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Tomida S, Nagae M, Kizuka Y. The stem region of α1,6-fucosyltransferase FUT8 is required for multimer formation but not catalytic activity. J Biol Chem 2022; 298:102676. [PMID: 36336076 PMCID: PMC9709245 DOI: 10.1016/j.jbc.2022.102676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 10/26/2022] [Accepted: 10/30/2022] [Indexed: 11/06/2022] Open
Abstract
Alpha-1,6-fucosyltransferase (FUT8) synthesizes core fucose in N-glycans, which plays critical roles in various physiological processes. FUT8, as with many other glycosyltransferases, is a type-II membrane protein, and its large C-terminal catalytic domain is linked to the FUT8 stem region, which comprises two α-helices. Although the stem regions of several glycosyltransferases are involved in the regulation of Golgi localization, the functions of the FUT8 stem region have not been clarified as yet. Here, we found that the FUT8 stem region is essential for enzyme oligomerization. We expressed FUT8Δstem mutants, in which the stem region was replaced with glycine/serine linkers, in FUT8-KO HEK293 cells. Our immunoprecipitation and native-PAGE analysis showed that FUT8 WT formed a multimer but FUT8Δstem impaired multimer formation in the cells, although the mutants retained specific activity. In addition, the mutant protein had lower steady-state levels, increased endoplasmic reticulum localization, and a shorter half-life than FUT8 WT, suggesting that loss of the stem region destabilized the FUT8 protein. Furthermore, immunoprecipitation analysis of another mutant lacking a part of the stem region revealed that the first helix in the FUT8 stem region is critical for multimer formation. Our findings demonstrated that the FUT8 stem region is essential for multimer formation but not for catalytic activity, providing insights into how the FUT8 protein matures and functions in mammalian cells.
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Affiliation(s)
- Seita Tomida
- The United Graduate School of Agricultural Science, Gifu University, Gifu, Japan
| | - Masamichi Nagae
- Department of Molecular Immunology, Research Institute for Microbial Diseases, Osaka University, Suita, Japan,Laboratory of Molecular Immunology, Immunology Frontier Research Center (IFReC), Osaka University, Suita, Japan
| | - Yasuhiko Kizuka
- The United Graduate School of Agricultural Science, Gifu University, Gifu, Japan,Institute for Glyco-core Research (iGCORE), Gifu University, Gifu, Japan,For correspondence: Yasuhiko Kizuka
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Medits I, Heinz FX, Stiasny K. An Absolutely Conserved Tryptophan in the Stem of the Envelope Protein E of Flaviviruses Is Essential for the Formation of Stable Particles. Viruses 2021; 13:1727. [PMID: 34578308 DOI: 10.3390/v13091727] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 08/27/2021] [Indexed: 11/17/2022] Open
Abstract
The major envelope protein E of flaviviruses contains an ectodomain that is connected to the transmembrane domain by the so-called “stem” region. In mature flavivirus particles, the stem is composed of two or three mostly amphipathic α-helices and a conserved sequence element (CS) with an undefined role in the viral life cycle. A tryptophan is the only residue within this region which is not only conserved in all vector-borne flaviviruses, but also in the group with no known vector. We investigated the importance of this residue in different stages of the viral life cycle by a mutagenesis-based approach using tick-borne encephalitis virus (TBEV). Replacing W421 by alanine or histidine strongly reduced the release of infectious virions and their thermostability, whereas fusion-related entry functions and virus maturation were still intact. Serial passaging of the mutants led to the emergence of a same-site compensatory mutation to leucine that largely restored these properties of the wildtype. The conserved tryptophan in CS (or another big hydrophobic amino acid at the same position) is thus essential for the assembly and infectivity of flaviviruses by being part of a network required for conferring stability to infectious particles.
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Lv J, Liu X, Cui S, Yang L, Qu S, Meng R, Yang B, Feng C, Wang X, Zhang D. The Neutralizing Antibody Response Elicited by Tembusu Virus Is Affected Dramatically by a Single Mutation in the Stem Region of the Envelope Protein. Front Microbiol 2020; 11:585194. [PMID: 33193231 PMCID: PMC7642334 DOI: 10.3389/fmicb.2020.585194] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 10/02/2020] [Indexed: 12/30/2022] Open
Abstract
Tembusu virus (TMUV) is a mosquito-borne flavivirus that most commonly affects adult breeder and layer ducks. However, a TMUV-caused neurological disease has also been found in ducklings below 7 weeks of age, highlighting the need to develop a safe vaccine for young ducklings. In this study, a plaque-purified PS TMUV strain was attenuated by serial passage in BHK-21 cells. Using 1-day-old Pekin ducklings as a model, the virus was confirmed to be attenuated sufficiently after 180 passages, whereas the neutralizing antibody response elicited by the 180th passage virus (PS180) was substantially impaired compared with PS. The findings suggest that sufficient attenuation results in loss of immunogenicity in the development of the live-attenuated TMUV vaccine. Comparative sequence analysis revealed that PS180 acquired one mutation (V41M) in prM and four mutations (T70A, Y176H, K313R, and F408L) in the envelope (E) protein. To identify the amino acid substitution(s) associated with loss of immunogenicity of PS180, we rescued parental viruses, rPS and rPS180, and produced mutant viruses, rPS180-M41V, rPS180-A70T, rPS180-H176Y, rPS180-R313K, rPS180-L408F, and rPS180-M5, which contained residue 41V in prM, residues 70T, 176Y, 313K, and 408F in E, and combination of the five residues, respectively, of PS in the backbone of the rPS180 genome. The neutralizing antibody response elicited by rPS180-L408F and rPS180-M5 was significantly higher than those by other mutant viruses and comparable to that by rPS. Furthermore, we produced mutant virus rPS-F408L, which contained residue 408L of PS180 in the backbone of the rPS genome. The F408L mutation conferred significantly decreased neutralizing antibody response to rPS-F408L, which was comparable to that elicited by rPS180. Based on homologous modeling, residue 408 was predicted to be located within the first helical domain of the stem region of the E protein (EH1). Together, these data demonstrate that a single mutation within the EH1 domain exerts a dramatical impact on the TMUV neutralizing antibody response. The present work may enhance our understanding of molecular basis of the TMUV neutralizing antibody response, and provides an important step for the development of a safe and efficient live-attenuated TMUV vaccine.
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Affiliation(s)
- Junfeng Lv
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Xiaoxiao Liu
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Shulin Cui
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Lixin Yang
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Shenghua Qu
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Runze Meng
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Baolin Yang
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Chonglun Feng
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Xiaoyan Wang
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Dabing Zhang
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China
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Ben Mahmoud A, Siala O, Mansour RB, Driss F, Baklouti-Gargouri S, Mkaouar-Rebai E, Belguith N, Fakhfakh F. First functional analysis of a novel splicing mutation in the B3GALTL gene by an ex vivo approach in Tunisian patients with typical Peters plus syndrome. Gene 2013; 532:13-7. [PMID: 23954224 DOI: 10.1016/j.gene.2013.07.058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 07/03/2013] [Accepted: 07/11/2013] [Indexed: 11/17/2022]
Abstract
Peters plus syndrome is a rare recessive autosomal disorder comprising ocular anterior segment dysgenesis, short stature, hand abnormalities and distinctive facial features. It was related only to mutations in the B3GALTL gene in the 13q12.3 region. In this study, we undertook the first functional analysis of a novel c.597-2 A>G splicing mutation within the B3GALTL gene using an ex-vivo approach. The results showed a complete skipping of exon 8 in the B3GALTL cDNA, which altered the open reading frame of the mutant transcript and generated a PTC within exon 9. This finding potentially elicits the nonsense mRNA to degradation by NMD (nonsense-mediated mRNA decay). The theoretical consequences of splice site mutations, predicted with the bioinformatics tool Human Splice Finder, were investigated and evaluated in relation to ex-vivo results. The findings confirmed the key role played by the B3GALTL gene in typical Peters-plus syndromes and the utility of mRNA analysis to understand the primary impacts of this mutation and the phenotype of the disease.
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Affiliation(s)
- Afif Ben Mahmoud
- Laboratoire de Génétique Moléculaire Humaine, Faculté de Médecine de Sfax, Université de Sfax, Tunisia.
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