The UDP - sugar - sensing P 2 Y 14 receptor promotes Rho - mediated signaling and chemotaxis 1 in human neutrophils

25 The Gi-coupled P2Y14 receptor (P2Y14-R) is potently activated by UDP-sugars and UDP. 26 Although P2Y14-R mRNA is prominently expressed in circulating neutrophils, the signaling 27 pathways and functional responses associated with this receptor are undefined. In this study, we 28 illustrate that incubation of isolated human neutrophils with UDP-glucose resulted in 29 cytoskeleton rearrangement, change of cell shape, and enhanced cell migration. We also 30 demonstrate that UDP-glucose promotes rapid, robust, and concentration-dependent activation of 31 RhoA in these cells. Ecto-nucleotidases expressed on neutrophils rapidly hydrolyzed 32 extracellular ATP, but incubation with UDP-glucose for up to 1 h resulted in negligible 33 metabolism of the nucleotide-sugar. HL60 human promyelocytic leukemic cells do not express 34 the P2Y14-R, but neutrophil differentiation of HL60 cells with DMSO resulted in markedly 35 enhanced P2Y14-R expression. Accordingly, UDP-glucose, UDP-galactose, and UDP-N36 acetylglucosamine promoted Rho activation in differentiated but not in undifferentiated HL60 37 cells. Stable expression of recombinant human P2Y14-R conferred UDP-sugar-promoted 38 responses to undifferentiated HL60 cells. UDP-glucose-promoted RhoA activation also was 39 accompanied by enhanced cell migration in differentiated HL60 cells, and these responses were 40 blocked by Rho kinase inhibitors. These results support the notion that UDP-glucose is a stable 41 and potent pro-inflammatory mediator that promotes P2Y14-R-mediated neutrophil motility via 42 Rho/Rho kinase activation. 43