Browse
Submit Data
Databases
API
Help

Dataset Information

24 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Newcomer insulin secretory granules as a highly calcium-sensitive pool.

ABSTRACT: Insulin secretion is biphasic in response to a step in glucose stimulation. Recent experiments suggest that 2 different mechanisms operate during the 2 phases, with transient first-phase secretion due to exocytosis of docked granules but the second sustained phase due largely to newcomer granules. Another line of research has shown that there exist 2 pools of releasable granules with different Ca(2+) sensitivities. An immediately releasable pool (IRP) is located in the vicinity of Ca(2+) channels, whereas a highly Ca(2+)-sensitive pool (HCSP) resides mainly away from Ca(2+) channels. We extend a previous model of exocytosis and insulin release by adding an HCSP and show that the inclusion of this pool naturally leads to insulin secretion mainly from newcomer granules during the second phase of secretion. We show that the model is compatible with data from single cells on the HCSP and from stimulation of islets by glucose, including L- and R-type Ca(2+) channel knockouts, as well as from Syntaxin-1A-deficient cells. We also use the model to investigate the relative contribution of calcium signaling and pool depletion in controlling biphasic secretion.

SUBMITTER: Pedersen MG

PROVIDER: S-EPMC2678592 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Insulin sensitive muscle sample pool 5

Project description:Muscle sample pool #5 from 4 insulin sensitive subjects. Keywords: parallel sample

2002-08-26 | GSE68 | GEO

Insulin sensitive muscle sample pool 4

Project description:Muscle sample pool #4 from 3 insulin sensitive subjects. Keywords: parallel sample

2002-08-26 | GSE67 | GEO

Insulin sensitive muscle sample pool 2

Project description:Muscle sample pool #2 from 4 insulin sensitive subjects. Keywords: parallel sample

2002-08-26 | GSE65 | GEO

Insulin sensitive muscle sample pool 1

Project description:Muscle sample pool #1 from 4 insulin sensitive subjects. Keywords: parallel sample

2002-08-26 | GSE64 | GEO

Insulin sensitive muscle sample pool 3

Project description:Muscle sample pool #3 from 3 insulin sensitive subjects. Keywords: parallel sample

2002-08-26 | GSE66 | GEO

VAMP4 regulates insulin levels by targeting secretory granules to lysosomes.

Project description:Insulin levels are essential for the maintenance of glucose homeostasis, and deviations lead to pathoglycemia or diabetes. However, the metabolic mechanism controlling insulin quantity and quality is poorly understood. In pancreatic β cells, insulin homeostasis and release are tightly governed by insulin secretory granule (ISG) trafficking, but the required regulators and mechanisms are largely unknown. Here, we identified that VAMP4 controlled the insulin levels in response to glucose challenge. VAMP4 deficiency led to increased blood insulin levels and hyperresponsiveness to glucose. In β cells, VAMP4 is packaged into immature ISGs (iISGs) at trans-Golgi networks and subsequently resorted to clathrin-coated vesicles during granule maturation. VAMP4-positive iISGs and resorted vesicles then fuse with lysosomes facilitated by a SNARE complex consisting of VAMP4, STX7, STX8, and VTI1B, which ensures the breakdown of excess (pro)insulin and obsolete materials and thus maintenance of intracellular insulin homeostasis. Thus, VAMP4 is a key factor regulating the insulin levels and a potential target for the treatment of diabetes.

| S-EPMC9441717 | biostudies-literature

A fluorescent timer reporter enables sorting of insulin secretory granules by age.

Project description:Within the pancreatic β-cells, insulin secretory granules (SGs) exist in functionally distinct pools, displaying variations in motility as well as docking and fusion capability. Current therapies that increase insulin secretion do not consider the existence of these distinct SG pools. Accordingly, these approaches are effective only for a short period, with a worsening of glycemia associated with continued decline in β-cell function. Insulin granule age is underappreciated as a determinant for why an insulin granule is selected for secretion and may explain why newly synthesized insulin is preferentially secreted from β-cells. Here, using a novel fluorescent timer protein, we aimed to investigate the preferential secretion model of insulin secretion and identify how granule aging is affected by variation in the β-cell environment, such as hyperglycemia. We demonstrate the use of a fluorescent timer construct, syncollin-dsRedE5TIMER, which changes its fluorescence from green to red over 18 h, in both microscopy and fluorescence-assisted organelle-sorting techniques. We confirm that the SG-targeting construct localizes to insulin granules in β-cells and does not interfere with normal insulin SG behavior. We visualize insulin SG aging behavior in MIN6 and INS1 β-cell lines and in primary C57BL/6J mouse and nondiabetic human islet cells. Finally, we separated young and old insulin SGs, revealing that preferential secretion of younger granules occurs in glucose-stimulated insulin secretion. We also show that SG population age is modulated by the β-cell environment in vivo in the db/db mouse islets and ex vivo in C57BL/6J islets exposed to different glucose environments.

| S-EPMC7335792 | biostudies-literature

Association with nitric oxide synthase on insulin secretory granules regulates glucokinase protein levels.

Project description:Glucokinase (GCK) association with insulin-secretory granules is controlled by interaction with nitric oxide synthase (NOS) and is reversed by GCK S-nitrosylation. Nonetheless, the function of GCK sequestration on secretory granules is unknown. Here we report that the S-nitrosylation blocking V367M mutation prevents GCK accumulation on secretory granules by inhibiting association with NOS. Expression of this mutant is reduced compared with a second S-nitrosylation blocking GCK mutant (C371S) that accumulates to secretory granules and is expressed at levels greater than wild type. Even so, the rate of degradation for wild type and mutant GCK proteins were not significantly different from one another, and neither mutation disrupted the ability of GCK to be ubiquitinated. Furthermore, gene silencing of NOS reduced endogenous GCK content but did not affect β-actin content. Treatment of GCK(C371S) expressing cells with short interfering RNA specific for NOS also blocked accumulation of this protein to secretory granules and reduced expression levels to that of GCK(V367M). Conversely, cotransfection of catalytically inactive NOS increased GCK-mCherry levels. Expression of GCK(C371S) in βTC3 cells enhanced glucose metabolism compared with untransfected cells and cells expressing wild type GCK, even though this mutant has slightly reduced enzymatic activity in vitro. Finally, molecular dynamics simulations revealed that V367M induces conformational changes in GCK that are similar to S-nitrosylated GCK, thereby suggesting a mechanism for V367M-inhibition of NOS association. Our findings suggest that sequestration of GCK on secretory granules regulates cellular GCK protein content, and thus cellular GCK activity, by acting as a storage pool for GCK proteins.

| S-EPMC3434526 | biostudies-literature

Insulin secretory granules release exosomal miR-503 to promote insulin resistance and β-cell senescence.

Project description:Since β cell specific miR-503 transgenic (βTG) mice showed metabolic stress induced insulin resistance and β cell dysfunction, we applied single cell sequencing (scSeq) technology to distinguish different cell type in β TG islets and define different phases of β cell subtypes through pseudotime analysis. Islets were isolated and digested at 37℃for 5 min by 0.08 % trypsin containing 0.006 % EDTA to generate islet single cell, cell suspension was centrifuged and resuspended in cold PBS buffer with 0.4% of BSA at the concentration of ~1000/μl, which then was loaded onto the 10X Chromium Controller using Chromium Single Cell 3’ v2 reagents. Sequencing library was prepared following the manufacturer’s instructions (10X Genomics), and sequenced via a Illumina HiSeq PE150 instrument. 8698 cells were detected from 10-week old wild type (WT, n = 4540 cells) and βTG (n = 4158 cells) mice islets, cells were split to 12 subtypes by using cell ranger software and k-means algorithm. According to specific gene profile we found that βTG islets was infiltrated with Ccr6/Ccr7 positive immune cells, and most β cells in βTG mice islets were defined senescent cells by using GO enrichment and pseudotime analysis. Our study represents the analysis of islet single cell transcriptomes, the results showed that miR-503 highly expression in β cells promotes β cell senescence and diabetes onset.

2022-07-08 | GSE155798 | GEO

?2-Syntrophin is a Cdk5 substrate that restrains the motility of insulin secretory granules.

Project description:The molecular basis for the interaction of insulin granules with the cortical cytoskeleton of pancreatic ?-cells remains unknown. We have proposed that binding of the granule protein ICA512 to the PDZ domain of ?2-syntrophin anchors granules to actin filaments and that the phosphorylation/dephosphorylation of ?2-syntrophin regulates this association. Here we tested this hypothesis by analyzing INS-1 cells expressing GFP-?2-syntrophin through the combined use of biochemical approaches, imaging studies by confocal and total internal reflection fluorescence microscopy as well as electron microscopy. Our results support the notion that ?2-syntrophin restrains the mobility of cortical granules in insulinoma INS-1 cells, thereby reducing insulin secretion and increasing insulin stores in resting cells, while increasing insulin release upon stimulation. Using mass spectrometry, in vitro phosphorylation assays and ?2-syntrophin phosphomutants we found that phosphorylation of ?2-syntrophin on S75 near the PDZ domain decreases its binding to ICA512 and correlates with increased granule motility, while phosphorylation of S90 has opposite effects. We further show that Cdk5, which regulates insulin secretion, phosphorylates S75. These findings provide mechanistic insight into how stimulation displaces insulin granules from cortical actin, thus promoting their motility and exocytosis.

| S-EPMC2944849 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data