scholarly journals MyRIP interaction with MyoVa on secretory granules is controlled by the cAMP-PKA pathway

2012 ◽  
Vol 23 (22) ◽  
pp. 4444-4455 ◽  
Author(s):  
Flora Brozzi ◽  
Sophie Lajus ◽  
Frederique Diraison ◽  
Shavanthi Rajatileka ◽  
Katy Hayward ◽  
...  
Keyword(s):  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Secretory Granules ◽  
Hormone Secretion ◽  
Motor Protein ◽  
Functional Protein ◽  
Interacting Protein ◽  
Myosin Va ◽  
Glucose Stimulated Insulin Secretion

Myosin- and Rab-interacting protein (MyRIP), which belongs to the protein kinase A (PKA)–anchoring family, is implicated in hormone secretion. However, its mechanism of action is not fully elucidated. Here we investigate the role of MyRIP in myosin Va (MyoVa)-dependent secretory granule (SG) transport and secretion in pancreatic beta cells. These cells solely express the brain isoform of MyoVa (BR-MyoVa), which is a key motor protein in SG transport. In vitro pull-down, coimmunoprecipitation, and colocalization studies revealed that MyRIP does not interact with BR-MyoVa in glucose-stimulated pancreatic beta cells, suggesting that, contrary to previous notions, MyRIP does not link this motor protein to SGs. Glucose-stimulated insulin secretion is augmented by incretin hormones, which increase cAMP levels and leads to MyRIP phosphorylation, its interaction with BR-MyoVa, and phosphorylation of the BR-MyoVa receptor rabphilin-3A (Rph-3A). Rph-3A phosphorylation on Ser-234 was inhibited by small interfering RNA knockdown of MyRIP, which also reduced cAMP-mediated hormone secretion. Demonstrating the importance of this phosphorylation, nonphosphorylatable and phosphomimic Rph-3A mutants significantly altered hormone release when PKA was activated. These data suggest that MyRIP only forms a functional protein complex with BR-MyoVa on SGs when cAMP is elevated and under this condition facilitates phosphorylation of SG-associated proteins, which in turn can enhance secretion.

Glucose-dependent expansion of pancreatic beta-cells by the protein p8 in vitro and in vivo

2007 ◽  
Vol 115 (S 1) ◽  
Author(s):  
G Päth ◽  
A Opel ◽  
M Gehlen ◽  
V Rothhammer ◽  
X Niu ◽  
...  
Keyword(s):  
Beta Cells ◽  
Pancreatic Beta Cells

scholarly journals Disruption of Beta-Cell Mitochondrial Networks by the Orphan Nuclear Receptor Nor1/Nr4a3

Cells ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 168 ◽  
Author(s):  
Anne-Françoise Close ◽  
Nidheesh Dadheech ◽  
Hélène Lemieux ◽  
Qian Wang ◽  
Jean Buteau
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Nuclear Receptor ◽  
Pancreatic Beta Cells ◽  
Orphan Nuclear Receptor ◽  
Atp Production ◽  
Human Beta Cells ◽  
Glucose Stimulated Insulin Secretion ◽  
Mitochondrial Networks

Nor1, the third member of the Nr4a subfamily of nuclear receptor, is garnering increased interest in view of its role in the regulation of glucose homeostasis. Our previous study highlighted a proapoptotic role of Nor1 in pancreatic beta cells and showed that Nor1 expression was increased in islets isolated from type 2 diabetic individuals, suggesting that Nor1 could mediate the deterioration of islet function in type 2 diabetes. However, the mechanism remains incompletely understood. We herein investigated the subcellular localization of Nor1 in INS832/13 cells and dispersed human beta cells. We also examined the consequences of Nor1 overexpression on mitochondrial function and morphology. Our results show that, surprisingly, Nor1 is mostly cytoplasmic in beta cells and undergoes mitochondrial translocation upon activation by proinflammatory cytokines. Mitochondrial localization of Nor1 reduced glucose oxidation, lowered ATP production rates, and inhibited glucose-stimulated insulin secretion. Western blot and microscopy images revealed that Nor1 could provoke mitochondrial fragmentation via mitophagy. Our study unveils a new mode of action for Nor1, which affects beta-cell viability and function by disrupting mitochondrial networks.

Lysosomal acid lipase and lipophagy are constitutive negative regulators of glucose-stimulated insulin secretion from pancreatic beta cells

Diabetologia ◽  
2013 ◽  
Vol 57 (1) ◽  
pp. 129-139 ◽  
Author(s):  
Gemma L. Pearson ◽  
Natalie Mellett ◽  
Kwan Yi Chu ◽  
James Cantley ◽  
Aimee Davenport ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Acid Lipase ◽  
Negative Regulators ◽  
Lysosomal Acid ◽  
Lysosomal Acid Lipase ◽  
Glucose Stimulated Insulin Secretion

scholarly journals Precise expression of Fis1 is important for glucose responsiveness of beta cells

2016 ◽  
Vol 230 (1) ◽  
pp. 81-91 ◽  
Author(s):  
Julia Schultz ◽  
Rica Waterstradt ◽  
Tobias Kantowski ◽  
Annekatrin Rickmann ◽  
Florian Reinhardt ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Morphology ◽  
Mitochondrial Network ◽  
Primary Mouse ◽  
Glucose Stimulated Insulin Secretion ◽  
Glucose Responsiveness ◽  
Precise Expression

Mitochondrial network functionality is vital for glucose-stimulated insulin secretion in pancreatic beta cells. Altered mitochondrial dynamics in pancreatic beta cells are thought to trigger the development of type 2 diabetes mellitus. Fission protein 1 (Fis1) might be a key player in this process. Thus, the aim of this study was to investigate mitochondrial morphology in dependence of beta cell function, after knockdown and overexpression of Fis1. We demonstrate that glucose-unresponsive cells with impaired glucose-stimulated insulin secretion (INS1-832/2) showed decreased mitochondrial dynamics compared with glucose-responsive cells (INS1-832/13). Accordingly, mitochondrial morphology visualised using MitoTracker staining differed between the two cell lines. INS1-832/2 cells formed elongated and clustered mitochondria, whereas INS1-832/13 cells showed a homogenous mitochondrial network. Fis1 overexpression using lentiviral transduction significantly improved glucose-stimulated insulin secretion and mitochondrial network homogeneity in glucose-unresponsive cells. Conversely, Fis1 downregulation by shRNA, both in primary mouse beta cells and glucose-responsive INS1-832/13 cells, caused unresponsiveness and significantly greater numbers of elongated mitochondria. Overexpression of FIS1 in primary mouse beta cells indicated an upper limit at which higher FIS1 expression reduced glucose-stimulated insulin secretion. Thus, FIS1 was overexpressed stepwise up to a high concentration in RINm5F cells using the RheoSwitch system. Moderate FIS1 expression improved glucose-stimulated insulin secretion, whereas high expression resulted in loss of glucose responsiveness and in mitochondrial artificial loop structures and clustering. Our data confirm that FIS1 is a key regulator in pancreatic beta cells, because both glucose-stimulated insulin secretion and mitochondrial dynamics were clearly adapted to precise expression levels of this fission protein.

scholarly journals Involvement of receptor-interacting protein 140 in palmitate-stimulated macrophage infiltration of pancreatic beta cells

2017 ◽  
Vol 14 (1) ◽  
pp. 483-494
Author(s):  
Runmei Zou ◽  
Junli Xue ◽  
Qi Huang ◽  
Zhe Dai ◽  
Yancheng Xu
Keyword(s):  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Macrophage Infiltration ◽  
Interacting Protein

Comparative toxicity of alloxan, N-alkylalloxans and ninhydrin to isolated pancreatic islets in vitro

1997 ◽  
Vol 155 (2) ◽  
pp. 283-293 ◽  
Author(s):  
A Jorns ◽  
R Munday ◽  
M Tiedge ◽  
S Lenzen
Keyword(s):  
Beta Cell ◽  
Pancreatic Islets ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Ultrastructural Changes ◽  
Cell Necrosis ◽  
High Concentrations ◽  
Beta Cell Necrosis

The in vitro toxicity of the diabetogenic agent alloxan as documented by the induction of beta cell necrosis was studied in isolated ob/ob mouse pancreatic islets. The effect of alloxan has been compared with that of a number of N-alkyl alloxan derivatives and with that of the structurally related compound, ninhydrin. Alloxan and its derivatives were selectively toxic to pancreatic beta cells, with other endocrine cells and exocrine parenchymal cells being well preserved, even at high concentration. In contrast, ninhydrin was selectively toxic to pancreatic beta cells only at comparatively low concentration, destroying all islet cell types at high concentrations. The ultrastructural changes induced by all the test compounds in pancreatic beta cells in vitro were very similar to those observed during the development of alloxan diabetes in vivo. The relative toxicity of the various compounds to pancreatic beta cells in vitro was not, however, related to their ability to cause diabetes in vivo. Indeed, the non-diabetogenic substances ninhydrin, N-butylalloxan and N-isobutylalloxan were very much more toxic to isolated islets than the diabetogenic compounds alloxan and N-methylalloxan. These results suggest that the differences in diabetogenicity among alloxan derivatives are not due to intrinsic differences in the susceptibility of the pancreatic beta cells to their toxicity, but may reflect differences in distribution or metabolism. High concentrations of glucose protected islets against the harmful effects of alloxan and its derivatives, but not those of ninhydrin. Low levels of glucose, and non-carbohydrate nutrients, afforded little protection, indicating that the effect of glucose is not due to the production of reducing equivalents within the cell, 3-O-Methylglucose, which protects against alloan diabetes in vivo, did not protect against alloxan toxicity in vitro. Since 3-O-methylglucose is known to prevent uptake of alloxan by pancreatic beta cells, it appears that uptake of alloxan by the cell is not a prerequisite for the induction of beta cell necrosis.

scholarly journals Electron microscopic immunocytochemical evidence for the involvement of the convertases PC1 and PC2 in the processing of proinsulin in pancreatic beta-cells.

1995 ◽  
Vol 43 (1) ◽  
pp. 11-19 ◽  
Author(s):  
D Malide ◽  
N G Seidah ◽  
M Chrétien ◽  
M Bendayan
Keyword(s):  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Secretory Pathway ◽  
Secretory Granules ◽  
Protein A ◽  
Gold Complex ◽  
Immunocytochemical Study ◽  
Electron Microscopic ◽  
Double Labeling ◽  
Endoproteolytic Cleavage

Endoproteolytic cleavage of pairs of basic amino acids is the key mechanism in the specific processing of precursor hormone molecules. Two endoproteases, PC1 (or PC3) and PC2, have recently been implicated in the conversion of proinsulin. Using antibodies against these proteases and proinsulin, followed by protein A-gold complex, we performed an immunocytochemical study for precise identification of the subcellular compartments involved in the processing of insulin. Both PC1 and PC2 immunoreactivities followed a pattern of gradually increasing density along the secretory pathway, being higher in the immature granules. Proinsulin labeling was detected in the Golgi apparatus and in the coated immature secretory granules located mainly in the Golgi area. Using double labeling, we demonstrated the presence of PC1 and/or PC2 in the majority of proinsulin-rich granules. In addition, we provided evidence that PC1 and PC2 are co-localized within the same granules. Co-expression of PC1 and PC2 with proinsulin in islet beta-cells indicates that these proteases are actively involved, probably in a sequential manner, in the conversion of proinsulin into insulin.

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