Abstract
The Weibel–Palade body (WPB) is one of the lysosome-related organelles (LROs) in endothelial cells, whose main content is von Willebrand factor (vWF). The biogenesis of LROs is regulated by the Hermansky–Pudlak syndrome (HPS) protein-associated complexes through transporting cargo proteins to WPBs. Our previous studies have shown that HPS6, a subunit of BLOC-2 complex, is likely involved in the maturation of WPBs. However, the underlying mechanism remains unknown. In this study, we found that the knockdown of HPS6 in human umbilical vein endothelial cells (HUVECs) resulted in misshaped WPBs, decreased WPB number, and impaired vWF tubulation, which are similar to the characteristics of HPS6-deficient mouse endothelial cells. We observed similar morphological changes of WPBs in HUVECs after the knockdown of ATP6V0D1 (a subunit of v-ATPase). Furthermore, we found that HPS6 interacted with ATP6V0D1, suggesting that HPS6 transports ATP6V0D1 to the WPB limiting membrane for the assembly of the v-ATPase complex to maintain its acidic luminal pH, which is critical for the formation of vWF tubules during WPB maturation. In conclusion, HPS6 likely regulates the biogenesis of WPBs by participating in the trafficking of v-ATPase to the WPB membrane.
Highlights
Endothelial cells (ECs) form a layer of flat and polygonal cells that line the vascular wall, which is the biological barrier between the circulating blood and the blood vessel wall and is of great significance to maintain vascular homeostasis (Aird, 2007)
Immunofluorescence staining and statistical analysis showed that the average number of Weibel–Palade body (WPB) per cell in ru mice was higher than that in WT mice at 0-h time point after PMA treatment (Figures 1A,E) because there may be more immature WPBs that have not been released completely in ru mice compared with WT mice
Our results showed that most WPBs in the bafilomycin A1 (Baf A1) group lost their elongated phenotype (Figure 4B), which was consistent with the phenotype of the knockdown of HPS6 (KD-HPS6) group (Figure 2B), whereas no obvious abnormality was found in the DMSO control group (Figure 4A)
Summary
Endothelial cells (ECs) form a layer of flat and polygonal cells that line the vascular wall, which is the biological barrier between the circulating blood and the blood vessel wall and is of great significance to maintain vascular homeostasis (Aird, 2007). The Weibel–Palade body (WPB) is a type of lysosome-related organelles (LROs) (Marks et al, 2013), which was discovered in 1964 by Ewald Weibel and George Palade in rat and human ECs (Weibel and Palade, 1964; Warhol and Sweet, 1984). As a morphological marker of ECs, WPBs are rod-shaped granules with a diameter of 0.1–0.3 μm and a length of 1–5 μm (Arribas and Cutler, 2000; Michaux and Cutler, 2004; Valentijn et al, 2008). WPBs contain various bioactive molecules, such as von Willebrand factor (vWF), angiopoietin-2, interleukin-6 and -8, monocyte chemoattractant protein-1, and P-selectin, which are released in response to the activation of ECs (Schillemans et al, 2019). VWF forms a highly multimerized tubular structure that is closely related to the shape and size of WPBs (Wagner et al, 1982; Karampini et al, 2020). Upon release into the plasma, the vWF tubules will unfurl into long strings that recruit platelets to prevent bleeding (Savage et al, 2002)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
