Yang Xiaofei, Xu Pingyong, Xiao Yang, Xiong Xiong, Xu Tao
Joint Laboratory of Institute of Biophysics & Huazhong University of Science and Technology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
J Biol Chem. 2006 Jun 2;281(22):15457-63. doi: 10.1074/jbc.M513246200. Epub 2006 Apr 4.
Syntaxin plays a key role in intracellular membrane fusion in eukaryotic cells. The function of syntaxin relies on its proper trafficking to and targeting at the target membrane. The mechanisms underlying the trafficking and targeting of syntaxin to its physiological sites remain poorly understood. Here we have analyzed the trafficking of syntaxin 1A in INS-1 and CHO cells. We have identified the transmembrane domain together with several flanking positive-charged amino acids as the minimal domain required for the membrane delivery. Interestingly, we found that SNARE motif-exposed syntaxin 1A mutants were retained in endoplasmic reticulum (ER) and failed to transport to the cell surface in the absence of SNAP-25, suggesting that the exposure of the SNARE motif causes ER retention and complexation with SNAP-25 helps the ER escape. Finally, our data propose two key roles for the H(abc) domain: to protect nonspecific interaction by masking the SNARE motif and to participate in the clustering of syntaxin 1A to the fusion sites in the plasma membrane.
Syntaxin在真核细胞的细胞内膜融合中起关键作用。Syntaxin的功能依赖于其向靶膜的正确运输和靶向定位。Syntaxin运输和靶向其生理位点的潜在机制仍知之甚少。在此，我们分析了Syntaxin 1A在INS-1和CHO细胞中的运输情况。我们已确定跨膜结构域以及几个侧翼带正电荷的氨基酸是膜递送所需的最小结构域。有趣的是，我们发现暴露SNARE基序的Syntaxin 1A突变体在内质网（ER）中滞留，并且在没有SNAP-25的情况下无法运输到细胞表面，这表明SNARE基序的暴露导致ER滞留，而与SNAP-25的复合有助于ER逃逸。最后，我们的数据提出了H(abc)结构域的两个关键作用：通过掩盖SNARE基序来保护非特异性相互作用，以及参与Syntaxin 1A在质膜融合位点的聚集。
