Syntaxin 11 regulates the stimulus-dependent transport of Toll-like receptor 4 to the plasma membrane by cooperating with SNAP-23 in macrophages
Syntaxin 11 regulates the stimulus-dependent transport of Toll-like receptor 4 to the plasma membrane by cooperating with SNAP-23 in macrophages
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DOI：
10.1091/mbc.e18-10-0653
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发表时间：
2019-04-15
影响因子：
3.3
通讯作者：
Hatsuzawa, Kiyotaka
中科院分区：
文献类型：
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作者：
Kinoshita, Daiki;Sakurai, Chiye;Hatsuzawa, Kiyotaka
Syntaxin 11（stx 11）是一种可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE），在免疫细胞中选择性表达;然而，其在巨噬细胞中的确切作用尚不清楚。我们发现，stx 11敲低降低了大肠杆菌在干扰素-γ-激活的巨噬细胞中的吞噬作用。stx 11敲低降低了Toll样受体4（TLR 4）在质膜上的定位，而不影响总表达。质膜定位的TLR 4主要内吞1小时内的脂多糖（LPS）刺激和逐渐重新定位4小时后，去除LPS。stx 11基因敲除显著削弱了这种重新定位。TLR 4转运至质膜的缺乏可能与TLR 4在酸性内体细胞器中的降解有关。此外，免疫沉淀实验表明，stx 11与SNAP-23相互作用，SNAP-23是一种质膜定位的SNARE蛋白，其消耗也抑制了LPS刺激细胞中TLR 4的补充。使用SNAP-23的分子内Forster共振能量转移（FRET）探针，我们表明LPS刺激引起的高FRET效率通过stx 11敲低而降低。这些发现表明，stx 11通过与巨噬细胞中的SNAP-23合作来调节TLR 4向质膜的刺激依赖性转运。我们的研究结果阐明了TLR 4细胞内转运的调控机制，并对微生物的发病机制和免疫反应产生影响。
Syntaxin 11 (stx11) is a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) that is selectively expressed in immune cells; however, its precise role in macrophages is unclear. We showed that stx11 knockdown reduces the phagocytosis of Escherichia coli in interferon-gamma-activated macrophages. stx11 knockdown decreased Toll-like receptor 4 (TLR4) localization on the plasma membrane without affecting total expression. Plasma membrane-localized TLR4 was primarily endocytosed within 1 h by lipopolysaccharide (LPS) stimulation and gradually relocalized 4 h after removal of LPS. This re-localization was significantly impaired by stx11 knockdown. The lack of TLR4 transport to the plasma membrane is presumably related to TLR4 degradation in acidic endosomal organelles. Additionally, an immunoprecipitation experiment suggested that stx11 interacts with SNAP-23, a plasma membrane-localized SNARE protein, whose depletion also inhibits TLR4 replenishment in LPS-stimulated cells. Using an intramolecular Forster resonance energy transfer (FRET) probe for SNAP-23, we showed that the high FRET efficiency caused by LPS stimulation is reduced by stx11 knockdown. These findings suggest that stx11 regulates the stimulus-dependent transport of TLR4 to the plasma membrane by cooperating with SNAP-23 in macrophages. Our results clarify the regulatory mechanisms underlying intracellular transport of TLR4 and have implications for microbial pathogenesis and immune responses.