Molecular cloning of pour human rgs12 cdnas, genomic organization and chromosomal localization of the rgs12 gene and functional analysis of the brain-specific variant of rgs12

RGS proteins represent a newly discovered protein family that acts HS regulators of heterot rimeric G protoin signaling- We report here the cloning of a new member of the human RGS protein family, RGS 12. We amplified and doned cDNAs encoding four distinct isoforms of human RGS12, whose trans( ripts are expressed in a tissue-specific manner. These RGS12 cDNAs encode proteins ranging in size from 646 to 1447 amino acids. The RGS 12 gene is located in the huntington disease region of chromosome 4 (4pl6.3), spans 70 kb of genornic DNA and conî.ains 16 exons. Tissue-specific transcripts of RGS12 are generated by both ris- and trans-splicing mechanisms. The four RGS12 isoforms differ in their amino-terminal .sequences but share a large protein domain carboxyl to the RGS domain. RGS12TS, the trans-spliced RGS12 isofonn. also has a large amino terminal domain in which <\ PDZ protein binding module is located. Transient expression of the brain-specific isoforms of RGS 12 (RGS12B) in COS-7 cells attenuated phosphorylation of mitogen-activated protein kinase mediated by the Gi-couplod lysophosphatidic acid receptor. Our findings provide the first evidencp for the existence of splice variants of an RGS protein arid document the negative regulatory effects of one isofonn on G protein-mediated signaling. The large size of RGS12 proteins and the existence of other protein binding modules in RGS 12 raises the possibility that the functional role of some RGS proteins may be more complex than currently believed.