G Protein‐coupled Receptor as a Mechanosensor for Fluid Shear in Neutrophil

Abstract

Physiological fluid shear affects cell functions in a cell-types specific fashion. Fluid shear applied to leukocytes serves to control pseudopod formation, migration, and other functions. Specifically, activated fresh neutrophils or neutrophilic leukocytes derived from differentiated HL60 cells respond to fluid shear by cytoplasmic pseudopod retraction. The membrane elements that sense fluid shear and induce such a specific response are, however, still unknown. We found that fluid shear decreased constitutive activity of G-protein coupled receptor (GPCR) and inhibition of GPCR constitutive activity by inverse agonists abolished shear-induced cell area reduction. Formyl peptide receptor (FPR) exhibits relatively high constitutive activity among GPCRs in neutrophils. Undifferentiated HL60 cells with lack of FPR forms few pseudopods and no detectable response to fluid shear, while expression of FPR in undifferentiated HL60 cells caused pseudopod projection and robust retraction during fluid shear. FPR siRNA-transfected differentiated HL60 cells exhibited no response to fluid shear. We propose that in neutrophils FPR serves as a mechanosensor for fluid shear by decreasing its constitutive activity and reducing pseudopod projection. Supported by HL 42036.