Institute of Medical Biochemistry, Center for Molecular Biology of Inflammation, University of Muenster, Muenster, Germany.
Kekulé Institute of Organic Chemistry and Biochemistry, University of Bonn, Bonn, Germany.
PLoS One. 2022 Jun 29;17(6):e0270299. doi: 10.1371/journal.pone.0270299. eCollection 2022.
Weibel-Palade bodies (WPB) are unique secretory granules of endothelial cells that store the procoagulant von-Willebrand factor (VWF) in a highly compacted form. Upon exocytosis the densely packed VWF unfurls into long strands that expose binding sites for circulating platelets and thereby initiate the formation of a platelet plug at sites of blood vessel injury. Dense packing of VWF requires the establishment of an acidic pH in the lumen of maturing WPB but the mechanism responsible for this acidification has not yet been fully established. We show here that subunits of the vacuolar-type H+-ATPase are present on mature WPB and that interference with the proton pump activity of the ATPase employing inhibitors of different chemical nature blocks a reduction in the relative internal pH of WPB. Furthermore, depletion of the V-ATPase subunit V0d1 from primary endothelial cells prevents WPB pH reduction and the establishment of an elongated morphology of WPB that is dictated by the densely packed VWF tubules. Thus, the vacuolar-type H+-ATPase present on WPB is required for proper acidification and maturation of the organelle.
血管内皮细胞特有的分泌颗粒 Weibel-Palade 体 (WPB) 以高度紧凑的形式储存促凝血因子 von-Willebrand 因子 (VWF)。WPB 通过胞吐作用将紧密包装的 VWF 展开成长链，暴露出与循环血小板结合的位点，从而在血管损伤部位启动血小板栓子的形成。VWF 的紧密包装需要在成熟 WPB 的腔中建立酸性 pH 值，但负责这种酸化的机制尚未完全确定。我们在这里表明，液泡型 H+-ATPase 的亚基存在于成熟的 WPB 上，并且使用不同化学性质的抑制剂干扰 ATPase 的质子泵活性会阻止 WPB 相对内部 pH 值的降低。此外，从原代内皮细胞中耗尽 V-ATPase 亚基 V0d1 会阻止 WPB pH 值降低以及 WPB 呈现出由紧密包装的 VWF 管决定的拉长形态。因此，WPB 上存在的液泡型 H+-ATPase 对于细胞器的适当酸化和成熟是必需的。
