RESUMO
The 2021 Gairdner Prize is awarded to Daniel Drucker, Joel Habener, and Jens Juul Holst for the discovery of novel peptides encoded in the proglucagon sequence and the establishment of their physiological roles. These discoveries underpinned the development of therapeutics that are now benefiting patients with type 2 diabetes and other disorders worldwide.
Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Peptídeo 1 Semelhante ao Glucagon/uso terapêutico , Peptídeo 2 Semelhante ao Glucagon/uso terapêutico , Proglucagon/química , Diabetes Mellitus Tipo 2/metabolismo , Peptídeo 1 Semelhante ao Glucagon/química , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Peptídeo 2 Semelhante ao Glucagon/química , Peptídeo 2 Semelhante ao Glucagon/metabolismo , Humanos , Ilhotas Pancreáticas/metabolismo , Proglucagon/metabolismo , Receptores de Glucagon/metabolismo , Síndrome do Intestino Curto/tratamento farmacológico , Síndrome do Intestino Curto/metabolismoRESUMO
The pancreatic islets of Langerhans regulate glucose homeostasis. The loss of insulin-producing ß cells within islets results in diabetes, and islet transplantation from cadaveric donors can cure the disease. In vitro production of whole islets, not just ß cells, will benefit from a better understanding of endocrine differentiation and islet morphogenesis. We used single-cell mRNA sequencing to obtain a detailed description of pancreatic islet development. Contrary to the prevailing dogma, we find islet morphology and endocrine differentiation to be directly related. As endocrine progenitors differentiate, they migrate in cohesion and form bud-like islet precursors, or "peninsulas" (literally "almost islands"). α cells, the first to develop, constitute the peninsular outer layer, and ß cells form later, beneath them. This spatiotemporal collinearity leads to the typical core-mantle architecture of the mature, spherical islet. Finally, we induce peninsula-like structures in differentiating human embryonic stem cells, laying the ground for the generation of entire islets in vitro.
Assuntos
Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/embriologia , Animais , Diferenciação Celular , Células Cultivadas , Células-Tronco Embrionárias Humanas/citologia , Humanos , Insulina/metabolismo , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/metabolismo , Transplante das Ilhotas Pancreáticas/métodos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos SCID , Morfogênese , Pâncreas/citologiaRESUMO
Autoreactive lymphocytes that infiltrate the pancreatic islet environment and target ß cells are primary drivers of type 1 diabetes. In this issue of Immunity, Srivastava et al.1 examine the role of the islet microenvironment in autoimmunity and find that the scavenging receptor CXCL16 on islet-resident macrophages uptakes oxidized low-density lipoproteins and promotes the differentiation and survival of infiltrating pathogenic CD8+ T cells.
Assuntos
Autoimunidade , Linfócitos T CD8-Positivos , Diabetes Mellitus Tipo 1 , Ilhotas Pancreáticas , Macrófagos , Autoimunidade/imunologia , Diabetes Mellitus Tipo 1/imunologia , Ilhotas Pancreáticas/imunologia , Ilhotas Pancreáticas/metabolismo , Humanos , Animais , Macrófagos/imunologia , Macrófagos/metabolismo , Linfócitos T CD8-Positivos/imunologia , Células Secretoras de Insulina/imunologia , Células Secretoras de Insulina/metabolismo , Lipoproteínas LDL/metabolismo , Lipoproteínas LDL/imunologiaRESUMO
The pancreatic islet microenvironment is highly oxidative, rendering ß cells vulnerable to autoinflammatory insults. Here, we examined the role of islet resident macrophages in the autoimmune attack that initiates type 1 diabetes. Islet macrophages highly expressed CXCL16, a chemokine and scavenger receptor for oxidized low-density lipoproteins (OxLDLs), regardless of autoimmune predisposition. Deletion of Cxcl16 in nonobese diabetic (NOD) mice suppressed the development of autoimmune diabetes. Mechanistically, Cxcl16 deficiency impaired clearance of OxLDL by islet macrophages, leading to OxLDL accumulation in pancreatic islets and a substantial reduction in intra-islet transitory (Texint) CD8+ T cells displaying proliferative and effector signatures. Texint cells were vulnerable to oxidative stress and diminished by ferroptosis; PD-1 blockade rescued this population and reversed diabetes resistance in NOD.Cxcl16-/- mice. Thus, OxLDL scavenging in pancreatic islets inadvertently promotes differentiation of pathogenic CD8+ T cells, presenting a paradigm wherein tissue homeostasis processes can facilitate autoimmune pathogenesis in predisposed individuals.
Assuntos
Autoimunidade , Linfócitos T CD8-Positivos , Diferenciação Celular , Quimiocina CXCL16 , Diabetes Mellitus Tipo 1 , Ilhotas Pancreáticas , Lipoproteínas LDL , Macrófagos , Camundongos Endogâmicos NOD , Camundongos Knockout , Animais , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Camundongos , Lipoproteínas LDL/metabolismo , Lipoproteínas LDL/imunologia , Diabetes Mellitus Tipo 1/imunologia , Diabetes Mellitus Tipo 1/metabolismo , Quimiocina CXCL16/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Ilhotas Pancreáticas/imunologia , Ilhotas Pancreáticas/metabolismo , Camundongos Endogâmicos C57BLRESUMO
Glucose homeostasis is mainly under the control of the pancreatic islet hormones insulin and glucagon, which, respectively, stimulate glucose uptake and utilization by liver, fat, and muscle and glucose production by the liver. The balance between the secretions of these hormones is under the control of blood glucose concentrations. Indeed, pancreatic islet ß-cells and α-cells can sense variations in glycemia and respond by an appropriate secretory response. However, the secretory activity of these cells is also under multiple additional metabolic, hormonal, and neuronal signals that combine to ensure the perfect control of glycemia over a lifetime. The central nervous system (CNS), which has an almost absolute requirement for glucose as a source of metabolic energy and thus a vital interest in ensuring that glycemic levels never fall below â¼5 mM, is equipped with populations of neurons responsive to changes in glucose concentrations. These neurons control pancreatic islet cell secretion activity in multiple ways: through both branches of the autonomic nervous system, through the hypothalamic-pituitary-adrenal axis, and by secreting vasopressin (AVP) in the blood at the level of the posterior pituitary. Here, we present the autonomic innervation of the pancreatic islets; the mechanisms of neuron activation by a rise or a fall in glucose concentration; how current viral tracing, chemogenetic, and optogenetic techniques allow integration of specific glucose sensing neurons in defined neuronal circuits that control endocrine pancreas function; and, finally, how genetic screens in mice can untangle the diversity of the hypothalamic mechanisms controlling the response to hypoglycemia.
Assuntos
Glucagon , Glucose , Insulina , Neurônios , Animais , Glucagon/metabolismo , Humanos , Insulina/metabolismo , Neurônios/metabolismo , Glucose/metabolismo , Secreção de Insulina/fisiologia , Ilhotas Pancreáticas/metabolismoRESUMO
Consumption of a high-energy Western diet triggers mild adaptive ß cell proliferation to compensate for peripheral insulin resistance; however, the underlying molecular mechanism remains unclear. In the present study we show that the toll-like receptors TLR2 and TLR4 inhibited the diet-induced replication of ß cells in mice and humans. The combined, but not the individual, loss of TLR2 and TLR4 increased the replication of ß cells, but not that of α cells, leading to enlarged ß cell area and hyperinsulinemia in diet-induced obesity. Loss of TLR2 and TLR4 increased the nuclear abundance of the cell cycle regulators cyclin D2 and Cdk4 in a manner dependent on the signaling mediator Erk. These data reveal a regulatory mechanism controlling the proliferation of ß cells in diet-induced obesity and suggest that selective targeting of the TLR2/TLR4 pathways may reverse ß cell failure in patients with diabetes.
Assuntos
Células Secretoras de Insulina/metabolismo , Obesidade/etiologia , Obesidade/metabolismo , Receptor 2 Toll-Like/genética , Receptor 4 Toll-Like/genética , Animais , Proliferação de Células , Ciclina D2/metabolismo , Quinase 4 Dependente de Ciclina/metabolismo , Dieta Hiperlipídica/efeitos adversos , Modelos Animais de Doenças , Feminino , Humanos , Insulina/sangue , Insulina/metabolismo , Células Secretoras de Insulina/ultraestrutura , Ilhotas Pancreáticas/efeitos dos fármacos , Ilhotas Pancreáticas/metabolismo , Sistema de Sinalização das MAP Quinases , Masculino , Camundongos , Camundongos Knockout , Complexos Multiproteicos/metabolismo , Obesidade/tratamento farmacológico , Parabiose , Ligação Proteica , Receptor 2 Toll-Like/metabolismo , Receptor 4 Toll-Like/metabolismoRESUMO
The homeodomain transcription factor (TF) Nkx2.2 governs crucial cell fate decisions in several developing organs, including the central nervous system (CNS), pancreas, and intestine. How Nkx2.2 regulates unique targets in these different systems to impact their individual transcriptional programs remains unclear. In this issue of Genes & Development Abarinov and colleagues (pp. 490-504) generated and analyzed mice in which the Nkx2.2 SD is mutated and found that the SD is required for normal pancreatic islet differentiation but dispensable for most aspects of neuronal differentiation.
Assuntos
Proteínas de Homeodomínio , Ilhotas Pancreáticas , Camundongos , Animais , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Proteína Homeobox Nkx-2.2 , Proteínas de Peixe-Zebra/genética , Ilhotas Pancreáticas/metabolismo , Diferenciação Celular/genética , Neurônios/metabolismo , Regulação da Expressão Gênica no DesenvolvimentoRESUMO
Type 2 diabetes (T2D) is a heterogeneous disease that develops through diverse pathophysiological processes1,2 and molecular mechanisms that are often specific to cell type3,4. Here, to characterize the genetic contribution to these processes across ancestry groups, we aggregate genome-wide association study data from 2,535,601 individuals (39.7% not of European ancestry), including 428,452 cases of T2D. We identify 1,289 independent association signals at genome-wide significance (P < 5 × 10-8) that map to 611 loci, of which 145 loci are, to our knowledge, previously unreported. We define eight non-overlapping clusters of T2D signals that are characterized by distinct profiles of cardiometabolic trait associations. These clusters are differentially enriched for cell-type-specific regions of open chromatin, including pancreatic islets, adipocytes, endothelial cells and enteroendocrine cells. We build cluster-specific partitioned polygenic scores5 in a further 279,552 individuals of diverse ancestry, including 30,288 cases of T2D, and test their association with T2D-related vascular outcomes. Cluster-specific partitioned polygenic scores are associated with coronary artery disease, peripheral artery disease and end-stage diabetic nephropathy across ancestry groups, highlighting the importance of obesity-related processes in the development of vascular outcomes. Our findings show the value of integrating multi-ancestry genome-wide association study data with single-cell epigenomics to disentangle the aetiological heterogeneity that drives the development and progression of T2D. This might offer a route to optimize global access to genetically informed diabetes care.
Assuntos
Diabetes Mellitus Tipo 2 , Progressão da Doença , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Humanos , Adipócitos/metabolismo , Cromatina/genética , Cromatina/metabolismo , Doença da Artéria Coronariana/complicações , Doença da Artéria Coronariana/genética , Diabetes Mellitus Tipo 2/classificação , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/patologia , Diabetes Mellitus Tipo 2/fisiopatologia , Nefropatias Diabéticas/complicações , Nefropatias Diabéticas/genética , Células Endoteliais/metabolismo , Células Enteroendócrinas , Epigenômica , Predisposição Genética para Doença/genética , Ilhotas Pancreáticas/metabolismo , Herança Multifatorial/genética , Doença Arterial Periférica/complicações , Doença Arterial Periférica/genética , Análise de Célula ÚnicaRESUMO
Depending on endoplasmic reticulum (ER) stress levels, the ER transmembrane multidomain protein IRE1α promotes either adaptation or apoptosis. Unfolded ER proteins cause IRE1α lumenal domain homo-oligomerization, inducing trans autophosphorylation that further drives homo-oligomerization of its cytosolic kinase/endoribonuclease (RNase) domains to activate mRNA splicing of adaptive XBP1 transcription factor. However, under high/chronic ER stress, IRE1α surpasses an oligomerization threshold that expands RNase substrate repertoire to many ER-localized mRNAs, leading to apoptosis. To modulate these effects, we developed ATP-competitive IRE1α Kinase-Inhibiting RNase Attenuators-KIRAs-that allosterically inhibit IRE1α's RNase by breaking oligomers. One optimized KIRA, KIRA6, inhibits IRE1α in vivo and promotes cell survival under ER stress. Intravitreally, KIRA6 preserves photoreceptor functional viability in rat models of ER stress-induced retinal degeneration. Systemically, KIRA6 preserves pancreatic ß cells, increases insulin, and reduces hyperglycemia in Akita diabetic mice. Thus, IRE1α powerfully controls cell fate but can itself be controlled with small molecules to reduce cell degeneration.
Assuntos
Estresse do Retículo Endoplasmático , Endorribonucleases/antagonistas & inibidores , Inibidores de Proteínas Quinases/farmacologia , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Regulação Alostérica , Animais , Apoptose/efeitos dos fármacos , Linhagem Celular , Endorribonucleases/química , Endorribonucleases/metabolismo , Ativação Enzimática/efeitos dos fármacos , Humanos , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos , Proteínas Serina-Treonina Quinases/química , Proteínas Serina-Treonina Quinases/metabolismo , Ratos , Retina/metabolismo , Ribonucleases/antagonistas & inibidoresRESUMO
Clec16a has been identified as a disease susceptibility gene for type 1 diabetes, multiple sclerosis, and adrenal dysfunction, but its function is unknown. Here we report that Clec16a is a membrane-associated endosomal protein that interacts with E3 ubiquitin ligase Nrdp1. Loss of Clec16a leads to an increase in the Nrdp1 target Parkin, a master regulator of mitophagy. Islets from mice with pancreas-specific deletion of Clec16a have abnormal mitochondria with reduced oxygen consumption and ATP concentration, both of which are required for normal ß cell function. Indeed, pancreatic Clec16a is required for normal glucose-stimulated insulin release. Moreover, patients harboring a diabetogenic SNP in the Clec16a gene have reduced islet Clec16a expression and reduced insulin secretion. Thus, Clec16a controls ß cell function and prevents diabetes by controlling mitophagy. This pathway could be targeted for prevention and control of diabetes and may extend to the pathogenesis of other Clec16a- and Parkin-associated diseases.
Assuntos
Diabetes Mellitus Tipo 1/genética , Ilhotas Pancreáticas/patologia , Lectinas Tipo C/metabolismo , Mitofagia , Proteínas de Transporte de Monossacarídeos/metabolismo , Sequência de Aminoácidos , Animais , Proteínas de Transporte/química , Diabetes Mellitus Tipo 1/patologia , Predisposição Genética para Doença , Glucose/metabolismo , Humanos , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Lectinas Tipo C/química , Lectinas Tipo C/genética , Lisossomos/química , Lisossomos/metabolismo , Proteínas de Membrana/metabolismo , Camundongos , Dados de Sequência Molecular , Proteínas de Transporte de Monossacarídeos/química , Proteínas de Transporte de Monossacarídeos/genética , Polimorfismo de Nucleotídeo Único , Ubiquitina-Proteína LigasesRESUMO
Type 2 diabetes mellitus (T2D), a major cause of worldwide morbidity and mortality, is characterized by dysfunction of insulin-producing pancreatic islet ß cells1,2. T2D genome-wide association studies (GWAS) have identified hundreds of signals in non-coding and ß cell regulatory genomic regions, but deciphering their biological mechanisms remains challenging3-5. Here, to identify early disease-driving events, we performed traditional and multiplexed pancreatic tissue imaging, sorted-islet cell transcriptomics and islet functional analysis of early-stage T2D and control donors. By integrating diverse modalities, we show that early-stage T2D is characterized by ß cell-intrinsic defects that can be proportioned into gene regulatory modules with enrichment in signals of genetic risk. After identifying the ß cell hub gene and transcription factor RFX6 within one such module, we demonstrated multiple layers of genetic risk that converge on an RFX6-mediated network to reduce insulin secretion by ß cells. RFX6 perturbation in primary human islet cells alters ß cell chromatin architecture at regions enriched for T2D GWAS signals, and population-scale genetic analyses causally link genetically predicted reduced RFX6 expression with increased T2D risk. Understanding the molecular mechanisms of complex, systemic diseases necessitates integration of signals from multiple molecules, cells, organs and individuals, and thus we anticipate that this approach will be a useful template to identify and validate key regulatory networks and master hub genes for other diseases or traits using GWAS data.
Assuntos
Diabetes Mellitus Tipo 2 , Perfilação da Expressão Gênica , Redes Reguladoras de Genes , Predisposição Genética para Doença , Ilhotas Pancreáticas , Humanos , Estudos de Casos e Controles , Separação Celular , Cromatina/metabolismo , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Diabetes Mellitus Tipo 2/fisiopatologia , Redes Reguladoras de Genes/genética , Estudo de Associação Genômica Ampla , Secreção de Insulina , Ilhotas Pancreáticas/metabolismo , Ilhotas Pancreáticas/patologia , Reprodutibilidade dos TestesRESUMO
The circadian clock is encoded by a negative transcriptional feedback loop that coordinates physiology and behavior through molecular programs that remain incompletely understood. Here, we reveal rhythmic genome-wide alternative splicing (AS) of pre-mRNAs encoding regulators of peptidergic secretion within pancreatic ß cells that are perturbed in Clock-/- and Bmal1-/- ß-cell lines. We show that the RNA-binding protein THRAP3 (thyroid hormone receptor-associated protein 3) regulates circadian clock-dependent AS by binding to exons at coding sequences flanking exons that are more frequently skipped in clock mutant ß cells, including transcripts encoding Cask (calcium/calmodulin-dependent serine protein kinase) and Madd (MAP kinase-activating death domain). Depletion of THRAP3 restores expression of the long isoforms of Cask and Madd, and mimicking exon skipping in these transcripts through antisense oligonucleotide delivery in wild-type islets reduces glucose-stimulated insulin secretion. Finally, we identify shared networks of alternatively spliced exocytic genes from islets of rodent models of diet-induced obesity that significantly overlap with clock mutants. Our results establish a role for pre-mRNA alternative splicing in ß-cell function across the sleep/wake cycle.
Assuntos
Processamento Alternativo , Relógios Circadianos/genética , Exocitose , Glucose/metabolismo , Secreção de Insulina/genética , Fatores de Transcrição ARNTL/genética , Fatores de Transcrição ARNTL/fisiologia , Animais , Proteínas CLOCK/genética , Proteínas CLOCK/fisiologia , Células Cultivadas , Proteínas Adaptadoras de Sinalização de Receptores de Domínio de Morte/genética , Proteínas Adaptadoras de Sinalização de Receptores de Domínio de Morte/metabolismo , Fatores de Troca do Nucleotídeo Guanina/genética , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Guanilato Quinases/genética , Guanilato Quinases/metabolismo , Homeostase , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Proteínas Nucleares/fisiologia , Obesidade/genética , Obesidade/metabolismo , Proteína 25 Associada a Sinaptossoma/genética , Proteína 25 Associada a Sinaptossoma/metabolismo , Fatores de Transcrição/fisiologiaRESUMO
Most studies on TCF7L2 SNP variants in the pathogenesis of type 2 diabetes (T2D) focus on a role of the encoded transcription factor TCF4 in ß cells. Here, a mouse genetics approach shows that removal of TCF4 from ß cells does not affect their function, whereas manipulating TCF4 levels in the liver has major effects on metabolism. In Tcf7l2(-/-) mice, the immediate postnatal surge in liver metabolism does not occur. Consequently, pups die due to hypoglycemia. By combining chromatin immunoprecipitation with gene expression profiling, we identify a TCF4-controlled metabolic gene program that is acutely activated in the postnatal liver. In concordance, adult liver-specific Tcf7l2 knockout mice show reduced hepatic glucose production during fasting and display improved glucose homeostasis when maintained on high-fat diet. Furthermore, liver-specific TCF4 overexpression increases hepatic glucose production. These observations imply that TCF4 directly activates metabolic genes and that inhibition of Wnt signaling may be beneficial in metabolic disease.
Assuntos
Diabetes Mellitus/genética , Diabetes Mellitus/metabolismo , Glucose/metabolismo , Fígado/metabolismo , Redes e Vias Metabólicas , Proteína 2 Semelhante ao Fator 7 de Transcrição/metabolismo , Animais , Animais Recém-Nascidos , Dieta Hiperlipídica , Jejum/metabolismo , Ilhotas Pancreáticas/metabolismo , Camundongos , Camundongos Knockout , Proteína 2 Semelhante ao Fator 7 de Transcrição/genética , Ativação TranscricionalRESUMO
Mammalian two-pore channel proteins (TPC1, TPC2; TPCN1, TPCN2) encode ion channels in intracellular endosomes and lysosomes and were proposed to mediate endolysosomal calcium release triggered by the second messenger, nicotinic acid adenine dinucleotide phosphate (NAADP). By directly recording TPCs in endolysosomes from wild-type and TPC double-knockout mice, here we show that, in contrast to previous conclusions, TPCs are in fact sodium-selective channels activated by PI(3,5)P(2) and are not activated by NAADP. Moreover, the primary endolysosomal ion is Na(+), not K(+), as had been previously assumed. These findings suggest that the organellar membrane potential may undergo large regulatory changes and may explain the specificity of PI(3,5)P(2) in regulating the fusogenic potential of intracellular organelles.
Assuntos
Canais de Cálcio/metabolismo , Lisossomos/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Animais , Cálcio/metabolismo , Canais de Cálcio/genética , Linhagem Celular , Glucose/metabolismo , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Camundongos , Camundongos Knockout , NADP/análogos & derivados , NADP/metabolismo , Canais de Sódio/metabolismoRESUMO
One of the hallmarks of type 1 but also type 2 diabetes is pancreatic islet inflammation, associated with altered pancreatic islet function and structure, if unresolved. IL-1ß is a proinflammatory cytokine which detrimentally affects ß-cell function. In the course of diabetes, complement components, including the central complement protein C3, are deregulated. Previously, we reported high C3 expression in human pancreatic islets, with upregulation after IL-1ß treatment. In the current investigation, using primary human and rodent material and CRISPR/Cas9 gene-edited ß-cells deficient in C3, or producing only cytosolic C3 from a noncanonical in-frame start codon, we report a protective effect of C3 against IL-1ß-induced ß-cell death, that is attributed to the cytosolic fraction of C3. Further investigation revealed that intracellular C3 alleviates IL-1ß-induced ß-cell death, by interaction with and inhibition of Fyn-related kinase (FRK), which is involved in the response of ß-cells to cytokines. Furthermore, these data were supported by increased ß-cell death in vivo in a ß-cell-specific C3 knockout mouse. Our data indicate that a functional, cytoprotective association exists between FRK and cytosolic C3.
Assuntos
Diabetes Mellitus Tipo 2 , Células Secretoras de Insulina , Ilhotas Pancreáticas , Camundongos , Animais , Humanos , Diabetes Mellitus Tipo 2/metabolismo , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Morte Celular , Citocinas/metabolismo , Camundongos KnockoutRESUMO
Persistent antigen exposure results in the differentiation of functionally impaired, also termed exhausted, T cells which are maintained by a distinct population of precursors of exhausted T (TPEX) cells. T cell exhaustion is well studied in the context of chronic viral infections and cancer, but it is unclear whether and how antigen-driven T cell exhaustion controls progression of autoimmune diabetes and whether this process can be harnessed to prevent diabetes. Using nonobese diabetic (NOD) mice, we show that some CD8+ T cells specific for the islet antigen, islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) displayed terminal exhaustion characteristics within pancreatic islets but were maintained in the TPEX cell state in peripheral lymphoid organs (PLO). More IGRP-specific T cells resided in the PLO than in islets. To examine the impact of extraislet antigen exposure on T cell exhaustion in diabetes, we generated transgenic NOD mice with inducible IGRP expression in peripheral antigen-presenting cells. Antigen exposure in the extraislet environment induced severely exhausted IGRP-specific T cells with reduced ability to produce interferon (IFN)γ, which protected these mice from diabetes. Our data demonstrate that T cell exhaustion induced by delivery of antigen can be harnessed to prevent autoimmune diabetes.
Assuntos
Diabetes Mellitus Tipo 1 , Ilhotas Pancreáticas , Camundongos , Animais , Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 1/prevenção & controle , Proteínas/metabolismo , Exaustão das Células T , Glucose-6-Fosfatase/genética , Glucose-6-Fosfatase/metabolismo , Camundongos Transgênicos , Camundongos Endogâmicos NOD , Ilhotas Pancreáticas/metabolismo , Linfócitos T CD8-PositivosRESUMO
Many molecular mechanisms underlying blood glucose homeostasis remain elusive. Juan-Mateu et al. find that pancreatic islet cells utilize a regulatory program, originally identified in neurons, that involves alternative splicing of microexons in genes important for insulin secretion or diabetes risk.
Assuntos
Processamento Alternativo , Ilhotas Pancreáticas , Processamento Alternativo/genética , Homeostase/genética , Glucose/genética , Glucose/metabolismo , Insulina/genética , Insulina/metabolismo , Ilhotas Pancreáticas/metabolismoRESUMO
The definitive demonstration of protein localization on primary cilia has been a challenge for cilia biologists. Primary cilia are solitary thread-like projections that have a specialized protein composition, but as the ciliary structure overlays the cell membrane and other cell parts, the identity of ciliary proteins are difficult to ascertain by conventional imaging approaches like immunofluorescence microscopy. Surface scanning electron microscopy combined with immunolabeling (immuno-SEM) bypasses some of these indeterminacies by unambiguously showing protein expression in the context of the three-dimensional ultrastructure of the cilium. Here, we apply immuno-SEM to specifically identify proteins on the primary cilia of mouse and human pancreatic islets, including post-translationally modified tubulin, intraflagellar transport (IFT)88, the small GTPase Arl13b, as well as subunits of axonemal dynein. Key parameters in sample preparation, immunolabeling and imaging acquisition are discussed to facilitate similar studies by others in the cilia research community.
Assuntos
Cílios , Ilhotas Pancreáticas , Cílios/ultraestrutura , Cílios/metabolismo , Animais , Humanos , Camundongos , Ilhotas Pancreáticas/ultraestrutura , Ilhotas Pancreáticas/metabolismo , Microscopia Eletrônica de Varredura/métodosRESUMO
Hormone secretion from pancreatic islets is essential for glucose homeostasis, and loss or dysfunction of islet cells is a hallmark of type 2 diabetes. Maf transcription factors are crucial for establishing and maintaining adult endocrine cell function. However, during pancreas development, MafB is not only expressed in insulin- and glucagon-producing cells, but also in Neurog3+ endocrine progenitor cells, suggesting additional functions in cell differentiation and islet formation. Here, we report that MafB deficiency impairs ß cell clustering and islet formation, but also coincides with loss of neurotransmitter and axon guidance receptor gene expression. Moreover, the observed loss of nicotinic receptor gene expression in human and mouse ß cells implied that signaling through these receptors contributes to islet cell migration/formation. Inhibition of nicotinic receptor activity resulted in reduced ß cell migration towards autonomic nerves and impaired ß cell clustering. These findings highlight a novel function of MafB in controlling neuronal-directed signaling events required for islet formation.
Assuntos
Diabetes Mellitus Tipo 2 , Células Secretoras de Insulina , Ilhotas Pancreáticas , Camundongos , Adulto , Animais , Humanos , Glucagon/genética , Glucagon/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Ilhotas Pancreáticas/metabolismo , Insulina/metabolismo , Pâncreas/metabolismo , Fator de Transcrição MafB/genética , Fator de Transcrição MafB/metabolismoRESUMO
Rab26 is known to regulate multiple membrane trafficking events, but its role in insulin secretion in pancreatic ß cells remains unclear despite it was first identified in the pancreas. In this study, we generated Rab26-/- mice through CRISPR/Cas9 technique. Surprisingly, insulin levels in the blood of the Rab26-/- mice do not decrease upon glucose stimulation but conversely increase. Deficiency of Rab26 promotes insulin secretion, which was independently verified by Rab26 knockdown in pancreatic insulinoma cells. Conversely, overexpression of Rab26 suppresses insulin secretion in both insulinoma cell lines and isolated mouse islets. Islets overexpressing Rab26, upon transplantation, also failed to restore glucose homeostasis in type 1 diabetic mice. Immunofluorescence microscopy revealed that overexpression of Rab26 results in clustering of insulin granules. GST-pulldown experiments reveal that Rab26 interacts with synaptotagmin-1 (Syt1) through directly binding to its C2A domain, which interfering with the interaction between Syt1 and SNAP25, and consequently inhibiting the exocytosis of newcomer insulin granules revealed by TIRF microscopy. Our results suggest that Rab26 serves as a negative regulator of insulin secretion, via suppressing insulin granule fusion with plasma membrane through sequestering Syt1.