Inceptor binds to and directs insulin towards lysosomal degradation in beta-cells
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE226346 | GEO | 2024/09/16
REPOSITORIES: GEO
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Project description:Blunted first-phase insulin secretion and insulin deficiency are early signs of -cell dysfunction and diabetes manifestation. Thus, insights into molecular mechanisms that regulate insulin homeostasis might provide entry sites to replenish insulin content and restore -cell function. Here, we identified the insulin inhibitory receptor (short: inceptor; encoded by the gene IIR) as an insulin-binding receptor that regulates insulin stores by lysosomal degradation. Using human induced pluripotent stem cell (iPSC)-derived islets, we show that IIR knockout (KO) results in enhanced stem cell (SC)--cell differentiation, maturation, and survival. Strikingly, extended in vitro culture of IIR KO SC--cells leads to greatly increased insulin content and glucose-stimulated insulin secretion (GSIS). We find inceptor localized to clathrin-coated vesicles close to the plasma membrane (PM) and in the trans-Golgi network (TGN), as well as in secretory granules (SGs), where it acts as a sorting receptor to direct proinsulin and insulin towards lysosomal degradation. Targeting inceptor using a monoclonal antibody increases insulin content and improves SC--cell function. Altogether, our findings revealed basic mechanisms of -cell insulin turnover and identified inceptor as a druggable insulin degradation receptor.
2024-09-09 | PXD040758 | Pride
Project description:Proinsulin is the precursor of insulin in pancreatic beta cells. Altered proinsulin and proinsulin to insulin ratio mark beta cell dysfunction, predictuing disease progression into type 1 and type 2 diabetes. Of essential role for beta cell function, knowledge about proinsulin production and its role in disease are currently very limited. Using genome wide CRISPR screen, we identified 84 proinsulin regulators including classical protein convertases Pcsk1 and Cpe, and novel factors like Pdia6. Among the list 29 proinsulin regulators were trajectory genes involved in disease progression in obesity and type 2 diabetes in humans. In vivo mouse genetics study revealed unique genetic architecture and quantitative trait loci (QTLs) modulating plasma proinsulin levels. Integrative analyzing and mapping of the QTL signals directly pinpointed to proinsulin regulators identified from the CRISPR screen, which in return greatly improved resolution of the mouse genetic study. 4 out of 5 overlapped genes can be individually validated. Knocking down the leading hits Pdia6 leads to decreased proinsulin content and remarkable loss of proinsulin granules in beta cells. Consequently, proinsulin secretion was greatly decreased. Mechanistically, protein translation rate was greatly impaired after knocking down Pdia6. Our study demonstrated the power of combining in vitro functional genomics with in vivo mouse genetics study to identify proinsulin regulatory network in pancreatic beta cells.
2023-11-15 | GSE245845 | GEO
Project description:Proinsulin is the precursor of insulin in pancreatic beta cells. Altered proinsulin and proinsulin to insulin ratio mark beta cell dysfunction, predictuing disease progression into type 1 and type 2 diabetes. Of essential role for beta cell function, knowledge about proinsulin production and its role in disease are currently very limited. Using genome wide CRISPR screen, we identified 84 proinsulin regulators including classical protein convertases Pcsk1 and Cpe, and novel factors like Pdia6. Among the list 29 proinsulin regulators were trajectory genes involved in disease progression in obesity and type 2 diabetes in humans. In vivo mouse genetics study revealed unique genetic architecture and quantitative trait loci (QTLs) modulating plasma proinsulin levels. Integrative analyzing and mapping of the QTL signals directly pinpointed to proinsulin regulators identified from the CRISPR screen, which in return greatly improved resolution of the mouse genetic study. 4 out of 5 overlapped genes can be individually validated. Knocking down the leading hits Pdia6 leads to decreased proinsulin content and remarkable loss of proinsulin granules in beta cells. Consequently, proinsulin secretion was greatly decreased. Mechanistically, protein translation rate was greatly impaired after knocking down Pdia6. Our study demonstrated the power of combining in vitro functional genomics with in vivo mouse genetics study to identify proinsulin regulatory network in pancreatic beta cells.
2023-11-15 | GSE245844 | GEO
Project description:Impaired proinsulin processing is observed in both type 1 and type 2 diabetes. We have previously shown that reductions in endoplasmic reticulum (ER) calcium (Ca2+) in the pancreatic β cell arising from impaired activity of the Sarcoendoplasmic Reticulum Ca2+ ATPase (SERCA) pump are associated with increased proinsulin secretion. However, the mechanisms responsible for reduced proinsulin processing in the context of SERCA2 deficiency remain incompletely understood. To test this, we developed mice with β cell specific SERCA2 deletion (βS2KO mice) and S2KO INS1 cells. βS2KO mice exhibited age-dependent glucose intolerance and reduced glucose-stimulated insulin secretion without evidence of impaired insulin sensitivity. ER Ca2+ levels in islets from βS2KO mice were significantly reduced, while serum proinsulin/insulin (PI/I) ratios and whole pancreas PI/I content were elevated. Immunoblot analysis of βS2KO islets and S2KO INS-1 cells revealed reduced active forms of the proinsulin processing enzymes, PC1/3, PC2 and CPE. Restoration of SERCA2b via adenoviral transduction in S2KO INS1 cells was sufficient to restore PC1/3 and PC2 maturation and enzyme activity. Brefeldin A treatment in INS1 cells recapitulated the impairments in PC1/3 and PC2 maturation observed in S2KO cells, suggesting a disturbance in protein trafficking between the ER and Golgi. Consistent with this, trafficking assays were performed using a vesicular stomatitis virus G (VSVG) protein construct and revealed a significantly slower rate of VSVG movement from the ER to the Golgi in S2KO INS1 cells. Moreover, pancreas sections from βS2KO mice showed increased co-localization of proinsulin and ProPC2 in the early compartments of the secretory pathway. Taken together, these data suggest that loss of SERCA2 activity and ER Ca2+ loss in the pancreatic β cell leads to impaired proinsulin processing via reduced maturation and trafficking of proinsulin processing enzymes.
2023-10-11 | GSE207498 | GEO
Project description:The pancreas plays a critical role in maintaining glucose homeostasis through the secretion of hormones from the islets of Langerhans. Glucose-stimulated insulin secretion (GSIS) by the pancreatic beta-cell is the main mechanism for reducing elevated plasma glucose.
Here we present a systematic modeling workflow for the development of kinetic pathway models using the Systems Biology Markup Language (SBML). An important factor was the reproducibility and exchangeability of the model, which allowed the use of various existing tools.
The workflow was applied to construct a novel data-driven kinetic model of GSIS in the pancreatic beta-cell based on experimental and clinical data from 39 studies spanning 50 years of pancreatic, islet, and beta-cell research in humans, rats, mice, and cell lines. The model consists of detailed glycolysis and phenomenological equations for insulin secretion coupled to cellular energy state, ATP dynamics and (ATP/ADP ratio).
Key findings of our work are that in GSIS there is a glucose-dependent increase in almost all intermediates of glycolysis. This increase in glycolytic metabolites is accompanied by an increase in energy metabolites, especially ATP and NADH. One of the few decreasing metabolites is ADP, which, in combination with the increase in ATP, results in a large increase in ATP/ADP ratios in the beta-cell with increasing glucose. Insulin secretion is dependent on ATP/ADP, resulting in glucose-stimulated insulin secretion.
2024-01-18 | MODEL2401110001 | BioModels
Project description:After the discovery of insulin a century ago, extensive work has been done to unravel the molecular network regulating insulin secretion. Here, we performed a chemical screen and identified AZD7762, a compound that potentiates glucose-stimulated insulin secretion (GSIS) of human β cell line, healthy and type 2 diabetic (T2D) human islets, and primary cynomolgus macaque islets. In vivo studies in diabetic mouse models and cynomolgus macaques demonstrated that AZD7762 enhances GSIS and improves glucose tolerance. Furthermore, genetic manipulation confirmed that ablation of CHEK2 in human β cells results in increased insulin secretion. Consistently, high-fat-diet fed Chk2-/- mice show elevated insulin secretion and improved glucose clearance. Finally, an untargeted metabolic profiling demonstrated the key role of the CHEK2-PP2A-PLK1-G6PD-PPP pathway in insulin secretion. This study successfully identifies a previously unknown insulin secretion regulating pathway that is conserved across rodents, cynomolgus macaques and human β cells in both healthy and T2D conditions.
2023-10-25 | GSE239335 | GEO
Project description:Expression studies in several models of type 2 Diabetes have suggested that exocytosis contributes to the modulation of insulin secretion during the 24h cycle. In agreement with the activity and feeding pattern of nocturnal rodents, we find that C57/Bl6J mice exhibit higher insulin secretion during the dark phase (ZT20 vs ZT8). Glucose-induced insulin secretion is increased by 21% despite normal intracellular Ca2+ signaling and depolarization-evoked exocytosis as measured by whole-cell capacitance measurements. This paradox is explained by a 1.37-fold increase in beta cell insulin content. Ultramorphological analysis show that vesicle size and density are unaltered but the intravesicular content per granule is modulated during the circadian rhythm. Proinsulin levels were not statistically different between the two time points despite a trend for reduction at ZT20. Islet glucagon content was inversely proportional to insulin content. Microarray data identified the differential expression of 301 transcripts of which, 54 known genes and 26 miRNA, including clock genes such as Bmal1 and Rev-erb . Differential expression of C2cd4b may contribute to the modulation of insulin content. Mice -cell secretion during the 24h cycle may rely on several distinct cellular functions but late night increase in insulin secretion depends solely on granule insulin content. A total of 301 genes were differentially expressed between ZT8 vs ZT20 islets . A majority were upregulated (199 between 1.3 to 2.71 fold) whilst 102 were down-regulated (<-1.3 fold). Given the focus of our study, current literature and our own results, genes involved in exocytosis, insulin production and of course, circadian rhythms were particularly interesting.
2018-01-31 | GSE109882 | GEO
Project description:Glucagon and insulin are counter-regulatory pancreatic hormones that precisely control blood glucose homeostasis1. Type 2 diabetes mellitus (T2DM) is characterized by inappropriately elevated blood glucagon2-5 levels as well as insufficient glucose stimulated insulin secretion (GSIS) by pancreatic ß-cells6. Early in the pathogenesis of T2DM, hyperglucagonemia is observable antecedent to ß-cell dysfunction7-9; and in mice, liver-specific activation of glucagon receptor-dependent signaling results in impaired GSIS10. However, the mechanistic relationship between hyperglucagonemia, hepatic glucagon action, and ß-cell dysfunction remains poorly understood. Here we show that glucagon action stimulates hepatic production of the neuropeptide kisspeptin1, which acts in an endocrine manner on ß-cells to suppress GSIS. In vivo glucagon administration acutely stimulates hepatic kisspeptin1 production, and kisspeptin1 is increased in livers from humans with T2DM and from mouse models of diabetes mellitus. Synthetic kisspeptin1 potently suppresses GSIS in vivo and in vitro from normal isolated islets, which express the kisspeptin1 receptor Kiss1R. Administration of a Kiss1R antagonist in diabetic Leprdb/db mice potently augments GSIS and reduces glycemia. Our observations indicate in the pathogenesis of T2DM an endocrine mechanism sequentially linking hyperglucagonemia via hepatic kisspeptin1 production to impaired insulin secretion. In addition, our findings suggest Kiss1R antagonism as a therapeutic avenue to improve ß-cell function in T2DM. Total RNA from L-Δprkar1a KO mice compared to control D-glucose mice
2014-04-01 | E-GEOD-48815 | biostudies-arrayexpress
Project description:Pancreatic beta-cells are specialized for coupling glucose metabolism to insulin peptide production and secretion. Acute glucose exposure robustly and coordinately increases translation of proinsulin and proteins required for secretion of mature insulin peptide. By contrast, chronically elevated glucose levels that occur during diabetes impair beta-cell insulin secretion and have been shown experimentally to suppress insulin translation. Whether translation of other genes critical for insulin secretion are similarly downregulated by chronic high glucose is unknown. Here, we used high-throughput ribosome profiling and nascent proteomics in MIN6 insulinoma cells to elucidate the genome-wide impact of sustained high glucose on beta-cell mRNA translation. Prior to induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also of mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion. Translation of these mRNAs was also downregulated in primary rat and human islets following ex-vivo incubation with sustained high glucose and in an in vivo model of chronic mild hyperglycemia. Furthermore, translational downregulation decreased cellular abundance of these proteins. Our study uncovered a translational regulatory circuit during beta-cell glucose toxicity that impairs expression of proteins with critical roles in beta-cell function.
2023-12-01 | GSE248349 | GEO
Project description:The role of ER Ca2+ release via ryanodine receptors (RyR) in pancreatic B-cell function is not well defined. Deletion of RyR2 from the rat insulinoma INS-1 enhanced the Ca2+ integral (AUC) stimulated by glucose, and reduced levels of the protein IRBIT (AHCYL1). Deletion of IRBIT increased the Ca2+ AUC in response to glucose via enhanced IP3 receptor activity. Insulin content, basal and glucose-stimulated insulin secretion (GSIS), and INS2 mRNA levels were reduced in both RyR2KO and IRBITKO cells. Nuclear localization of S-adenosylhomocysteinase (AHCY) was increased in RyR2KO and IRBITKO cells, and exon 2 of the INS1 and INS2 genes was more extensively methylated in RyR2KO and IRBITKO cells. Deletion of RyR2 or IRBIT resulted in differential regulation of 314 and 137 proteins, respectively, with 41 in common. We conclude that RyR2 regulates IRBIT levels in INS-1 cells, and together regulate insulin content, GSIS, and the proteome, perhaps via DNA methylation.
2021-11-10 | MSV000088344 | MassIVE