Munc18-2, a functional partner of syntaxin 3, controls apical membrane trafficking in epithelial cells
Munc18-2, a functional partner of syntaxin 3, controls apical membrane trafficking in epithelial cells
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DOI：
10.1074/jbc.275.18.13476
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发表时间：
2000-05-05
影响因子：
4.8
通讯作者：
Olkkonen, VM
中科院分区：
文献类型：
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作者：
Riento, K;Kauppi, M;Olkkonen, VM
Sec 1相关蛋白以高亲和力与突触融合蛋白家族t-SNARE结合，从而控制突触融合蛋白与其同源SNARE伴侣的相互作用。Munc 18 -2是一种Sec 1同源物，在上皮细胞中富集，并与突触融合蛋白3形成复合物，突触融合蛋白3是一种定位于顶端质膜的t-SNARE。我们在这里产生了一组Munc 18 -2点突变体的保守氨基酸残基的取代。突变体显示出不同的突触融合蛋白结合效率的光谱。体外和体外结合模式高度相似，并且Munc 18 -2变体与突触融合蛋白3的关联与它们在Caco-2细胞中过表达时从突触融合蛋白3复合物中置换SNAP-23的能力密切相关。即使不能检测到结合突触融合蛋白3的Munc 18 -2突变体在Caco-2细胞中也是膜结合的，这表明突触融合蛋白相互作用不是Sec 1蛋白膜附着的唯一决定因素。野生型Munc 18 -2的过表达显示出抑制流感病毒血凝素（HA）的顶端递送。有趣的是，不能结合突触融合蛋白3的突变体在HA转运测定中表现不同。虽然测试的突变体之一没有效果，但一个抑制RA的顶端转运，一个增强RA的顶端转运。这意味着Munc 18 -2在顶端膜转运中的功能涉及独立于突触融合蛋白3相互作用的方面。
The Sec1-related proteins bind to syntaxin family t-SNAREs with high affinity, thus controlling the interaction of syntaxins with their cognate SNARE partners. Munc18-2 is a Sec1 homologue enriched in epithelial cells and forms a complex with syntaxin 3, a t-SNARE localized to the apical plasma membrane. We generated here a set of Munc18-2 point mutants with substitutions in conserved amino acid residues. The mutants displayed a spectrum of different syntaxin binding efficiencies. The in vitro and in vitro binding patterns were highly similar, and the association of the Munc18-2 variants with syntaxin 3 correlated well with their ability to displace SNAP-23 from syntaxin 3 complexes when overexpressed in Caco-2 cells. Even the Munc18-2 mutants that do not detectably bind syntaxin 3 were membrane associated in Caco-2 cells, suggesting that the syntaxin interaction is not the sole determinant of Sec1 protein membrane attachment, Overexpression of the wild-type Munc18-2 was shown to inhibit the apical delivery of influenza virus hemagglutinin (HA), Interestingly, mutants unable to bind syntaxin 3 behaved differently in the HA transport assay. While one of the mutants tested had no effect, one inhibited and one enhanced the apical transport of RA This implies that Munc18-2 function in apical membrane trafficking involves aspects independent of the syntaxin 3 interaction.