Gαq/11‐mediated AKT Activation and Intracellular Calcium Responses to Retrograde Flow in Endothelial Cells

Abstract

Temporal gradients in shear stress, including flow reversal, are key actors in the development of dysfunctional endothelial cells (EC) and atherosclerotic lesions. An almost immediate response of ECs to fluid shear stress is the increase in [Ca2+]i. We have previously shown that a change in flow direction (retrograde flow) on a flow‐adapted endothelial monolayer induced the realignment of the cell‐cell junction along with a dramatic [Ca2+]i burst. With an enriched expression at the junction Gαq/11 is a strong candidate in shear‐induced increase in [Ca2+]i and was previously shown to be activated within a second after onset of shear stress. In flow‐adapted human EC we have investigated multiple pathways leading to the increase of [Ca2+]i after reversal in flow direction. We observed that the average latency in [Ca2+]i response to a 10 dyn.cm−2 retrograde shear stress was increased by 15 sec in cells silenced for Gαq/11. A similar delay was observed after cells were treated with the PLCβγ inhibitor U73122 or the PI‐PLC inhibitor Edelfosine. Lower levels of IP3 production correlated with the increased latency in [Ca2+]i responses upon the different treatments. Gαq/11 silencing also led to complete abrogation of flow‐induced GSK‐3β and AKT activation. Taken together our results identify Gαq/11 activation as the initial trigger in retrograde flow‐induced [Ca2+]i and a major regulator of the AKT response to shear stress.