MRC National Institute for Medical Research, The Ridgeway, London, United Kingdom.
Structural Biology of Cells and Viruses Laboratory, Francis Crick Institute, London, United Kingdom; and.
Blood. 2019 Jun 20;133(25):2707-2717. doi: 10.1182/blood-2018-09-874552. Epub 2019 Feb 13.
Weibel-Palade bodies (WPBs) are secretory granules that contain von Willebrand factor and P-selectin, molecules that regulate hemostasis and inflammation, respectively. The presence of CD63/LAMP3 in the limiting membrane of WPBs has led to their classification as lysosome-related organelles. Many lysosome-related organelles contain intraluminal vesicles (ILVs) enriched in CD63 that are secreted into the extracellular environment during cell activation to mediate intercellular communication. To date, there are no reports that WPBs contain or release ILVs. By light microscopy and live-cell imaging, we show that CD63 is enriched in microdomains within WPBs. Extracellular antibody recycling studies showed that CD63 in WPB microdomains can originate from the plasma membrane. By cryo-electron tomography of frozen-hydrated endothelial cells, we identify internal vesicles as novel structural features of the WPB lumen. By live-cell fluorescence microscopy, we directly observe the exocytotic release of EGFP-CD63 ILVs as discrete particles from individual WPBs. WPB exocytosis provides a novel route for release of ILVs during endothelial cell stimulation.
Weibel-Palade 小体（WPBs）是含有 von Willebrand 因子和 P-选择素的分泌颗粒，分别调节止血和炎症。CD63/LAMP3 存在于 WPBs 的限制膜中，导致其被归类为溶酶体相关细胞器。许多溶酶体相关细胞器含有富含 CD63 的腔内囊泡（ILVs），在细胞激活时分泌到细胞外环境中，以介导细胞间通讯。迄今为止，尚无报道称 WPBs 含有或释放 ILVs。通过光镜和活细胞成像，我们表明 CD63 在 WPBs 的微域中富集。细胞外抗体回收研究表明，WPB 微域中的 CD63 可以源自质膜。通过冷冻水合内皮细胞的低温电子断层扫描，我们确定内部囊泡是 WPB 管腔的新结构特征。通过活细胞荧光显微镜，我们直接观察到 EGFP-CD63 ILVs 作为离散颗粒从单个 WPB 中出胞释放。WPB 胞吐作用为内皮细胞刺激时 ILVs 的释放提供了新途径。
