scholarly journals Granuphilin Modulates the Exocytosis of Secretory Granules through Interaction with Syntaxin 1a

2002 ◽  
Vol 22 (15) ◽  
pp. 5518-5526 ◽  
Author(s):  
Seiji Torii ◽  
Shengli Zhao ◽  
Zhaohong Yi ◽  
Toshiyuki Takeuchi ◽  
Tetsuro Izumi
Keyword(s):  
Insulin Secretion ◽  
Pancreatic Beta Cells ◽  
Endocrine Cells ◽  
Secretory Granules ◽  
Syntaxin 1A ◽  
Open Conformation ◽  
High K ◽  
Insulin Granules ◽  
Basal Insulin Secretion ◽  
Dense Core Granules

ABSTRACT The molecular mechanism for the regulated exocytosis of dense-core granules in endocrine cells remains relatively uncharacterized compared to that of synaptic vesicles in neurons. A novel set of Rab and its effector, Rab27a/granuphilin, which is localized on insulin granules in pancreatic beta cells, was recently identified. Here we demonstrate that granuphilin directly binds to syntaxin 1a on the plasma membrane, and this interaction is regulated by Rab27a. Granuphilin shows affinity to syntaxin 1a with a closed conformation but not to mutant syntaxin 1a, which adopts an open conformation constitutively. Overexpression of granuphilin significantly enhances basal insulin secretion but profoundly inhibits high K+-induced insulin secretion. The effect of granuphilin on insulin secretion was impaired by its mutation that disrupts the binding to either Rab27a or syntaxin 1a. Thus, granuphilin is the first regulator in the exocytotic pathway that functions by directly connecting two critical vesicle transport proteins, Rab and SNARE.

scholarly journals Novel organelle anion channels formed by chromogranin B drive normal granule maturation in endocrine cells

2018 ◽  
Author(s):  
Gaya Yadav ◽  
Hui Zheng ◽  
Qing Yang ◽  
Lauren Douma ◽  
Mani Annamalai ◽  
...  
Keyword(s):  
Pancreatic Beta Cells ◽  
Chloride Channels ◽  
Endocrine Cells ◽  
Secretory Granules ◽  
Neuroendocrine Cells ◽  
Anion Channels ◽  
Chromogranin B ◽  
Fast Kinetics ◽  
Anion Conductance ◽  
Granule Maturation

All endocrine cells need an anion conductance for maturation of secretory granules. Identity of this family of anion channels has been elusive for forty years. We now show that a family of granule proteins, CHGB, serves the long-sought conductance. CHGB interacts with membranes through two amphipathic helices, and forms a chloride channel with a large conductance and high anion selectivity. Fast kinetics and high cooperativity suggest that CHGB tetramerizes to form a functional channel. Nonconducting mutants separate CHGB channel function in granule maturation from its role in granule biogenesis. In neuroendocrine cells, CHGB channel and a H+-ATPase drive normal insulin maturation inside or catecholamine loading into secretory granules. Tight membrane-association of CHGB after exocytotic release of secretory granules separates its intracellular functions from the extracellular functions accomplished by its proteolytic peptides. CHGB-null mice show impairment of granule acidification in pancreatic beta-cells due to lack of anion conductance. These findings together support that the phylogenetically conserved CHGB proteins constitute a fifth family of chloride channels that function in various endocrine cells.

scholarly journals Human stem cell model of HNF1A deficiency shows uncoupled insulin to C-peptide secretion with accumulation of abnormal insulin granules

2021 ◽  
Author(s):  
Bryan J. González ◽  
Haoquan Zhao ◽  
Jacqueline Niu ◽  
Damian J. Williams ◽  
Jaeyop Lee ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Insulin Secretion ◽  
Intracellular Calcium ◽  
Cell Fate ◽  
Endocrine Cells ◽  
Secretory Granules ◽  
Β Cells ◽  
C Peptide ◽  
Pancreatic Endocrine Cells

AbstractMutations in HNF1A cause Maturity Onset Diabetes of the Young type 3 (MODY3), the most prevalent form of monogenic diabetes. We generated stem cell-derived pancreatic endocrine cells from human embryonic stem cells (hESCs) with induced hypomorphic mutations in HNF1A. Using these cells, we show that HNF1A orchestrates a transcriptional program required for distinct aspects of β-cell fate and function. During islet cell differentiation, HNF1A deficiency biases islet endocrine cells towards an α-cell fate associated with PAX4 down-regulation. HNF1A- deficient β-cells display impaired basal and glucose stimulated-insulin secretion in association with a reduction in CACNA1A and intracellular calcium levels, and impaired insulin granule exocytosis in association with SYT13 down-regulation. Knockout of PAX4, CACNA1A and SYT13 reproduce the relevant phenotypes. Reduction of insulin secretion is associated with accumulation of enlarged secretory granules, and altered stoichiometry of secreted insulin to C-peptide. In HNF1A deficient β-cells, glibenclamide, a sulfonylurea drug used in the treatment of MODY3 patients, increases intracellular calcium to levels beyond those achieved by glucose, and restores C-peptide and insulin secretion to a normal stoichiometric ratio. To study HNF1A deficiency in the context of a human disease model, we also generated stem cell-derived pancreatic endocrine cells from two MODY3 patient’s induced pluripotent stem cells (iPSCs). While insulin secretion defects are constitutive in cells with complete HNF1A loss of function, β-cells heterozygous for hypomorphic HNF1A mutations are initially normal, but lose the ability to secrete insulin and acquire abnormal stoichiometric secretion ratios. Importantly, the defects observed in these stem cell models are also seen in circulating proportions of insulin:C-peptide in nine MODY3 patients.One sentence of summaryDeficiency of the transcription factor HNF1A biases islet endocrine cell fate towards α-cells, impairs intracellular calcium homeostasis and insulin exocytosis, alters the stoichiometry of insulin to C-peptide release, and leads to an accumulation of abnormal insulin secretory granules in β-cells.

scholarly journals Kisspeptin-Activated Autophagy Independently Suppresses Non-Glucose-Stimulated Insulin Secretion from Pancreatic β-Cells

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Chien Huang ◽  
Hao-Yi Wang ◽  
Mu-En Wang ◽  
Meng-Chieh Hsu ◽  
Yi-Hsieng Samuel Wu ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Insulin Granules ◽  
Autophagic Degradation ◽  
Basal Insulin Secretion ◽  
Glucose Stimulated Insulin Secretion

AbstractPrevious studies have demonstrated the important role of kisspeptin in impaired glucose-stimulated insulin secretion (GSIS). In addition, it was reported that the activation of autophagy in pancreatic β-cells decreases insulin secretion by selectively degrading insulin granules. However, it is currently unknown whether kisspeptin suppresses GSIS in β-cells by activating autophagy. To investigate the involvement of autophagy in kisspeptin–regulated insulin secretion, we overexpressed Kiss1 in NIT-1 cells to mimic the long-term exposure of pancreatic β-cells to kisspeptin during type 2 diabetes (T2D). Interestingly, our data showed that although kisspeptin potently decreases the intracellular proinsulin and insulin ((pro)insulin) content and insulin secretion of NIT-1 cells, autophagy inhibition using bafilomycin A1 and Atg5 siRNAs only rescues basal insulin secretion, not kisspeptin-impaired GSIS. We also generated a novel in vivo model to investigate the long-term exposure of kisspeptin by osmotic pump. The in vivo data demonstrated that kisspeptin lowers GSIS and (pro)insulin levels and also activated pancreatic autophagy in mice. Collectively, our data demonstrated that kisspeptin suppresses both GSIS and non-glucose-stimulated insulin secretion of pancreatic β-cells, but only non-glucose-stimulated insulin secretion depends on activated autophagic degradation of (pro)insulin. Our study provides novel insights for the development of impaired insulin secretion during T2D progression.

scholarly journals Decreased basal insulin secretion from pancreatic islets of pups in a rat model of maternal obesity

2016 ◽  
Vol 231 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Elena Zambrano ◽  
Tonantzin Sosa-Larios ◽  
Lizbeth Calzada ◽  
Carlos A Ibáñez ◽  
Carmen A Mendoza-Rodríguez ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Pancreatic Islets ◽  
Basal Insulin ◽  
Pancreatic Beta Cells ◽  
Maternal Obesity ◽  
Metabolic Diseases ◽  
Model Assessment ◽  
Male And Female ◽  
Basal Insulin Secretion

Maternal obesity (MO) is a deleterious condition that enhances susceptibility of adult offspring to metabolic diseases such as type 2 diabetes. The objective is to study the effect of MO on in vitro insulin secretion and pancreatic cellular population in offspring. We hypothesize that a harmful antenatal metabolic environment due to MO diminishes the basal glucose-responsive secretory function of pancreatic beta cells in offspring. Mothers were fed a control (C) or high-fat diet from weaning through pregnancy (120 days) and lactation. At postnatal days (PNDs) 36 and 110, pups were killed, peripheral blood was collected and pancreatic islets were isolated. Basal insulin secretion was measured in vitro in islets for 60 min. It was found that blood insulin, glucose and homeostasis model assessment (HOMA) index were unaffected by maternal diet and age in females. However, male MO offspring at PND 110 showed hyperinsulinemia and insulin resistance compared with C. Body weight was not modified by MO, but fat content was higher in MO pups compared with C pups. Triglycerides and leptin concentrations were higher in MO than in C offspring in all groups except in females at PND 36. Pancreatic islet cytoarchitecture was unaffected by MO. At PND 36, islets of male and female C and MO offspring responded similarly to glucose, but at PND 110, male and female MO offspring islets showed a 50% decrease in insulin secretion. It was concluded that MO impairs basal insulin secretion of offspring with a greater impact on males than females, and this effect mainly manifests in adulthood.

scholarly journals Purification of age-distinct insulin secretory granules through antigen restriction using the CLIP-tag

2020 ◽  
Author(s):  
Martin Neukam ◽  
Katharina Ganß ◽  
Jovana Vasiljević ◽  
Johannes Broichhagen ◽  
Kai Johnsson ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Insulin Secretion ◽  
Beta Cells ◽  
Solid Phase ◽  
Secretory Granules ◽  
Islet Beta Cells ◽  
Temporal Variables ◽  
Pancreatic Islet Beta Cells ◽  
Insulin Granules ◽  
Insulin Granule

AbstractPancreatic islet beta cells employ secretory granules for the storage and glucose-stimulated release of the hormone insulin. The competence of an insulin granule for exocytosis depends on spatial and temporal variables such as its proximity to the plasma membrane as well as its age, with newly-generated granules being preferentially released. The molecular underpinnings for the control of these variables remain largely unknown and their uncovering is of high relevance for the study of diabetes, which results from deficient insulin secretion. However, we still lack a comprehensive view about the molecular composition of the insulin granules and how this may change over their lifetime. Here we report a strategy for the background-free purification of insulin secretory granules of distinct age from insulinoma INS-1 cells. We show that utilization of an immuno-based affinity approach for pulse-chase labeled insulin secretory granules, produces a highly enriched granular fraction. Our approach precludes typical contaminants from the solid phase and may be designed to purify secretory granules of a distinct age.

scholarly journals Aged insulin granules display reduced microtubule-dependent mobility and are disposed within actin-positive multigranular bodies

2015 ◽  
Vol 112 (7) ◽  
pp. E667-E676 ◽  
Author(s):  
Peter Hoboth ◽  
Andreas Müller ◽  
Anna Ivanova ◽  
Hassan Mziaut ◽  
Jaber Dehghany ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Glucose Homeostasis ◽  
Secretory Granules ◽  
Glucose Stimulation ◽  
Actin Depolymerization ◽  
Insulin Granules ◽  
Dependent Transport ◽  
Over Time ◽  
Dynamic Microtubule ◽  
Three Components

Insulin secretion is key for glucose homeostasis. Insulin secretory granules (SGs) exist in different functional pools, with young SGs being more mobile and preferentially secreted. However, the principles governing the mobility of age-distinct SGs remain undefined. Using the time-reporter insulin-SNAP to track age-distinct SGs we now show that their dynamics can be classified into three components: highly dynamic, restricted, and nearly immobile. Young SGs display all three components, whereas old SGs are either restricted or nearly immobile. Both glucose stimulation and F-actin depolymerization recruit a fraction of nearly immobile young, but not old, SGs for highly dynamic, microtubule-dependent transport. Moreover, F-actin marks multigranular bodies/lysosomes containing aged SGs. These data demonstrate that SGs lose their responsiveness to glucose stimulation and competence for microtubule-mediated transport over time while changing their relationship with F-actin.

scholarly journals SEL BETA PANKREAS SINTESIS DAN SEKRESI INSULIN

2013 ◽  
Vol 4 (3) ◽  
Author(s):  
Eka Banjarnahor ◽  
Sunny Wangko
Keyword(s):  
Insulin Secretion ◽  
Blood Glucose ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Plasma Membranes ◽  
Secretory Granules ◽  
Chromosome 11 ◽  
Insulin Synthesis ◽  
Glucose Levels ◽  
Blood Glucose Levels

Abstract: Insulin synthesis and secretion are done by pancreatic beta cells. Preceding the insulin synthesis, there is a gen translation in chromosome 11 that produces insulin, packed in secretory granules. Insulin secretion is induced by the alteration of blood glucose levels, resulting in the occurence of intracellular reactions preceded by changes of ATP/ADP ratios that trigger the depolarisation of plasma membranes. Furthermore, extracellular Ca2+ ions move inward to beta cells to activate exocytosis. There are still many unknown problems so far in either the synthesis or secretion of insulin that cause unfulfilled insulin needs in the body.Keywords: beta cells, insulin, synthesis, secretionAbstrak: Sintesis dan sekresi insulin dilakukan oleh sel beta pankreas. Sintesis insulin diawali oleh salinan gen pada kromosom 11, yang akan menghasilkan insulin, di kemas di dalam granul-granul sekretorik. Sekresi insulin diinduksi oleh perubahan kadar glukosa, yang berakibat terjadinya reaksi intrasel yang diikuti adanya perbedaan rasio ATP/ADP yang memicu reaksi depolarisasi membran plasma. Sebagai akibat lanjut Ca2+ ekstrasel akan masuk ke dalam sel beta yang berfungsi mengaktifkan eksositosis. Sampai saat ini masih banyak ditemui masalah baik dalam hal sintesis maupun sekresi insulin yang mengakibatkan kebutuhan insulin tubuh tidak terpenuhi.Kata kunci: sel beta, insulin, sintesis, sekresi

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