Defective protein histidine phosphorylation in islets from the Goto-Kakizaki diabetic rat

2003 ◽  
Vol 285 (3) ◽  
pp. E498-E503 ◽  
Author(s):  
Anjaneyulu Kowluru
Keyword(s):  
G Proteins ◽  
Nucleoside Diphosphate Kinase ◽  
Diabetic Rat ◽  
Β Cells ◽  
Gk Rat ◽  
Β Cell ◽  
Histidine Kinases ◽  
Insulin Dependent ◽  
Endogenous Proteins ◽  
Histidine Phosphorylation

We recently described novel regulatory roles for protein histidine phosphorylation of key islet proteins (e.g., nucleoside diphosphate kinase and succinyl thiokinase) in insulin secretion from the islet β-cell (Kowluru A. Diabetologia 44: 89-94, 2001; Kowluru A, Tannous M, and Chen HQ. Arch Biochem Biophys 398: 160-169, 2002). In this context, we also characterized a novel, ATP- and GTP-sensitive protein histidine kinase in isolated β-cells that catalyzed the histidine phosphorylation of islet (endogenous) proteins as well as exogenously added histone 4, and we implicated this kinase in the activation of islet endogenous G proteins (Kowluru A. Biochem Pharmacol 63: 2091-2100, 2002). In the present study, we describe abnormalities in ATP- or GTP-mediated histidine phosphorylation of nucleoside diphosphate kinase in islets derived from the Goto-Kakizaki (GK) rat, a model for non-insulin-dependent diabetes. Furthermore, we provide evidence for a marked reduction in the activities of ATP- or GTP-sensitive histidine kinases in GK rat islets. On the basis of these observations, we propose that alterations in protein histidine phosphorylation could contribute toward insulin-secretory abnormalities demonstrable in the diabetic islet.

Pioglitazone preserves pancreatic islet structure and insulin secretory function in three murine models of type 2 diabetes

2004 ◽  
Vol 286 (1) ◽  
pp. E116-E122 ◽  
Author(s):  
A. R. Diani ◽  
Geri Sawada ◽  
Beatrice Wyse ◽  
F. T. Murray ◽  
Mehmood Khan
Keyword(s):  
Type 2 Diabetes ◽  
Plasma Insulin ◽  
Glycosylated Hemoglobin ◽  
Β Cells ◽  
Β Cell ◽  
Insulin Dependent ◽  
Plasma Insulin Levels ◽  
And Function ◽  
And Control

Thiazolidinediones may slow the progression of type 2 diabetes by preserving pancreatic β-cells. The effects of pioglitazone (PIO) on structure and function of β-cells in KKA(y), C57BL/6J ob/ob, and C57BL/KsJ db/db mice (genetic models of type 2 diabetes) were examined. ob/ob ( n = 7) and db/db ( n = 9) mice were randomly assigned to 50-125 mg·kg body wt-1·day-1of PIO in chow beginning at 6-10 wk of age. Control ob/ob ( n = 7) and db/db mice ( n = 9) were fed chow without PIO. KKA(y) mice ( n = 15) were fed PIO daily at doses of 62-144 mg·kg body wt-1·day-1. Control KKA(y) mice ( n = 10) received chow without PIO. Treatment continued until euthanasia at 14-26 wk of age. Blood was collected at baseline (before treatment) and just before euthanasia and was analyzed for glucose, glycosylated hemoglobin, and plasma insulin. Some of the splenic pancreas of each animal was resected and partially sectioned for light or electron microscopy. The remainder of the pancreas was assayed for insulin content. Compared with baseline and control groups, PIO treatment significantly reduced blood glucose and glycosylated hemoglobin levels. Plasma insulin levels decreased significantly in ob/ob mice treated with PIO. All groups treated with PIO exhibited significantly greater β-cell granulation, evidence of reduced β-cell stress, and 1.5- to 15-fold higher levels of pancreatic insulin. The data from these studies suggest that comparable effects would be expected to slow the progression of type 2 diabetes, either delaying or possibly preventing progression to an insulin-dependent state.

scholarly journals Ca2+–Secretion Coupling Is Impaired in Diabetic Goto Kakizaki rats

2007 ◽  
Vol 129 (6) ◽  
pp. 493-508 ◽  
Author(s):  
Tobias Rose ◽  
Suad Efendic ◽  
Marjan Rupnik
Keyword(s):  
Insulin Secretion ◽  
Pancreatic Tissue ◽  
Diabetic Rat ◽  
High Time Resolution ◽  
Β Cells ◽  
Gk Rat ◽  
Tissue Slices ◽  
Apparent Contradiction ◽  
Large Dense Core Vesicles ◽  
Activity Dependent

The Goto Kakizaki (GK) rat is a widely used animal model to study defective glucose-stimulated insulin release in type-2 diabetes (T2D). As in T2D patients, the expression of several proteins involved in Ca2+-dependent exocytosis of insulin-containing large dense-core vesicles is dysregulated in this model. So far, a defect in late steps of insulin secretion could not be demonstrated. To resolve this apparent contradiction, we studied Ca2+–secretion coupling of healthy and GK rat β cells in acute pancreatic tissue slices by assessing exocytosis with high time-resolution membrane capacitance measurements. We found that β cells of GK rats respond to glucose stimulation with a normal increase in the cytosolic Ca2+ concentration. During trains of depolarizing pulses, the secretory activity from GK rat β cells was defective in spite of upregulated cell size and doubled voltage-activated Ca2+ currents. In GK rat β cells, evoked Ca2+ entry was significantly less efficient in triggering release than in nondiabetic controls. This impairment was neither due to a decrease of functional vesicle pool sizes nor due to different kinetics of pool refilling. Strong stimulation with two successive trains of depolarizing pulses led to a prominent activity-dependent facilitation of release in GK rat β cells, whereas secretion in controls was unaffected. Broad-spectrum inhibition of PKC sensitized Ca2+-dependent exocytosis, whereas it prevented the activity-dependent facilitation in GK rat β cells. We conclude that a decrease in the sensitivity of the GK rat β-cell to depolarization-evoked Ca2+ influx is involved in defective glucose-stimulated insulin secretion. Furthermore, we discuss a role for constitutively increased activity of one or more PKC isoenzymes in diabetic rat β cells.

scholarly journals Minireview: Novel Aspects of M3 Muscarinic Receptor Signaling in Pancreatic β-Cells

2013 ◽  
Vol 27 (8) ◽  
pp. 1208-1216 ◽  
Author(s):  
Kenichiro Nakajima ◽  
Shalini Jain ◽  
Inigo Ruiz de Azua ◽  
Sara M. McMillin ◽  
Mario Rossi ◽  
...  
Keyword(s):  
G Proteins ◽  
Mouse Models ◽  
Acetylcholine Receptors ◽  
Cell Function ◽  
Muscarinic Acetylcholine Receptors ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Phenotypic Analysis ◽  
Physiological Importance

The release of insulin from pancreatic β-cells is regulated by a considerable number of G protein–coupled receptors. During the past several years, we have focused on the physiological importance of β-cell M3 muscarinic acetylcholine receptors (M3Rs). At the molecular level, the M3R selectively activates G proteins of the Gq family. Phenotypic analysis of several M3R mutant mouse models, including a mouse strain that lacks M3Rs only in pancreatic β-cells, indicated that β-cell M3Rs play a key role in maintaining blood glucose levels within a normal range. Additional studies with transgenic M3R mouse models strongly suggest that strategies aimed to enhance signaling through β-cell M3Rs may prove useful in the treatment of type 2 diabetes. More recently, we analyzed transgenic mice that expressed an M3R-based designer receptor in a β-cell–specific fashion, which enabled us to chronically activate a β-cell Gq-coupled receptor by a drug that is otherwise pharmacologically inert. Drug-dependent activation of this designer receptor stimulated the sequential activation of Gq, phospholipase C, ERK1/2, and insulin receptor substrate 2 signaling, thus triggering a series of events that greatly improved β-cell function. Most importantly, chronic stimulation of this pathway protected mice against experimentally induced diabetes and glucose intolerance, induced either by streptozotocin or by the consumption of an energy-rich, high-fat diet. Because β-cells are endowed with numerous receptors that mediate their cellular effects via activation of Gq-type G proteins, these findings provide a rational basis for the development of novel antidiabetic drugs targeting this class of receptors.

Regulatory roles for small G proteins in the pancreatic β-cell: lessons from models of impaired insulin secretion

2003 ◽  
Vol 285 (4) ◽  
pp. E669-E684 ◽  
Author(s):  
Anjaneyulu Kowluru
Keyword(s):  
Insulin Secretion ◽  
G Proteins ◽  
Posttranslational Modifications ◽  
Protein Function ◽  
Future Research ◽  
Signaling Proteins ◽  
Β Cell ◽  
Impaired Insulin Secretion ◽  
Impaired Insulin ◽  
Histidine Phosphorylation

Emerging evidence suggests that GTP-binding proteins (G proteins) play important regulatory roles in physiological insulin secretion from the islet β-cell. Such conclusions were drawn primarily from experimental data derived through the use of specific inhibitors of G protein function. Data from gene depletion experiments appear to further substantiate key roles for these signaling proteins in the islet metabolism. The first part of this review will focus on findings supporting the hypothesis that activation of specific G proteins is essential for insulin secretion, including regulation of their function by posttranslational modifications at their COOH-terminal cysteines (e.g., isoprenylation). The second part will overview novel, non-receptor-dependent mechanism(s) whereby glucose might activate specific G proteins via protein histidine phosphorylation. The third section will review findings that appear to link abnormalities in the expression and/or functional activation of these key signaling proteins to impaired insulin secretion. It is hoped that this review will establish a basis for future research in this area of islet signal transduction, which presents a significant potential, not only in identifying key signaling proteins that are involved in physiological insulin secretion, but also in examining potential abnormalities in this signaling cascade that lead to islet dysfunction and onset of diabetes.

Subcellular Localization and Characterization of Nucleoside Diphosphate Kinase in Rat Retina: Effect of Diabetes

1998 ◽  
Vol 18 (4) ◽  
pp. 187-198 ◽  
Author(s):  
Anjaneyulu Kowluru ◽  
Renu A. Kowluru
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Kinase Activity ◽  
Critical Role ◽  
Nucleoside Diphosphate Kinase ◽  
Diabetic Rat ◽  
Ndp Kinase ◽  
Rat Retina ◽  
Nucleotide Triphosphates

Nucleoside diphosphate kinase (NDP kinase) catalyzes the transfer of terminal phosphate from nucleotide triphosphates (e.g. ATP) to nucleotide diphosphates (e.g. GDP) to yield nucleotide triphosphates (e.g. GTP). Since guanine nucleotides play critical role(s) in GTP-binding protein (G-protein)-mediated signal transduction mechanisms in retina, we quantitated NDP kinase activity in subcellular fraction-derived from normal rat retina. A greater than 85% of the total specific activity was present in the soluble fraction, which was stimulated (up to 7 fold) by 2 mM magnesium. NDP kinase exhibited saturation kinetics towards di- and tri-phosphate substrates, and was inhibited by known inhibitors of NDP kinase, uridine diphosphate (UDP) or cromoglycate (CRG). We have previously reported significant abnormalities in the activation of G-proteins in streptozotocin (STZ)-diabetic rat retina (Kowluru et al. Diabetologia35:624–631, 1992). Since NDP kinase hasbeen implicated in direct interaction with and/or activation of various G-proteins, we quantitated both basal and magnesium-stimulated NDP kinase activity in soluble and particulate fractions of retina derived from STZ-diabetic rats to examine whether abnormalities in G-protein function in diabetes are attributable to alterations in retinal NDP kinase. There was no effect of diabetes either on the basal or the magnesium-activated retinal NDP kinase activity. This study represents the first characterization of NDP kinase activity in rat retina, and suggests that in diabetes, this enzyme may not be rate-limiting and/or causal for the observed alterations in retinal G-protein functions.

scholarly journals Integration of single-cell datasets reveals novel transcriptomic signatures of β-cells in human type 2 diabetes

2020 ◽  
Vol 2 (4) ◽  
Author(s):  
Emanuele Bosi ◽  
Lorella Marselli ◽  
Carmela De Luca ◽  
Mara Suleiman ◽  
Marta Tesi ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Single Cell ◽  
Single Cells ◽  
Diabetic Rat ◽  
Rna Seq ◽  
Β Cells ◽  
Β Cell ◽  
Transcriptomic Changes ◽  
Laser Capture

Abstract Pancreatic islet β-cell failure is key to the onset and progression of type 2 diabetes (T2D). The advent of single-cell RNA sequencing (scRNA-seq) has opened the possibility to determine transcriptional signatures specifically relevant for T2D at the β-cell level. Yet, applications of this technique have been underwhelming, as three independent studies failed to show shared differentially expressed genes in T2D β-cells. We performed an integrative analysis of the available datasets from these studies to overcome confounding sources of variability and better highlight common T2D β-cell transcriptomic signatures. After removing low-quality transcriptomes, we retained 3046 single cells expressing 27 931 genes. Cells were integrated to attenuate dataset-specific biases, and clustered into cell type groups. In T2D β-cells (n = 801), we found 210 upregulated and 16 downregulated genes, identifying key pathways for T2D pathogenesis, including defective insulin secretion, SREBP signaling and oxidative stress. We also compared these results with previous data of human T2D β-cells from laser capture microdissection and diabetic rat islets, revealing shared β-cell genes. Overall, the present study encourages the pursuit of single β-cell RNA-seq analysis, preventing presently identified sources of variability, to identify transcriptomic changes associated with human T2D and underscores specific traits of dysfunctional β-cells across different models and techniques.

Biologically active lipids promote trafficking and membrane association of Rac1 in insulin-secreting INS 832/13 cells

2007 ◽  
Vol 292 (3) ◽  
pp. C1216-C1220 ◽  
Author(s):  
Phillip McDonald ◽  
Rajakrishnan Veluthakal ◽  
Hitchintan Kaur ◽  
Anjaneyulu Kowluru
Keyword(s):  
G Proteins ◽  
Direct Evidence ◽  
Effector Proteins ◽  
Biologically Active ◽  
Membrane Association ◽  
Subcellular Trafficking ◽  
Β Cells ◽  
Β Cell ◽  
Glucose Stimulated Insulin Secretion ◽  
Small G Proteins

Despite emerging evidence to suggest that glucose-stimulated insulin secretion (GSIS) requires membrane targeting of specific small G proteins (e.g., Rac1), very little is known with regard to the precise mechanisms underlying subcellular trafficking of these proteins in the glucose-stimulated islet β-cell. We previously reported activation of small G proteins by biologically active lipids via potentiation of relevant GDP/GTP exchange activities within the β-cell. Herein, we studied putative regulatory roles for these lipids in the trafficking and membrane association of Rac1 in cell-free preparations derived from INS 832/13 β-cells. Incubation of INS 832/13 cell lysates with polyphosphoinositides (e.g., PIP2), phosphatidic acid, phosphatidylcholine, and phosphatidylserine significantly promoted trafficking of cytosolic Rac1 to the membrane fraction. Lysophosphatidic acid, but not lysophosphatidylcholine or lysophosphatidylserine, also promoted translocation and membrane association of Rac1. Arachidonic acid, diacylglycerol, calcium, and cAMP failed to exert any clear effects on Rac1 translocation to the membrane. Together, our findings provide the first direct evidence in support of our recent hypothesis (Kowluru A, Veluthakal R. Diabetes 54: 3523–3529, 2005), which states that generation of biologically active lipids, known to occur in the glucose-stimulated β-cell, may mediate targeting of Rac1 to the membrane for optimal interaction with its putative effector proteins leading to GSIS.

scholarly journals Interferon-γ Is Essential for Destruction of β Cells and Development of Insulin-dependent Diabetes Mellitus

1997 ◽  
Vol 185 (3) ◽  
pp. 531-540 ◽  
Author(s):  
Matthias G. von Herrath ◽  
Michael B.A. Oldstone
Keyword(s):  
Transgenic Mice ◽  
Cell Injury ◽  
Insulin Dependent Diabetes Mellitus ◽  
Interferon Γ ◽  
Dependent Diabetes Mellitus ◽  
Β Cells ◽  
Β Cell ◽  
Insulin Dependent ◽  
Ifn Γ ◽  
Deficient Mice

Autoimmune mediated destruction of β cells of the islets of Langerhans leads to insulin-dependent diabetes mellitus (IDDM). Rat insulin promoter (RIP) lymphocytic choriomeningitis virus (LCMV) transgenic mice that express the nucleoprotein (NP) or glycoprotein (GP) of LCMV under control of the RIP in their β cells develop IDDM after infection with LCMV and serve as a model for virus-induced IDDM. Recently, Kagi et al. (Kagi, D., B. Odermatt, P. Ohashi, R.M. Zinkernagel, and H. Hengartner. 1996. J. Exp. Med. 183:2143–2149) showed, using RIP LCMV perforin-deficient mice, that IDDM does not occur in the absence of perforin. They concluded that perforin-mediated killing by cytotoxic T lymphocytes (CTLs) is the main factor needed for β cell injury and destruction. Here we provide evidence that killing of β cells is more complex and multifactorial. By the use of our RIP LCMV model, we show that in perforin competent but interferon-γ (IFN-γ)–deficient mice, β cell injury is limited and IDDM does not occur. For these studies, double transgenic mice were generated that were genetically deficient in the production of IFN-γ and express LCMV NP or GP in their β cells. In such mice, IDDM was aborted despite the generation of LCMV-specific antiself CTLs that displayed normal cytolytic activity in vitro and in vivo and entered the pancreas. However, mononuclear infiltration into the islets did not occur, and upregulation of class I and II molecules usually found in islets of RIP LCMV single transgenic mice after LCMV infection preceding the onset of clinical IDDM was not present in these bigenic mice. Our findings indicate that in addition to perforin, β cell destruction, development of insulitis, and IDDM also depend on the cytokine INF-γ, presumably through enhancement of major histocompatibility complex expression and antigen presentation.

scholarly journals An autophagy enhancer ameliorates diabetes of human IAPP-transgenic mice through clearance of amyloidogenic oligomer

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jinyoung Kim ◽  
Kihyoun Park ◽  
Min Jung Kim ◽  
Hyejin Lim ◽  
Kook Hwan Kim ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Function ◽  
Therapeutic Potential ◽  
Therapeutic Modality ◽  
Protective Effects ◽  
Β Cells ◽  
Β Cell ◽  
Islet Amyloid ◽  
Amyloid Accumulation ◽  
Human Diabetes

AbstractWe have reported that autophagy is crucial for clearance of amyloidogenic human IAPP (hIAPP) oligomer, suggesting that an autophagy enhancer could be a therapeutic modality against human diabetes with amyloid accumulation. Here, we show that a recently identified autophagy enhancer (MSL-7) reduces hIAPP oligomer accumulation in human induced pluripotent stem cell-derived β-cells (hiPSC-β-cells) and diminishes oligomer-mediated apoptosis of β-cells. Protective effects of MSL-7 against hIAPP oligomer accumulation and hIAPP oligomer-mediated β-cell death are significantly reduced in cells with knockout of MiTF/TFE family members such as Tfeb or Tfe3. MSL-7 improves glucose tolerance and β-cell function of hIAPP+ mice on high-fat diet, accompanied by reduced hIAPP oligomer/amyloid accumulation and β-cell apoptosis. Protective effects of MSL-7 against hIAPP oligomer-mediated β-cell death and the development of diabetes are also significantly reduced by β-cell-specific knockout of Tfeb. These results suggest that an autophagy enhancer could have therapeutic potential against human diabetes characterized by islet amyloid accumulation.

Sign in / Sign up

Export Citation Format

Share Document