Regulators of G-Protein Signaling (RGS) Proteins: Region-Specific Expression of Nine Subtypes in Rat Brain

Abstract

The recently discovered regulators of G-protein signaling (RGS) proteins potently modulate the functioning of heterotrimeric G-proteins by stimulating the GTPase activity of G-protein ␣ subunits. The mRNAs for numerous subtypes of putative RGS proteins have been identified in mammalian tissues, but little is known about their expression in brain. We performed a systematic survey of the localization of mRNAs encoding nine of these RGSs, RGS3-RGS11, in brain by in situ hybridization. Striking region-specific patterns of expression were observed. Five subtypes, RGS4, RGS7, RGS8, RGS9, and RGS10 mRNAs, are densely expressed in brain, whereas the other subtypes (RGS3, RGS5, RGS6, and RGS11) are expressed at lower density and in more restricted regions. RGS4 mRNA is notable for its dense expression in neocortex, piriform cortex, caudoputamen, and ventrobasal thalamus. RGS8 mRNA is highly expressed in the cerebellar Purkinje cell layer as well as in several midbrain nuclei. RGS9 mRNA is remarkable for its nearly exclusive enrichment in striatal regions. RGS10 mRNA is densely expressed in dentate gyrus granule cells, superficial layers of neocortex, and dorsal raphe. To assess whether the expression of RGS mRNAs can be regulated, we examined the effect of an acute seizure on levels of RGS7, RGS8, and RGS10 mRNAs in hippocampus. Of the three subtypes, changes in RGS10 levels were most pronounced, decreasing by ϳ40% in a timedependent manner in response to a single seizure. These results, which document highly specific patterns of RGS mRNA expression in brain and their ability to be regulated in a dynamic manner, support the view that RGS proteins may play an important role in determining the intensity and specificity of signaling pathways in brain as well as their adaptations to synaptic activity. Key words: seizure; gene expression; striatum; neocortex; GTPase-activating proteins; Sst2; GAIPThe heterotrimeric G-proteins play a critical role in brain signal transduction by coupling extracellular receptors to intracellular signaling pathways. G-proteins are composed of single ␣, ␤, and ␥ subunits. The ␣ subunits are guanine nucleotide-binding proteins that are regulated through cycles of GTP and GDP binding. In the inactive state, the ␣ subunits are bound to GDP. They are activated by G-protein-coupled receptors (bound to ligand), which trigger the dissociation of GDP and the subsequent binding of GTP, which activates the ␣ subunit. The active state is terminated when the intrinsic GTPase activity contained within the ␣ subunit hydrolyzes GTP to GDP (for review, see Neer, 1995).Recently, a newly discovered class of protein, termed regulators of G-protein signaling (RGS) proteins, has been shown to modulate the f unctioning of G-proteins by activating the intrinsic GTPase activity of the ␣ subunits (for review, see Dohlman and Thorner, 1997;Koelle, 1997;Neer, 1997). RGS proteins thereby reduce the duration of the activated GTPbound state of the ␣ subunit, which inhibits G-protein f unction. RGS proteins were first discover...

Isolation, tissue expression, and chromosomal assignment of human RGS5, a novel G-protein signaling regulator gene

“…These observations are similar to findings for mouse RGS5 (Chen et al 1997). Recently, the localization of nine rat RGSs, including RGS5, was investigated systematically in rat brain, using an in-situ hybridization technique; the RGS5 mRNA was expressed at lower density in rat brain than in the other tissues examined (Gold et al 1997).…”

Repeated Unpredictable Stress and Antidepressants Differentially Regulate Expression of the Bcl-2 Family of Apoptotic Genes in Rat Cortical, Hippocampal, and Limbic Brain Structures

“…Labeling densities for each region studied were taken from each brain section per animal (both hemispheres). Polynomial calibration curves were fitted to relative optical density values measured from known 14 C-labeled radioactive step standards (Amersham) that were coexposed to the film along with the brain tissue sections (Gold et al, 1997). For the Bcl-xl and Bax film autoradiograms, analysis was done on films exposed to the slides for 4 days.…”

“…The partial cDNAs used as templates for riboprobe generation were generated by RT-PCR amplification using rat spleen and thymus cDNA as templates and Bcl-2-, Bclxl-, and Bax-specific primers with a T7 promoter sequence appended to the corresponding -3 0 primer as previously described (Gold et al, 1997). The cDNAs were confirmed by sequencing (Keck Facility, Yale University, CT).…”

“…Cresyl violet staining on adjacent cryostat cut sections was carried out according to published procedures (Gold et al, 1997). Briefly, sections were dehydrated in an alcohol series, rehydrated in distilled water, and stained in 0.3% cresyl violet solution for 15 s. After brief rinses in distilled water, followed by alcohol gradients, sections were mounted with Permount and observed by light microscopy.…”

The R7 Subfamily of RGS Proteins Assists Tachyphylaxis and Acute Tolerance at μ-Opioid Receptors

“…Contrary to that observed for other Gb1-4 subunits, the expression of Gb5 proteins is restricted to the brain (Watson et al, 1994;Fmost are found in the plasma membrane of neural cells (Watson et al, 1996;Betty et al, 1998). The mammalian R7 proteins are also found in the CNS (Gold et al, 1997;Snow et al, 1998; Thomas et al, 1998), where they are mostly associated with cell membranes (Rose et al, 2000;. In nervous tissues, the R7 proteins and Gb5 proteins are always found as dimers, indicating that this association is required for their GAP function on the corresponding Ga-GTP subunits (Snow et al, 1998;.…”