Force sensing by Piezo1 regulates endothelial secretory granule exocytosis

Abstract

Endothelial cells (ECs) rapidly alter their phenotype to support haemostasis and inflammation through the exocytosis of specialised storage organelles, known as Weibel-Palade bodies (WPBs). This exocytic response is stimulated by a variety of physiological and pathological triggers which act through well-described transmembrane receptors. However, the influence of mechanical forces and how they shape this fundamental endothelial response remains relatively unexplored. Here we demonstrate that opening of the mechanosensitive cation channel Piezo1 on the EC surface triggers rapid WPB exocytosis. The dynamics and mechanisms were investigated using the Piezo1 agonist (Yoda1) and by modelling mechanical opening through EC-ICAM-1 ligation by THP-1 cells under low shear flow. In vitro, localised von Willebrand Factor (VWF) secretion occurred at THP-1 adhesion sites, suggesting a reciprocity of VWF release alongside leukocyte capture. In vivo, Yoda1 stimulation of tissues resulted in a dramatic increase in neutrophil and platelet adhesion to postcapillary venular walls, spatially aligned with cargo release (VWF). The rapid dynamics of this response was revealed by the application of high resolution confocal intravital microscopy to transgenic EGFP-Rab27a mice that exhibit fluorescent WPBs and neutrophils. These data reveal a previously unrecognised instigator of WPB exocytosis and uncover a mechanosensitive molecular pathway coupling inflammation with haemostasis. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=166 SRC="FIGDIR/small/678766v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@d8ed6org.highwire.dtl.DTLVardef@1cbc0corg.highwire.dtl.DTLVardef@7dd6a9org.highwire.dtl.DTLVardef@197f286_HPS_FORMAT_FIGEXP M_FIG Graphical abstract: Activation of Piezo1 by pharmacological agonism or leukocyte adherence to ICAM-1 under low flow promotes VWF secretion and platelet capture through a protein kinase C-dependent mechanism. C_FIG SUMMARYThis research describes how the mechanosensitive cation channel Piezo1 elicits the rapid exocytosis of endothelial secretory organelles, provoking platelet capture to sites of leukocyte adherence. The EGFP-Rab27a transgenic mouse demonstrates a technical advance, facilitating intravital imaging of endothelial secretory organelles.