Large membrane domains in hair bundles specify spatially constricted radixin activation.
Large membrane domains in hair bundles specify spatially constricted radixin activation.
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DOI：
10.1523/jneurosci.6184-11.2012
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发表时间：
2012-03-28
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影响因子：
--
通讯作者：
Gillespie PG
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文献类型：
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作者：
Zhao H;Williams DE;Shin JB;Brügger B;Gillespie PG
脊椎动物发束的质膜与发束细胞骨架密切相互作用，以支持机械转导和动态平衡。为了确定鸡前庭束的膜组成，我们用脂质谱对纯化的鸡前庭束进行了分析。虽然束甘油磷脂和酰化链与其他内膜相似，但束神经酰胺和鞘磷脂几乎只含有短链饱和的酰化链。对分离的牛蛙前庭毛细胞的共聚焦成像显示，该束膜在空间上至少分为三个大的结构和功能域。一个膜结构域，包括体纤毛基尖和干的~1μm，踝关节连接的位置，富含脂磷酸酶PTPRQ(蛋白酪氨酸磷酸酶Q)和多唾液酸神经节苷脂。锥形结构域与轴结构域形成尖锐的边界，轴结构域包含质膜钙-ATPase PMCA2和磷脂酰肌醇4，5-二磷酸(PI(4，5)P2)；此外，尖端结构域具有高水平的胆固醇、PMCA2和PI(4，5)P2。蛋白质质谱仪显示，鸡前庭毛细胞束含有一套完整的蛋白质，可以运输、合成和降解PI(4，5)P2。膜结构域具有功能意义；对毛束稳定至关重要的Radioxin以PI(4，5)P2依赖的方式在锥形-轴边界被激活，允许蛋白质复合体在该位置组装。因此，立体纤毛内的膜域定义了发束内的区域，这些区域允许钙离子挤出的分隔和蛋白质复合体在离散位置的组装。
The plasma membrane of vertebrate hair bundles interacts intimately with the bundle cytoskeleton to support mechanotransduction and homeostasis. To determine the membrane composition of bundles, we used lipid mass spectrometry with purified chick vestibular bundles. While the bundle glycerophospholipids and acyl chains resemble those of other endomembranes, bundle ceramide and sphingomyelin nearly exclusively contain short-chain, saturated acyl chains. Confocal imaging of isolated bullfrog vestibular hair cells shows that the bundle membrane segregates spatially into at least three large structural and functional domains. One membrane domain, including the stereocilia basal tapers and ~1 μm of the shaft, the location of the ankle links, is enriched in the lipid phosphatase PTPRQ (protein tyrosine phosphatase Q) and polysialylated gangliosides. The taper domain forms a sharp boundary with the shaft domain, which contains the plasma-membrane Ca2+-ATPase PMCA2 and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2); moreover, a tip domain has elevated levels of cholesterol, PMCA2, and PI(4,5)P2. Protein mass spectrometry shows that bundles from chick vestibular hair cells contain a complete set of proteins that transport, synthesize, and degrade PI(4,5)P2. The membrane domains have functional significance; radixin, essential for hair-bundle stability, is activated at the taper-shaft boundary in a PI(4,5)P2-dependent manner, allowing assembly of protein complexes at that site. Membrane domains within stereocilia thus define regions within hair bundles that allow compartmentalization of Ca2+ extrusion and assembly of protein complexes at discrete locations.