Homology with Vesicle Fusion Mediator Syntaxin-1a Predicts Determinants of Epimorphin/Syntaxin-2 Function in Mammary Epithelial Morphogenesis
Homology with Vesicle Fusion Mediator Syntaxin-1a Predicts Determinants of Epimorphin/Syntaxin-2 Function in Mammary Epithelial Morphogenesis
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DOI：
10.1074/jbc.m805908200
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发表时间：
2009-03-13
影响因子：
4.8
通讯作者：
Radisky, Derek C.
中科院分区：
文献类型：
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作者：
Chen, Connie S.;Nelson, Celeste M.;Radisky, Derek C.
我们已经证明，乳腺导管结构的分支形态发生需要形态发生素 Epimorphin/syntaxin-2 的作用。 Epimorphin 最初被认为是一种细胞外分子，与 Syntaxin-2 相同，后者是一种细胞内分子，属于广泛研究的介导囊泡运输的突触蛋白家族的成员。我们在此表明，虽然 Epimorphin/syntaxin-2 与 syntaxin-1a 高度同源，但只有 Epimorphin/syntaxin-2 可以刺激乳腺分支形态发生。我们根据已发表的 syntaxin-1a 结构构建了 Epimorphin/syntaxin-2 的同源模型，并使用该模型来识别负责形态发生活性的结构基序。我们鉴定出位于螺旋 B 和 C 之间的裂缝内的四个残基，它们在 Syntaxin-1a 和 Epimorphin/syntaxin-2 之间有所不同；通过这四种氨基酸的定点诱变，我们将 Epimorphin 的细胞粘附、基因激活和分支形态发生的特性赋予无活性的 Syntaxin-1a 模板。这些结果有力地证明了如何使用一个分子的结构信息来定义第二个分子的功能基序，该基序在序列水平上相关，但在功能上高度不同。
We have shown that branching morphogenesis of mammary ductal structures requires the action of the morphogen epimorphin/syntaxin-2. Epimorphin, originally identified as an extracellular molecule, is identical to syntaxin-2, an intracellular molecule that is a member of the extensively investigated syntaxin family of proteins that mediate vesicle trafficking. We show here that, although epimorphin/syntaxin-2 is highly homologous to syntaxin-1a, only epimorphin/syntaxin-2 can stimulate mammary branching morphogenesis. We construct a homology model of epimorphin/syntaxin-2 based on the published structure of syntaxin-1a, and we use this model to identify the structural motif responsible for the morphogenic activity. We identify four residues located within the cleft between helices B and C that differ between syntaxin-1a and epimorphin/syntaxin-2; through site-directed mutagenesis of these four amino acids, we confer the properties of epimorphin for cell adhesion, gene activation, and branching morphogenesis onto the inactive syntaxin-1a template. These results provide a dramatic demonstration of the use of structural information about one molecule to define a functional motif of a second molecule that is related at the sequence level but highly divergent functionally.