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Pronin AN, Wang Q, Slepak VZ. Teaching an Old Drug New Tricks: Agonism, Antagonism, and Biased Signaling of Pilocarpine through M3 Muscarinic Acetylcholine Receptor. Mol Pharmacol 2017; 92:601-612. [PMID: 28893976 DOI: 10.1124/mol.117.109678] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 09/06/2017] [Indexed: 12/27/2022] Open
Abstract
Pilocarpine is a prototypical drug used to treat glaucoma and dry mouth and is classified as either a full or partial muscarinic agonist. Here, we report several unexpected results pertaining to its interaction with muscarinic M3 receptor (M3R). We found that pilocarpine was 1000 times less potent in stimulating mouse-eye pupil constriction than muscarinic agonists oxotremorin-M (Oxo-M) or carbachol (CCh), although all three ligands have similar Kd values for M3R. In contrast to CCh or Oxo-M, pilocarpine does not induce Ca2+ mobilization via endogenous M3R in human embryonic kidney cell line 293T (HEK293T) or mouse insulinoma (MIN6) cells. Pilocarpine also fails to stimulate insulin secretion and, instead, antagonizes the insulinotropic effect of Oxo-M and CCh-induced Ca2+ upregulation; however, in HEK293T or Chinese hamster ovary-K1 cells overexpressing M3R, pilocarpine induces Ca2+ transients like those recorded with another cognate G protein-coupled muscarinic receptor, M1R. Stimulation of cells overexpressing M1R or M3R with CCh resulted in a similar reduction in phosphatidylinositol 4,5-bisphosphate (PIP2). In contrast to CCh, pilocarpine stimulated PIP2 hydrolysis only in cells overexpressing M1R but not M3R. Moreover, pilocarpine blocked CCh-stimulated PIP2 hydrolysis in M3R-overexpressing cells, thus, it acted as an antagonist. Pilocarpine activates extracellular regulated kinase 1/2 in MIN6 cells. The stimulatory effect on extracellular regulated kinase (ERK1/2) was blocked by the Src family kinase inhibitor PP2, indicating that the action of pilocarpine on endogenous M3R is biased toward β-arrestin. Taken together, our findings show that pilocarpine can act as either an agonist or antagonist of M3R, depending on the cell type, expression level, and signaling pathway downstream of this receptor.
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Affiliation(s)
- Alexey N Pronin
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida
| | - Qiang Wang
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida
| | - Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida
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Wang Q, Pronin AN, Levay K, Almaca J, Fornoni A, Caicedo A, Slepak VZ. Regulator of G-protein signaling Gβ5-R7 is a crucial activator of muscarinic M3 receptor-stimulated insulin secretion. FASEB J 2017; 31:4734-4744. [PMID: 28687610 DOI: 10.1096/fj.201700197rr] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 06/27/2017] [Indexed: 12/20/2022]
Abstract
In pancreatic β cells, muscarinic cholinergic receptor M3 (M3R) stimulates glucose-induced secretion of insulin. Regulator of G-protein signaling (RGS) proteins are critical modulators of GPCR activity, yet their role in β cells remains largely unknown. R7 subfamily RGS proteins are stabilized by the G-protein subunit Gβ5, such that the knockout of the Gnb5 gene results in degradation of all R7 subunits. We found that Gnb5 knockout in mice or in the insulin-secreting MIN6 cell line almost completely eliminates insulinotropic activity of M3R. Moreover, overexpression of Gβ5-RGS7 strongly promotes M3R-stimulated insulin secretion. Examination of this noncanonical mechanism in Gnb5-/- MIN6 cells showed that cAMP, diacylglycerol, or Ca2+ levels were not significantly affected. There was no reduction in the amplitude of free Ca2+ responses in islets from the Gnb5-/- mice, but the frequency of Ca2+ oscillations induced by cholinergic agonist was lowered by more than 30%. Ablation of Gnb5 impaired M3R-stimulated phosphorylation of ERK1/2. Stimulation of the ERK pathway in Gnb5-/- cells by epidermal growth factor restored M3R-stimulated insulin release to near normal levels. Identification of the novel role of Gβ5-R7 in insulin secretion may lead to a new therapeutic approach for improving pancreatic β-cell function.-Wang, Q., Pronin, A. N., Levay, K., Almaca, J., Fornoni, A., Caicedo, A., Slepak, V. Z. Regulator of G-protein signaling Gβ5-R7 is a crucial activator of muscarinic M3 receptor-stimulated insulin secretion.
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Affiliation(s)
- Qiang Wang
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA; and
| | - Alexey N Pronin
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA; and
| | - Konstantin Levay
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA; and
| | - Joana Almaca
- Department of Medicine, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Alessia Fornoni
- Department of Medicine, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Alejandro Caicedo
- Department of Medicine, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, USA; and
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Novel members of quinoline compound family enhance insulin secretion in RIN-5AH beta cells and in rat pancreatic islet microtissue. Sci Rep 2017; 7:44073. [PMID: 28272433 PMCID: PMC5341024 DOI: 10.1038/srep44073] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 01/31/2017] [Indexed: 11/08/2022] Open
Abstract
According to clinical data, some tyrosine kinase inhibitors (TKIs) possess antidiabetic effects. Several proposed mechanisms were assigned to them, however their mode of action is not clear. Our hypothesis was that they directly stimulate insulin release in beta cells. In our screening approach we demonstrated that some commercially available TKIs and many novel synthesized analogues were able to induce insulin secretion in RIN-5AH beta cells. Our aim was to find efficient, more selective and less toxic compounds. Out of several hits, we chose members from a compound family with quinoline core structure for further investigation. Here we present the studies done with these novel compounds and reveal structure activity relationships and mechanism of action. One of the most potent compounds (compound 9) lost its affinity to kinases, but efficiently increased calcium influx. In the presence of calcium channel inhibitors, the insulinotropic effect was attenuated or completely abrogated. While the quinoline TKI, bosutinib substantially inhibited tyrosine phosphorylation, compound 9 had no such effect. Molecular docking studies further supported our data. We confirmed that some TKIs possess antidiabetic effects, moreover, we present a novel compound family developed from the TKI, bosutinib and optimized for the modulation of insulin secretion.
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Pancreatic Beta Cell G-Protein Coupled Receptors and Second Messenger Interactions: A Systems Biology Computational Analysis. PLoS One 2016; 11:e0152869. [PMID: 27138453 PMCID: PMC4854486 DOI: 10.1371/journal.pone.0152869] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 03/21/2016] [Indexed: 12/17/2022] Open
Abstract
Insulin secretory in pancreatic beta-cells responses to nutrient stimuli and hormonal modulators include multiple messengers and signaling pathways with complex interdependencies. Here we present a computational model that incorporates recent data on glucose metabolism, plasma membrane potential, G-protein-coupled-receptors (GPCR), cytoplasmic and endoplasmic reticulum calcium dynamics, cAMP and phospholipase C pathways that regulate interactions between second messengers in pancreatic beta-cells. The values of key model parameters were inferred from published experimental data. The model gives a reasonable fit to important aspects of experimentally measured metabolic and second messenger concentrations and provides a framework for analyzing the role of metabolic, hormones and neurotransmitters changes on insulin secretion. Our analysis of the dynamic data provides support for the hypothesis that activation of Ca2+-dependent adenylyl cyclases play a critical role in modulating the effects of glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and catecholamines. The regulatory properties of adenylyl cyclase isoforms determine fluctuations in cytoplasmic cAMP concentration and reveal a synergistic action of glucose, GLP-1 and GIP on insulin secretion. On the other hand, the regulatory properties of phospholipase C isoforms determine the interaction of glucose, acetylcholine and free fatty acids (FFA) (that act through the FFA receptors) on insulin secretion. We found that a combination of GPCR agonists activating different messenger pathways can stimulate insulin secretion more effectively than a combination of GPCR agonists for a single pathway. This analysis also suggests that the activators of GLP-1, GIP and FFA receptors may have a relatively low risk of hypoglycemia in fasting conditions whereas an activator of muscarinic receptors can increase this risk. This computational analysis demonstrates that study of second messenger pathway interactions will improve understanding of critical regulatory sites, how different GPCRs interact and pharmacological targets for modulating insulin secretion in type 2 diabetes.
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Shim U, Kim HN, Lee H, Oh JY, Sung YA, Kim HL. Pathway Analysis Based on a Genome-Wide Association Study of Polycystic Ovary Syndrome. PLoS One 2015; 10:e0136609. [PMID: 26308735 PMCID: PMC4550465 DOI: 10.1371/journal.pone.0136609] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 08/06/2015] [Indexed: 12/20/2022] Open
Abstract
Background Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women of reproductive age, and it is affected by both environmental and genetic factors. Although the genetic component of PCOS is evident, studies aiming to identify susceptibility genes have shown controversial results. This study conducted a pathway-based analysis using a dataset obtained through a genome-wide association study (GWAS) to elucidate the biological pathways that contribute to PCOS susceptibility and the associated genes. Methods We used GWAS data on 636,797 autosomal single nucleotide polymorphisms (SNPs) from 1,221 individuals (432 PCOS patients and 789 controls) for analysis. A pathway analysis was conducted using meta-analysis gene-set enrichment of variant associations (MAGENTA). Top-ranking pathways or gene sets associated with PCOS were identified, and significant genes within the pathways were analyzed. Results The pathway analysis of the GWAS dataset identified significant pathways related to oocyte meiosis and the regulation of insulin secretion by acetylcholine and free fatty acids (all nominal gene-set enrichment analysis (GSEA) P-values < 0.05). In addition, INS, GNAQ, STXBP1, PLCB3, PLCB2, SMC3 and PLCZ1 were significant genes observed within the biological pathways (all gene P-values < 0.05). Conclusions By applying MAGENTA pathway analysis to PCOS GWAS data, we identified significant pathways and candidate genes involved in PCOS. Our findings may provide new leads for understanding the mechanisms underlying the development of PCOS.
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Affiliation(s)
- Unjin Shim
- Department of Internal Medicine, Seoul Seonam Hospital, Ewha Womans University Medical Center, Seoul, Korea
| | - Han-Na Kim
- Department of Biochemistry, Ewha Womans University School of Medicine, Seoul, Korea
| | - Hyejin Lee
- Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea
| | - Jee-Young Oh
- Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea
| | - Yeon-Ah Sung
- Department of Internal Medicine, Ewha Womans University School of Medicine, Seoul, Korea
- * E-mail: (YAS); (HLK)
| | - Hyung-Lae Kim
- Department of Biochemistry, Ewha Womans University School of Medicine, Seoul, Korea
- * E-mail: (YAS); (HLK)
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Role of free fatty acid receptors in the regulation of energy metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:1292-300. [DOI: 10.1016/j.bbalip.2014.06.002] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 05/26/2014] [Accepted: 06/02/2014] [Indexed: 12/25/2022]
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Zhang Q, Zhang F, Sjöholm A. BLX-1002 restores glucose sensitivity and enhances insulin secretion stimulated by GLP-1 and sulfonylurea in type 2 diabetic pancreatic islets. Physiol Rep 2014; 2:2/5/e12014. [PMID: 24872354 PMCID: PMC4098742 DOI: 10.14814/phy2.12014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
BLX-1002 is a novel thiazolidinedione with no peroxisome proliferator-activated receptor (PPAR) activity that has been shown to improve glycemia in type 2 diabetes without weight gain. We previously found that BLX-1002 selectively augments glucose-sensitive (but not basal) insulin secretion in normal mouse β-cells. We have now extended these observations to other insulin secretagogues and to diabetic rat islets. To this end, dynamics of insulin secretion stimulated by glucose, GLP-1, and the sulfonylurea tolbutamide were examined in pancreatic islets from nondiabetic Wistar and type 2 diabetic Goto-Kakizaki rats ex vivo. BLX-1002 restored normal glucose-sensitive insulin secretion in otherwise "glucose-blind" islets from GK rats, but did not affect basal or glucose-stimulated secretion in normal Wistar rat islets. The stimulatory effect of BLX-1002 on insulin secretion at high glucose required Ca(2+) and involved phosphatidylinositol 3-kinase (PI3K) activity. Consistent with its effects on insulin secretion, BLX-1002 also augmented insulin secretion and cytoplasmic-free Ca(2+) concentrations ([Ca(2+)]i) stimulated by high glucose, GLP-1, and tolbutamide in islets from GK, but not Wistar, rats. The inactive analog BLX-1237 had no effects. In conclusion, our findings suggest that BLX-1002 potentiates insulin secretion by different stimuli in diabetic β-cells only, in a Ca(2+)-dependent manner and involving PI3K.
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Affiliation(s)
- Qimin Zhang
- Department of Internal Medicine, Södertälje Hospital, Södertälje, Sweden
| | - Fan Zhang
- Department of Internal Medicine, Södertälje Hospital, Södertälje, Sweden
| | - Ake Sjöholm
- Department of Internal Medicine, Södertälje Hospital, Södertälje, Sweden Department of Biochemistry and Molecular Biology, College of Medicine, University of South Alabama, Mobile, Alabama
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Guerra ML, Wauson EM, McGlynn K, Cobb MH. Muscarinic control of MIN6 pancreatic β cells is enhanced by impaired amino acid signaling. J Biol Chem 2014; 289:14370-9. [PMID: 24695728 DOI: 10.1074/jbc.m114.565069] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have shown recently that the class C G protein-coupled receptor T1R1/T1R3 taste receptor complex is an early amino acid sensor in MIN6 pancreatic β cells. Amino acids are unable to activate ERK1/2 in β cells in which T1R3 has been depleted. The muscarinic receptor agonist carbachol activated ERK1/2 better in T1R3-depleted cells than in control cells. Ligands that activate certain G protein-coupled receptors in pancreatic β cells potentiate glucose-stimulated insulin secretion. Among these is the M3 muscarinic acetylcholine receptor, the major muscarinic receptor in β cells. We found that expression of M3 receptors increased in T1R3-depleted MIN6 cells and that calcium responses were altered. To determine whether these changes were related to impaired amino acid signaling, we compared responses in cells exposed to reduced amino acid concentrations. M3 receptor expression was increased, and some, but not all, changes in calcium signaling were mimicked. These findings suggest that M3 acetylcholine receptors are increased in β cells as a mechanism to compensate for amino acid deficiency.
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Affiliation(s)
- Marcy L Guerra
- From the Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9041
| | - Eric M Wauson
- From the Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9041
| | - Kathleen McGlynn
- From the Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9041
| | - Melanie H Cobb
- From the Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9041
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Russo L, Marsella C, Nardo G, Massignan T, Alessio M, Piermarini E, La Rosa S, Finzi G, Bonetto V, Bertuzzi F, Maechler P, Massa O. Transglutaminase 2 transamidation activity during first-phase insulin secretion: natural substrates in INS-1E. Acta Diabetol 2013; 50:61-72. [PMID: 22382775 DOI: 10.1007/s00592-012-0381-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 02/08/2012] [Indexed: 11/28/2022]
Abstract
Transglutaminase 2 (TG2) is a multifunctional protein with Ca(2+)-dependent transamidating and G protein activity. Previously, we reported that tgm2 -/- mice have an impaired insulin secretion and that naturally occurring TG2 mutations associated with familial, early-onset type 2 diabetes, show a defective transamidating activity. Aim of this study was to get a better insight into the role of TG2 in insulin secretion by identifying substrates of TG2 transamidating activity in the pancreatic beta cell line INS-1E. To this end, we labeled INS-1E that are capable of secreting insulin upon glucose stimulation in the physiologic range, with an artificial acyl acceptor (biotinamido-pentylamine) or donor (biotinylated peptide), in basal condition and after stimulus with glucose for 2, 5, and 8 min. Biotinylated proteins were analyzed by two-dimensional electrophoresis and mass spectrometry. In addition, subcellular localization of TG2 in human endocrine pancreas was studied by electron microscopy. Among several TG2's transamidating substrates in INS-1E, mass spectrometry identified cytoplasmic actin (a result confirmed in human pancreatic islet), tropomyosin, and molecules that participate in insulin granule structure (e.g., GAPDH), glucose metabolism, or [Ca(2+)] sensing (e.g., calreticulin). Physical interaction between TG2 and cytoplasmic actin during glucose-stimulated first-phase insulin secretion was confirmed by co-immunoprecipitation. Electron microscopy revealed that TG2 is localized close to insulin and glucagon granules in human pancreatic islet. We propose that TG2's role in insulin secretion may involve cytoplasmic actin remodeling and may have a regulative action on other proteins during granule movement. A similar role of TG2 in glucagon secretion is also suggested.
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Affiliation(s)
- Lucia Russo
- Laboratory of Mendelian Diabetes, Bambino Gesù Children's Hospital, Research Institute, Rome, Italy
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