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Hsu MF, Ito Y, Singh JP, Hsu SF, Wells A, Jen KY, Meng TC, Haj FG. Protein tyrosine phosphatase 1B is a regulator of alpha-actinin4 in the glomerular podocyte. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119590. [PMID: 37730132 PMCID: PMC11060668 DOI: 10.1016/j.bbamcr.2023.119590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 09/12/2023] [Accepted: 09/14/2023] [Indexed: 09/22/2023]
Abstract
Glomerular podocytes are instrumental for the barrier function of the kidney, and podocyte injury contributes to proteinuria and the deterioration of renal function. Protein tyrosine phosphatase 1B (PTP1B) is an established metabolic regulator, and the inactivation of this phosphatase mitigates podocyte injury. However, there is a paucity of data regarding the substrates that mediate PTP1B actions in podocytes. This study aims to uncover novel substrates of PTP1B in podocytes and validate a leading candidate. To this end, using substrate-trapping and mass spectroscopy, we identified putative substrates of this phosphatase and investigated the actin cross-linking cytoskeletal protein alpha-actinin4. PTP1B and alpha-actinin4 co-localized in murine and human glomeruli and transiently transfected E11 podocyte cells. Additionally, podocyte PTP1B deficiency in vivo and culture was associated with elevated tyrosine phosphorylation of alpha-actinin4. Conversely, reconstitution of the knockdown cells with PTP1B attenuated alpha-actinin4 tyrosine phosphorylation. We demonstrated co-association between alpha-actinin4 and the PTP1B substrate-trapping mutant, which was enhanced upon insulin stimulation and disrupted by vanadate, consistent with an enzyme-substrate interaction. Moreover, we identified alpha-actinin4 tandem tyrosine residues 486/487 as mediators of its interaction with PTP1B. Furthermore, knockdown studies in E11 cells suggest that PTP1B and alpha-actinin4 are modulators of podocyte motility. These observations indicate that PTP1B and alpha-actinin4 are likely interacting partners in a signaling node that modulates podocyte function. Targeting PTP1B and plausibly this one of its substrates may represent a new therapeutic approach for podocyte injury that warrants additional investigation.
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Affiliation(s)
- Ming-Fo Hsu
- Department of Nutrition, University of California Davis, Davis, CA, USA
| | - Yoshihiro Ito
- Department of Nutrition, University of California Davis, Davis, CA, USA
| | - Jai Prakash Singh
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - Shu-Fang Hsu
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - Alan Wells
- Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | - Kuang-Yu Jen
- Department of Pathology and Laboratory Medicine, University of California Davis, Sacramento, CA, USA
| | - Tzu-Ching Meng
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - Fawaz G Haj
- Department of Nutrition, University of California Davis, Davis, CA, USA; Comprehensive Cancer Center, University of California Davis, Sacramento, CA, USA; Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, University of California Davis, Sacramento, CA, USA.
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Pei J, Prasad M, Mohamed Helal G, El-Sherbiny M, Abdelmonem Elsherbini DM, Rajagopal P, Palanisamy CP, Veeraraghavan VP, Jayaraman S, Surapaneni KM. Beta-Sitosterol Facilitates GLUT4 Vesicle Fusion on the Plasma Membrane via the Activation of Rab/IRAP/Munc 18 Signaling Pathways in Diabetic Gastrocnemius Muscle of Adult Male Rats. Bioinorg Chem Appl 2022; 2022:7772305. [PMID: 35992048 PMCID: PMC9388314 DOI: 10.1155/2022/7772305] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 05/21/2022] [Indexed: 12/18/2022] Open
Abstract
Nutritional overload in the form of high-fat and nonglycolysis sugar intake contributes towards the accelerated creation of reactive oxygen species (ROS), hyperglycemia, and dyslipidemia. Glucose absorption and its subsequent oxidation processes in fat and muscle tissues alter as a consequence of these modifications. Insulin resistance (IR) caused glucose transporter 4 (GLUT4) translocation to encounter a challenge that manifested itself as changes in glycolytic pathways and insulin signaling. We previously found that beta (β)-sitosterol reduces IR in fat tissue via IRS-1/PI3K/Akt facilitated signaling due to its hypolipidemic and hypoglycemic activity. The intention of this research was to see whether the phytosterol β-sitosterol can aid in the translocation of GLUT4 in rats fed on high-fat diet (HFD) and sucrose by promoting Rab/IRAP/Munc 18 signaling molecules. The rats were labeled into four groups, namely control rats, HFD and sucrose-induced diabetic control rats, HFD and sucrose-induced diabetic rats given oral dose of 20 mg/kg body wt./day of β-sitosterol treatment for 30 days, and HFD and sucrose-induced diabetic animals given oral administration of 50 mg/kg body wt./day metformin for 30 days. Diabetic rats administered with β-sitosterol and normalized the titers of blood glucose, serum insulin, serum testosterone, and the status of insulin tolerance and oral glucose tolerance. In comparison with the control group, β-sitosterol effectively regulated both glycolytic and gluconeogenesis enzymes. Furthermore, qRT-PCR analysis of the mRNA levels of key regulatory genes such as SNAP23, VAMP-2, syntaxin-4, IRAP, vimentin, and SPARC revealed that β-sitosterol significantly regulated the mRNA levels of the above genes in diabetic gastrocnemius muscle. Protein expression analysis of Rab10, IRAP, vimentin, and GLUT4 demonstrated that β-sitosterol had a positive effect on these proteins, resulting in effective GLUT4 translocation in skeletal muscle. According to the findings, β-sitosterol reduced HFD and sucrose-induced IR and augmented GLUT4 translocation in gastrocnemius muscle through insulin signaling modulation via Rab/IRAP/Munc 18 and glucose metabolic enzymes. The present work is the first of its kind to show that β-sitosterol facilitates GLUT4 vesicle fusion on the plasma membrane via Rab/IRAP/Munc 18 signaling molecules in gastrocnemius muscle.
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Affiliation(s)
- JinJin Pei
- Qinba State Key Laboratory of Biological Resources and Ecological Environment, 2011 QinLing-Bashan Mountains, Bioresources Comprehensive Development C. I. C, Shaanxi Province Key Laboratory of Bio-Resources, College of Bioscience and Bioengineering, Shaanxi University of Technology, Hanzhong 723001, Shaanxi, China
| | - Monisha Prasad
- Centre of Molecular Medicine and Diagnostics (COMManD), Department of Biochemistry, Saveetha Dental College & Hospital, Saveetha Institute of Medical & Technical Sciences, Saveetha University, Chennai 600077, India
| | - Ghada Mohamed Helal
- Department of Medical Biochemistry, Faculty of Medicine, Mansoura University, Mansoura, Egypt
| | - Mohamed El-Sherbiny
- Department of Basic Medical Sciences, College of Medicine, AlMaarefa University, P.O. Box 71666, Riyadh 11597, Saudi Arabia
| | - Dalia Mahmoud Abdelmonem Elsherbini
- Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, Jouf University, P.O. Box 2014, Sakaka, Saudi Arabia
- Department of Anatomy, Faculty of Medicine, Mansoura University, Mansoura, Egypt
| | - Ponnulakshmi Rajagopal
- Central Research Laboratory, Meenakshi Academy of Higher Education and Research (Deemed to be University), Chennai 600078, India
| | - Chella Perumal Palanisamy
- State Key Laboratory of Biobased Material and Green Papermaking, College of Food Science and Engineering, Qilu University of Technology, Shandong Academy of Science, Jinan 250353, China
| | - Vishnu Priya Veeraraghavan
- Centre of Molecular Medicine and Diagnostics (COMManD), Department of Biochemistry, Saveetha Dental College & Hospital, Saveetha Institute of Medical & Technical Sciences, Saveetha University, Chennai 600077, India
| | - Selvaraj Jayaraman
- Centre of Molecular Medicine and Diagnostics (COMManD), Department of Biochemistry, Saveetha Dental College & Hospital, Saveetha Institute of Medical & Technical Sciences, Saveetha University, Chennai 600077, India
| | - Krishna Mohan Surapaneni
- Departments of Biochemistry,Molecular Virology,Medical Education,Research,Clinical Skills & Simulation, Panimalar Medical College Hospital & Research Institute, Varadharajapuram, Poonamallee, Chennai 600123, India
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3
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Hwang J, Thurmond DC. Exocytosis Proteins: Typical and Atypical Mechanisms of Action in Skeletal Muscle. Front Endocrinol (Lausanne) 2022; 13:915509. [PMID: 35774142 PMCID: PMC9238359 DOI: 10.3389/fendo.2022.915509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 05/11/2022] [Indexed: 11/18/2022] Open
Abstract
Insulin-stimulated glucose uptake in skeletal muscle is of fundamental importance to prevent postprandial hyperglycemia, and long-term deficits in insulin-stimulated glucose uptake underlie insulin resistance and type 2 diabetes. Skeletal muscle is responsible for ~80% of the peripheral glucose uptake from circulation via the insulin-responsive glucose transporter GLUT4. GLUT4 is mainly sequestered in intracellular GLUT4 storage vesicles in the basal state. In response to insulin, the GLUT4 storage vesicles rapidly translocate to the plasma membrane, where they undergo vesicle docking, priming, and fusion via the high-affinity interactions among the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) exocytosis proteins and their regulators. Numerous studies have elucidated that GLUT4 translocation is defective in insulin resistance and type 2 diabetes. Emerging evidence also links defects in several SNAREs and SNARE regulatory proteins to insulin resistance and type 2 diabetes in rodents and humans. Therefore, we highlight the latest research on the role of SNAREs and their regulatory proteins in insulin-stimulated GLUT4 translocation in skeletal muscle. Subsequently, we discuss the novel emerging role of SNARE proteins as interaction partners in pathways not typically thought to involve SNAREs and how these atypical functions reveal novel therapeutic targets for combating peripheral insulin resistance and diabetes.
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Affiliation(s)
| | - Debbie C. Thurmond
- Department of Molecular and Cellular Endocrinology, Arthur Riggs Diabetes and Metabolism Research Institute, Beckman Research Institute at City of Hope, Duarte, CA, United States
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Zhang Y, He L, Chen X, Shentu P, Xu Y, Jiao J. Omega-3 polyunsaturated fatty acids promote SNAREs mediated GLUT4 vesicle docking and fusion. J Nutr Biochem 2021; 101:108912. [PMID: 34801692 DOI: 10.1016/j.jnutbio.2021.108912] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 09/24/2021] [Accepted: 10/08/2021] [Indexed: 11/27/2022]
Abstract
Glucose homeostasis imbalance and insulin resistance (IR) are major contributors to the incidence of type 2 diabetes. Omega-3 polyunsaturated fatty acids (PUFAs) are key ingredients for maintaining cellular functions and improving insulin sensitivity. However, how omega-3 PUFAs modulate the dynamic process of glucose transport at the cellular level remains unclear. Here we unraveled eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may regulate the glucose transporter 4 (GLUT4) vesicle trafficking in both normal and IR adipocytes. Both omega-3 PUFAs significantly increase glucose consumption within a range of 10-32% in the basal state. Furthermore, both EPA (200 μM) and DHA (100 μM) may significantly promote the serine/threonine protein kinase (Akt) phosphorylation by 70% and 40% in the physiological state of adipocytes, respectively. Both omega-3 PUFAs significantly advanced the Akt phosphorylation in a dose-dependent way and showed a ∼2-fold increase at the dose of 200 μM in the IR pathological state. However, they could not up-regulate the expression of GLUT4 and insulin-regulated aminopeptidase protein. We further revealed that both omega-3 PUFAs dynamically promote insulin-stimulated GLUT4 vesicle translocation and soluble N-ethylmaleimide-sensitive factor attachment protein receptor mediated vesicle docking and fusion to the plasma membrane via specifically modulating the expression of vesicle-associated membrane protein 2. Understanding the mechanisms by which omega-3 PUFAs modulate cellular metabolism and IR in peripheral tissues may provide novel insights into the potential impact of omega-3 PUFAs on the metabolic function and the management of IR.
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Affiliation(s)
- Yu Zhang
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro-Food Processing, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Lilin He
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro-Food Processing, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiaoqian Chen
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro-Food Processing, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Ping Shentu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yingke Xu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China; Department of Endocrinology, The Affiliated Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
| | - Jingjing Jiao
- Department of Nutrition, School of Public Health, Department of Clinical Nutrition, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
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Tokarz VL, MacDonald PE, Klip A. The cell biology of systemic insulin function. J Cell Biol 2018; 217:2273-2289. [PMID: 29622564 PMCID: PMC6028526 DOI: 10.1083/jcb.201802095] [Citation(s) in RCA: 235] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 03/21/2018] [Accepted: 03/23/2018] [Indexed: 12/12/2022] Open
Abstract
Insulin is the paramount anabolic hormone, promoting carbon energy deposition in the body. Its synthesis, quality control, delivery, and action are exquisitely regulated by highly orchestrated intracellular mechanisms in different organs or "stations" of its bodily journey. In this Beyond the Cell review, we focus on these five stages of the journey of insulin through the body and the captivating cell biology that underlies the interaction of insulin with each organ. We first analyze insulin's biosynthesis in and export from the β-cells of the pancreas. Next, we focus on its first pass and partial clearance in the liver with its temporality and periodicity linked to secretion. Continuing the journey, we briefly describe insulin's action on the blood vasculature and its still-debated mechanisms of exit from the capillary beds. Once in the parenchymal interstitium of muscle and adipose tissue, insulin promotes glucose uptake into myofibers and adipocytes, and we elaborate on the intricate signaling and vesicle traffic mechanisms that underlie this fundamental function. Finally, we touch upon the renal degradation of insulin to end its action. Cellular discernment of insulin's availability and action should prove critical to understanding its pivotal physiological functions and how their failure leads to diabetes.
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Affiliation(s)
- Victoria L Tokarz
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Amira Klip
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
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6
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Sarabia-Sánchez MJ, Trejo-Soto PJ, Velázquez-López JM, Carvente-García C, Castillo R, Hernández-Campos A, Avitia-Domínguez C, Enríquez-Mendiola D, Sierra-Campos E, Valdez-Solana M, Salas-Pacheco JM, Téllez-Valencia A. Novel Mixed-Type Inhibitors of Protein Tyrosine Phosphatase 1B. Kinetic and Computational Studies. Molecules 2017; 22:molecules22122262. [PMID: 29261102 PMCID: PMC6150025 DOI: 10.3390/molecules22122262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 12/13/2017] [Accepted: 12/16/2017] [Indexed: 11/21/2022] Open
Abstract
The Atlas of Diabetes reports 415 million diabetics in the world, a number that has surpassed in half the expected time the twenty year projection. Type 2 diabetes is the most frequent form of the disease; it is characterized by a defect in the secretion of insulin and a resistance in its target organs. In the search for new antidiabetic drugs, one of the principal strategies consists in promoting the action of insulin. In this sense, attention has been centered in the protein tyrosine phosphatase 1B (PTP1B), a protein whose overexpression or increase of its activity has been related in many studies with insulin resistance. In the present work, a chemical library of 250 compounds was evaluated to determine their inhibition capability on the protein PTP1B. Ten molecules inhibited over the 50% of the activity of the PTP1B, the three most potent molecules were selected for its characterization, reporting Ki values of 5.2, 4.2 and 41.3 µM, for compounds 1, 2, and 3, respectively. Docking and molecular dynamics studies revealed that the three inhibitors made interactions with residues at the secondary binding site to phosphate, exclusive for PTP1B. The data reported here support these compounds as hits for the design more potent and selective inhibitors against PTP1B in the search of new antidiabetic treatment.
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Affiliation(s)
- Marie Jazmín Sarabia-Sánchez
- Facultad de Medicina y Nutrición, Universidad Juárez del Estado de Durango, Av. Universidad y Fanny Anitúa S/N, Durango, Durango C.P. 34000, Mexico.
| | - Pedro Josué Trejo-Soto
- Facultad de Química, Departamento de Farmacia, Universidad Nacional Autónoma de México, Ciudad de México C.P. 04510, Mexico.
| | - José Miguel Velázquez-López
- Facultad de Química, Departamento de Farmacia, Universidad Nacional Autónoma de México, Ciudad de México C.P. 04510, Mexico.
| | - Carlos Carvente-García
- Facultad de Química, Departamento de Farmacia, Universidad Nacional Autónoma de México, Ciudad de México C.P. 04510, Mexico.
| | - Rafael Castillo
- Facultad de Química, Departamento de Farmacia, Universidad Nacional Autónoma de México, Ciudad de México C.P. 04510, Mexico.
| | - Alicia Hernández-Campos
- Facultad de Química, Departamento de Farmacia, Universidad Nacional Autónoma de México, Ciudad de México C.P. 04510, Mexico.
| | - Claudia Avitia-Domínguez
- Facultad de Medicina y Nutrición, Universidad Juárez del Estado de Durango, Av. Universidad y Fanny Anitúa S/N, Durango, Durango C.P. 34000, Mexico.
| | - Daniel Enríquez-Mendiola
- Facultad de Medicina y Nutrición, Universidad Juárez del Estado de Durango, Av. Universidad y Fanny Anitúa S/N, Durango, Durango C.P. 34000, Mexico.
| | - Erick Sierra-Campos
- Facultad de Ciencias Químicas, Universidad Juárez del Estado de Durango, Av. Artículo 123 S/N Fracc. Filadelfia, Gómez Palacio, Durango C.P. 35010, Mexico.
| | - Mónica Valdez-Solana
- Facultad de Ciencias Químicas, Universidad Juárez del Estado de Durango, Av. Artículo 123 S/N Fracc. Filadelfia, Gómez Palacio, Durango C.P. 35010, Mexico.
| | - José Manuel Salas-Pacheco
- Instituto de Investigación Científica, Universidad Juárez del Estado de Durango, Av. Universidad S/N, Durango, Durango C.P. 34000, Mexico.
| | - Alfredo Téllez-Valencia
- Facultad de Medicina y Nutrición, Universidad Juárez del Estado de Durango, Av. Universidad y Fanny Anitúa S/N, Durango, Durango C.P. 34000, Mexico.
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7
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Ito Y, Hsu MF, Bettaieb A, Koike S, Mello A, Calvo-Rubio M, Villalba JM, Haj FG. Protein tyrosine phosphatase 1B deficiency in podocytes mitigates hyperglycemia-induced renal injury. Metabolism 2017; 76:56-69. [PMID: 28987240 PMCID: PMC5690491 DOI: 10.1016/j.metabol.2017.07.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 07/13/2017] [Accepted: 07/31/2017] [Indexed: 01/13/2023]
Abstract
OBJECTIVE Diabetic nephropathy is one of the most devastating complications of diabetes, and growing evidence implicates podocyte dysfunction in disease pathogenesis. The objective of this study was to investigate the contribution of protein tyrosine phosphatase 1B (PTP1B) in podocytes to hyperglycemia-induced renal injury. METHODS To determine the in vivo function of PTP1B in podocytes we generated mice with podocyte-specific PTP1B disruption (hereafter termed pod-PTP1B KO). Kidney functions were determined in control and pod-PTP1B KO mice under normoglycemia and high-fat diet (HFD)- and streptozotocin (STZ)-induced hyperglycemia. RESULTS PTP1B expression increased in murine kidneys following HFD and STZ challenges. Under normoglycemia control and pod-PTP1B KO mice exhibited comparable renal functions. However, podocyte PTP1B disruption attenuated hyperglycemia-induced albuminuria and renal injury and preserved glucose control. Also, podocyte PTP1B disruption was accompanied with improved renal insulin signaling and enhanced autophagy with decreased inflammation and fibrosis. Moreover, the beneficial effects of podocyte PTP1B disruption in vivo were recapitulated in E11 murine podocytes with lentiviral-mediated PTP1B knockdown. Reconstitution of PTP1B in knockdown podocytes reversed the enhanced insulin signaling and autophagy suggesting that they were likely a consequence of PTP1B deficiency. Further, pharmacological attenuation of autophagy in PTP1B knockdown podocytes mitigated the protective effects of PTP1B deficiency. CONCLUSIONS These findings demonstrate that podocyte PTP1B deficiency attenuates hyperglycemia-induced renal damage and suggest that PTP1B may present a therapeutic target in renal injury.
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Affiliation(s)
- Yoshihiro Ito
- Department of Nutrition, University of California Davis, One Shields Ave, Davis, CA 95616, United States
| | - Ming-Fo Hsu
- Department of Nutrition, University of California Davis, One Shields Ave, Davis, CA 95616, United States
| | - Ahmed Bettaieb
- Department of Nutrition, University of California Davis, One Shields Ave, Davis, CA 95616, United States
| | - Shinichiro Koike
- Department of Nutrition, University of California Davis, One Shields Ave, Davis, CA 95616, United States
| | - Aline Mello
- Department of Nutrition, University of California Davis, One Shields Ave, Davis, CA 95616, United States
| | - Miguel Calvo-Rubio
- Department of Cell Biology, Physiology and Immunology, Agrifood Campus of International Excellence ceiA3, University of Cordoba, 14014 Cordoba, Spain
| | - Jose M Villalba
- Department of Cell Biology, Physiology and Immunology, Agrifood Campus of International Excellence ceiA3, University of Cordoba, 14014 Cordoba, Spain
| | - Fawaz G Haj
- Department of Nutrition, University of California Davis, One Shields Ave, Davis, CA 95616, United States; Comprehensive Cancer Center, University of California Davis, Sacramento, CA 95817, United States; Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, University of California Davis, Sacramento, CA 95817, United States.
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8
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Jaldin-Fincati JR, Pavarotti M, Frendo-Cumbo S, Bilan PJ, Klip A. Update on GLUT4 Vesicle Traffic: A Cornerstone of Insulin Action. Trends Endocrinol Metab 2017; 28:597-611. [PMID: 28602209 DOI: 10.1016/j.tem.2017.05.002] [Citation(s) in RCA: 180] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/08/2017] [Accepted: 05/09/2017] [Indexed: 12/20/2022]
Abstract
Glucose transport is rate limiting for dietary glucose utilization by muscle and fat. The glucose transporter GLUT4 is dynamically sorted and retained intracellularly and redistributes to the plasma membrane (PM) by insulin-regulated vesicular traffic, or 'GLUT4 translocation'. Here we emphasize recent findings in GLUT4 translocation research. The application of total internal reflection fluorescence microscopy (TIRFM) has increased our understanding of insulin-regulated events beneath the PM, such as vesicle tethering and membrane fusion. We describe recent findings on Akt-targeted Rab GTPase-activating proteins (GAPs) (TBC1D1, TBC1D4, TBC1D13) and downstream Rab GTPases (Rab8a, Rab10, Rab13, Rab14, and their effectors) along with the input of Rac1 and actin filaments, molecular motors [myosinVa (MyoVa), myosin1c (Myo1c), myosinIIA (MyoIIA)], and membrane fusion regulators (syntaxin4, munc18c, Doc2b). Collectively these findings reveal novel events in insulin-regulated GLUT4 traffic.
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Affiliation(s)
| | - Martin Pavarotti
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5J 2L4, Canada; IHEM, Universidad Nacional de Cuyo, CONICET, Mendoza 5500, Argentina
| | - Scott Frendo-Cumbo
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5J 2L4, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Philip J Bilan
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5J 2L4, Canada
| | - Amira Klip
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5J 2L4, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
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9
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Da Q, Shaw T, Pradhan S, Roche PA, Cruz MA, Vijayan KV. Disruption of protein complexes containing protein phosphatase 2B and Munc18c reduces the secretion of von Willebrand factor from endothelial cells. J Thromb Haemost 2017; 15:1032-1039. [PMID: 28294518 PMCID: PMC5413388 DOI: 10.1111/jth.13671] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Indexed: 12/01/2022]
Abstract
Essentials Endothelial secretion of von Willebrand factor (VWF) promotes inflammation and thrombosis. We studied the role of protein phosphatase 2B (PP2B) and Munc18c protein complex in VWF secretion. Disruption of PP2B-Munc18c complex in endothelial cells reduced agonist-induced VWF secretion. PP2B-Munc18c complex represents a potential target for thrombotic and inflammatory conditions. SUMMARY Background Aberrant secretion of von Willebrand factor (VWF) from endothelial cells contributes to inflammation and vascular thrombosis. Agonist-induced VWF secretion is facilitated by protein kinase and phosphatase-mediated signaling. Although the catalytic subunit of protein phosphatase 2B (PP2B-Aα) is targeted to the secretory machinery via an interaction with the vesicle trafficking protein Munc18c in endothelial cells, the functional relevance of this phosphatase complex is unclear. Objective To assess the contribution of the PP2B-Aα-Munc18c complex to endothelial VWF secretion. Results Here, we show that amino acids 120-130 of PP2B-Aα are important to support an interaction with Munc18c. A synthetic myristylated cell-permeable peptide, which is derived from amino acids 121-130 of PP2B-Aα, disrupted endogenous PP2B-Aα-Munc18c complexes in human umbilical vein endothelial cells, and decreased low-dose histamine-stimulated and thrombin-stimulated VWF secretion. Conclusion These studies indicate that PP2B-Aα-Munc18c complex supports agonist-induced VWF secretion, and suggest the potential of targeting this phosphatase complex in thrombotic and inflammatory conditions.
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Affiliation(s)
- Qi Da
- Department of Medicine, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Baylor College of Medicine and Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
| | - Tanner Shaw
- Department of Medicine, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Baylor College of Medicine and Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
| | - Subhashree Pradhan
- Department of Medicine, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Baylor College of Medicine and Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
| | - Paul A. Roche
- National Cancer Institute, Bethesda, MD 20892, U.S.A
| | - Miguel A. Cruz
- Department of Medicine, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Baylor College of Medicine and Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Department of Pediatrics, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Department of Molecular Physiology and Biophysics, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
| | - K. Vinod Vijayan
- Department of Medicine, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Baylor College of Medicine and Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Department of Pediatrics, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
- Department of Molecular Physiology and Biophysics, Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, U.S.A
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10
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Lutz SZ, Ullrich A, Häring HU, Ullrich S, Gerst F. Sunitinib specifically augments glucose-induced insulin secretion. Cell Signal 2017; 36:91-97. [PMID: 28449948 DOI: 10.1016/j.cellsig.2017.04.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 04/07/2017] [Accepted: 04/23/2017] [Indexed: 01/01/2023]
Abstract
The tyrosine kinase inhibitor sunitinib is used for the treatment of numerous cancers in humans. In diabetic patients, sunitinib lowers blood glucose levels and improves glycaemic control. This study aims to analyse whether sunitinib has specific and direct effects on insulin secreting β-cells. Regulation of insulin secretion, of cellular cAMP levels and activation of signalling pathways were examined upon exposure of rat insulinoma INS-1E cells to sunitinib under specific stimulatory and inhibitory conditions. Secreted insulin and cellular cAMP levels were measured using RIA and ELISA, respectively. Protein phosphorylations were examined on western blots. Sunitinib enhanced glucose-induced insulin secretion (GIIS) concentration-dependently, reaching a maximal stimulation at 2μM. Sunitinib further augmented insulin secretion in the presence of elevated cAMP levels and the FFAR1 agonists. Adrenaline and the PKA inhibitor H89 counteracted the stimulatory effect of sunitinib on secretion. However, sunitinib altered neither the cellular levels of cAMP nor the phosphorylation of PKA. Sunitinib did not reduce IGF-1-induced phosphorylation of AKT/PKB and ERK1/2. In conclusion, these results suggest that sunitinib stimulates GIIS by a direct effect on β-cells, which may contribute to the glucose-lowering action of the tyrosine kinase inhibitor in humans.
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Affiliation(s)
- Stefan Z Lutz
- German Center for Diabetes Research (DZD e.V.), Germany; Institute for Diabetes Research and Metabolic Diseases IDM of the Helmholtz Center Munich at the Eberhard-Karls-University of Tübingen, Germany; University Hospital Tübingen, Internal Medicine IV, Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Otfried-Müller-Str. 10, 72076 Tübingen, Germany
| | - Axel Ullrich
- Department of Molecular Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany
| | - Hans-Ulrich Häring
- German Center for Diabetes Research (DZD e.V.), Germany; Institute for Diabetes Research and Metabolic Diseases IDM of the Helmholtz Center Munich at the Eberhard-Karls-University of Tübingen, Germany; University Hospital Tübingen, Internal Medicine IV, Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Otfried-Müller-Str. 10, 72076 Tübingen, Germany
| | - Susanne Ullrich
- German Center for Diabetes Research (DZD e.V.), Germany; Institute for Diabetes Research and Metabolic Diseases IDM of the Helmholtz Center Munich at the Eberhard-Karls-University of Tübingen, Germany; University Hospital Tübingen, Internal Medicine IV, Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Otfried-Müller-Str. 10, 72076 Tübingen, Germany
| | - Felicia Gerst
- German Center for Diabetes Research (DZD e.V.), Germany; Institute for Diabetes Research and Metabolic Diseases IDM of the Helmholtz Center Munich at the Eberhard-Karls-University of Tübingen, Germany; University Hospital Tübingen, Internal Medicine IV, Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Otfried-Müller-Str. 10, 72076 Tübingen, Germany.
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11
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Jialal I, Devaraj S, Bettaieb A, Haj F, Adams-Huet B. Increased adipose tissue secretion of Fetuin-A, lipopolysaccharide-binding protein and high-mobility group box protein 1 in metabolic syndrome. Atherosclerosis 2015; 241:130-7. [PMID: 25978344 DOI: 10.1016/j.atherosclerosis.2015.04.814] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 04/24/2015] [Accepted: 04/24/2015] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Adipose Tissue (AT) dysregulation contributes to the pro-inflammatory state and insulin resistance of Metabolic Syndrome (MetS). We examined AT secretion of the hepatokine, Fetuin-A, LBP, sCD14 and HMGB-1, and toll-like receptor 2 and 4 protein levels in MetS and controls. DESIGN AND METHODS Secreted levels of Fetuin-A, LBP, HMGB-1 and sCD14 and TLR2 and TLR4 protein in AT of controls and MetS patients were assayed. Also mRNA and protein for Fetuin-A, LBP, sCD14 and HMGB-1 were studied in subcutaneous fat depot of mice and during adipocyte differentiation. RESULTS Secretion of Fetuin-A, LBP and HMGB-1 from AT were significantly increased in MetS (n = 28) compared to controls (n = 25), even after adjustment for adiposity. There were no significant differences in sCD14. Both LBP and Fetuin-A correlated significantly with HOMA-IR and increased significantly with increasing features of MetS. There was a significant increase in AT TLR2 and TLR4 protein in MetS compared to controls. Expression of Fetuin-A and LBP were significantly higher in subcutaneous white adipose tissue of HFD fed mice as well as in ob/ob mice compared to C57BL6/J control mice (n = 6 per group). Additionally mRNA and protein levels of FetA, LBP and HMGB-1 increased during differentiation of 3T3-L1 adipocytes. CONCLUSIONS We make the novel observation of increased secretion of Fetuin A, LBP and HMGB-1 from AT and hypothesize that these engage TLRs in AT and other tissues contributing to the pro-inflammatory state and insulin resistance of MetS.
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Affiliation(s)
- Ishwarlal Jialal
- Laboratory for Atherosclerosis and Metabolic Research, Department of Pathology, Division of Endocrinology, Diabetes and Metabolism, University of California Davis Medical Center, Sacramento, CA, USA; Medical Services, VA Medical Center, Mather, CA, USA.
| | - Sridevi Devaraj
- Department of Pathology & Immunology, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, USA
| | - Ahmed Bettaieb
- Department of Nutrition, University of California Davis, Davis, CA, USA
| | - Fawaz Haj
- Department of Nutrition, University of California Davis, Davis, CA, USA
| | - Beverley Adams-Huet
- Department of Clinical Sciences, Division of Biostatistics, University of Texas Southwestern Medical Center, Dallas, TX, USA
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12
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Doc2b serves as a scaffolding platform for concurrent binding of multiple Munc18 isoforms in pancreatic islet β-cells. Biochem J 2015; 464:251-8. [PMID: 25190515 DOI: 10.1042/bj20140845] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Biphasic glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells involves soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor (SNARE) protein-regulated exocytosis. SNARE complex assembly further requires the regulatory proteins Munc18c, Munc18-1 and Doc2b. Munc18-1 and Munc18c are required for first- and second-phase GSIS respectively. These distinct Munc18-1 and Munc18c roles are related to their transient high-affinity binding with their cognate target (t-)SNAREs, Syntaxin 1A and Syntaxin 4 respectively. Doc2b is essential for both phases of GSIS, yet the molecular basis for this remains unresolved. Because Doc2b binds to Munc18-1 and Munc18c via its distinct C2A and C2B domains respectively, we hypothesized that Doc2b may provide a plasma membrane-localized scaffold/platform for transient docking of these Munc18 isoforms during GSIS. Towards this, macromolecular complexes composed of Munc18c, Doc2b and Munc18-1 were detected in β-cells. In vitro interaction assays indicated that Doc2b is required to bridge the interaction between Munc18c and Munc18-1 in the macromolecular complex; Munc18c and Munc18-1 failed to associate in the absence of Doc2b. Competition-based GST-Doc2b interaction assays revealed that Doc2b could simultaneously bind both Munc18-1 and Munc18c. Hence these data support a working model wherein Doc2b functions as a docking platform/scaffold for transient interactions with the multiple Munc18 isoforms operative in insulin release, promoting SNARE assembly.
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13
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Ramalingam L, Yoder SM, Oh E, Thurmond DC. Munc18c: a controversial regulator of peripheral insulin action. Trends Endocrinol Metab 2014; 25:601-8. [PMID: 25028245 PMCID: PMC4253632 DOI: 10.1016/j.tem.2014.06.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 06/12/2014] [Accepted: 06/20/2014] [Indexed: 12/19/2022]
Abstract
Insulin resistance, a hallmark of impaired glucose tolerance and type 2 diabetes (T2D), arises from dysfunction of insulin action and subsequent glucose uptake by peripheral tissues, predominantly skeletal muscle and fat. Exocytosis of glucose transporter (GLUT4)-containing vesicles facilitated by soluble NSF (N-ethylmaleimide-sensitive factor) attachment receptor (SNARE) protein isoforms, and Munc18c (mammalian homolog of Unc-18c) mediates this glucose uptake. Emerging evidences, including recent human clinical studies, point to pivotal roles for Munc18c in peripheral insulin action in adipose and skeletal muscle. Intriguing new advances are also initiating debates regarding the molecular mechanism(s) controlling Munc18c action. The objective of this review is therefore to present a balanced perspective of new continuities and controversies surrounding the regulation and requirement for Munc18c in the regulation of peripheral insulin action.
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Affiliation(s)
- Latha Ramalingam
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Stephanie M Yoder
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Eunjin Oh
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Debbie C Thurmond
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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14
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Bakke J, Haj FG. Protein-tyrosine phosphatase 1B substrates and metabolic regulation. Semin Cell Dev Biol 2014; 37:58-65. [PMID: 25263014 DOI: 10.1016/j.semcdb.2014.09.020] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 09/15/2014] [Accepted: 09/21/2014] [Indexed: 01/19/2023]
Abstract
Metabolic homeostasis requires integration of complex signaling networks which, when deregulated, contribute to metabolic syndrome and related disorders. Protein-tyrosine phosphatase 1B (PTP1B) has emerged as a key regulator of signaling networks that are implicated in metabolic diseases such as obesity and type 2 diabetes. In this review, we examine mechanisms that regulate PTP1B-substrate interaction, enzymatic activity and experimental approaches to identify PTP1B substrates. We then highlight findings that implicate PTP1B in metabolic regulation. In particular, insulin and leptin signaling are discussed as well as recently identified PTP1B substrates that are involved in endoplasmic reticulum stress response, cell-cell communication, energy balance and vesicle trafficking. In summary, PTP1B exhibits exquisite substrate specificity and is an outstanding pharmaceutical target for obesity and type 2 diabetes.
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Affiliation(s)
- Jesse Bakke
- Department of Nutrition, University of California Davis, One Shields Ave, Davis, CA 95616, United States
| | - Fawaz G Haj
- Department of Nutrition, University of California Davis, One Shields Ave, Davis, CA 95616, United States; Division of Endocrinology, Diabetes and Metabolism, Department of Internal Medicine, University of California Davis, Sacramento, CA 95817, United States; Comprehensive Cancer Center, University of California Davis, Sacramento, CA 95817, United States.
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15
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Liu S, Xi Y, Bettaieb A, Matsuo K, Matsuo I, Kulkarni RN, Haj FG. Disruption of protein-tyrosine phosphatase 1B expression in the pancreas affects β-cell function. Endocrinology 2014; 155:3329-38. [PMID: 24956127 PMCID: PMC4138572 DOI: 10.1210/en.2013-2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Protein-tyrosine phosphatase 1B (PTP1B) is a physiological regulator of glucose homeostasis and energy balance. However, the role of PTP1B in pancreatic endocrine function remains largely unknown. To investigate the metabolic role of pancreatic PTP1B, we generated mice with pancreas PTP1B deletion (panc-PTP1B KO). Mice were fed regular chow or a high-fat diet, and metabolic parameters, insulin secretion and glucose tolerance were determined. On regular chow, panc-PTP1B KO and control mice exhibited comparable glucose tolerance whereas aged panc-PTP1B KO exhibited mild glucose intolerance. Furthermore, high-fat feeding promoted earlier impairment of glucose tolerance and attenuated glucose-stimulated insulin secretion in panc-PTP1B KO mice. The secretory defect in glucose-stimulated insulin secretion was recapitulated in primary islets ex vivo, suggesting that the effects were likely cell-autonomous. At the molecular level, PTP1B deficiency in vivo enhanced basal and glucose-stimulated tyrosyl phosphorylation of EphA5 in islets. Consistently, PTP1B overexpression in the glucose-responsive MIN6 β-cell line attenuated EphA5 tyrosyl phosphorylation, and substrate trapping identified EphA5 as a PTP1B substrate. In summary, these studies identify a novel role for PTP1B in pancreatic endocrine function.
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Affiliation(s)
- Siming Liu
- Nutrition Department (S.L., Y.X., A.B., K.M., I.M., F.G.H.), University of California Davis, Davis, California 95616; Joslin Diabetes Center (R.N.K.), Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215; and Division of Endocrinology, Diabetes and Metabolism (F.G.H.), Department of Internal Medicine, and Comprehensive Cancer Center, University of California Davis, Sacramento, California 95817
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16
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Ramalingam L, Oh E, Thurmond DC. Doc2b enrichment enhances glucose homeostasis in mice via potentiation of insulin secretion and peripheral insulin sensitivity. Diabetologia 2014; 57:1476-84. [PMID: 24705606 PMCID: PMC4055500 DOI: 10.1007/s00125-014-3227-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 03/11/2014] [Indexed: 01/08/2023]
Abstract
AIMS/HYPOTHESIS Insulin secretion from pancreatic beta cells and insulin-stimulated glucose uptake into skeletal muscle are processes regulated by similar isoforms of the soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) and mammalian homologue of unc-18 (Munc18) protein families. Double C2 domain β (Doc2b), a SNARE- and Munc18-interacting protein, is implicated as a crucial effector of glycaemic control. However, whether Doc2b is naturally limiting for these processes, and whether Doc2b enrichment might exert a beneficial effect upon glycaemia in vivo, remains undetermined. METHODS Tetracycline-repressible transgenic (Tg) mice engineered to overexpress Doc2b simultaneously in the pancreas, skeletal muscle and adipose tissues were compared with wild-type (Wt) littermate mice regarding glucose and insulin tolerance, islet function in vivo and ex vivo, and skeletal muscle GLUT4 accumulation in transverse tubule/sarcolemmal surface membranes. SNARE complex formation was further assessed using Doc2b overexpressing L6-GLUT4-myc myoblasts to derive mechanisms relatable to physiological in vivo analyses. RESULTS Doc2b Tg mice cleared glucose substantially faster than Wt mice, correlated with enhancements in both phases of insulin secretion and peripheral insulin sensitivity. Heightened peripheral insulin sensitivity correlated with elevated insulin-stimulated GLUT4 vesicle accumulation in cell surface membranes of Doc2b Tg mouse skeletal muscle. Mechanistic studies demonstrated Doc2b enrichment to enhance syntaxin-4-SNARE complex formation in skeletal muscle cells. CONCLUSIONS/INTERPRETATION Doc2b is a limiting factor in SNARE exocytosis events pertinent to glycaemic regulation in vivo. Doc2b enrichment may provide a novel means to simultaneously boost islet and skeletal muscle function in vivo in the treatment and/or prevention of diabetes.
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Affiliation(s)
- Latha Ramalingam
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
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17
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Klip A, Sun Y, Chiu TT, Foley KP. Signal transduction meets vesicle traffic: the software and hardware of GLUT4 translocation. Am J Physiol Cell Physiol 2014; 306:C879-86. [DOI: 10.1152/ajpcell.00069.2014] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Skeletal muscle is the major tissue disposing of dietary glucose, a function regulated by insulin-elicited signals that impart mobilization of GLUT4 glucose transporters to the plasma membrane. This phenomenon, also central to adipocyte biology, has been the subject of intense and productive research for decades. We focus on muscle cell studies scrutinizing insulin signals and vesicle traffic in a spatiotemporal manner. Using the analogy of an integrated circuit to approach the intersection between signal transduction and vesicle mobilization, we identify signaling relays (“software”) that engage structural/mechanical elements (“hardware”) to enact the rapid mobilization and incorporation of GLUT4 into the cell surface. We emphasize how insulin signal transduction switches from tyrosine through lipid and serine phosphorylation down to activation of small G proteins of the Rab and Rho families, describe key negative regulation step of Rab GTPases through the GTPase-activating protein activity of the Akt substrate of 160 kDa (AS160), and focus on the mechanical effectors engaged by Rabs 8A and 10 (the molecular motor myosin Va), and the Rho GTPase Rac1 (actin filament branching and severing through Arp2/3 and cofilin). Finally, we illustrate how actin filaments interact with myosin 1c and α-Actinin4 to promote vesicle tethering as preamble to fusion with the membrane.
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Affiliation(s)
- Amira Klip
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada; and
- Department of Biochemistry, The University of Toronto, Ontario, Canada
| | - Yi Sun
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada; and
| | - Tim Ting Chiu
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada; and
- Department of Biochemistry, The University of Toronto, Ontario, Canada
| | - Kevin P. Foley
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada; and
- Department of Biochemistry, The University of Toronto, Ontario, Canada
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18
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Xu E, Schwab M, Marette A. Role of protein tyrosine phosphatases in the modulation of insulin signaling and their implication in the pathogenesis of obesity-linked insulin resistance. Rev Endocr Metab Disord 2014; 15:79-97. [PMID: 24264858 DOI: 10.1007/s11154-013-9282-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Insulin resistance is a major disorder that links obesity to type 2 diabetes mellitus (T2D). It involves defects in the insulin actions owing to a reduced ability of insulin to trigger key signaling pathways in major metabolic tissues. The pathogenesis of insulin resistance involves several inhibitory molecules that interfere with the tyrosine phosphorylation of the insulin receptor and its downstream effectors. Among those, growing interest has been developed toward the protein tyrosine phosphatases (PTPs), a large family of enzymes that can inactivate crucial signaling effectors in the insulin signaling cascade by dephosphorylating their tyrosine residues. Herein we briefly review the role of several PTPs that have been shown to be implicated in the regulation of insulin action, and then focus on the Src homology 2 (SH2) domain-containing SHP1 and SHP2 enzymes, since recent reports have indicated major roles for these PTPs in the control of insulin action and glucose metabolism. Finally, the therapeutic potential of targeting PTPs for combating insulin resistance and alleviating T2D will be discussed.
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Affiliation(s)
- Elaine Xu
- Department of Medicine, Cardiology Axis of the Institut Universitaire de Cardiologie et de Pneumologie de Québec (Hôpital Laval), Ste-Foy, Québec, Canada, G1V 4G2
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