Conditional expression of the FTO gene product in rat INS-1 cells reveals its rapid turnover and a role in the profile of glucose-induced insulin secretion

2011 ◽  
Vol 120 (9) ◽  
pp. 403-413 ◽  
Author(s):  
Mark A. Russell ◽  
Noel G. Morgan
Keyword(s):  
Insulin Secretion ◽  
Expression System ◽  
Proteasome Inhibitors ◽  
Inducible Promoter ◽  
Insulin Biosynthesis ◽  
Second Phase ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Peripheral Tissues ◽  
Conditional Expression

Common polymorphisms within the FTO (fat mass and obesity-associated) gene correlate with increased BMI (body mass index) and a rising risk of Type 2 diabetes. FTO is highly expressed in the brain but has also been detected in peripheral tissues, including the endocrine pancreas, although its function there is unclear. The aim of the present study was to investigate the role of FTO protein in pancreatic β-cells using a conditional expression system developed in INS-1 cells. INS-1 cells were stably transfected with FTO–HA (haemagluttinin) incorporated under the control of a tetracycline-inducible promoter. Induction of FTO protein resulted in localization of the tagged protein to the nucleus. The level of FTO–HA protein achieved in transfected cells was tightly regulated, and experiments with selective inhibitors revealed that FTO–HA is rapidly degraded via the ubiquitin/proteasome pathway. The nuclear localization was not altered by proteasome inhibitors, although following treatment with PYR-41, an inhibitor of ubiquitination, some of the protein adopted a perinuclear localization. Unexpectedly, modestly increased expression of FTO–HA selectively enhanced the first phase of insulin secretion when INS-1 monolayers or pseudoislets were stimulated with 20 mM glucose, whereas the second phase remained unchanged. The mechanism responsible for the potentiation of glucose-induced insulin secretion is unclear; however, further experiments revealed that it did not involve an increase in insulin biosynthesis or any changes in STAT3 (signal transducer and activator of transcription 3) expression. Taken together, these results suggest that the FTO protein may play a hitherto unrecognized role in the control of first-phase insulin secretion in pancreatic β-cells.

scholarly journals Protein Kinase CK2 Controls CaV2.1-Dependent Calcium Currents and Insulin Release in Pancreatic β-cells

2020 ◽  
Vol 21 (13) ◽  
pp. 4668
Author(s):  
Rebecca Scheuer ◽  
Stephan Ernst Philipp ◽  
Alexander Becker ◽  
Lisa Nalbach ◽  
Emmanuel Ampofo ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Calcium Currents ◽  
Insulin Biosynthesis ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Voltage Dependent ◽  
Regulatory Impact ◽  
Kinase Ck2

The regulation of insulin biosynthesis and secretion in pancreatic β-cells is essential for glucose homeostasis in humans. Previous findings point to the highly conserved, ubiquitously expressed serine/threonine kinase CK2 as having a negative regulatory impact on this regulation. In the cell culture model of rat pancreatic β-cells INS-1, insulin secretion is enhanced after CK2 inhibition. This enhancement is preceded by a rise in the cytosolic Ca2+ concentration. Here, we identified the serine residues S2362 and S2364 of the voltage-dependent calcium channel CaV2.1 as targets of CK2 phosphorylation. Furthermore, co-immunoprecipitation experiments revealed that CaV2.1 binds to CK2 in vitro and in vivo. CaV2.1 knockdown experiments showed that the increase in the intracellular Ca2+ concentration, followed by an enhanced insulin secretion upon CK2 inhibition, is due to a Ca2+ influx through CaV2.1 channels. In summary, our results point to a modulating role of CK2 in the CaV2.1-mediated exocytosis of insulin.

scholarly journals Secretagogin affects insulin secretion in pancreatic β-cells by regulating actin dynamics and focal adhesion

2016 ◽  
Vol 473 (12) ◽  
pp. 1791-1803 ◽  
Author(s):  
Seo-Yun Yang ◽  
Jae-Jin Lee ◽  
Jin-Hee Lee ◽  
Kyungeun Lee ◽  
Seung Hoon Oh ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Focal Adhesion ◽  
Underlying Mechanism ◽  
Neuroendocrine Cells ◽  
Actin Dynamics ◽  
Second Phase ◽  
Dependent Manner ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Insulinoma Cells

Secretagogin (SCGN), a Ca2+-binding protein having six EF-hands, is selectively expressed in pancreatic β-cells and neuroendocrine cells. Previous studies suggested that SCGN enhances insulin secretion by functioning as a Ca2+-sensor protein, but the underlying mechanism has not been elucidated. The present study explored the mechanism by which SCGN enhances glucose-induced insulin secretion in NIT-1 insulinoma cells. To determine whether SCGN influences the first or second phase of insulin secretion, we examined how SCGN affects the kinetics of insulin secretion in NIT-1 cells. We found that silencing SCGN suppressed the second phase of insulin secretion induced by glucose and H2O2, but not the first phase induced by KCl stimulation. Recruitment of insulin granules in the second phase of insulin secretion was significantly impaired by knocking down SCGN in NIT-1 cells. In addition, we found that SCGN interacts with the actin cytoskeleton in the plasma membrane and regulates actin remodelling in a glucose-dependent manner. Since actin dynamics are known to regulate focal adhesion, a critical step in the second phase of insulin secretion, we examined the effect of silencing SCGN on focal adhesion molecules, including FAK (focal adhesion kinase) and paxillin, and the cell survival molecules ERK1/2 (extracellular-signal-regulated kinase 1/2) and Akt. We found that glucose- and H2O2-induced activation of FAK, paxillin, ERK1/2 and Akt was significantly blocked by silencing SCGN. We conclude that SCGN controls glucose-stimulated insulin secretion and thus may be useful in the therapy of Type 2 diabetes.

Insulin/phosphoinositide 3-kinase pathway accelerates the glucose-induced first-phase insulin secretion through TrpV2 recruitment in pancreatic β-cells

2010 ◽  
Vol 432 (2) ◽  
pp. 375-386 ◽  
Author(s):  
Kyota Aoyagi ◽  
Mica Ohara-Imaizumi ◽  
Chiyono Nishiwaki ◽  
Yoko Nakamichi ◽  
Shinya Nagamatsu
Keyword(s):  
Insulin Secretion ◽  
Transient Receptor Potential ◽  
Rapid Development ◽  
Fluorescent Microscopy ◽  
Physiological Role ◽  
Second Phase ◽  
Dependent Manner ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Phosphoinositide 3 Kinase

Functional insulin receptor and its downstream effector PI3K (phosphoinositide 3-kinase) have been identified in pancreatic β-cells, but their involvement in the regulation of insulin secretion from β-cells remains unclear. In the present study, we investigated the physiological role of insulin and PI3K in glucose-induced biphasic insulin exocytosis in primary cultured β-cells and insulinoma Min6 cells using total internal reflection fluorescent microscopy. The pretreatment of β-cells with insulin induced the rapid increase in intracellular Ca2+ levels and accelerated the exocytotic response without affecting the second-phase insulin secretion. The inhibition of PI3K not only abolished the insulin-induced rapid development of the exocytotic response, but also potentiated the second-phase insulin secretion. The rapid development of Ca2+ and accelerated exocytotic response induced by insulin were accompanied by the translocation of the Ca2+-permeable channel TrpV2 (transient receptor potential V2) in a PI3K-dependent manner. Inhibition of TrpV2 by the selective blocker tranilast, or the expression of shRNA (short-hairpin RNA) against TrpV2 suppressed the effect of insulin in the first phase, but the second phase was not affected. Thus our results demonstrate that insulin treatment induced the acceleration of the exocytotic response during the glucose-induced first-phase response by the insertion of TrpV2 into the plasma membrane in a PI3K-dependent manner.

scholarly journals Modulation of Insulin Sensitivity by Insulin-Degrading Enzyme

Biomedicines ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 86
Author(s):  
Carlos M. González-Casimiro ◽  
Beatriz Merino ◽  
Elena Casanueva-Álvarez ◽  
Tamara Postigo-Casado ◽  
Patricia Cámara-Torres ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Insulin Sensitivity ◽  
Current Knowledge ◽  
Insulin Degrading Enzyme ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Peripheral Tissues ◽  
Physiological Functions ◽  
Degrading Enzyme ◽  
Sugar Levels

Insulin-degrading enzyme (IDE) is a highly conserved and ubiquitously expressed metalloprotease that degrades insulin and several other intermediate-size peptides. For many decades, IDE had been assumed to be involved primarily in hepatic insulin clearance, a key process that regulates availability of circulating insulin levels for peripheral tissues. Emerging evidence, however, suggests that IDE has several other important physiological functions relevant to glucose and insulin homeostasis, including the regulation of insulin secretion from pancreatic β-cells. Investigation of mice with tissue-specific genetic deletion of Ide in the liver and pancreatic β-cells (L-IDE-KO and B-IDE-KO mice, respectively) has revealed additional roles for IDE in the regulation of hepatic insulin action and sensitivity. In this review, we discuss current knowledge about IDE’s function as a regulator of insulin secretion and hepatic insulin sensitivity, both evaluating the classical view of IDE as an insulin protease and also exploring evidence for several non-proteolytic functions. Insulin proteostasis and insulin sensitivity have both been highlighted as targets controlling blood sugar levels in type 2 diabetes, so a clearer understanding the physiological functions of IDE in pancreas and liver could led to the development of novel therapeutics for the treatment of this disease.

scholarly journals IRE1–XBP1 pathway regulates oxidative proinsulin folding in pancreatic β cells

2018 ◽  
Vol 217 (4) ◽  
pp. 1287-1301 ◽  
Author(s):  
Yuichi Tsuchiya ◽  
Michiko Saito ◽  
Hiroshi Kadokura ◽  
Jun-ichi Miyazaki ◽  
Fumi Tashiro ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Conditional Knockout ◽  
Insulin Biosynthesis ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Oxidative Folding ◽  
Insulinoma Cell ◽  
Disulfide Isomerases ◽  
Insulinoma Cells ◽  
Protein Disulfide

In mammalian pancreatic β cells, the IRE1α–XBP1 pathway is constitutively and highly activated under physiological conditions. To elucidate the precise role of this pathway, we constructed β cell–specific Ire1α conditional knockout (CKO) mice and established insulinoma cell lines in which Ire1α was deleted using the Cre–loxP system. Ire1α CKO mice showed the typical diabetic phenotype including impaired glycemic control and defects in insulin biosynthesis postnatally at 4–20 weeks. Ire1α deletion in pancreatic β cells in mice and insulinoma cells resulted in decreased insulin secretion, decreased insulin and proinsulin contents in cells, and decreased oxidative folding of proinsulin along with decreased expression of five protein disulfide isomerases (PDIs): PDI, PDIR, P5, ERp44, and ERp46. Reconstitution of the IRE1α–XBP1 pathway restored the proinsulin and insulin contents, insulin secretion, and expression of the five PDIs, indicating that IRE1α functions as a key regulator of the induction of catalysts for the oxidative folding of proinsulin in pancreatic β cells.

Congenital hyperinsulinism due to compound heterozygous mutations in ABCC8 responsive to diazoxide therapy

2020 ◽  
Vol 33 (5) ◽  
pp. 671-674
Author(s):  
Tashunka Taylor-Miller ◽  
Jayne Houghton ◽  
Paul Munyard ◽  
Yadlapalli Kumar ◽  
Clinda Puvirajasinghe ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Compound Heterozygous ◽  
Congenital Hyperinsulinism ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Newborn Period ◽  
Case Presentation ◽  
Male Baby ◽  
Common Causes ◽  
Compound Heterozygous Mutations

AbstractBackgroundCongenital hyperinsulinism (CHI), a condition characterized by dysregulation of insulin secretion from the pancreatic β cells, remains one of the most common causes of hyperinsulinemic, hypoketotic hypoglycemia in the newborn period. Mutations in ABCC8 and KCNJ11 constitute the majority of genetic forms of CHI.Case presentationA term macrosomic male baby, birth weight 4.81 kg, born to non-consanguineous parents, presented on day 1 of life with severe and persistent hypoglycemia. The biochemical investigations confirmed a diagnosis of CHI. Diazoxide was started and progressively increased to 15 mg/kg/day to maintain normoglycemia. Sequence analysis identified compound heterozygous mutations in ABCC8 c.4076C>T and c.4119+1G>A inherited from the unaffected father and mother, respectively. The mutations are reported pathogenic. The patient is currently 7 months old with a sustained response to diazoxide.ConclusionsBiallelic ABCC8 mutations are known to result in severe, diffuse, diazoxide-unresponsive hypoglycemia. We report a rare patient with CHI due to compound heterozygous mutations in ABCC8 responsive to diazoxide.

scholarly journals Author Correction: CD44 variant inhibits insulin secretion in pancreatic β cells by attenuating LAT1-mediated amino acid uptake

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Nana Kobayashi ◽  
Shogo Okazaki ◽  
Oltea Sampetrean ◽  
Junichiro Irie ◽  
Hiroshi Itoh ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Amino Acid ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Cd44 Variant

scholarly journals D2-Like Receptors Mediate Dopamine-Inhibited Insulin Secretion via Ion Channels in Rat Pancreatic β-Cells

2020 ◽  
Vol 11 ◽  
Author(s):  
Mengmeng Liu ◽  
Lele Ren ◽  
Xiangqin Zhong ◽  
Yaqin Ding ◽  
Tao Liu ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Ion Channels ◽  
Β Cells ◽  
Pancreatic Β Cells

Jiawei Erzhiwan improves menopausal metabolic syndrome by enhancing insulin secretion in pancreatic β cells

2016 ◽  
Vol 14 (11) ◽  
pp. 823-834 ◽  
Author(s):  
Xiao-Meng WAN ◽  
Mu ZHANG ◽  
Pei ZHANG ◽  
Zhi-Shen XIE ◽  
Feng-Guo XU ◽  
...  
Keyword(s):  
Metabolic Syndrome ◽  
Insulin Secretion ◽  
Β Cells ◽  
Pancreatic Β Cells
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