E-selectin permits communication between PAF receptors and TRPC channels in human neutrophils

Abstract

The selectin family of molecules (L-, P-, and E-selectin) mediates adhesive interactions between leukocytes and endothelial cells required for recruitment of leukocytes to inflammatory sites. Soluble E-selectin levels are elevated in inflammatory diseases and act to promote neutrophil β2-integrin- mediated adhesion by prolonging Ca2+ mobilization. Although soluble E-selectin alone was unable to initiate Ca2+ signaling, it allowed a novel "permissive" store-operative calcium entry (SOCE) following the initial platelet-activating factor (PAF)-induced release of Ca2+ from inositol 1,4,5-trisphosphate (IP3)-sensitive stores. This induction of permissive SOCE in response to soluble E-selectin and PAF was shown to act through a G protein-coupled receptor (GPCR) coupled to pertussis toxin-insensitive Gq/11. Furthermore, we demonstrated that permissive SOCE was mediated by canonical transient receptor potential channel (TRPC) due to its sensitivity to specific inhibition by MRS1845 and Gd3+ and that TRPC6 was the principal TRPC family member expressed by human neutrophils. In terms of mechanism, we demonstrated that soluble E-selectin activated Src family tyrosine kinases, an effect that was upstream of phosphatidylinositol 3′-kinase in a signaling pathway that regulates permissive SOCE following exposure of neutrophils to PAF. In summary, this report provides the first evidence for communication between an inflammatory mediator and adhesion receptors at a molecular level, through selectin receptor ligation allowing permissive SOCE to occur following PAF stimulation of human neutrophils. © 2006 by The American Society of Hematology.