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Eskesen NO, Kjøbsted R, Birk JB, Henriksen NS, Andersen NR, Ringholm S, Pilegaard H, Wojtaszewski JFP. The human AMPKγ3 R225W mutation negatively impacts site-1 nucleotide binding and does not enhance basal AMPKγ3-associated activity nor glycogen production in human or mouse skeletal muscle. Acta Physiol (Oxf) 2024:e14213. [PMID: 39171449 DOI: 10.1111/apha.14213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 06/13/2024] [Accepted: 07/06/2024] [Indexed: 08/23/2024]
Abstract
AIM AMP-activated protein kinase (AMPK) is activated during cellular energy perturbation. AMPK complexes are composed of three subunits and several variants of AMPK are expressed in skeletal muscle. The regulatory AMPKγ3 subunit is predominantly expressed in fast-twitch muscle fibers. A human AMPKγ3 R225W mutation has been described. The mutation increases the total pool of AMPK activity in cells cultured from R225W carrier muscle and is associated with increased glycogen levels in mature skeletal muscle. This led to the idea of AMPKγ3 being involved in the regulation of skeletal muscle glycogen levels. Evidence for this causative link remains to be provided. METHODS We studied muscle biopsies from human carriers of the AMPKγ3 R225W mutation and we developed a novel AMPKγ3 R225W knock-in mouse model (KI HOM). Through in vitro, in situ, and ex vivo techniques, we investigated AMPK activity, AMPK function, and glycogen levels in skeletal muscle of humans and mice. RESULTS In human carriers, the basal AMPKγ3-associated activity was reduced when assayed in the absence of exogenous AMP. No difference was observed when assayed under AMP saturation, which was supported by findings in muscle of KI HOM mice. Furthermore, effects of AICAR/muscle contraction on AMPKγ3-associated activity were absent in KI HOM muscle. Muscle glycogen levels were not affected by the mutation in human carriers or in KI HOM mice. CONCLUSIONS The AMPKγ3 R225W mutation does not impact the AMPK-associated activity in human skeletal muscle and the mutation is not linked to glycogen accumulation. The R225W mutation ablates the AMPKγ3-associated activation by AICAR/muscle contractions, presumably due to loss of nucleotide binding in the CBS 1 domain of AMPKγ3.
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Affiliation(s)
- Nicolas O Eskesen
- Department of Nutrition, Exercise and Sports, August Krogh Section for Molecular Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Rasmus Kjøbsted
- Department of Nutrition, Exercise and Sports, August Krogh Section for Molecular Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Jesper Bratz Birk
- Department of Nutrition, Exercise and Sports, August Krogh Section for Molecular Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Nicolai S Henriksen
- Department of Nutrition, Exercise and Sports, August Krogh Section for Molecular Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Nicoline R Andersen
- Department of Nutrition, Exercise and Sports, August Krogh Section for Molecular Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Stine Ringholm
- Department of Biology, Section of Cell Biology and Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Henriette Pilegaard
- Department of Biology, Section of Cell Biology and Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Jørgen F P Wojtaszewski
- Department of Nutrition, Exercise and Sports, August Krogh Section for Molecular Physiology, University of Copenhagen, Copenhagen, Denmark
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Ashraf N, Van Nostrand JL. Fine-tuning AMPK in physiology and disease using point-mutant mouse models. Dis Model Mech 2024; 17:dmm050798. [PMID: 39136185 PMCID: PMC11340815 DOI: 10.1242/dmm.050798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2024] Open
Abstract
AMP-activated protein kinase (AMPK) is an evolutionarily conserved serine/threonine kinase that monitors the cellular energy status to adapt it to the fluctuating nutritional and environmental conditions in an organism. AMPK plays an integral part in a wide array of physiological processes, such as cell growth, autophagy and mitochondrial function, and is implicated in diverse diseases, including cancer, metabolic disorders, cardiovascular diseases and neurodegenerative diseases. AMPK orchestrates many different physiological outcomes by phosphorylating a broad range of downstream substrates. However, the importance of AMPK-mediated regulation of these substrates in vivo remains an ongoing area of investigation to better understand its precise role in cellular and metabolic homeostasis. Here, we provide a comprehensive overview of our understanding of the kinase function of AMPK in vivo, as uncovered from mouse models that harbor phosphorylation mutations in AMPK substrates. We discuss some of the inherent limitations of these mouse models, highlight the broader implications of these studies for understanding human health and disease, and explore the valuable insights gained that could inform future therapeutic strategies for the treatment of metabolic and non-metabolic disorders.
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Affiliation(s)
- Naghmana Ashraf
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jeanine L. Van Nostrand
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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3
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Kido K, Eskesen NO, Henriksen NS, Onslev J, Kristensen JM, Larsen MR, Hingst JR, Knudsen JR, Birk JB, Andersen NR, Jensen TE, Pehmøller C, Wojtaszewski JF, Kjøbsted R. AMPKγ3 Controls Muscle Glucose Uptake in Recovery From Exercise to Recapture Energy Stores. Diabetes 2023; 72:1397-1408. [PMID: 37506328 PMCID: PMC10545559 DOI: 10.2337/db23-0358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Accepted: 07/23/2023] [Indexed: 07/30/2023]
Abstract
Exercise increases muscle glucose uptake independently of insulin signaling and represents a cornerstone for the prevention of metabolic disorders. Pharmacological activation of the exercise-responsive AMPK in skeletal muscle has been proven successful as a therapeutic approach to treat metabolic disorders by improving glucose homeostasis through the regulation of muscle glucose uptake. However, conflicting observations cloud the proposed role of AMPK as a necessary regulator of muscle glucose uptake during exercise. We show that glucose uptake increases in human skeletal muscle in the absence of AMPK activation during exercise and that exercise-stimulated AMPKγ3 activity strongly correlates to muscle glucose uptake in the postexercise period. In AMPKγ3-deficient mice, muscle glucose uptake is normally regulated during exercise and contractions but impaired in the recovery period from these stimuli. Impaired glucose uptake in recovery from exercise and contractions is associated with a lower glucose extraction, which can be explained by a diminished permeability to glucose and abundance of GLUT4 at the muscle plasma membrane. As a result, AMPKγ3 deficiency impairs muscle glycogen resynthesis following exercise. These results identify a physiological function of the AMPKγ3 complex in human and rodent skeletal muscle that regulates glucose uptake in recovery from exercise to recapture muscle energy stores. ARTICLE HIGHLIGHTS Exercise-induced activation of AMPK in skeletal muscle has been proposed to regulate muscle glucose uptake in recovery from exercise. This study investigated whether the muscle-specific AMPKγ3-associated heterotrimeric complex was involved in regulating muscle glucose metabolism in recovery from exercise. The findings support that exercise-induced activation of the AMPKγ3 complex in human and mouse skeletal muscle enhances glucose uptake in recovery from exercise via increased translocation of GLUT4 to the plasma membrane. This work uncovers the physiological role of the AMPKγ3 complex in regulating muscle glucose uptake that favors replenishment of the muscle cellular energy stores.
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Affiliation(s)
- Kohei Kido
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
- Health and Medical Research Institute, Department of Life Science and Biotechnology, National Institute of Advanced Industrial Science and Technology (AIST), Takamatsu, Kagawa, Japan
| | - Nicolas O. Eskesen
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Nicolai S. Henriksen
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Johan Onslev
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Jonas M. Kristensen
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Magnus R. Larsen
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Janne R. Hingst
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Jonas R. Knudsen
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Jesper B. Birk
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Nicoline R. Andersen
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Thomas E. Jensen
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Christian Pehmøller
- Internal Medicine Research Unit, Pfizer Global Research and Development, Cambridge, MA
| | - Jørgen F.P. Wojtaszewski
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Rasmus Kjøbsted
- August Krogh Section for Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
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4
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Steinberg GR, Hardie DG. New insights into activation and function of the AMPK. Nat Rev Mol Cell Biol 2023; 24:255-272. [PMID: 36316383 DOI: 10.1038/s41580-022-00547-x] [Citation(s) in RCA: 201] [Impact Index Per Article: 201.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2022] [Indexed: 11/06/2022]
Abstract
The classical role of AMP-activated protein kinase (AMPK) is as a cellular energy sensor activated by falling energy status, signalled by increases in AMP to ATP and ADP to ATP ratios. Once activated, AMPK acts to restore energy homeostasis by promoting ATP-producing catabolic pathways while inhibiting energy-consuming processes. In this Review, we provide an update on this canonical (AMP/ADP-dependent) activation mechanism, but focus mainly on recently described non-canonical pathways, including those by which AMPK senses the availability of glucose, glycogen or fatty acids and by which it senses damage to lysosomes and nuclear DNA. We also discuss new findings on the regulation of carbohydrate and lipid metabolism, mitochondrial and lysosomal homeostasis, and DNA repair. Finally, we discuss the role of AMPK in cancer, obesity, diabetes, nonalcoholic steatohepatitis (NASH) and other disorders where therapeutic targeting may exert beneficial effects.
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Affiliation(s)
- Gregory R Steinberg
- Centre for Metabolism, Obesity and Diabetes Research, McMaster University, Hamilton, Ontario, Canada.
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
| | - D Grahame Hardie
- Division of Cell Signalling & Immunology, School of Life Sciences, University of Dundee, Dundee, UK.
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5
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Ouyang Q, Chen Q, Ke S, Ding L, Yang X, Rong P, Feng W, Cao Y, Wang Q, Li M, Su S, Wei W, Liu M, Liu J, Zhang X, Li JZ, Wang HY, Chen S. Rab8a as a mitochondrial receptor for lipid droplets in skeletal muscle. Dev Cell 2023; 58:289-305.e6. [PMID: 36800997 DOI: 10.1016/j.devcel.2023.01.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 11/17/2022] [Accepted: 01/26/2023] [Indexed: 02/18/2023]
Abstract
Dynamic interaction between lipid droplets (LDs) and mitochondria controls the mobilization of long-chain fatty acids (LCFAs) from LDs for mitochondrial β-oxidation in skeletal muscle in response to energy stress. However, little is known about the composition and regulation of the tethering complex mediating LD-mitochondrion interaction. Here, we identify Rab8a as a mitochondrial receptor for LDs forming the tethering complex with the LD-associated PLIN5 in skeletal muscle. In rat L6 skeletal muscle cells, the energy sensor AMPK increases the GTP-bound active Rab8a that promotes LD-mitochondrion interaction through binding to PLIN5 upon starvation. The assembly of the Rab8a-PLIN5 tethering complex also recruits the adipose triglyceride lipase (ATGL), which couples LCFA mobilization from LDs with its transfer into mitochondria for β-oxidation. Rab8a deficiency impairs fatty acid utilization and decreases endurance during exercise in a mouse model. These findings may help to elucidate the regulatory mechanisms underlying the beneficial effects of exercise on lipid homeostasis control.
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Affiliation(s)
- Qian Ouyang
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China; Department of Cardiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Qiaoli Chen
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China; Department of Cardiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Shunyuan Ke
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Longfei Ding
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Xinyu Yang
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Ping Rong
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Weikuan Feng
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Ye Cao
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Qi Wang
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Min Li
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Shu Su
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Wen Wei
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Minjun Liu
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China
| | - Jin Liu
- The Key Laboratory of Rare Metabolic Disease, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 211166, China; The Key Laboratory of Human Functional Genomics of Jiangsu Province, Key Laboratory of Targeted Intervention of Cardiovascular Disease, Collaborative Innovation Center for Cardiovascular Disease Translational Medicine, Nanjing Medical University, Nanjing 211166, China
| | - Xu Zhang
- The Key Laboratory of Rare Metabolic Disease, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 211166, China; The Key Laboratory of Human Functional Genomics of Jiangsu Province, Key Laboratory of Targeted Intervention of Cardiovascular Disease, Collaborative Innovation Center for Cardiovascular Disease Translational Medicine, Nanjing Medical University, Nanjing 211166, China
| | - John Zhong Li
- The Key Laboratory of Rare Metabolic Disease, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing 211166, China; The Key Laboratory of Human Functional Genomics of Jiangsu Province, Key Laboratory of Targeted Intervention of Cardiovascular Disease, Collaborative Innovation Center for Cardiovascular Disease Translational Medicine, Nanjing Medical University, Nanjing 211166, China
| | - Hong-Yu Wang
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China; Department of Cardiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China.
| | - Shuai Chen
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animal for Disease Study, Department of Endocrinology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China; Department of Cardiology, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Model Animal Research Center, Nanjing University, Nanjing 210061, China.
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6
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Deng T, Du J, Yin Y, Cao B, Wang Z, Zhang Z, Yang M, Han J. Rhein for treating diabetes mellitus: A pharmacological and mechanistic overview. Front Pharmacol 2023; 13:1106260. [PMID: 36699072 PMCID: PMC9868719 DOI: 10.3389/fphar.2022.1106260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 12/26/2022] [Indexed: 01/11/2023] Open
Abstract
With the extension of life expectancy and changes in lifestyle, the prevalence of diabetes mellitus is increasing worldwide. Rheum palmatum L. a natural botanical medicine, has been used for thousands of years to prevent and treat diabetes mellitus in Eastern countries. Rhein, the main active component of rhubarb, is a 1, 8-dihydroxy anthraquinone derivative. Previous studies have extensively explored the clinical application of rhein. However, a comprehensive review of the antidiabetic effects of rhein has not been conducted. This review summarizes studies published over the past decade on the antidiabetic effects of rhein, covering the biological characteristics of Rheum palmatum L. and the pharmacological effects and pharmacokinetic characteristics of rhein. The review demonstrates that rhein can prevent and treat diabetes mellitus by ameliorating insulin resistance, possess anti-inflammatory and anti-oxidative stress properties, and protect islet cells, thus providing a theoretical basis for the application of rhein as an antidiabetic agent.
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Affiliation(s)
- Tingting Deng
- Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Jinxin Du
- Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Ying Yin
- Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Baorui Cao
- NHC Key Laboratory of Biotechnology Drugs (Shandong Academy of Medical Sciences), Biomedical Sciences College, Shandong First Medical University, Jinan, China
| | - Zhiying Wang
- Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Zhongwen Zhang
- Department of Endocrinology and Metabolism, The First Affiliated Hospital of Shandong First Medical University, Jinan, China
| | - Meina Yang
- NHC Key Laboratory of Biotechnology Drugs (Shandong Academy of Medical Sciences), Biomedical Sciences College, Shandong First Medical University, Jinan, China,Department of Endocrinology and Metabolism, The First Affiliated Hospital of Shandong First Medical University, Jinan, China,*Correspondence: Meina Yang, ; Jinxiang Han,
| | - Jinxiang Han
- NHC Key Laboratory of Biotechnology Drugs (Shandong Academy of Medical Sciences), Biomedical Sciences College, Shandong First Medical University, Jinan, China,Department of Endocrinology and Metabolism, The First Affiliated Hospital of Shandong First Medical University, Jinan, China,*Correspondence: Meina Yang, ; Jinxiang Han,
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7
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Ren G, Ding YW, Wang LL, Jiang JD. Berberine stimulates lysosomal AMPK independent of PEN2 and maintains cellular AMPK activity through inhibiting the dephosphorylation regulator UHRF1. Front Pharmacol 2023; 14:1148611. [PMID: 37144221 PMCID: PMC10151516 DOI: 10.3389/fphar.2023.1148611] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 04/06/2023] [Indexed: 05/06/2023] Open
Abstract
Aim: AMPK is the key regulatory kinase mediating the effect of berberine (BBR) and metformin on metabolic improvement. The present study investigated the mechanism of BBR on AMPK activation at low doses, which was different from that of metformin. Methods: Lysosomes were isolated, and AMPK activity assay was performed. PEN2, AXIN1 and UHRF1 were investigated through gain/loss of function approaches, including overexpression, RNA interfering and CRISPR/Cas9-mediated gene knockout. Immunoprecipitation was utilized for detecting the interaction of UHRF1 and AMPKα1 after BBR treatment. Results: BBR activated lysosomal AMPK, but weaker than metformin. AXIN1 mediated BBR's effect on lysosomal AMPK activation, while PEN2 did not. BBR, but not metformin, decreased UHRF1 expression by promoting its degradation. BBR reduced the interaction between UHRF1 and AMPKα1. And overexpression of UHRF1 abolished the effect of BBR on AMPK activation. Conclusion: BBR activated lysosomal AMPK as dependent on AXIN1, but not PEN2. BBR maintained cellular AMPK activity by reducing UHRF1 expression and its interaction with AMPKα1. The mode of action of BBR was different from that of metformin on AMPK activation.
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Affiliation(s)
- Gang Ren
- Department of Virology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
- Diabetes Research Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
- *Correspondence: Gang Ren, ; Jian-Dong Jiang,
| | - Yu-Wei Ding
- Department of Virology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Lu-Lu Wang
- Department of Virology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jian-Dong Jiang
- Department of Virology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
- *Correspondence: Gang Ren, ; Jian-Dong Jiang,
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8
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Blocking AMPK β1 myristoylation enhances AMPK activity and protects mice from high-fat diet-induced obesity and hepatic steatosis. Cell Rep 2022; 41:111862. [PMID: 36543129 DOI: 10.1016/j.celrep.2022.111862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 10/07/2022] [Accepted: 11/30/2022] [Indexed: 12/24/2022] Open
Abstract
AMP-activated protein kinase (AMPK) is a master regulator of cellular energy homeostasis and a therapeutic target for metabolic diseases. Co/post-translational N-myristoylation of glycine-2 (Gly2) of the AMPK β subunit has been suggested to regulate the distribution of the kinase between the cytosol and membranes through a "myristoyl switch" mechanism. However, the relevance of AMPK myristoylation for metabolic signaling in cells and in vivo is unclear. Here, we generated knockin mice with a Gly2-to-alanine point mutation of AMPKβ1 (β1-G2A). We demonstrate that non-myristoylated AMPKβ1 has reduced stability but is associated with increased kinase activity and phosphorylation of the Thr172 activation site in the AMPK α subunit. Using proximity ligation assays, we show that loss of β1 myristoylation impedes colocalization of the phosphatase PPM1A/B with AMPK in cells. Mice carrying the β1-G2A mutation have improved metabolic health with reduced adiposity, hepatic lipid accumulation, and insulin resistance under conditions of high-fat diet-induced obesity.
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9
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Structure-function analysis of the AMPK activator SC4 and identification of a potent pan AMPK activator. Biochem J 2022; 479:1181-1204. [PMID: 35552369 PMCID: PMC9317966 DOI: 10.1042/bcj20220067] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 05/11/2022] [Accepted: 05/13/2022] [Indexed: 11/17/2022]
Abstract
The AMP-activated protein kinase (AMPK) αβγ heterotrimer is a primary cellular energy sensor and central regulator of energy homeostasis. Activating skeletal muscle AMPK with small molecule drugs improves glucose uptake and provides an opportunity for new strategies to treat type 2 diabetes and insulin resistance, with recent genetic and pharmacological studies indicating the α2β2γ1 isoform combination as the heterotrimer complex primarily responsible. With the goal of developing α2β2-specific activators, here we perform structure/function analysis of the 2-hydroxybiphenyl group of SC4, an activator with tendency for α2-selectivity that is also capable of potently activating β2 complexes. Substitution of the LHS 2-hydroxyphenyl group with polar-substituted cyclohexene-based probes resulted in two AMPK agonists, MSG010 and MSG011, which did not display α2-selectivity when screened against a panel of AMPK complexes. By radiolabel kinase assay, MSG010 and MSG011 activated α2β2γ1 AMPK with one order of magnitude greater potency than the pan AMPK activator MK-8722. A crystal structure of MSG011 complexed to AMPK α2β1γ1 revealed a similar binding mode to SC4 and the potential importance of an interaction between the SC4 2-hydroxyl group and α2-Lys31 for directing α2-selectivity. MSG011 induced robust AMPK signalling in mouse primary hepatocytes and commonly used cell lines, and in most cases this occurred in the absence of changes in phosphorylation of the kinase activation loop residue α-Thr172, a classical marker of AMP-induced AMPK activity. These findings will guide future design of α2β2-selective AMPK activators, that we hypothesise may avoid off-target complications associated with indiscriminate activation of AMPK throughout the body.
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10
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Sanders MJ, Ratinaud Y, Neopane K, Bonhoure N, Day EA, Ciclet O, Lassueur S, Naranjo Pinta M, Deak M, Brinon B, Christen S, Steinberg GR, Barron D, Sakamoto K. Natural (dihydro)phenanthrene plant compounds are direct activators of AMPK through its allosteric drug and metabolite-binding site. J Biol Chem 2022; 298:101852. [PMID: 35331736 PMCID: PMC9108889 DOI: 10.1016/j.jbc.2022.101852] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/15/2022] [Accepted: 03/16/2022] [Indexed: 11/26/2022] Open
Abstract
AMP-activated protein kinase (AMPK) is a central energy sensor that coordinates the response to energy challenges to maintain cellular ATP levels. AMPK is a potential therapeutic target for treating metabolic disorders, and several direct synthetic activators of AMPK have been developed that show promise in preclinical models of type 2 diabetes. These compounds have been shown to regulate AMPK through binding to a novel allosteric drug and metabolite (ADaM)–binding site on AMPK, and it is possible that other molecules might similarly bind this site. Here, we performed a high-throughput screen with natural plant compounds to identify such direct allosteric activators of AMPK. We identified a natural plant dihydrophenathrene, Lusianthridin, which allosterically activates and protects AMPK from dephosphorylation by binding to the ADaM site. Similar to other ADaM site activators, Lusianthridin showed preferential activation of AMPKβ1-containing complexes in intact cells and was unable to activate an AMPKβ1 S108A mutant. Lusianthridin dose-dependently increased phosphorylation of acetyl-CoA carboxylase in mouse primary hepatocytes, which led to a corresponding decrease in de novo lipogenesis. This ability of Lusianthridin to inhibit lipogenesis was impaired in hepatocytes from β1 S108A knock-in mice and mice bearing a mutation at the AMPK phosphorylation site of acetyl-CoA carboxylase 1/2. Finally, we show that activation of AMPK by natural compounds extends to several analogs of Lusianthridin and the related chemical series, phenanthrenes. The emergence of natural plant compounds that regulate AMPK through the ADaM site raises the distinct possibility that other natural compounds share a common mechanism of regulation.
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Affiliation(s)
- Matthew J Sanders
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland.
| | - Yann Ratinaud
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Katyayanee Neopane
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland; School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Nicolas Bonhoure
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Emily A Day
- Centre for Metabolism, Obesity, and Diabetes Research, McMaster University, Hamilton, Ontario, Canada; Department of Medicine and Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Olivier Ciclet
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Steve Lassueur
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Martine Naranjo Pinta
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Maria Deak
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Benjamin Brinon
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Stefan Christen
- Nestle Institute of Food Safety and Analytical Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Gregory R Steinberg
- Centre for Metabolism, Obesity, and Diabetes Research, McMaster University, Hamilton, Ontario, Canada; Department of Medicine and Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Denis Barron
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland
| | - Kei Sakamoto
- Nestlé Institute of Health Sciences, Nestlé Research, Société des Produits Nestlé S.A., Lausanne, Switzerland; Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark.
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11
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Wang H, Zheng A, Arias EB, Cartee GD. Prior AICAR induces elevated glucose uptake concomitant with greater γ3-AMPK activation and reduced membrane cholesterol in skeletal muscle from 26-month-old rats. Facets (Ott) 2022; 7:774-791. [PMID: 36381195 PMCID: PMC9648397 DOI: 10.1139/facets-2021-0166] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2024] Open
Abstract
Attenuated skeletal muscle glucose uptake (GU) has been observed with advancing age. It is important to elucidate the mechanisms linked to interventions that oppose this detrimental outcome. Earlier research using young rodents and (or) cultured myocytes reported that treatment with 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR; an AMP-activated protein kinase (AMPK) activator) can increase γ3-AMPK activity and reduce membrane cholesterol content, each of which has been proposed to elevate GU. However, the effect of AICAR treatment on γ3-AMPK activity and membrane cholesterol in skeletal muscle of aged animals has not been reported. Our purpose was to evaluate the effects of AICAR treatment on these potential mechanisms for enhanced glucose uptake in the skeletal muscle of aged animals. Epitrochlearis muscles from 26-27-month-old male rats were isolated and incubated ± AICAR, followed by 3 h incubation without AICAR, and then incubation with 3-O-methyl-[3 H] glucose (to assess GU ± insulin). Muscles were also analyzed for γ3-AMPK activity and membrane cholesterol content. Prior AICAR treatment led to increased γ3-AMPK activity, reduced membrane cholesterol content, and enhanced glucose uptake in skeletal muscle from aged rats. These observations revealed that two potential mechanisms for greater GU previously observed in younger animals and (or) cell models are also potentially relevant for enhanced GU by muscles from older animals.
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Affiliation(s)
- Haiyan Wang
- Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Amy Zheng
- Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Edward B. Arias
- Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Gregory D. Cartee
- Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
- Institute of Gerontology, University of Michigan, Ann Arbor, MI, USA
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12
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Jørgensen NO, Kjøbsted R, Larsen MR, Birk JB, Andersen NR, Albuquerque B, Schjerling P, Miller R, Carling D, Pehmøller CK, Wojtaszewski JFP. Direct small molecule ADaM-site AMPK activators reveal an AMPKγ3-independent mechanism for blood glucose lowering. Mol Metab 2021; 51:101259. [PMID: 34033941 PMCID: PMC8381035 DOI: 10.1016/j.molmet.2021.101259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 05/13/2021] [Accepted: 05/14/2021] [Indexed: 10/31/2022] Open
Abstract
OBJECTIVE Skeletal muscle is an attractive target for blood glucose-lowering pharmacological interventions. Oral dosing of small molecule direct pan-activators of AMPK that bind to the allosteric drug and metabolite (ADaM) site, lowers blood glucose through effects in skeletal muscle. The molecular mechanisms responsible for this effect are not described in detail. This study aimed to illuminate the mechanisms by which ADaM-site activators of AMPK increase glucose uptake in skeletal muscle. Further, we investigated the consequence of co-stimulating muscles with two types of AMPK activators i.e., ADaM-site binding small molecules and the prodrug AICAR. METHODS The effect of the ADaM-site binding small molecules (PF739 and 991), AICAR or co-stimulation with PF739 or 991 and AICAR on muscle glucose uptake was investigated ex vivo in m. extensor digitorum longus (EDL) excised from muscle-specific AMPKα1α2 as well as whole-body AMPKγ3-deficient mouse models. In vitro complex-specific AMPK activity was measured by immunoprecipitation and molecular signaling was assessed by western blotting in muscle lysate. To investigate the transferability of these studies, we treated diet-induced obese mice in vivo with PF739 and measured complex-specific AMPK activation in skeletal muscle. RESULTS Incubation of skeletal muscle with PF739 or 991 increased skeletal muscle glucose uptake in a dose-dependent manner. Co-incubating PF739 or 991 with a maximal dose of AICAR increased glucose uptake to a greater extent than any of the treatments alone. Neither PF739 nor 991 increased AMPKα2β2γ3 activity to the same extent as AICAR, while co-incubation led to potentiated effects on AMPKα2β2γ3 activation. In muscle from AMPKγ3 KO mice, AICAR-stimulated glucose uptake was ablated. In contrast, the effect of PF739 or 991 on glucose uptake was not different between WT and AMPKγ3 KO muscles. In vivo PF739 treatment lowered blood glucose levels and increased muscle AMPKγ1-complex activity 2-fold, while AMPKα2β2γ3 activity was not affected. CONCLUSIONS ADaM-site binding AMPK activators increase glucose uptake independently of AMPKγ3. Co-incubation with PF739 or 991 and AICAR potentiates the effects on muscle glucose uptake and AMPK activation. In vivo, PF739 lowers blood glucose and selectively activates muscle AMPKγ1-complexes. Collectively, this suggests that pharmacological activation of AMPKγ1-containing complexes in skeletal muscle can increase glucose uptake and can lead to blood glucose lowering.
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Affiliation(s)
- Nicolas O Jørgensen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Rasmus Kjøbsted
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Magnus R Larsen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Jesper B Birk
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Nicoline R Andersen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Bina Albuquerque
- Internal Medicine Research Unit, Pfizer Global Research and Development, Cambridge, MA, USA
| | - Peter Schjerling
- Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Copenhagen University Hospital - Bispebjerg and Frederiksberg, Copenhagen, Denmark; Center for Healthy Aging, Institute for Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Russell Miller
- Internal Medicine Research Unit, Pfizer Global Research and Development, Cambridge, MA, USA
| | - David Carling
- MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital, London W12 0NN, UK
| | - Christian K Pehmøller
- Internal Medicine Research Unit, Pfizer Global Research and Development, Cambridge, MA, USA
| | - Jørgen F P Wojtaszewski
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
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13
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Ahwazi D, Neopane K, Markby GR, Kopietz F, Ovens AJ, Dall M, Hassing AS, Gräsle P, Alshuweishi Y, Treebak JT, Salt IP, Göransson O, Zeqiraj E, Scott JW, Sakamoto K. Investigation of the specificity and mechanism of action of the ULK1/AMPK inhibitor SBI-0206965. Biochem J 2021; 478:2977-2997. [PMID: 34259310 PMCID: PMC8370752 DOI: 10.1042/bcj20210284] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 07/12/2021] [Accepted: 07/13/2021] [Indexed: 11/17/2022]
Abstract
SBI-0206965, originally identified as an inhibitor of the autophagy initiator kinase ULK1, has recently been reported as a more potent and selective AMP-activated protein kinase (AMPK) inhibitor relative to the widely used, but promiscuous inhibitor Compound C/Dorsomorphin. Here, we studied the effects of SBI-0206965 on AMPK signalling and metabolic readouts in multiple cell types, including hepatocytes, skeletal muscle cells and adipocytes. We observed SBI-0206965 dose dependently attenuated AMPK activator (991)-stimulated ACC phosphorylation and inhibition of lipogenesis in hepatocytes. SBI-0206965 (≥25 μM) modestly inhibited AMPK signalling in C2C12 myotubes, but also inhibited insulin signalling, insulin-mediated/AMPK-independent glucose uptake, and AICA-riboside uptake. We performed an extended screen of SBI-0206965 against a panel of 140 human protein kinases in vitro, which showed SBI-0206965 inhibits several kinases, including members of AMPK-related kinases (NUAK1, MARK3/4), equally or more potently than AMPK or ULK1. This screen, together with molecular modelling, revealed that most SBI-0206965-sensitive kinases contain a large gatekeeper residue with a preference for methionine at this position. We observed that mutation of the gatekeeper methionine to a smaller side chain amino acid (threonine) rendered AMPK and ULK1 resistant to SBI-0206965 inhibition. These results demonstrate that although SBI-0206965 has utility for delineating AMPK or ULK1 signalling and cellular functions, the compound potently inhibits several other kinases and critical cellular functions such as glucose and nucleoside uptake. Our study demonstrates a role for the gatekeeper residue as a determinant of the inhibitor sensitivity and inhibitor-resistant mutant forms could be exploited as potential controls to probe specific cellular effects of SBI-0206965.
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Affiliation(s)
- Danial Ahwazi
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Katyayanee Neopane
- Nestlé Institute of Health Sciences, Nestlé Research, Societé Produit de Nestlé S.A
- School of Life Sciences, École polytechnique fédérale de Lausanne, Lausanne, Switzerland
| | - Greg R. Markby
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Franziska Kopietz
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Ashley J. Ovens
- St Vincent's Institute of Medical Research, Fitzroy, Melbourne, Australia
- Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia
| | - Morten Dall
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Anna S. Hassing
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Pamina Gräsle
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Yazeed Alshuweishi
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, U.K
- Department of Clinical Laboratory Sciences, King Saud University, Riyadh, Kingdom of Saudi Arabia
| | - Jonas T. Treebak
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Ian P. Salt
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, U.K
| | - Olga Göransson
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Elton Zeqiraj
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, U.K
| | - John W. Scott
- St Vincent's Institute of Medical Research, Fitzroy, Melbourne, Australia
- Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia
- The Florey Institute of Neuroscience and Mental Health, Parkville, Melbourne, Australia
| | - Kei Sakamoto
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
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