ABSTRACT
Along with functionally intact insulin, diabetes-associated insulin peptides are secreted by ß cells. By screening the expression and functional characterization of olfactory receptors (ORs) in pancreatic islets, we identified Olfr109 as the receptor that detects insulin peptides. The engagement of one insulin peptide, insB:9-23, with Olfr109 diminished insulin secretion through Gi-cAMP signaling and promoted islet-resident macrophage proliferation through a ß cell-macrophage circuit and a ß-arrestin-1-mediated CCL2 pathway, as evidenced by ß-arrestin-1-/- mouse models. Systemic Olfr109 deficiency or deficiency induced by Pdx1-Cre+/-Olfr109fl/fl specifically alleviated intra-islet inflammatory responses and improved glucose homeostasis in Akita- and high-fat diet (HFD)-fed mice. We further determined the binding mode between insB:9-23 and Olfr109. A pepducin-based Olfr109 antagonist improved glucose homeostasis in diabetic and obese mouse models. Collectively, we found that pancreatic ß cells use Olfr109 to autonomously detect self-secreted insulin peptides, and this detection arrests insulin secretion and crosstalks with macrophages to increase intra-islet inflammation.
Subject(s)
Insulin-Secreting Cells , Islets of Langerhans , Animals , Blood Glucose/metabolism , Diet, High-Fat , Glucose/metabolism , Insulin/metabolism , Insulin-Secreting Cells/metabolism , Islet Amyloid Polypeptide/metabolism , Islets of Langerhans/metabolism , Mice , Mice, Inbred C57BL , Receptors, G-Protein-Coupled/metabolismABSTRACT
Arrestins, in addition to desensitizing GPCR-induced G protein activation, also mediate G protein-independent signaling by interacting with various signaling proteins. Among these, arrestins regulate MAPK signal transduction by scaffolding mitogen-activated protein kinase (MAPK) signaling components such as MAPKKK, MAPKK, and MAPK. In this study, we investigated the binding mode and interfaces between arrestin-3 and JNK3 using hydrogen/deuterium exchange mass spectrometry, 19F-NMR, and tryptophan-induced Atto 655 fluorescence-quenching techniques. Results suggested that the ß1 strand of arrestin-3 is the major and potentially only interaction site with JNK3. The results also suggested that C-lobe regions near the activation loop of JNK3 form the potential binding interface, which is variable depending on the ATP binding status. Because the ß1 strand of arrestin-3 is buried by the C-terminal strand in its basal state, C-terminal truncation (i.e., pre-activation) of arrestin-3 facilitates the arrestin-3/JNK3 interaction.
