Mechanochemical signal transduction occurs when mechanical forces, such as fluid shear stress, are converted into biochemical responses within the cell. The molecular mechanisms by which endothelial cells (ECs) sense/transduce shear stress into biological signals, including the nature of the mechanosensor, are still unclear. G proteins and G protein-coupled receptors (GPCRs) have been postulated independently to mediate mechanotransduction. In this study, we used in situ proximity ligation assay (PLA) to investigate the role of a specific GPCR/Gαq/11 pair in EC shear stress-induced mechanotransduction. We demonstrated that S1P stimulation causes a rapid dissociation at 0.5 min of Gαq/11 from its receptor, S1P3, followed by an increased association within 2 min of GRK2 and β-arrestin 1/2 with S1P3 in human coronary artery ECs, which are consistent with GPCR/Gαq/11 activation and receptor desensitization/internalization. The G protein activator, AlF4-, resulted in increased dissociation of Gαq/11 from S1P3, but no increase in association between S1P3 and either GRK2 or β-arrestin 1/2. The G protein inhibitor, GDP-β-S, and the S1P3 antagonist, VPC23019, both prevented S1P-induced activation. Shear stress also caused the rapid activation within 7 sec of S1P3/Gαq/11. There were no increased associations between S1P3 and GRK2 or S1P3 and β-arrestin 1/2 until 5 min. GDP-β-S, but not VPC23019, prevented dissociation of Gαq/11 from S1P3 in response to shear stress. Shear stress did not induce rapid dephosphorylation of β-arrestin 1 nor rapid internalization of S1P3, indicating no GPCR activation. These findings suggest that Gαq/11 participates in the sensing/transducing of shear stress independent of GPCR activation in ECs.
- endothelial cell
- G protein-coupled receptors (GPCR)
- heterotrimeric G proteins
- shear stress
- Copyright © 2017, American Journal of Physiology-Cell Physiology