TY - JOUR
T1 - Molecular analysis of the novel L243R mutation in STXBP2 reveals impairment of degranulation activity
AU - Viñas-Giménez, Laura
AU - Donadeu, Laura
AU - Alsina, Laia
AU - Rincón, Rafael
AU - de la Campa, Elena Álvarez
AU - Esteve-Sole, Ana
AU - Català, Albert
AU - Colobran, Roger
AU - de la Cruz, Xavier
AU - Sayós, Joan
AU - Martínez-Gallo, Mónica
N1 - Publisher Copyright:
© 2019, Japanese Society of Hematology.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/3/1
Y1 - 2020/3/1
N2 - The presence of mutations in PRF1, UNC13D, STX11 and STXBP2 genes in homozygosis or compound heterozygosis results in immune deregulation. Most such cases lead to clinical manifestations of haemophagocytic lymphohistiocytosis (HLH). In the present study, we analyzed degranulation and cytotoxicity in a pediatric patient with a late presentation of HLH associated with Epstein–Barr virus infection. Remarkably, the results of the degranulation assay showed reduction of CD107a median fluorescence intensity (MFI) and absent cytotoxicity. Genetic analysis identified compound heterozygous mutations in STXBP2 gene: a previously reported splicing defect in exon 15 (c.1247-1G>C, p.V417LfsX126) and a novel missense mutation in exon 9 (c.728T>G, p.L243R). Transfection experiments of STXBP2-L243R or STXBP2-WT constructs showed an undetectable protein expression of the STXBP2-L243R mutation. The residue L243 is highly preserved evolutionarily; moreover, computational analysis of its structure revealed its participation in the rich network of interactions that stabilizes domains 2 and 3 of the protein. Altogether, we demonstrated by molecular and in silico analysis that the new L243R mutation in STXBP2 plays a pathogenic role that, together with the p.Val417Leufsc mutation, shows the synergistic negative effect of these two mutations on STXBP2 function, leading to a decrease of degranulatory activity in vivo.
AB - The presence of mutations in PRF1, UNC13D, STX11 and STXBP2 genes in homozygosis or compound heterozygosis results in immune deregulation. Most such cases lead to clinical manifestations of haemophagocytic lymphohistiocytosis (HLH). In the present study, we analyzed degranulation and cytotoxicity in a pediatric patient with a late presentation of HLH associated with Epstein–Barr virus infection. Remarkably, the results of the degranulation assay showed reduction of CD107a median fluorescence intensity (MFI) and absent cytotoxicity. Genetic analysis identified compound heterozygous mutations in STXBP2 gene: a previously reported splicing defect in exon 15 (c.1247-1G>C, p.V417LfsX126) and a novel missense mutation in exon 9 (c.728T>G, p.L243R). Transfection experiments of STXBP2-L243R or STXBP2-WT constructs showed an undetectable protein expression of the STXBP2-L243R mutation. The residue L243 is highly preserved evolutionarily; moreover, computational analysis of its structure revealed its participation in the rich network of interactions that stabilizes domains 2 and 3 of the protein. Altogether, we demonstrated by molecular and in silico analysis that the new L243R mutation in STXBP2 plays a pathogenic role that, together with the p.Val417Leufsc mutation, shows the synergistic negative effect of these two mutations on STXBP2 function, leading to a decrease of degranulatory activity in vivo.
KW - Cell degranulation
KW - Cytotoxic T-lymphocytes
KW - Epstein–Barr virus infection
KW - Familial hemophagocytic lymphohistiocytosis
KW - Munc18-1 protein
KW - Munc18-2 protein
KW - Natural killer cells
UR - http://www.scopus.com/inward/record.url?scp=85076926240&partnerID=8YFLogxK
U2 - 10.1007/s12185-019-02796-7
DO - 10.1007/s12185-019-02796-7
M3 - Article
C2 - 31865540
AN - SCOPUS:85076926240
SN - 0925-5710
VL - 111
SP - 440
EP - 450
JO - International Journal of Hematology
JF - International Journal of Hematology
IS - 3
ER -