<p>The maintenance of glucose homeostasis is an intricately coordinated physiological process that requires the precise regulation of pancreatic β-cell insulin secretion in response to surrounding glucose, hormones, neuronal signals, and nutrients. Among the diverse inputs that shape β-cell activity, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) play important roles by potentiating insulin secretion in a glucose-dependent manner. Both hormones exert their actions primarily through G protein–coupled receptors (GPCRs) that engage the stimulatory G protein α-subunit (Gαs) to activate adenylyl cyclase, increase cyclic AMP (cAMP) levels, and stimulate downstream signaling via protein kinase A (PKA) and exchange proteins activated by cyclic AMP-2 (EPAC2). However, recent advances in receptor pharmacology have illuminated the complexity of incretin receptor signaling, revealing roles for Gαq, β-arrestin, and alternative G protein couplings.</p><p>Capozzi <i>et al</i>.<span><sup>1</sup></span> sought to delineate the precise contribution of β-cell Gαs to insulin secretory function and incretin responsiveness using a conditional, inducible mouse model that lacks <i>guanine nucleotide-binding protein, alpha stimulating</i> (<i>Gnas</i>), the gene encoding Gαs, specifically in β-cells after development. This experimental design avoided confounding developmental abnormalities observed in earlier models and allowed for the dissection of Gαs-dependent vs. Gαs-independent mechanisms in β-cell physiology. Within days of gene deletion, inducible β-cell-specific <i>Gnas</i>-knockout (iβGnasKO) mice developed stable hyperglycemia, unaffected by age or metabolic status. Interestingly, despite the profound loss of glycemic control, iβGnasKO mice maintained normal body weight, islet area, and β-cell mass. Insulin content and proinsulin processing within the islets were unaltered, supporting the notion that β-cells were synthesized but failed to effectively secrete insulin. These observations suggest that Gαs signaling is indispensable for maintaining dynamic insulin secretory capacity at the level of stimulus–secretion coupling. iβGnasKO mice exhibited severe glucose intolerance with markedly impaired insulin responses during glucose and mixed-meal tolerance tests. Both fasting and postprandial insulin secretions were blunted, indicating a generalized β-cell secretory defect. This phenotype persisted under both normal and high-fat diets, reflecting a compensated yet stable diabetic state driven by β-cell dysfunction rather than insulin deficiency.</p><p>Perfusion studies of isolated islets from iβGnasKO mice revealed a dramatic suppression of insulin secretion in response to diverse secretagogues, including glucose, acetylcholine, and potassium chloride depolarization. Correspondingly, intracellular cAMP generation was severely blunted, and the phosphorylation of PKA substrates was markedly decreased. Even stimuli that nominall
{"title":"Gαs defines the fundamental coupling mechanism of insulin secretion","authors":"Jun Shirakawa","doi":"10.1111/jdi.70208","DOIUrl":"10.1111/jdi.70208","url":null,"abstract":"<p>The maintenance of glucose homeostasis is an intricately coordinated physiological process that requires the precise regulation of pancreatic β-cell insulin secretion in response to surrounding glucose, hormones, neuronal signals, and nutrients. Among the diverse inputs that shape β-cell activity, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) play important roles by potentiating insulin secretion in a glucose-dependent manner. Both hormones exert their actions primarily through G protein–coupled receptors (GPCRs) that engage the stimulatory G protein α-subunit (Gαs) to activate adenylyl cyclase, increase cyclic AMP (cAMP) levels, and stimulate downstream signaling via protein kinase A (PKA) and exchange proteins activated by cyclic AMP-2 (EPAC2). However, recent advances in receptor pharmacology have illuminated the complexity of incretin receptor signaling, revealing roles for Gαq, β-arrestin, and alternative G protein couplings.</p><p>Capozzi <i>et al</i>.<span><sup>1</sup></span> sought to delineate the precise contribution of β-cell Gαs to insulin secretory function and incretin responsiveness using a conditional, inducible mouse model that lacks <i>guanine nucleotide-binding protein, alpha stimulating</i> (<i>Gnas</i>), the gene encoding Gαs, specifically in β-cells after development. This experimental design avoided confounding developmental abnormalities observed in earlier models and allowed for the dissection of Gαs-dependent vs. Gαs-independent mechanisms in β-cell physiology. Within days of gene deletion, inducible β-cell-specific <i>Gnas</i>-knockout (iβGnasKO) mice developed stable hyperglycemia, unaffected by age or metabolic status. Interestingly, despite the profound loss of glycemic control, iβGnasKO mice maintained normal body weight, islet area, and β-cell mass. Insulin content and proinsulin processing within the islets were unaltered, supporting the notion that β-cells were synthesized but failed to effectively secrete insulin. These observations suggest that Gαs signaling is indispensable for maintaining dynamic insulin secretory capacity at the level of stimulus–secretion coupling. iβGnasKO mice exhibited severe glucose intolerance with markedly impaired insulin responses during glucose and mixed-meal tolerance tests. Both fasting and postprandial insulin secretions were blunted, indicating a generalized β-cell secretory defect. This phenotype persisted under both normal and high-fat diets, reflecting a compensated yet stable diabetic state driven by β-cell dysfunction rather than insulin deficiency.</p><p>Perfusion studies of isolated islets from iβGnasKO mice revealed a dramatic suppression of insulin secretion in response to diverse secretagogues, including glucose, acetylcholine, and potassium chloride depolarization. Correspondingly, intracellular cAMP generation was severely blunted, and the phosphorylation of PKA substrates was markedly decreased. Even stimuli that nominall","PeriodicalId":51250,"journal":{"name":"Journal of Diabetes Investigation","volume":"17 1","pages":"9-11"},"PeriodicalIF":3.0,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jdi.70208","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145601404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}