Orai3 Surface Accumulation and Calcium Entry Evoked by Vascular Endothelial Growth Factor

Vascular endothelial growth factor (VEGF) acts, in part, by triggering calcium ion (Ca(2+)) entry. Here, we sought understanding of a Synta66-resistant Ca(2+) entry pathway activated by VEGF.

Measurement of intracellular Ca(2+) in human umbilical vein endothelial cells detected a Synta66-resistant component of VEGF-activated Ca(2+) entry that occurred within 2 minutes after VEGF exposure. Knockdown of the channel-forming protein Orai3 suppressed this Ca(2+) entry. Similar effects occurred in 3 further types of human endothelial cell. Orai3 knockdown was inhibitory for VEGF-dependent endothelial tube formation in Matrigel in vitro and in vivo in the mouse. Unexpectedly, immunofluorescence and biotinylation experiments showed that Orai3 was not at the surface membrane unless VEGF was applied, after which it accumulated in the membrane within 2 minutes. The signaling pathway coupling VEGF to the effect on Orai3 involved activation of phospholipase Cγ1, Ca(2+) release, cytosolic group IV phospholipase A2α, arachidonic acid production, and, in part, microsomal glutathione S-transferase 2, an enzyme which catalyses the formation of leukotriene C4 from arachidonic acid. Shear stress reduced microsomal glutathione S-transferase 2 expression while inducing expression of leukotriene C4 synthase, suggesting reciprocal regulation of leukotriene C4-synthesizing enzymes and greater role of microsomal glutathione S-transferase 2 in low shear stress.

VEGF signaling via arachidonic acid and arachidonic acid metabolism causes Orai3 to accumulate at the cell surface to mediate Ca(2+) entry and downstream endothelial cell remodeling.