Fan Junmei, Yang Xiaofei, Lu Jingze, Chen Liangyi, Xu Pingyong
Joint Laboratory of the Institute of Biophysics & Huazhong University of Science and Technology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China.
Biochem Biophys Res Commun. 2007 Jul 27;359(2):245-50. doi: 10.1016/j.bbrc.2007.05.065. Epub 2007 May 21.
Membrane syntaxin plays essential roles in exocytosis in eukaryotic cells. The conservative H(abc) domain in plasma membrane syntaxins implies important roles for syntaxin targeting and function. Our previous study showed H(abc) domain was necessary for the trafficking and cluster distribution of syntaxin 1A on the plasma membrane. Here we identified which of the three domains (H(a), H(b) and H(c)) was essential for Stx1A trafficking and clustering. We found that, in INS-1 cells, the mutant truncated with either H(a), H(b) or H(c) domain could be sorted to the cell surface by a different mechanism compared to that of whole H(abc) truncated mutant. In contrast to wild type Stx1A, none of the mutants showed cluster distribution at the functional sites, suggesting that the physiological localization of Stx1A relies on intact H(abc) domain. Furthermore Munc18-1 is found not to be essential for Stx1A cluster distribution, despite important role in stabilizing membrane delivery of Stx1A.
膜 syntaxin 在真核细胞的胞吐作用中发挥着重要作用。质膜 syntaxin 中保守的 H(abc) 结构域暗示了 syntaxin 靶向和功能的重要作用。我们之前的研究表明，H(abc) 结构域对于 syntaxin 1A 在质膜上的运输和簇状分布是必需的。在这里，我们确定了三个结构域（H(a)、H(b) 和 H(c)）中的哪一个对于 Stx1A 的运输和聚集至关重要。我们发现，在 INS-1 细胞中，与整个 H(abc) 截短突变体相比，截去 H(a)、H(b) 或 H(c) 结构域的突变体可以通过不同的机制被分选到细胞表面。与野生型 Stx1A 不同，这些突变体在功能位点均未显示出簇状分布，这表明 Stx1A 的生理定位依赖于完整的 H(abc) 结构域。此外，尽管 Munc18-1 在稳定 Stx1A 的膜转运中起重要作用，但发现它对于 Stx1A 的簇状分布并非必需。
