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Ragupathi A, Kim C, Jacinto E. The mTORC2 signaling network: targets and cross-talks. Biochem J 2024; 481:45-91. [PMID: 38270460 PMCID: PMC10903481 DOI: 10.1042/bcj20220325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 11/29/2023] [Accepted: 12/18/2023] [Indexed: 01/26/2024]
Abstract
The mechanistic target of rapamycin, mTOR, controls cell metabolism in response to growth signals and stress stimuli. The cellular functions of mTOR are mediated by two distinct protein complexes, mTOR complex 1 (mTORC1) and mTORC2. Rapamycin and its analogs are currently used in the clinic to treat a variety of diseases and have been instrumental in delineating the functions of its direct target, mTORC1. Despite the lack of a specific mTORC2 inhibitor, genetic studies that disrupt mTORC2 expression unravel the functions of this more elusive mTOR complex. Like mTORC1 which responds to growth signals, mTORC2 is also activated by anabolic signals but is additionally triggered by stress. mTORC2 mediates signals from growth factor receptors and G-protein coupled receptors. How stress conditions such as nutrient limitation modulate mTORC2 activation to allow metabolic reprogramming and ensure cell survival remains poorly understood. A variety of downstream effectors of mTORC2 have been identified but the most well-characterized mTORC2 substrates include Akt, PKC, and SGK, which are members of the AGC protein kinase family. Here, we review how mTORC2 is regulated by cellular stimuli including how compartmentalization and modulation of complex components affect mTORC2 signaling. We elaborate on how phosphorylation of its substrates, particularly the AGC kinases, mediates its diverse functions in growth, proliferation, survival, and differentiation. We discuss other signaling and metabolic components that cross-talk with mTORC2 and the cellular output of these signals. Lastly, we consider how to more effectively target the mTORC2 pathway to treat diseases that have deregulated mTOR signaling.
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Affiliation(s)
- Aparna Ragupathi
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
| | - Christian Kim
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
| | - Estela Jacinto
- Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ, U.S.A
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2
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Rodrigues-dos-Santos K, Roy G, Binns DD, Grzemska MG, Barella LF, Armoo F, McCoy MK, Huynh AV, Yang JZ, Posner BA, Cobb MH, Kalwat MA. Small Molecule-mediated Insulin Hypersecretion Induces Transient ER Stress Response and Loss of Beta Cell Function. Endocrinology 2022; 163:6596276. [PMID: 35641126 PMCID: PMC9225822 DOI: 10.1210/endocr/bqac081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Indexed: 11/19/2022]
Abstract
Pancreatic islet beta cells require a fine-tuned endoplasmic reticulum (ER) stress response for normal function; abnormal ER stress contributes to diabetes pathogenesis. Here, we identified a small molecule, SW016789, with time-dependent effects on beta cell ER stress and function. Acute treatment with SW016789 potentiated nutrient-induced calcium influx and insulin secretion, while chronic exposure to SW016789 transiently induced ER stress and shut down secretory function in a reversible manner. Distinct from the effects of thapsigargin, SW016789 did not affect beta cell viability or apoptosis, potentially due to a rapid induction of adaptive genes, weak signaling through the eIF2α kinase PERK, and lack of oxidative stress gene Txnip induction. We determined that SW016789 acted upstream of voltage-dependent calcium channels (VDCCs) and potentiated nutrient- but not KCl-stimulated calcium influx. Measurements of metabolomics, oxygen consumption rate, and G protein-coupled receptor signaling did not explain the potentiating effects of SW016789. In chemical cotreatment experiments, we discovered synergy between SW016789 and activators of protein kinase C and VDCCs, suggesting involvement of these pathways in the mechanism of action. Finally, chronically elevated calcium influx was required for the inhibitory impact of SW016789, as blockade of VDCCs protected human islets and MIN6 beta cells from hypersecretion-induced dysfunction. We conclude that beta cells undergoing this type of pharmacological hypersecretion have the capacity to suppress their function to mitigate ER stress and avoid apoptosis. These results have the potential to uncover beta cell ER stress mitigation factors and add support to beta cell rest strategies to preserve function.
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Affiliation(s)
| | | | | | | | - Luiz F Barella
- Lilly Diabetes Center of Excellence, Indiana Biosciences Research Institute, Indianapolis, IN, USA
| | - Fiona Armoo
- Lilly Diabetes Center of Excellence, Indiana Biosciences Research Institute, Indianapolis, IN, USA
| | - Melissa K McCoy
- Departments of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Andy V Huynh
- Departments of Pharmacology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Jonathan Z Yang
- Departments of Pharmacology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Bruce A Posner
- Departments of Biochemistry, UT Southwestern Medical Center, Dallas, TX, USA
| | - Melanie H Cobb
- Departments of Pharmacology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Michael A Kalwat
- Correspondence: Michael A. Kalwat, PhD, Lilly Diabetes Center of Excellence, Indiana Biosciences Research Institute, 1210 Waterway Blvd Ste, 2000 Indianapolis, IN 46202, USA. or
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Ježek P, Holendová B, Jabůrek M, Dlasková A, Plecitá-Hlavatá L. Contribution of Mitochondria to Insulin Secretion by Various Secretagogues. Antioxid Redox Signal 2022; 36:920-952. [PMID: 34180254 PMCID: PMC9125579 DOI: 10.1089/ars.2021.0113] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Significance: Mitochondria determine glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells by elevating ATP synthesis. As the metabolic and redox hub, mitochondria provide numerous links to the plasma membrane channels, insulin granule vesicles (IGVs), cell redox, NADH, NADPH, and Ca2+ homeostasis, all affecting insulin secretion. Recent Advances: Mitochondrial redox signaling was implicated in several modes of insulin secretion (branched-chain ketoacid [BCKA]-, fatty acid [FA]-stimulated). Mitochondrial Ca2+ influx was found to enhance GSIS, reflecting cytosolic Ca2+ oscillations induced by action potential spikes (intermittent opening of voltage-dependent Ca2+ and K+ channels) or the superimposed Ca2+ release from the endoplasmic reticulum (ER). The ATPase inhibitory factor 1 (IF1) was reported to tune the glucose sensitivity range for GSIS. Mitochondrial protein kinase A was implicated in preventing the IF1-mediated inhibition of the ATP synthase. Critical Issues: It is unknown how the redox signal spreads up to the plasma membrane and what its targets are, what the differences in metabolic, redox, NADH/NADPH, and Ca2+ signaling, and homeostasis are between the first and second GSIS phase, and whether mitochondria can replace ER in the amplification of IGV exocytosis. Future Directions: Metabolomics studies performed to distinguish between the mitochondrial matrix and cytosolic metabolites will elucidate further details. Identifying the targets of cell signaling into mitochondria and of mitochondrial retrograde metabolic and redox signals to the cell will uncover further molecular mechanisms for insulin secretion stimulated by glucose, BCKAs, and FAs, and the amplification of secretion by glucagon-like peptide (GLP-1) and metabotropic receptors. They will identify the distinction between the hub β-cells and their followers in intact and diabetic states. Antioxid. Redox Signal. 36, 920-952.
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Affiliation(s)
- Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Blanka Holendová
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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Jia Q, Sieburth D. Mitochondrial hydrogen peroxide positively regulates neuropeptide secretion during diet-induced activation of the oxidative stress response. Nat Commun 2021; 12:2304. [PMID: 33863916 PMCID: PMC8052458 DOI: 10.1038/s41467-021-22561-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 03/17/2021] [Indexed: 12/17/2022] Open
Abstract
Mitochondria play a pivotal role in the generation of signals coupling metabolism with neurotransmitter release, but a role for mitochondrial-produced ROS in regulating neurosecretion has not been described. Here we show that endogenously produced hydrogen peroxide originating from axonal mitochondria (mtH2O2) functions as a signaling cue to selectively regulate the secretion of a FMRFamide-related neuropeptide (FLP-1) from a pair of interneurons (AIY) in C. elegans. We show that pharmacological or genetic manipulations that increase mtH2O2 levels lead to increased FLP-1 secretion that is dependent upon ROS dismutation, mitochondrial calcium influx, and cysteine sulfenylation of the calcium-independent PKC family member PKC-1. mtH2O2-induced FLP-1 secretion activates the oxidative stress response transcription factor SKN-1/Nrf2 in distal tissues and protects animals from ROS-mediated toxicity. mtH2O2 levels in AIY neurons, FLP-1 secretion and SKN-1 activity are rapidly and reversibly regulated by exposing animals to different bacterial food sources. These results reveal a previously unreported role for mtH2O2 in linking diet-induced changes in mitochondrial homeostasis with neuropeptide secretion.
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Affiliation(s)
- Qi Jia
- PIBBS program, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Derek Sieburth
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
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Ježek P, Holendová B, Jabůrek M, Tauber J, Dlasková A, Plecitá-Hlavatá L. The Pancreatic β-Cell: The Perfect Redox System. Antioxidants (Basel) 2021; 10:antiox10020197. [PMID: 33572903 PMCID: PMC7912581 DOI: 10.3390/antiox10020197] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/20/2021] [Accepted: 01/25/2021] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β-cell insulin secretion, which responds to various secretagogues and hormonal regulations, is reviewed here, emphasizing the fundamental redox signaling by NADPH oxidase 4- (NOX4-) mediated H2O2 production for glucose-stimulated insulin secretion (GSIS). There is a logical summation that integrates both metabolic plus redox homeostasis because the ATP-sensitive K+ channel (KATP) can only be closed when both ATP and H2O2 are elevated. Otherwise ATP would block KATP, while H2O2 would activate any of the redox-sensitive nonspecific calcium channels (NSCCs), such as TRPM2. Notably, a 100%-closed KATP ensemble is insufficient to reach the -50 mV threshold plasma membrane depolarization required for the activation of voltage-dependent Ca2+ channels. Open synergic NSCCs or Cl- channels have to act simultaneously to reach this threshold. The resulting intermittent cytosolic Ca2+-increases lead to the pulsatile exocytosis of insulin granule vesicles (IGVs). The incretin (e.g., GLP-1) amplification of GSIS stems from receptor signaling leading to activating the phosphorylation of TRPM channels and effects on other channels to intensify integral Ca2+-influx (fortified by endoplasmic reticulum Ca2+). ATP plus H2O2 are also required for branched-chain ketoacids (BCKAs); and partly for fatty acids (FAs) to secrete insulin, while BCKA or FA β-oxidation provide redox signaling from mitochondria, which proceeds by H2O2 diffusion or hypothetical SH relay via peroxiredoxin "redox kiss" to target proteins.
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Yan Y, Yan Q, Qian L, Jiang Y, Chen X, Zeng S, Xu Z, Gong Z. S-adenosylmethionine administration inhibits levodopa-induced vascular endothelial growth factor-A expression. Aging (Albany NY) 2020; 12:21290-21307. [PMID: 33170152 PMCID: PMC7695432 DOI: 10.18632/aging.103863] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 07/17/2020] [Indexed: 02/06/2023]
Abstract
Background: Studies have demonstrated that S-adenosylmethionine could effectively affect the clinical wearing-off phenomena of levodopa, an antiparkinsonian agent; however, the detailed mechanisms for this effect need to be further clarified. Results: S-adenosylmethionine and levodopa had opposite effects on the protein stability of vascular endothelial growth factor-A. The analysis of tube formation and cell viability also showed the nonconforming functions of S-adenosylmethionine and levodopa on cell angiogenesis and proliferation. Meanwhile, S-adenosylmethionine could significantly abolish the increased angiogenesis and cell viability induced by levodopa. S-adenosylmethionine resulted in G1/S phase arrest, with decreased cyclin dependent kinase 4/6 and increased p16, a specific cyclin dependent kinase inhibitor. Mechanically, the different effects of levodopa and S-adenosylmethionine were dependent on the phosphorylation and activation of extracellular signal-regulated kinase. S-adenosylmethionine could be fitted into the predicted docking pocket in the crystal structure of vascular endothelial growth factor-A, enhancing its acetylation level and reducing half-life. Conclusions: These observations suggested that methyl donor S-adenosylmethionine could act as a potential agent against vascular endothelial growth factor-A-related diseases induced by levodopa treatment. Methods: We performed in vitro cytological analyses to assess whether S-adenosylmethionine intake could influence levodopa-induced vascular endothelial growth factor-A expression in human umbilical vein endothelial cells.
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Affiliation(s)
- Yuanliang Yan
- Department of Pharmacy, Xiangya Hospital, Central South University, Hunan, China.,Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Hunan, China
| | - Qijia Yan
- Department of Pathology, Xiangya Hospital, Central South University, Hunan, China
| | - Long Qian
- Department of Pharmacy, Xiangya Hospital, Central South University, Hunan, China.,Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Hunan, China
| | - Yueping Jiang
- Department of Pharmacy, Xiangya Hospital, Central South University, Hunan, China
| | - Xi Chen
- Department of Pharmacy, Xiangya Hospital, Central South University, Hunan, China.,Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Hunan, China
| | - Shuangshuang Zeng
- Department of Pharmacy, Xiangya Hospital, Central South University, Hunan, China.,Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Hunan, China
| | - Zhijie Xu
- Department of Pathology, Xiangya Hospital, Central South University, Hunan, China
| | - Zhicheng Gong
- Department of Pharmacy, Xiangya Hospital, Central South University, Hunan, China.,Institute for Rational and Safe Medication Practices, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Hunan, China
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7
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Kolczynska K, Loza-Valdes A, Hawro I, Sumara G. Diacylglycerol-evoked activation of PKC and PKD isoforms in regulation of glucose and lipid metabolism: a review. Lipids Health Dis 2020; 19:113. [PMID: 32466765 PMCID: PMC7257441 DOI: 10.1186/s12944-020-01286-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/14/2020] [Indexed: 12/15/2022] Open
Abstract
Protein kinase C (PKC) and Protein kinase D (PKD) isoforms can sense diacylglycerol (DAG) generated in the different cellular compartments in various physiological processes. DAG accumulates in multiple organs of the obese subjects, which leads to the disruption of metabolic homeostasis and the development of diabetes as well as associated diseases. Multiple studies proved that aberrant activation of PKCs and PKDs contributes to the development of metabolic diseases. DAG-sensing PKC and PKD isoforms play a crucial role in the regulation of metabolic homeostasis and therefore might serve as targets for the treatment of metabolic disorders such as obesity and diabetes.
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Affiliation(s)
- Katarzyna Kolczynska
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093, Warszawa, Poland
| | - Angel Loza-Valdes
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093, Warszawa, Poland
| | - Izabela Hawro
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093, Warszawa, Poland
| | - Grzegorz Sumara
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093, Warszawa, Poland.
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Hashimoto T, Mogami H, Tsuriya D, Morita H, Sasaki S, Kumada T, Suzuki Y, Urano T, Oki Y, Suda T. G-protein-coupled receptor 40 agonist GW9508 potentiates glucose-stimulated insulin secretion through activation of protein kinase Cα and ε in INS-1 cells. PLoS One 2019; 14:e0222179. [PMID: 31498851 PMCID: PMC6733457 DOI: 10.1371/journal.pone.0222179] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Accepted: 08/23/2019] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE The mechanism by which G-protein-coupled receptor 40 (GPR40) signaling amplifies glucose-stimulated insulin secretion through activation of protein kinase C (PKC) is unknown. We examined whether a GPR40 agonist, GW9508, could stimulate conventional and novel isoforms of PKC at two glucose concentrations (3 mM and 20 mM) in INS-1D cells. METHODS Using epifluorescence microscopy, we monitored relative changes in the cytosolic fluorescence intensity of Fura2 as a marker of change in intracellular Ca2+ ([Ca2+]i) and relative increases in green fluorescent protein (GFP)-tagged myristoylated alanine-rich C kinase substrate (MARCKS-GFP) as a marker of PKC activation in response to GW9508 at 3 mM and 20 mM glucose. To assess the activation of the two PKC isoforms, relative increases in membrane fluorescence intensity of PKCα-GFP and PKCε-GFP were measured by total internal reflection fluorescence microscopy. Specific inhibitors of each PKC isotype were constructed and synthesized as peptide fusions with the third α-helix of the homeodomain of Antennapedia. RESULTS At 3 mM glucose, GW9508 induced sustained MARCKS-GFP translocation to the cytosol, irrespective of changes in [Ca2+]i. At 20 mM glucose, GW9508 induced sustained MARCKS-GFP translocation but also transient translocation that followed sharp increases in [Ca2+]i. Although PKCα translocation was rarely observed, PKCε translocation to the plasma membrane was sustained by GW9508 at 3 mM glucose. At 20 mM glucose, GW9508 induced transient translocation of PKCα and sustained translocation as well as transient translocation of PKCε. While the inhibitors (75 μM) of each PKC isotype reduced GW9508-potentiated, glucose-stimulated insulin secretion in INS-1D cells, the PKCε inhibitor had a more potent effect. CONCLUSION GW9508 activated PKCε but not PKCα at a substimulatory concentration of glucose. Both PKC isotypes were activated at a stimulatory concentration of glucose and contributed to glucose-stimulated insulin secretion in insulin-producing cells.
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Affiliation(s)
- Takuya Hashimoto
- 2nd Department of Internal Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan
- * E-mail:
| | - Hideo Mogami
- Department of Health and Nutrition, Tokoha University, Shizuoka, Japan
| | - Daisuke Tsuriya
- 2nd Department of Internal Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Hiroshi Morita
- 2nd Department of Internal Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Shigekazu Sasaki
- 2nd Department of Internal Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Tatsuro Kumada
- Department of Occupational Therapy, Tokoha University, Shizuoka, Japan
| | - Yuko Suzuki
- Department of Medical Physiology, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Tetsumei Urano
- Department of Medical Physiology, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Yutaka Oki
- 2nd Department of Internal Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan
- Department of Family and Community Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Takafumi Suda
- 2nd Department of Internal Medicine, Hamamatsu University School of Medicine, Shizuoka, Japan
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Santo-Domingo J, Galindo AN, Cominetti O, De Marchi U, Cutillas P, Dayon L, Wiederkehr A. Glucose-dependent phosphorylation signaling pathways and crosstalk to mitochondrial respiration in insulin secreting cells. Cell Commun Signal 2019; 17:14. [PMID: 30786936 PMCID: PMC6381748 DOI: 10.1186/s12964-019-0326-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 02/08/2019] [Indexed: 01/13/2023] Open
Abstract
Background Glucose is the main secretagogue of pancreatic beta-cells. Uptake and metabolism of the nutrient stimulates the beta-cell to release the blood glucose lowering hormone insulin. This metabolic activation is associated with a pronounced increase in mitochondrial respiration. Glucose stimulation also initiates a number of signal transduction pathways for the coordinated regulation of multiple biological processes required for insulin secretion. Methods Shotgun proteomics including TiO2 enrichment of phosphorylated peptides followed by liquid chromatography tandem mass spectrometry on lysates from glucose-stimulated INS-1E cells was used to identify glucose regulated phosphorylated proteins and signal transduction pathways. Kinase substrate enrichment analysis (KSEA) was applied to identify key regulated kinases and phosphatases. Glucose-induced oxygen consumption was measured using a XF96 Seahorse instrument to reveal cross talk between glucose-regulated kinases and mitochondrial activation. Results Our kinetic analysis of substrate phosphorylation reveal the molecular mechanism leading to rapid activation of insulin biogenesis, vesicle trafficking, insulin granule exocytosis and cytoskeleton remodeling. Kinase-substrate enrichment identified upstream kinases and phosphatases and time-dependent activity changes during glucose stimulation. Activity trajectories of well-known glucose-regulated kinases and phosphatases are described. In addition, we predict activity changes in a number of kinases including NUAK1, not or only poorly studied in the context of the pancreatic beta-cell. Furthermore, we pharmacologically tested whether signaling pathways predicted by kinase-substrate enrichment analysis affected glucose-dependent acceleration of mitochondrial respiration. We find that phosphoinositide 3-kinase, Ca2+/calmodulin dependent protein kinase and protein kinase C contribute to short-term regulation of energy metabolism. Conclusions Our results provide a global view into the regulation of kinases and phosphatases in insulin secreting cells and suggest cross talk between glucose-induced signal transduction and mitochondrial activation. Electronic supplementary material The online version of this article (10.1186/s12964-019-0326-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jaime Santo-Domingo
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland.
| | - Antonio Núñez Galindo
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Ornella Cominetti
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Umberto De Marchi
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Pedro Cutillas
- Analytical Signalling Group, Centre for Cell Signalling, Queen Mary University of London, London, UK
| | - Loïc Dayon
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
| | - Andreas Wiederkehr
- Nestlé Institute of Health Sciences, Nestlé Research, EPFL Innovation Park Bâtiment G, 1015, Lausanne, Switzerland
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Xie B, Nguyen PM, Idevall-Hagren O. Feedback regulation of insulin secretion by extended synaptotagmin-1. FASEB J 2018; 33:4716-4728. [PMID: 30589572 DOI: 10.1096/fj.201801878r] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Endoplasmic reticulum (ER)-plasma membrane (PM) contacts are dynamic structures with important roles in the regulation of calcium (Ca2+) and lipid homeostasis. The extended synaptotagmins (E-Syts) are ER-localized lipid transport proteins that interact with PM phosphatidylinositol 4,5-bisphosphate in a Ca2+-dependent manner. E-Syts bidirectionally transfer glycerolipids, including diacylglycerol (DAG), between the 2 juxtaposed membranes, but the biologic significance of this transport is still unclear. Using insulin-secreting cells and live-cell imaging, we now show that Ca2+-triggered exocytosis of insulin granules is followed, in sequence, by PM DAG formation and E-Syt1 recruitment. E-Syt1 counteracted the depolarization-induced DAG formation through a mechanism that required both voltage-dependent Ca2+ influx and Ca2+ release from the ER. E-Syt1 knockdown resulted in prolonged accumulation of DAG in the PM, resulting in increased glucose-stimulated insulin secretion. We conclude that Ca2+-triggered exocytosis is temporally coupled to Ca2+-triggered E-Syt1 PM recruitment and removal of DAG to negatively regulate the same process.-Xie, B., Nguyen, P. M., Idevall-Hagren, O. Feedback regulation of insulin secretion by extended synaptotagmin-1.
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Affiliation(s)
- Beichen Xie
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Phuoc My Nguyen
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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Zhu Y, Ye P, Chen SL, Zhang DM. Functional regulation of large conductance Ca 2+-activated K + channels in vascular diseases. Metabolism 2018; 83:75-80. [PMID: 29373813 DOI: 10.1016/j.metabol.2018.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Revised: 01/03/2018] [Accepted: 01/18/2018] [Indexed: 12/17/2022]
Abstract
The large conductance Ca2+-activated potassium channels, the BK channels, is widely expressed in various tissues and activated in a Ca2+- and voltage-dependent manner. The activation of BK channels hyperpolarizes vascular smooth muscle cell membrane potential, resulting in vasodilation. Under pathophysiological conditions, such as diabetes mellitus and hypertension, impaired BK channel function exacerbates vascular vasodilation and leads to organ ischemia. The vascular BK channel is composed of 4 pore-forming subunits, BK-α together with 4 auxiliary subunits: β1 subunits (BK-β1) or γ1 subunits (BK-γ1). Recent studies have shown that down-regulation of the BK β1 subunit in diabetes mellitus induced vascular dysfunction; however, the molecular mechanism of these vascular diseases is not well understood. In this review, we summarize the potential mechanisms regarding BK channelopathy and the potential therapeutic targets of BK channels for vascular diseases.
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Affiliation(s)
- Yanrong Zhu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Peng Ye
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Shao-Liang Chen
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Dai-Min Zhang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China.
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12
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Massenavette L, Paul W, Corriveau S, Pasquier JC, Rousseau É. Phorbol 12,13-dibutyrate-induced protein kinase C activation triggers sustained contracture in human myometrium in vitro. Am J Obstet Gynecol 2017; 217:358.e1-358.e9. [PMID: 28479286 DOI: 10.1016/j.ajog.2017.04.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 03/28/2017] [Accepted: 04/25/2017] [Indexed: 10/24/2022]
Abstract
BACKGROUND Although physiologic transition from rhythmic contractions to uterine retraction postpartum remains a poorly understood process, it has been shown that the latter is essential in the prevention of hemorrhage and its negative consequences. OBJECTIVE To investigate the transition from oscillatory contractions to tonic contracture in human myometrium after delivery, a mechanism purported to facilitate postpartum hemostasis. Protein kinase C (PKC) plays a key regulatory role in human uterine contractions because it can prevent dephosphorylation of regulatory proteins and sensitize the contractile machinery to low Ca2+. Thus, activation of PKC by phorbol 12,13-dibutyrate (PDBu) may act as a strong uterotonic agent. STUDY DESIGN Uterine biopsies were obtained from consenting women undergoing elective caesarian delivery at term without labor (N = 19). Isometric tension measurements were performed on uterine strips (n = 114). The amplitudes and area under the curve of phasic contractions and tonic responses were measured and compared. A total of 1 μM PDBu was added to the isolated organ baths, and maximal tension of the uterine contracture was determined in the absence and presence of either 1 μM of staurosporine, 100 nM nifedipine, or 10 μM cyclopiazonic acid to assess the role of PKC and calcium sensitivity on uterine contractility. RESULTS On the addition of PDBu on either basal or oxytocin-induced activity, consistent contractures were obtained concomitant with complete inhibition of phasic contractions. After a 30-minute incubation period, the mean amplitude of the PDBu-induced tone represented 65.3% of the amplitude of spontaneous contraction. Staurosporine, a protein kinase inhibitor, induced a 91.9% inhibition of PDBu contractures, a process not affected by nifedipine or cyclopiazonic acid, thus indicating that this mechanism is largely Ca2+ independent. CONCLUSION Pharmacologic activation of PKC leads to a significant contracture of the myometrium. Together, these data suggest that the up-regulation of PKC plays a physiologic role in the modulation of uterine contracture after delivery. A switch from phasic to strong tonic contractions potentially may facilitate postpartum hemostasis.
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Kristinsson H, Sargsyan E, Manell H, Smith DM, Göpel SO, Bergsten P. Basal hypersecretion of glucagon and insulin from palmitate-exposed human islets depends on FFAR1 but not decreased somatostatin secretion. Sci Rep 2017; 7:4657. [PMID: 28680093 PMCID: PMC5498543 DOI: 10.1038/s41598-017-04730-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 06/01/2017] [Indexed: 12/19/2022] Open
Abstract
In obesity fasting levels of both glucagon and insulin are elevated. In these subjects fasting levels of the free fatty acid palmitate are raised. We have demonstrated that palmitate enhances glucose-stimulated insulin secretion from isolated human islets via free fatty acid receptor 1 (FFAR1/GPR40). Since FFAR1 is also present on glucagon-secreting alpha-cells, we hypothesized that palmitate simultaneously stimulates secretion of glucagon and insulin at fasting glucose concentrations. In addition, we hypothesized that concomitant hypersecretion of glucagon and insulin was also contributed by reduced somatostatin secretion. We found basal glucagon, insulin and somatostatin secretion and respiration from human islets, to be enhanced during palmitate treatment at normoglycemia. Secretion of all hormones and mitochondrial respiration were lowered when FFAR1 or fatty acid β-oxidation was inhibited. The findings were confirmed in the human beta-cell line EndoC-βH1. We conclude that fatty acids enhance both glucagon and insulin secretion at fasting glucose concentrations and that FFAR1 and enhanced mitochondrial metabolism but not lowered somatostatin secretion are crucial in this effect. The ability of chronically elevated palmitate levels to simultaneously increase basal secretion of glucagon and insulin positions elevated levels of fatty acids as potential triggering factors for the development of obesity and impaired glucose control.
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Affiliation(s)
- H Kristinsson
- Department of Medical Cell Biology, Uppsala University, BMC, Husargatan 3, Uppsala, Sweden.
| | - E Sargsyan
- Department of Medical Cell Biology, Uppsala University, BMC, Husargatan 3, Uppsala, Sweden
| | - H Manell
- Department of Medical Cell Biology, Uppsala University, BMC, Husargatan 3, Uppsala, Sweden
| | - D M Smith
- Discovery Sciences, Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Cambridge, UK
| | - S O Göpel
- AstraZeneca R&D Gothenburg, CVMD Bioscience, Gothenburg, Sweden
| | - P Bergsten
- Department of Medical Cell Biology, Uppsala University, BMC, Husargatan 3, Uppsala, Sweden
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