The five transmembrane vasoactive intestinal peptide receptor 1 isoform is expressed in human blood CD14+ monocyte cells

Abstract

Vasoactive intestinal peptide receptor 1 (VPAC1) is a 7 transmembrane (TM) G protein coupled receptor that couples to Gαs and increases intracellular cAMP levels in response to external stimuli. Recently, a novel VPAC1 isoform was identified in human peripheral blood mononuclear cells (PBMC) that lacks exons 10‐12 to form a 5TM receptor that lacks Gαs coupling, but elicits significant tyrosine phosphorylation when treated with exogenous ligand in ectopically overexpressed CHO cells. VPAC1 is a deactivating factor for peripheral blood monocytes by inhibiting the production of many proinflammatory cytokines, but fails to increase intracellular cAMP levels. We hypothesize dual expression of 5 and 7TM VPAC1 may act antagonistically with regard to intracellular cAMP elevation. Uncovering the expression profile of the 5TM VPAC1 splice variant is a necessary first step at understanding the biological role of this novel receptor isoform. To this end, mRNA was collected from CD14+ cells separated from human PBMC by magnetic beads. First strand cDNA was synthesized with anchored primers and the expression profile of the 7TM and 5TM assessed by RT‐PCR, sequence analysis, and Southern hybridization. Our findings suggest preferential 5TM expression in blood monocytes (CD14+). Research supported by NIH‐KO1 1K01DK064828 and COBRE 2P20RR05566.