Immunohistochemical distribution of RGS7 protein and cellular selectivity in colocalizing with G alpha q proteins in the adult rat brain

Regulators of G protein signaling (RGS) proteins serve as potent GTPase-act ivating proteins for the heterotrimeric G proteins alpha i/o and alpha q/11 . This study describes the immunohistochemical distribution of RGS7 through out the adult rat brain and its cellular colocalization with G alpha q/11, an important G protein-coupled receptor signal transducer for phospholipase C beta-mediated activity. In general, both RGS7 and G alpha q/11 displayed a heterogeneous and overlapping regional distribution. RGS7 immunoreactivi ty was observed in cortical layers I-VI, being most intense in the neuropil of layer I. In the hippocampal formation, RGS7 immunoreactivity was concen trated in the strata oriens, strata radiatum, mossy fibers, and polymorphic cells, with faint to nondetectable immunolabeling within the dentate gyrus granule cells and CA1-CA3 subfield pyramidal cells. Numerous diencephalic and brainstem nuclei also displayed dense RGS7 immunostaining. Dual immunof luorescence labeling studies with the two protein-specific antibodies indic ated a cellular selectivity in the colocalization between RGS7 and G alpha q/11 within many discrete brain regions, such as the superficial cortical l ayer I, hilus area of the hippocampal formation, and cerebellar Golgi cells . To assess the ability of G alpha q/11-mediated signaling pathways to modu late dynamically RGS expression, primary cortical neuronal cultures were in cubated with phorbol 12,13-dibutyrate, a selective protein kinase C activat or. A time-dependent increase in levels of mRNA for RGS7, but not RGS4, was observed. Our results provide novel information on the region- and cell-sp ecific pattern of distribution of RGS7 with the transmembrane signal transd ucer, G alpha q/11. We also describe a possible RGS7-selective neuronal fee dback adaptation on G alpha q/11-mediated pathway function, which may play an important role in signaling specificity in the brain.