scholarly journals Metabolic Stress Induces Caspase-3 Mediated Degradation and Inactivation of Farnesyl and Geranylgeranyl Transferase Activities in Pancreatic β-Cells

2016 ◽  
Vol 39 (6) ◽  
pp. 2110-2120 ◽  
Author(s):  
Rajakrishnan Veluthakal ◽  
Daleep K. Arora ◽  
Marc L. Goalstone ◽  
Renu A. Kowluru ◽  
Anjaneyulu Kowluru
Keyword(s):  
G Proteins ◽  
Caspase 3 ◽  
Metabolic Stress ◽  
Human Islets ◽  
Protein Prenylation ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Α Subunit ◽  
Zdf Rat ◽  
The Impact

Background/Aims: At least 300 prenylated proteins are identified in the human genome; the majority of which partake in a variety of cellular processes including growth, differentiation, cytoskeletal organization/dynamics and vesicle trafficking. Aberrant prenylation of proteins is implicated in human pathologies including cancer; neurodegenerative diseases, retinitis pigmentosa, and premature ageing syndromes. Original observations from our laboratory have demonstrated that prenylation of proteins [small G-proteins and γ-subunits of trimeric G-proteins] is requisite for physiological insulin secretion. Herein, we assessed the impact of metabolic stress [gluco-, lipotoxicity and ER-stress] on the functional status of protein prenylation pathway in pancreatic β-cells. Methods: Farnesyltransferase [FTase] and geranylgeranyltransferase [GGTase] activities were quantified by radioisotopic methods. Caspase-3 activation and FTase/GGTase-α subunit degradation were determined by Western blotting. Results: We observed that metabolic stress activates caspase-3 and induces degradation of the common α-subunit of FTase and GGTase-I in INS-1 832/13 cells, normal rodent islets and human islets leading to functional defects [inactivation] in FTase and GGTase activities. Caspase-3 activation and FTase/GGTase-α degradation were also seen in islets from the Zucker diabetic fatty [ZDF] rat, a model for Type 2 diabetes. Consequential to defects in FTase/GGTase-α signaling, we observed significant accumulation of unprenylated proteins [Rap1] in β-cells exposed to glucotoxic conditions. These findings were replicated in β-cells following pharmacological inhibition of generation of prenylpyrophosphate substrates [Simvastatin] or catalytic activity of prenylating enzymes [GGTI-2147]. Conclusions: Our findings provide the first evidence to suggest that metabolic stress induced dysfunction of the islet β-cell may, in part, be due to defective protein prenylation signaling pathway.

scholarly journals AKT1 Regulates Endoplasmic Reticulum Stress and Mediates the Adaptive Response of Pancreatic β Cells

2020 ◽  
Vol 40 (11) ◽  
Author(s):  
Zhechu Peng ◽  
Richa Aggarwal ◽  
Ni Zeng ◽  
Lina He ◽  
Eileen X. Stiles ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Adaptive Response ◽  
Metabolic Stress ◽  
Cell Phenotype ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Α Subunit ◽  
Growth And Survival

ABSTRACT Isoforms of protein kinase B (also known as AKT) play important roles in mediating insulin and growth factor signals. Previous studies have suggested that the AKT2 isoform is critical for insulin-regulated glucose metabolism, while the role of the AKT1 isoform remains less clear. This study focuses on the effects of AKT1 on the adaptive response of pancreatic β cells. Using a mouse model with inducible β-cell-specific deletion of the Akt1 gene (βA1KO mice), we showed that AKT1 is involved in high-fat-diet (HFD)-induced growth and survival of β cells but is unnecessary for them to maintain a population in the absence of metabolic stress. When unchallenged, βA1KO mice presented the same metabolic profile and β-cell phenotype as the control mice with an intact Akt1 gene. When metabolic stress was induced by HFD, β cells in control mice with intact Akt1 proliferated as a compensatory mechanism for metabolic overload. Similar effects were not observed in βA1KO mice. We further demonstrated that AKT1 protein deficiency caused endoplasmic reticulum (ER) stress and potentiated β cells to undergo apoptosis. Our results revealed that AKT1 protein loss led to the induction of eukaryotic initiation factor 2 α subunit (eIF2α) signaling and ER stress markers under normal-chow-fed conditions, indicating chronic low-level ER stress. Together, these data established a role for AKT1 as a growth and survival factor for adaptive β-cell response and suggest that ER stress induction is responsible for this effect of AKT1.

scholarly journals Inhibition of Prenylation Promotes Caspase 3 Activation, Lamin B Degradation and Loss in Metabolic Cell Viability in Pancreatic β-Cells

2017 ◽  
Vol 43 (3) ◽  
pp. 1052-1063 ◽  
Author(s):  
Khadija G. Syeda ◽  
Anjan Kowluru
Keyword(s):  
Cell Viability ◽  
Caspase 3 ◽  
Cell Function ◽  
Protein Prenylation ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Intermediate Filament Proteins ◽  
Lamin B ◽  
Metabolic Defects ◽  
Cell Proliferation Inhibition

Background/Aims: Lamins are intermediate filament proteins that constitute the main components of the lamina underlying the inner-nuclear membrane and serve to organize chromatin. Lamins (e.g., lamin B) undergo posttranslational modifications (e.g., isoprenylation) at their C-terminal cysteine residues. Such modifications are thought to render optimal association of lamins with the nuclear envelop. Using human islets, rodent islets, and INS-1 832/13 cells, we recently reported significant metabolic defects under glucotoxic and endoplasmic reticulum (ER) stress conditions, including caspase 3 activation and lamin B degradation. The current study is aimed at further understanding the regulatory roles of protein prenylation in the induction of the aforestated metabolic defects. Methods: Subcellular phase partitioning assay was done using Triton X-114. Cell morphology and metabolic cell viability assays were carried out using standard methodologies. Results: We report that exposure of pancreatic β-cells to Simvastatin, an inhibitor of mevalonic acid (MVA) biosynthesis, and its downstream isoprenoid derivatives, or FTI-277, an inhibitor of farnesyltransferase that mediates farnesylation of lamins, leads to activation of caspase 3 and lamin B degradation. Furthermore, Simvastatin-treatment increased activation of p38MAPK (a stress kinase) and inhibited ERK1/2 (regulator of cell proliferation). Inhibition of farnesylation also resulted in the release of degraded lamin B into the cytosolic fraction and promoted loss in metabolic cell viability. Conclusion: Based on these findings we conclude that protein prenylation plays key roles in islet β-cell function. These findings affirm further support to the hypothesis that defects in prenylation pathway induce caspase-3 activation and nuclear lamin degradation in pancreatic β-cells under the duress of metabolic stress (e.g., glucotoxicity).

scholarly journals PDX1LOW MAFALOW β-cells contribute to islet function and insulin release

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Daniela Nasteska ◽  
Nicholas H. F. Fine ◽  
Fiona B. Ashford ◽  
Federica Cuozzo ◽  
Katrina Viloria ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Insulin Release ◽  
Metabolic Stress ◽  
Human Islets ◽  
Islet Function ◽  
Β Cells ◽  
Β Cell ◽  
Ionic Fluxes ◽  
Transcriptomic Level ◽  
Adult Islet

AbstractTranscriptionally mature and immature β-cells co-exist within the adult islet. How such diversity contributes to insulin release remains poorly understood. Here we show that subtle differences in β-cell maturity, defined using PDX1 and MAFA expression, contribute to islet operation. Functional mapping of rodent and human islets containing proportionally more PDX1HIGH and MAFAHIGH β-cells reveals defects in metabolism, ionic fluxes and insulin secretion. At the transcriptomic level, the presence of increased numbers of PDX1HIGH and MAFAHIGH β-cells leads to dysregulation of gene pathways involved in metabolic processes. Using a chemogenetic disruption strategy, differences in PDX1 and MAFA expression are shown to depend on islet Ca2+ signaling patterns. During metabolic stress, islet function can be restored by redressing the balance between PDX1 and MAFA levels across the β-cell population. Thus, preserving heterogeneity in PDX1 and MAFA expression, and more widely in β-cell maturity, might be important for the maintenance of islet function.

The mTORC2/PKC pathway sustains compensatory insulin secretion of pancreatic β cells in response to metabolic stress

2017 ◽  
Vol 1861 (8) ◽  
pp. 2039-2047 ◽  
Author(s):  
Yun Xie ◽  
Canqi Cui ◽  
Aifang Nie ◽  
Yan Wang ◽  
Qicheng Ni ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Metabolic Stress ◽  
Β Cells ◽  
Pancreatic Β Cells

scholarly journals Metabolic stress activates an ERK/hnRNPK/DDX3X pathway in pancreatic β cells

2019 ◽  
Vol 26 ◽  
pp. 45-56 ◽  
Author(s):  
Austin L. Good ◽  
Matthew W. Haemmerle ◽  
Alexis U. Oguh ◽  
Nicolai M. Doliba ◽  
Doris A. Stoffers
Keyword(s):  
Metabolic Stress ◽  
Β Cells ◽  
Pancreatic Β Cells

scholarly journals Glycated Albumin Causes Pancreatic β-Cells Dysfunction Through Autophagy Dysfunction

Endocrinology ◽  
2013 ◽  
Vol 154 (8) ◽  
pp. 2626-2639 ◽  
Author(s):  
Young Mi Song ◽  
Sun Ok Song ◽  
Young-Hye You ◽  
Kun-Ho Yoon ◽  
Eun Seok Kang ◽  
...  
Keyword(s):  
Caspase 3 ◽  
Glycated Albumin ◽  
Nuclear Factor Κb ◽  
Nuclear Factor ◽  
Bafilomycin A1 ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Autophagy Induction ◽  
Interfering Rna

Abstract Growing evidence suggests that advanced glycation end-products (AGEs) are cytotoxic to pancreatic β-cells. The aims of this study were to investigate whether glycated albumin (GA), an early precursor of AGEs, would induce dysfunction in pancreatic β-cells and to determine which kinds of cellular mechanisms are activated in GA-induced β-cell apoptosis. Decreased viability and increased apoptosis were induced in INS-1 cells treated with 2.5 mg/mL GA under 16.7mM high-glucose conditions. Insulin content and glucose-stimulated secretion from isolated rat islets were reduced in 2.5 mg/mL GA-treated cells. In response to 2.5 mg/mL GA in INS-1 cells, autophagy induction and flux decreased as assessed by green fluorescent protein–microtubule-associated protein 1 light chain 3 dots, microtubule-associated protein 1 light chain 3-II conversion, and SQSTM1/p62 in the presence and absence of bafilomycin A1. Accumulated SQSTM1/p62 through deficient autophagy activated the nuclear factor-κB (p65)-inducible nitric oxide synthase-caspase-3 cascade, which was restored by treatment with small interfering RNA against p62. Small interfering RNA treatment against autophagy-related protein 5 significantly inhibited the autophagy machinery resulting in a significant increase in iNOS-cleaved caspase-3 expression. Treatment with 500μM 4-phenyl butyric acid significantly alleviated the expression of endoplasmic reticulum stress markers and iNOS in parallel with upregulated autophagy induction. However, in the presence of bafilomycin A1, the decreased viability of INS-1 cells was not recovered. Glycated albumin, an early precursor of AGE, caused pancreatic β-cell death by inhibiting autophagy induction and flux, resulting in nuclear factor-κB (p65)-iNOS-caspase-3 cascade activation as well as by increasing susceptibility to endoplasmic reticulum stress and oxidative stress.

scholarly journals Silymarin Protects Pancreatic β-Cells against Cytokine-Mediated Toxicity: Implication of c-Jun NH2-Terminal Kinase and Janus Kinase/Signal Transducer and Activator of Transcription Pathways

Endocrinology ◽  
2005 ◽  
Vol 146 (1) ◽  
pp. 175-185 ◽  
Author(s):  
Takeru Matsuda ◽  
Kevin Ferreri ◽  
Ivan Todorov ◽  
Yoshikazu Kuroda ◽  
Craig V. Smith ◽  
...  
Keyword(s):  
Cell Death ◽  
Human Islets ◽  
Janus Kinase ◽  
Time Dependent ◽  
No Production ◽  
Rinm5f Cells ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Ifn Γ

Silymarin is a polyphenolic flavonoid that has a strong antioxidant activity and exhibits anticarcinogenic, antiinflammatory, and cytoprotective effects. Although its hepatoprotective effect has been well documented, the effect of silymarin on pancreatic β-cells is largely unknown. In this study, the effect of silymarin on IL-1β and/or interferon (IFN)-γ-induced β-cell damage was investigated using RINm5F cells and human islets. IL-1β and/or IFN-γ induced cell death in a time-dependent manner in RINm5F cells. The time-dependent increase in cytokine-induced cell death appeared to correlate with the time-dependent nitric oxide (NO) production. Silymarin dose-dependently inhibited both cytokine-induced NO production and cell death in RINm5F cells. Treatment of human islets with a combination of IL-1β and IFN-γ (IL-1β+IFN-γ), for 48 h and 5 d, resulted in an increase of NO production and the impairment of glucose-stimulated insulin secretion, respectively. Silymarin prevented IL-1β+IFN-γ-induced NO production and β-cell dysfunction in human islets. These cytoprotective effects of silymarin appeared to be mediated through the suppression of c-Jun NH2-terminal kinase and Janus kinase/signal transducer and activator of transcription pathways. Our data show a direct cytoprotective effect of silymarin in pancreatic β-cells and suggest that silymarin may be therapeutically beneficial for type 1 diabetes.

Cell-permeable peptide-based disruption of endogenous PKA-AKAP complexes: a tool for studying the molecular roles of AKAP-mediated PKA subcellular anchoring

2009 ◽  
Vol 296 (2) ◽  
pp. C306-C316 ◽  
Author(s):  
Omar M. Faruque ◽  
Dung Le-Nguyen ◽  
Anne-Dominique Lajoix ◽  
Eric Vives ◽  
Pierre Petit ◽  
...  
Keyword(s):  
Camp Response Element Binding ◽  
Subcellular Targeting ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Anchoring Proteins ◽  
Element Binding Protein ◽  
Cell Permeable Peptide ◽  
Subcellular Compartmentalization ◽  
The Impact

Stimulation of numerous G protein-coupled receptors leads to the elevation of intracellular concentrations of cAMP, which subsequently activates the PKA pathway. Specificity of the PKA signaling module is determined by a sophisticated subcellular targeting network that directs the spatiotemporal activation of the kinase. This specific compartmentalization mechanism occurs through high-affinity interactions of PKA with A-kinase anchoring proteins (AKAPs), the role of which is to target the kinase to discrete subcellular microdomains. Recently, a peptide designated “AKAPis” has been proposed to competitively inhibit PKA-AKAP interactions in vitro. We therefore sought to characterize a cell-permeable construct of the AKAPis inhibitor and use it as a tool to characterize the impact of PKA compartmentalization by AKAPs. Using insulin-secreting pancreatic β-cells (INS-1 cells), we showed that TAT-AKAPis (at a micromolar range) dose dependently disrupted a significant fraction of endogenous PKA-AKAP interactions. Immunoflurescent analysis also indicated that TAT-AKAPis significantly affected PKA subcellular localization. Furthermore, TAT-AKAPis markedly attenuated glucagon-induced phosphorylations of p44/p42 MAPKs and cAMP response element binding protein, which are downstream effectors of PKA. In parallel, TAT-AKAPis dose dependently inhibited the glucagon-induced potentiation of insulin release. Therefore, AKAP-mediated subcellular compartmentalization of PKA represents a key mechanism for PKA-dependent phosphorylation events and potentiation of insulin secretion in intact pancreatic β-cells. More interestingly, our data highlight the effectiveness of the cell-permeable peptide-mediated approach to monitoring in cellulo PKA-AKAP interactions and delineating PKA-dependent phosphorylation events underlying specific cellular responses.

scholarly journals The nuclear receptor FXR is expressed in pancreatic β-cells and protects human islets from lipotoxicity

FEBS Letters ◽  
2010 ◽  
Vol 584 (13) ◽  
pp. 2845-2851 ◽  
Author(s):  
Iuliana Ristea Popescu ◽  
Audrey Helleboid-Chapman ◽  
Anthony Lucas ◽  
Brigitte Vandewalle ◽  
Julie Dumont ◽  
...  
Keyword(s):  
Nuclear Receptor ◽  
Human Islets ◽  
Β Cells ◽  
Pancreatic Β Cells

scholarly journals Antioxidant activity of a new multiflorane-type triterpene from seeds of Cucurbita Argyrosperma and their protective role on hydrogen peroxide induced oxidative stress

2020 ◽  
Vol 10 (2) ◽  
pp. 95
Author(s):  
Rosa Martha Perez Gutierrez ◽  
Alethia Muñiz Ramirez ◽  
Jose Maria Mota Flores ◽  
Abraham Heriberto Garcia Campoy
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Free Radical ◽  
Cell Viability ◽  
Caspase 3 ◽  
Radical Scavenging ◽  
Free Radical Scavenging ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells

Background: Cucurbita Argyrosperma seeds have acquired a reputation as an herbal remedy to treat various diseases because this plant is a predominant source of natural compounds with potent anti-inflammatory, antioxidant properties, and seed supplementation improves oxidative stress. Previous studies indicated that an imbalance between H2O2 production and elimination capacity is responsible for β-cell vulnerability, making β-cell a target susceptible to pathological disasters.This investigation aimed to evaluate the protective effects of one new multiflorane-type triterpene  3β-trans-caffeoyloxymultiflor-8-ene- 7α,12β, 18 β-triol (1)  from MeOH extract from C. Argyrosperma, on rat pancreatic β cells (INS-1 cells) exposed to hydrogen peroxide (H2O2) induced oxidative stress conditions.Methods: The chemical structure of the novel triterpene, which was identified as 3β-trans-caffeoyloxymultiflor-8-ene- 7α,12β, 18 β-triol (1), was established based on the interpretation of spectroscopic analyses. The antioxidant activities of 1 were leaded by detect radical scavenging potential of 2,2-dyphenyl-1-picrylhydrazyl (DPPH) and 3.1 2,2′-Azino-bis(3-Ethylbenzothiazoline-6-Sulfonic Acid) ABTS. The assays were conducted on INS-1 cells line exposed to increasing concentrations of 1 at 5,10 and 20 µg/mL and H2O2 at 250 µM. Then, the experiments, cell viability, cell integrity ((LDH; lactate dehydrogenase release), mitochondrial function (ATP analysis), ROS formation, lipid peroxidation (MDA) and caspase-3, 9 activities were measured in the cells. We also determined the effect of 1 on antioxidant enzyme levels and cytotoxicity in pancreatic β cells under oxidant conditions.Results: The results showed that triterpene displayed high free-radical-scavenging activity, which is similar to that of standard antioxidants used. At concentrations of 5, 10, and 20 𝜇g/mL protect INS-1 cells against H2O2 induced cytotoxicity decrease in cell death, with a marked increase in cell viability, sustained cellular functionality (ATP). Antioxidant enzymes such as glutathione peroxidase (GPx), glutathione reduced (GSH), catalase (CAT), superoxide dismutase (SOD), and the non-antioxidant enzyme (GSH) increased in INS-1 cells with 1 pretreatment. MDA in pancreatic cells was ameliorated by 1 pretreatment reducing intracellular reactive oxygen species level. Findings also demonstrated that H2O2-induced apoptosis in INS-1 cells and produced modulation of the caspase-3, 9 expressions in INS-1 cells exposed to 1. Exposure to 1significantly inhibited ROS and apoptosis production, reducing β cell dysfunction under oxidant conditions.Conclusions: Triterpene consequently could be a promising natural antioxidant for use in maintaining the integrity of pancreatic β-cells exposed to oxidative stress conditions being able to participate in the control type 2 diabetes.Keywords: Cucurbita Argyrosperma; antioxidants; multiflorane; free radical scavenging: oxidative stress

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