatitis C virus involving unusual organization of the secretory pathway

Cis and trans interactions between atlastin molecules during membrane fusion

Endoplasmatic reticulum shaping by generic mechanisms and protein-induced spontaneous curvature

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