STIM1 for stimulation of phagocyte NADPH oxidase

Abstract

In this issue of Blood, Zhang et al show that mice lacking the stromal-interacting molecule 1 (STIM1) gene in bone marrow cells are more susceptible to bacterial infection but are resistant to ischemia/reperfusion injury because of defective activation of phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase.

Activation of the formyl peptide receptor 1 (FPR1) by fMet-Leu-Phe (fMLF), the integrin by pRGD (an Arg-Gly-Asp-containing fibronectin-like binding fragment), and the Fcg receptors (not shown) leads to phospholipase C (PLC) activation, hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP₂), and IP₃ production. The resulting release of Ca²⁺ from ER triggers STIM1-dependent Ca²⁺ influx, causing sustained increase of intracellular Ca²⁺ concentration through the opening of the ORAI calcium release-activated calcium modulator, and the transient receptor potential (TRP) channel, TRPC. Ca²⁺-dependent and diacylglycerol (DAG)-dependent activation of PKCa and PKCb leads to phosphorylation of p47^phox (circled P's in the figure) and assembly of a functional NADPH oxidase in neutrophils. FAK, focal adhesion kinase that mediates integrin signaling; p47^phox, a cytosolic component of the phagocyte NADPH oxidase (phox) with an apparent molecular weigh of 47 kDa. Professional illustration by Debra T. Dartez.