Biogenesis of Weibel-Palade bodies.

Weibel-Palade bodies (WPBs) are the lysosome-related secretory organelles of endothelial cells. Their content protein von Willebrand factor, plays a key role in haemostasis, whilst P-selectin in the membranes is critical in the initiation of inflammation. Biogenesis of these rod-shaped structures is driven by von Willebrand factor, since its heterologous expression leads to formation of organelles morphologically indistinguishable from bona fide WPBs. The two main membrane proteins of WPBs, CD63 and P-selectin, have complex itineraries controlled largely by cytoplasmic targeting signals. We are only just beginning to understand the way in which these three proteins come together to form mature WPBs.