State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing 100871, China; National Center for Nanoscience and Technology, Beijing 100871, China.
National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Dev Cell. 2015 Oct 12;35(1):120-30. doi: 10.1016/j.devcel.2015.09.004. Epub 2015 Oct 1.
Many receptor-mediated endocytic processes are mediated by constitutive budding of clathrin-coated pits (CCPs) at spatially randomized sites before slowly pinching off from the plasma membrane (60-100 s). In contrast, clathrin-mediated endocytosis (CME) coupled with regulated exocytosis in excitable cells occurs at peri-exocytic sites shortly after vesicle fusion (∼10 s). The molecular mechanism underlying this spatiotemporal coupling remains elusive. We show that coupled endocytosis makes use of pre-formed CCPs, which hop to nascent fusion sites nearby following vesicle exocytosis. A dynamic cortical microtubular network, anchored at the cell surface by the cytoplasmic linker-associated protein on microtubules and the LL5β/ELKS complex on the plasma membrane, provides the track for CCP hopping. Local diacylglycerol gradients generated upon exocytosis guide the direction of hopping. Overall, the CCP-cytoskeleton-lipid interaction demonstrated here mediates exocytosis-coupled fast recycling of both plasma membrane and vesicular proteins, and it is required for the sustained exocytosis during repetitive stimulations.
许多受受体介导的内吞过程是通过网格蛋白包被陷窝（CCP）在空间随机位置的组成型出芽来介导的，然后从质膜缓慢地脱离（60-100 秒）。相比之下，在兴奋细胞中与调节性胞吐作用偶联的网格蛋白介导的内吞作用（CME）发生在囊泡融合后不久的胞吐作用位点附近（约 10 秒）。这种时空偶联的分子机制仍然难以捉摸。我们表明，偶联的内吞作用利用了预先形成的 CCP，这些 CCP 在囊泡胞吐作用后会跳跃到附近的新生融合位点。一个动态的皮质微管网络，通过微管上的细胞质连接蛋白和质膜上的 LL5β/ELKS 复合物锚定在质膜上，为 CCP 跳跃提供了轨道。胞吐作用产生的局部二酰基甘油梯度指导跳跃的方向。总的来说，这里展示的 CCP-细胞骨架-脂质相互作用介导了质膜和囊泡蛋白的快速再循环，这是在重复刺激期间持续胞吐作用所必需的。
