Differential contributions of G protein‐ or arrestin subtype‐mediated signalling underlie urocortin 3‐induced somatostatin secretion in pancreatic δ cells

Abstract

AbstractBackground and PurposePancreatic islets are modulated by cross‐talk among different cell types and paracrine signalling plays important roles in maintaining glucose homeostasis. Urocortin 3 (UCN3) secreted by pancreatic β cells activates the CRF2 receptor (CRF2R) and downstream pathways mediated by different G protein or arrestin subtypes in δ cells to cause somatostatin (SST) secretion, and constitutes an important feedback circuit for glucose homeostasis.Experimental ApproachHere, we used Arrb1−/−, Arrb2−/−, Gsfl/fl and Gqfl/fl knockout mice, the G11‐shRNA‐GFPfl/fl lentivirus, as well as functional assays and pharmacological characterization to study how the coupling of Gs, G11 and β‐arrestin1 to CRF2R contributed to UCN3‐induced SST secretion in pancreatic δ cells.Key ResultsOur study showed that CRF2R coupled to a panel of G protein and arrestin subtypes in response to UCN3 engagement. While RyR3 phosphorylation by PKA at the S156, S2706 and S4697 sites may underlie the Gs‐mediated UCN3‐ CRF2R axis for SST secretion, the interaction of SYT1 with β‐arrestin1 is also essential for efficient SST secretion downstream of CRF2R. The specific expression of the transcription factor Stat6 may contribute to G11 expression in pancreatic δ cells. Furthermore, we found that different UCN3 concentrations may have distinct effects on glucose homeostasis, and these effects may depend on different CRF2R downstream effectors.Conclusions and ImplicationsCollectively, our results provide a landscape view of signalling mediated by different G protein or arrestin subtypes downstream of paracrine UCN3‐ CRF2R signalling in pancreatic β‐δ‐cell circuits, which may facilitate the understanding of fine‐tuned glucose homeostasis networks.