2 research outputs found
The Effect of RGS4 on Autophagic Flux in Min6 Pancreatic Beta Cells
Defective autophagy can lead to dysregulation of metabolic homeostasis. Previous studies in our laboratory have shown that RGS4-overexpressing HEK cells show increased autophagic activity. Herein, we study the potential role of RGS4 as a regulator of autophagy in the Min6 mouse pancreatic beta cell line, via inhibition of Gαi3, an established attenuator of autophagy. Min6 cells exposed to nutrient-deprived conditions undergo autophagic initiation demonstrated by increased expression of autophagy markers. When RGS4-YFP is ectopically expressed in Min6 cells, confocal microscopy imaging revealed colocalization between RGS4-YFP (both wild type and loss-of-function mutants), Gαi3 (RC)-CFP, and autophagy markers including Beclin1-DsRed and Atg12-RFP on intracellular punctae. Despite its colocalization with known regulators of autophagy, RGS4 was apparently unable to modulate the activity of known mediators and markers of autophagic activity (phospho-p76S6K, LC3 II, phospho-Bcl-2). We conclude that Gαi3 and RGS4 are not major factors in the regulation of autophagic flux in Min6 cells.M.Sc.2017-11-20 00:00:0
RGS4-Deficiency Alters Intracellular Calcium and PKA-Mediated Control of Insulin Secretion in Glucose-Stimulated Beta Islets
A number of diverse G-protein signaling pathways have been shown to regulate insulin secretion from pancreatic β-cells. Accordingly, regulator of G-protein signaling (RGS) proteins have also been implicated in coordinating this process. One such protein, RGS4, is reported to show both positive and negative effects on insulin secretion from β-cells depending on the physiologic context under which it was studied. We here use an RGS4-deficient mouse model to characterize previously unknown G-protein signaling pathways that are regulated by RGS4 during glucose-stimulated insulin secretion from the pancreatic islets. Our data show that loss of RGS4 results in a marked deficiency in glucose-stimulated insulin secretion during both phase I and phase II of insulin release in intact mice and isolated islets. These deficiencies are associated with lower cAMP/PKA activity and a loss of normal calcium surge (phase I) and oscillatory (phase II) kinetics behavior in the RGS4-deficient β-cells, suggesting RGS4 may be important for regulation of both Gαi and Gαq signaling control during glucose-stimulated insulin secretion. Together, these studies add to the known list of G-protein coupled signaling events that are controlled by RGS4 during glucose-stimulated insulin secretion and highlight the importance of maintaining normal levels of RGS4 function in healthy pancreatic tissues