IDENTIFICATION OF ADDITIONAL MEMBERS OF HUMAN G-PROTEIN-COUPLED RECEPTOR KINASE MULTIGENE FAMILY

Human neutrophils express several distinct guanine nucleotide binding (G)-protein-coupled receptors that mediate their responsiveness to che moattractants. Phosphorylation by receptor-specific and second messeng er-activated protein kinases is a common mechanism for regulation of G -protein-coupled receptors. To explore the possibility that chemoattra ctant receptors are regulated by unique receptor kinases, we utilized PCR to identify receptor kinases in human neutrophils. Here, we report the isolation of three G-protein-coupled-receptor kinase (GPRK)-like sequences termed GPRK5, GPRK6, and GPRK7 in addition to the beta-adren ergic receptor kinase (betaARK) 1 and 2 isoforms (betaARK1 and betaARK 2). Two, GPRK5 and GPRK6, showed high homology at the amino acid level to the recently identified receptor-kinase-like sequence localized cl ose to the Huntington disease locus. GPRK7 is of interest in that it c ontains a DLG (Asp-Leu-Gly) amino acid motif of receptor kinases prece ded by a DFD (Asp-Phe-Asp) motif. We isolated cDNAs corresponding to G PRK6; the complete sequence shows >66% identity and 81% similarity at the amino acid level to the GPRK from the Huntington disease locus. Th e GPRK6 cDNA probe hybridizes to two mRNAs of 2.9 and 2.1 kb that were expressed in all the tested human tissues including HL-60 cells and n eutrophils. Genomic Southern blot analysis and chromosome mapping show ed that GPRK6 hybridizes to two closely related genes located on chrom osomes 5 and 13 and are, therefore, distinct from the GPRK located nea r the Huntington disease locus on chromosome 4. The identification her ein of three putative receptor kinases indicates that in addition to b etaARK and rhodopsin kinase subfamilies, there are other receptor-kina se subfamilies that regulate the broad spectrum of G-protein-coupled r eceptors.