Browsing by Subject "RGS Proteins"
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Item Rgs16 is a Pancreatic Reporter of Chronic Hyperglycemia in Diabetes(2012-07-20) Ocal, Ozhan; Wilkie, ThomasDiabetes mellitus is a collection of metabolic diseases with chronic hyperglycemia as their common syndrome. Type 1 diabetes results from pancreatic insulin producing beta cell loss due to autoimmune attack and consequent insulin insufficiency, whereas type 2 diabetes occurs as a result of somatic cell insulin resistance under metabolic stress. Therapies include insulin supplementation for type 1 diabetics and diet control and augmented insulin release for type 2 diabetics. G-protein coupled receptors (GPCR) represent the largest non-antibiotic drug targets and several family members are expressed in beta cells. Regulators of G-protein Signaling (RGS) proteins are feedback regulators of GPCRs. Their expression can be induced by GPCR or cross-talk signals to inhibit GPCR pathway, thereby indicating when and where GPCR signaling occurs. Our studies utilizing Rgs16::GFP transgenic mouse previously showed that Rgs16 was expressed in embryonic pancreatic progenitor cells, endocrine cells, and postnatal vessel and ductal associated cells (VDAC). Euglycemic adults lacked pancreatic Rgs16::GFP expression. We investigated diabetic mice to determine if Rgs16::GFP would reactivate during beta cell expansion in adulthood. The type 1 diabetic models of beta cell death were streptozotocin (STZ) treatment and PANIC-ATTAC mice. Type 2 diabetic models consisted of ob/ob mice and diet induced obesity. In each case, Rgs16::GFP expression initiated in islets and VDAC after at least 6 days of chronic hyperglycemia. STZ induced Rgs16::GFP expression was reduced after lowering blood glucose levels with systematic insulin administrations. Furthermore, hyperglycemia dependent Rgs16::GFP expression required metabolic transcription factor Carbohydrate Response Element Binding Protein (ChREBP), as pancreatic Rgs16::GFP was absent in STZ-treated ChREBP KO mice. We found that Rgs16::GFP is also expressed in Pancreatic Ductal Adenocarcinoma (PDAC) tumors and primary tissue culture cells. RNA-Seq analysis revealed that cultured PDAC cells express many genes in common with embryonic progenitors of ductal and endocrine cells and identified expression of 63 GPCRs. In summary, our results suggest that Rgs16::GFP is stimulated by GPCR signals relayed from a "hyperglycemia sensor". We propose that Rgs16 is a faithful pancreatic biomarker of diabetes and Rgs16::GFP PDAC culture and diabetic reporter mice are beneficial resources to identify ligands that stimulate beta cell expansion without promoting cancer.Item A Structural/Behavioral Analysis of the Regulation of Dopamine Signaling by Striatal RGS Proteins(2005-08-11) Waugh, Jeffrey Lynn; Gold, Stephen J.The regulators of G-protein signaling (RGS) proteins negatively modulate heterotrimeric G protein signaling by acting as GTPase activating proteins for Galpha subunits. In the striatum and nucleus accumbens, brain regions critical for control of movement, motivation and reward, overlapping RGS expression profiles suggested that functional specificity could not be explained by anatomical localization alone. We set out to assess striatal specificity within two distinct RGS pools, the R7 RGS subfamily and RGS10. The highly striatal-specific splice form RGS9-2 is a negative modulator of dopamine D2 receptor signaling, and has been shown to inhibit drug stimulated (cocaine or direct dopamine receptor agonists) locomotor activity. RGS9-2 is a member of the R7 subfamily, comprised of RGS6, -7, -9, and -11, which share highly similar subdomain structure. We analyzed the specificity of R7 modulation of dopamine receptor signaling using a novel behavioral assay. R7 RGS proteins were virally-overexpressed in rat or mouse accumbens via a stereotaxic injection of an engineered HSV virus. Following this surgery, drug-stimulated locomotor responses were assayed. We found that in rats and RGS9 KO mice, overexpression of R7 RGS proteins produces distinct locomotor and drug sensitization phenotypes, each of which occurs only during the period of RGS overexpression. Moreover, studies using truncation and chimeric RGS mutants demonstrated that while all tested subdomains were necessary for activity, only the C-terminus of RGS9-2 was sufficient to convey activity to RGS7. Lastly, RGS overexpression leads to distinct acute changes in weight: loss (RGS9-2) or gain (RGS7, RGS11). To elucidate RGS10 function in the brain, we mapped RGS10 protein in rodent brain using light microscopic and electron microscopic immunohistochemical techniques. Light microscopic analyses showed that RGS10 immunoreactivity labels all subcompartments of neurons and microglia, including their nuclei. Electron microscopy confirmed the presence of dense RGS10 immunoreactivity in euchromatin and resolved dense staining on terminals at symmetric synapses onto pyramidal cell somata. Dual-labeling histochemistry showed that RGS10 is expressed in specific neuronal cell types and circuits. Taken together, these data support a role for RGS10 in diverse processes including modulation of pre- and postsynaptic G-protein signaling and a potential role in modulating gene expression.