The G protein β3 subunit splice variant Gβ3-s causes enhanced chemotaxis of human neutrophils in response to interleukin-8

Abstract

A C825T polymorphism was recently described in GNB3, the gene encoding the Gβ3 subunit of heterotrimeric G proteins. The 825T allele is associated with the expression of a shorter splice variant (Gβ3-s) and enhanced signal transduction via pertussis toxin (PTX)-sensitive G proteins. Given the pivotal role of G protein βγ dimers in chemotaxis, we related the genotype at the GNB3 locus as a marker for Gβ3-s expression to chemotaxis of human neutrophils in response to stimulation with interleukin-8 (IL-8). IL-8, which activates a CXC receptor coupled to PTX-sensitive G proteins, induced at 10 nM an enhanced maximum chemotaxis of neutrophils from individuals with TC/TT genotype compared to CC genotype. Furthermore, migration of neutrophils from 825T allele carriers was 2.5-fold higher at 0.1 nM and 1 nM IL-8. At these concentrations of IL-8, no significant chemotaxis was observed in neutrophils from homozygous C825 allele carriers, indicating a genotype-dependent, different potency of IL-8 to chemoattract neutrophils. In contrast, IL-8-induced Ca²⁺ signals and O^2– generation were independent of genotype. The role of Gβ3-s in enhanced chemotaxis could be confirmed by determination of chemotaxis of COS-7 cells following transfection with either Gβ3-s or "wild-type" Gβ3. Upon stimulation of the transfected cells with the chemoattractant lysophosphatidic acid (LPA), we observed an enhanced chemotactic response of Gβ3-s-transfected compared to Gβ3-transfected COS-7 cells, confirming that Gβ3-s actually causes enhanced chemotaxis.