TMEM16B, A Novel Protein with Calcium-Dependent Chloride Channel Activity, Associates with a Presynaptic Protein Complex in Photoreceptor Terminals
TMEM16B, A Novel Protein with Calcium-Dependent Chloride Channel Activity, Associates with a Presynaptic Protein Complex in Photoreceptor Terminals
复制标题
DOI：
10.1523/jneurosci.5546-08.2009
复制
发表时间：
2009-05-27
影响因子：
5.3
通讯作者：
Schulz, Heidi L.
中科院分区：
文献类型：
--
作者：
Stoehr, Heidi;Heisig, Julia B.;Schulz, Heidi L.
光感受器带状突触释放谷氨酸，以响应由巨大的对数可伸缩的光强度引起的膜电位的分级变化。神经递质的释放受细胞内钙水平的调节。大的钙离子依赖的氯电流是光感受器向二级神经元突触传递的重要调节器；这些电流的分子基础尚不清楚。我们克隆了人和小鼠的TMEM16B，TMEM16B是TMEM16家族跨膜蛋白家族的成员，并表明它丰富地存在于小鼠视网膜的光感受器突触终末。TMEM16B与接头蛋白PSD95、VELI3和MPP4共定位在突触带上，并包含一个共同的PDZ I类结合基序，能够与PSD95的PDZ结构域相互作用。此外，TMEM16B在MPP4基因缺陷小鼠的光感受器膜上丢失。这表明TMEM16B是一种新的突触前蛋白复合体，募集到光感受器的特定质膜域。通过卤化物敏感的荧光蛋白分析和全细胞膜片钳记录，当TMEM16B在哺乳动物细胞中过表达时，TMEM16B提供了钙依赖的氯电流。TMEM16B的分区定位和电生理特性表明，TMEM16B是光感受器突触中长期追逐的钙依赖氯通道的有力候选者。
Photoreceptor ribbon synapses release glutamate in response to graded changes in membrane potential evoked by vast, logarithmically scalable light intensities. Neurotransmitter release is modulated by intracellular calcium levels. Large Ca2+-dependent chloride currents are important regulators of synaptic transmission from photoreceptors to second-order neurons; the molecular basis underlying these currents is unclear. We cloned human and mouse TMEM16B, a member of the TMEM16 family of transmembrane proteins, and show that it is abundantly present in the photoreceptor synaptic terminals in mouse retina. TMEM16B colocalizes with adaptor proteins PSD95, VELI3, and MPP4 at the ribbon synapses and contains a consensus PDZ class I binding motif capable of interacting with PDZ domains of PSD95. Furthermore, TMEM16B is lost from photoreceptor membranes of MPP4-deficient mice. This suggests that TMEM16B is a novel component of a presynaptic protein complex recruited to specialized plasma membrane domains of photoreceptors. TMEM16B confers Ca2+-dependent chloride currents when overexpressed in mammalian cells as measured by halide sensitive fluorescent protein assays and whole-cell patch-clamp recordings. The compartmentalized localization and the electrophysiological properties suggest TMEM16B to be a strong candidate for the long sought-after Ca2+-dependent chloride channel in the photoreceptor synapse.