Hemophagocytic lymphohistiocytosis caused by dominant-negative mutations in STXBP2 that inhibit SNARE-mediated membrane fusion

Spessott, Waldo; Sanmillan, Maria L.; McCormick, Margaret E.; Patel, Nilay A.; Villanueva, Joyce; Zhang, Kejian; Nichols, Kim E.; Giraudo, Claudio G.

doi:10.1182/blood-2014-11-610816

Cited by 111 publications

(89 citation statements)

References 41 publications

(79 reference statements)

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“…Previous studies have suggested that Munc18-2 can interact with the monomeric Syntaxins STX3 (39,40), STX2 (41), and STX11 (13,(33)(34)(35). However, other SM proteins have distinct binding modes in which they engage either monomeric syntaxins or SNARE complexes (42-45).…”

Section: Resultsmentioning

confidence: 99%

“…Munc18-2 R65Q is a recently described disease-associated mutant that displayed stronger binding to STX11 and inhibits membrane fusion in vitro and in vivo in a dominant-negative manner (33). Addition of Munc18-2 R65Q to the flipped SNARE fusion assay with STX11-GPI drastically reduced both lipid mixing and complete fusion ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…binding studies that show that the mutation E132A, which lies within Munc18-2 N-lobe domain, severely affects the interaction with STX11 N-terminal domain (34,35). On the other hand, Munc18-2 R65Q mutant, which binds SNARE complexes more efficiently than Munc18-2 WT but acts in dominant-negative fashion most likely arresting SNAREpin formation (33), had an inhibitory effect on the extent of both lipid mixing and complete fusion mediated by either STX11-GPI or STX11 H3 -GPI. These results suggest that the Munc18-2 R65Q mutant stabilizes the assembly of SNARE complexes at an intermediate state before lipid mixing and interferes with complete zippering of the SNARE complex.…”

Section: Discussionmentioning

confidence: 99%

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SM protein Munc18-2 facilitates transition of Syntaxin 11-mediated lipid mixing to complete fusion for T-lymphocyte cytotoxicity

Spessott

Sanmillan

McCormick

et al. 2017

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

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The atypical lipid-anchored Syntaxin 11 (STX11) and its binding partner, the Sec/Munc (SM) protein Munc18-2, facilitate cytolytic granule release by cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Patients carrying mutations in these genes develop familial hemophagocytic lymphohistiocytosis, a primary immunodeficiency characterized by impaired lytic granule exocytosis. However, whether a SNARE such as STX11, which lacks a transmembrane domain, can support membrane fusion in vivo is uncertain, as is the precise role of Munc18-2 during lytic granule exocytosis. Here, using a reconstituted "flipped" cell-cell fusion assay, we show that lipidanchored STX11 and its cognate SNARE proteins mainly support exchange of lipids but not cytoplasmic content between cells, resembling hemifusion. Strikingly, complete fusion is stimulated by addition of wild-type Munc18-2 to the assay, but not of Munc18-2 mutants with abnormal STX11 binding. Our data reveal that Munc18-2 is not just a chaperone of STX11 but also directly contributes to complete membrane merging by promoting SNARE complex assembly. These results further support the concept that SM proteins in general are part of the core fusion machinery. This fusion mechanism likely contributes to other cell-type-specific exocytic processes such as platelet secretion.SNARE | Syntaxin 11 | Munc18-2 | CTL | SM protein

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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SM protein Munc18-2 facilitates transition of Syntaxin 11-mediated lipid mixing to complete fusion for T-lymphocyte cytotoxicity

Spessott

Sanmillan

McCormick

et al. 2017

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

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“…Some monoallelic mutations may also potentially act in a dominant-negative manner. 39 It is probably too early to be able to appreciate the exact relevance of polygenic inheritance in the secondary forms of HLH. Few retrospective studies reported in some patients the presence of deleterious monoallelic mutations in one or two HLH genes, among the few analyzed.…”

Section: Discussionmentioning

confidence: 99%

Polygenic mutations in the cytotoxicity pathway increase susceptibility to develop HLH immunopathology in mice

Sepulveda

Garrigue

Maschalidi

et al. 2016

Blood

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Key Points• The accumulation of monoallelic mutations in HLH-causing genes impairs lymphocyte cytotoxicity contributing to HLH immunopathology in mice. • A polygenic model may account for some of the cases of secondary HLH observed in humans.Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory disease. Inherited forms of HLH are caused by biallelic mutations in several effectors of granule-dependent lymphocyte-mediated cytotoxicity. A small proportion of patients with a so-called "secondary" form of HLH, which develops in the aftermath of infection, autoimmunity, or cancer, carry a monoallelic mutation in one or more HLH-associated genes. Although this observation suggests that HLH may have a polygenic mode of inheritance, the latter is very difficult to prove in humans. In order to determine whether the accumulation of partial genetic defects in lymphocyte-mediated cytotoxicity can contribute to the development of HLH, we generated mice that were doubly or triply heterozygous for mutations in HLH-associated genes, those coding for perforin, Rab27a, and syntaxin-11. We found that the accumulation of monoallelic mutations did indeed increase the risk of developing HLH immunopathology after lymphocytic choriomeningitis virus infection. In mechanistic terms, the accumulation of heterozygous mutations in the two degranulation genes Rab27a and syntaxin-11, impaired the dynamics and secretion of cytotoxic granules at the immune synapse of T lymphocytes. In addition, the accumulation of heterozygous mutations within the three genes impaired natural killer lymphocyte cytotoxicity in vivo. The genetic defects can be ranked in terms of the severity of the resulting HLH manifestations. Our results form the basis of a polygenic model of the occurrence of secondary HLH. (Blood. 2016;127(17):2113-2121

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“…Some mutations may even display dominant negative effects, which are determined through advanced cellular assays. 8 Second, with less severe impairments in lymphocyte cytotoxicity, environmental factors play an increasing role in determining HLH susceptibility. 3 Nonetheless, the concept of gene dosages in determining the efficacy of target cell killing may have wider implications for the risk of developing a spectrum of diseases associated with impaired lymphocyte cytotoxicity.…”

mentioning

confidence: 99%

HLH susceptibility: genetic lesions add up

Meeths

Bryceson

2016

Blood

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Hemophagocytic lymphohistiocytosis caused by dominant-negative mutations in STXBP2 that inhibit SNARE-mediated membrane fusion

Abstract: Key Points Monoallelic STXBP2 mutations affecting codon 65 impair lymphocyte cytotoxicity and contribute to hemophagocytic lymphohistiocytosis. Munc18-2R65Q/W mutant proteins function in a dominant-negative manner to impair membrane fusion and arrest SNARE-complex assembly.

Cited by 111 publications

References 41 publications

SM protein Munc18-2 facilitates transition of Syntaxin 11-mediated lipid mixing to complete fusion for T-lymphocyte cytotoxicity

SM protein Munc18-2 facilitates transition of Syntaxin 11-mediated lipid mixing to complete fusion for T-lymphocyte cytotoxicity

Polygenic mutations in the cytotoxicity pathway increase susceptibility to develop HLH immunopathology in mice

HLH susceptibility: genetic lesions add up

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