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Chan MP, Takenaka N, Abe Y, Satoh T. Insulin-stimulated translocation of the fatty acid transporter CD36 to the plasma membrane is mediated by the small GTPase Rac1 in adipocytes. Cell Signal 2024; 117:111102. [PMID: 38365113 DOI: 10.1016/j.cellsig.2024.111102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 02/10/2024] [Accepted: 02/13/2024] [Indexed: 02/18/2024]
Abstract
Cluster of differentiation 36 (CD36) is a scavenger receptor (SR), recognizing diverse extracellular ligands in various types of mammalian cells. Long-chain fatty acids (FAs), which are important constituents of phospholipids and triglycerides, also utilize CD36 as a predominant membrane transporter, being incorporated from the circulation across the plasma membrane in several cell types, including cardiac and skeletal myocytes and adipocytes. CD36 is localized in intracellular vesicles as well as the plasma membrane, and its distribution is modulated by extracellular stimuli. Herein, we aimed to clarify the molecular basis of insulin-stimulated translocation of CD36, which leads to the enhanced uptake of long-chain FAs, in adipocytes. To this end, we developed a novel exofacial epitope-tagged reporter to specifically detect cell surface-localized CD36. By employing this reporter, we demonstrate that the small GTPase Rac1 plays a pivotal role in insulin-stimulated translocation of CD36 to the plasma membrane in 3T3-L1 adipocytes. Additionally, phosphoinositide 3-kinase and the protein kinase Akt2 are shown to be involved in the regulation of Rac1. Downstream of Rac1, another small GTPase RalA directs CD36 translocation. Collectively, these results suggest that CD36 is translocated to the plasma membrane by insulin through mechanisms similar to those for the glucose transporter GLUT4 in adipocytes.
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Affiliation(s)
- Man Piu Chan
- Laboratory of Cell Biology, Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Sakai 599-8531, Japan
| | - Nobuyuki Takenaka
- Laboratory of Cell Biology, Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Sakai 599-8531, Japan
| | - Yuki Abe
- Laboratory of Cell Biology, Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Sakai 599-8531, Japan
| | - Takaya Satoh
- Laboratory of Cell Biology, Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Sakai 599-8531, Japan.
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2
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Chan MP, Takenaka N, Satoh T. Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse. Int J Mol Sci 2023; 24:11531. [PMID: 37511290 PMCID: PMC10380855 DOI: 10.3390/ijms241411531] [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] [Received: 05/31/2023] [Revised: 07/05/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
Insulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4. The small GTPase Rac1 acts as a switch of signal transduction that regulates GLUT4 translocation to the plasma membrane following insulin stimulation. However, it remains obscure whether signaling cascades upstream and downstream of Rac1 in skeletal muscle are impaired by obesity that causes insulin resistance and type 2 diabetes. In an attempt to clarify this point, we investigated Rac1 signaling in the leptin-deficient (Lepob/ob) mouse model. Here, we show that insulin-stimulated GLUT4 translocation and Rac1 activation are almost completely abolished in Lepob/ob mouse skeletal muscle. Phosphorylation of the protein kinase Akt2 and plasma membrane translocation of the guanine nucleotide exchange factor FLJ00068 following insulin stimulation were also diminished in Lepob/ob mice. On the other hand, the activation of another small GTPase RalA, which acts downstream of Rac1, by the constitutively activated form of Akt2, FLJ00068, or Rac1, was partially abrogated in Lepob/ob mice. Taken together, we conclude that insulin-stimulated glucose uptake is impaired by two mechanisms in Lepob/ob mouse skeletal muscle: one is the complete inhibition of Akt2-mediated activation of Rac1, and the other is the partial inhibition of RalA activation downstream of Rac1.
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Affiliation(s)
| | | | - Takaya Satoh
- Laboratory of Cell Biology, Department of Biological Chemistry, Graduate School of Science, Osaka Metropolitan University, Sakai 599-8531, Japan; (M.P.C.); (N.T.)
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Møller LLV, Ali MS, Davey J, Raun SH, Andersen NR, Long JZ, Qian H, Jeppesen JF, Henriquez-Olguin C, Frank E, Jensen TE, Højlund K, Wojtaszewski JFP, Nielsen J, Chiu TT, Jedrychowski MP, Gregorevic P, Klip A, Richter EA, Sylow L. The Rho guanine dissociation inhibitor α inhibits skeletal muscle Rac1 activity and insulin action. Proc Natl Acad Sci U S A 2023; 120:e2211041120. [PMID: 37364105 PMCID: PMC10318982 DOI: 10.1073/pnas.2211041120] [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] [Received: 07/11/2022] [Accepted: 05/22/2023] [Indexed: 06/28/2023] Open
Abstract
The molecular events governing skeletal muscle glucose uptake have pharmacological potential for managing insulin resistance in conditions such as obesity, diabetes, and cancer. With no current pharmacological treatments to target skeletal muscle insulin sensitivity, there is an unmet need to identify the molecular mechanisms that control insulin sensitivity in skeletal muscle. Here, the Rho guanine dissociation inhibitor α (RhoGDIα) is identified as a point of control in the regulation of insulin sensitivity. In skeletal muscle cells, RhoGDIα interacted with, and thereby inhibited, the Rho GTPase Rac1. In response to insulin, RhoGDIα was phosphorylated at S101 and Rac1 dissociated from RhoGDIα to facilitate skeletal muscle GLUT4 translocation. Accordingly, siRNA-mediated RhoGDIα depletion increased Rac1 activity and elevated GLUT4 translocation. Consistent with RhoGDIα's inhibitory effect, rAAV-mediated RhoGDIα overexpression in mouse muscle decreased insulin-stimulated glucose uptake and was detrimental to whole-body glucose tolerance. Aligning with RhoGDIα's negative role in insulin sensitivity, RhoGDIα protein content was elevated in skeletal muscle from insulin-resistant patients with type 2 diabetes. These data identify RhoGDIα as a clinically relevant controller of skeletal muscle insulin sensitivity and whole-body glucose homeostasis, mechanistically by modulating Rac1 activity.
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Affiliation(s)
- Lisbeth L. V. Møller
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
- Department of Biomedical Sciences, Faculty of Medical and Health Sciences, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Mona S. Ali
- Department of Biomedical Sciences, Faculty of Medical and Health Sciences, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Jonathan Davey
- The Centre for Muscle Research, Department of Physiology, The University of Melbourne, Parkville, VIC3010, Australia
| | - Steffen H. Raun
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
- Department of Biomedical Sciences, Faculty of Medical and Health Sciences, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Nicoline R. Andersen
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Jonathan Z. Long
- Department of Pathology, Stanford University School of Medicine and Stanford, Stanford University, Stanford, CA94305
| | - Hongwei Qian
- The Centre for Muscle Research, Department of Physiology, The University of Melbourne, Parkville, VIC3010, Australia
| | - Jacob F. Jeppesen
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Carlos Henriquez-Olguin
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
- Exercise Science Laboratory, Faculty of Medicine, Universidad Finis Terrae, 7501015Santiago, Chile
| | - Emma Frank
- Department of Biomedical Sciences, Faculty of Medical and Health Sciences, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Thomas E. Jensen
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Kurt Højlund
- Steno Diabetes Center Odense, Odense University Hospital, 5000Odense C, Denmark
- Department of Clinical Research, University of Southern Denmark, 5000Odense C, Denmark
- Department of Molecular Medicine, University of Southern Denmark, 5000Odense C, Denmark
| | - Jørgen F. P. Wojtaszewski
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Joachim Nielsen
- Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, 5230Odense M, Denmark
| | - Tim T. Chiu
- Cell Biology Program, The Hospital for Sick Children, Toronto, ONM5G 0A4, Canada
- Department of Biochemistry, University of Toronto, Toronto, ONM5S 1A1, Canada
- Department of Physiology, University of Toronto, Toronto, ONM5S 1A1, Canada
- Department of Paediatrics, University of Toronto, Toronto, ONM5S 1A1, Canada
| | - Mark P. Jedrychowski
- Department of Cell Biology, Harvard Medical School, Boston, MA02115
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA02215
| | - Paul Gregorevic
- The Centre for Muscle Research, Department of Physiology, The University of Melbourne, Parkville, VIC3010, Australia
| | - Amira Klip
- Cell Biology Program, The Hospital for Sick Children, Toronto, ONM5G 0A4, Canada
- Department of Biochemistry, University of Toronto, Toronto, ONM5S 1A1, Canada
- Department of Physiology, University of Toronto, Toronto, ONM5S 1A1, Canada
- Department of Paediatrics, University of Toronto, Toronto, ONM5S 1A1, Canada
| | - Erik A. Richter
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
| | - Lykke Sylow
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, 2200Copenhagen N, Denmark
- Department of Biomedical Sciences, Faculty of Medical and Health Sciences, University of Copenhagen, 2200Copenhagen N, Denmark
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Regulation of De Novo Lipid Synthesis by the Small GTPase Rac1 in the Adipogenic Differentiation of Progenitor Cells from Mouse White Adipose Tissue. Int J Mol Sci 2023; 24:ijms24054608. [PMID: 36902044 PMCID: PMC10003776 DOI: 10.3390/ijms24054608] [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: 01/07/2023] [Revised: 02/19/2023] [Accepted: 02/21/2023] [Indexed: 03/02/2023] Open
Abstract
White adipocytes act as lipid storage, and play an important role in energy homeostasis. The small GTPase Rac1 has been implicated in the regulation of insulin-stimulated glucose uptake in white adipocytes. Adipocyte-specific rac1-knockout (adipo-rac1-KO) mice exhibit atrophy of subcutaneous and epididymal white adipose tissue (WAT); white adipocytes in these mice are significantly smaller than controls. Here, we aimed to investigate the mechanisms underlying the aberrations in the development of Rac1-deficient white adipocytes by employing in vitro differentiation systems. Cell fractions containing adipose progenitor cells were obtained from WAT and subjected to treatments that induced differentiation into adipocytes. In concordance with observations in vivo, the generation of lipid droplets was significantly attenuated in Rac1-deficient adipocytes. Notably, the induction of various enzymes responsible for de novo synthesis of fatty acids and triacylglycerol in the late stage of adipogenic differentiation was almost completely suppressed in Rac1-deficient adipocytes. Furthermore, the expression and activation of transcription factors, such as the CCAAT/enhancer-binding protein (C/EBP) β, which is required for the induction of lipogenic enzymes, were largely inhibited in Rac1-deficient cells in both early and late stages of differentiation. Altogether, Rac1 is responsible for adipogenic differentiation, including lipogenesis, through the regulation of differentiation-related transcription.
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Class I PI3K Biology. Curr Top Microbiol Immunol 2022; 436:3-49. [DOI: 10.1007/978-3-031-06566-8_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Hasegawa K, Takenaka N, Tanida K, Chan MP, Sakata M, Aiba A, Satoh T. Atrophy of White Adipose Tissue Accompanied with Decreased Insulin-Stimulated Glucose Uptake in Mice Lacking the Small GTPase Rac1 Specifically in Adipocytes. Int J Mol Sci 2021; 22:ijms221910753. [PMID: 34639094 PMCID: PMC8509237 DOI: 10.3390/ijms221910753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 09/28/2021] [Accepted: 09/29/2021] [Indexed: 12/03/2022] Open
Abstract
Insulin stimulates glucose uptake in adipose tissue and skeletal muscle by inducing plasma membrane translocation of the glucose transporter GLUT4. Although the small GTPase Rac1 is a key regulator downstream of phosphoinositide 3-kinase (PI3K) and the protein kinase Akt2 in skeletal muscle, it remains unclear whether Rac1 also regulates glucose uptake in white adipocytes. Herein, we investigated the physiological role of Rac1 in white adipocytes by employing adipocyte-specific rac1 knockout (adipo-rac1-KO) mice. Subcutaneous and epididymal white adipose tissues (WATs) in adipo-rac1-KO mice showed significant reductions in size and weight. Actually, white adipocytes lacking Rac1 were smaller than controls. Insulin-stimulated glucose uptake and GLUT4 translocation were abrogated in rac1-KO white adipocytes. On the other hand, GLUT4 translocation was augmented by constitutively activated PI3K or Akt2 in control, but not in rac1-KO, white adipocytes. Similarly, to skeletal muscle, the involvement of another small GTPase RalA downstream of Rac1 was demonstrated. In addition, mRNA levels of various lipogenic enzymes were down-regulated in rac1-KO white adipocytes. Collectively, these results suggest that Rac1 is implicated in insulin-dependent glucose uptake and lipogenesis in white adipocytes, and reduced insulin responsiveness due to the deficiency of Rac1 may be a likely explanation for atrophy of WATs.
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Affiliation(s)
- Kiko Hasegawa
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan; (K.H.); (N.T.); (K.T.); (M.P.C.); (M.S.)
| | - Nobuyuki Takenaka
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan; (K.H.); (N.T.); (K.T.); (M.P.C.); (M.S.)
| | - Kenya Tanida
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan; (K.H.); (N.T.); (K.T.); (M.P.C.); (M.S.)
| | - Man Piu Chan
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan; (K.H.); (N.T.); (K.T.); (M.P.C.); (M.S.)
| | - Mizuki Sakata
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan; (K.H.); (N.T.); (K.T.); (M.P.C.); (M.S.)
| | - Atsu Aiba
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan;
| | - Takaya Satoh
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan; (K.H.); (N.T.); (K.T.); (M.P.C.); (M.S.)
- Correspondence: ; Tel.: +81-72-254-7650
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7
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Maier G, Delezie J, Westermark PO, Santos G, Ritz D, Handschin C. Transcriptomic, proteomic and phosphoproteomic underpinnings of daily exercise performance and zeitgeber activity of training in mouse muscle. J Physiol 2021; 600:769-796. [PMID: 34142717 PMCID: PMC9290843 DOI: 10.1113/jp281535] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 06/11/2021] [Indexed: 12/14/2022] Open
Abstract
Key points Maximal endurance performance is greater in the early daytime. Timed exercise differentially alters the muscle transcriptome and (phospho)‐proteome. Early daytime exercise triggers energy provisioning and tissue regeneration. Early night‐time exercise activates stress‐related and catabolic pathways. Scheduled training has limited effects on the muscle and liver circadian clocks.
Abstract Timed physical activity might potentiate the health benefits of training. The underlying signalling events triggered by exercise at different times of day are, however, poorly understood. Here, we found that time‐dependent variations in maximal treadmill exercise capacity of naïve mice were associated with energy stores, mostly hepatic glycogen levels. Importantly, running at different times of day resulted in a vastly different activation of signalling pathways, e.g. related to stress response, vesicular trafficking, repair and regeneration. Second, voluntary wheel running at the opposite phase of the dark, feeding period surprisingly revealed a minimal zeitgeber (i.e. phase‐shifting) effect of training on the muscle clock. This integrated study provides important insights into the circadian regulation of endurance performance and the control of the circadian clock by exercise. In future studies, these results could contribute to better understanding circadian aspects of training design in athletes and the application of chrono‐exercise‐based interventions in patients.
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Affiliation(s)
- Geraldine Maier
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Julien Delezie
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Pål O Westermark
- Leibniz-Institut für Nutztierbiologie, Institut für Genetik und Biometrie, Wilhelm-Stahl-Allee 2, Dummerstorf, D-18196, Germany
| | - Gesa Santos
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Danilo Ritz
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Christoph Handschin
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
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Takenaka N, Nakao M, Hasegawa K, Chan MP, Satoh T. The guanine nucleotide exchange factor FLJ00068 activates Rac1 in adipocyte insulin signaling. FEBS Lett 2020; 594:4370-4380. [PMID: 32978791 DOI: 10.1002/1873-3468.13939] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/31/2020] [Accepted: 09/10/2020] [Indexed: 12/26/2022]
Abstract
Insulin stimulates glucose uptake via the translocation of the glucose transporter GLUT4 to the plasma membrane in adipocytes. Several lines of evidence suggest that the small GTPase Rac1 plays an important role in insulin-stimulated glucose uptake in skeletal muscle and adipocytes. The purpose of this study is to investigate the mechanisms whereby Rac1 is regulated in adipocyte insulin signaling. Here, we show that knockdown of the guanine nucleotide exchange factor FLJ00068 inhibits Rac1 activation and GLUT4 translocation by insulin and a constitutively activated form of the protein kinase Akt2. Furthermore, constitutively activated FLJ00068 induced Rac1 activation and Rac1-dependent GLUT4 translocation. Collectively, these results suggest the involvement of FLJ00068 downstream of Akt2 in insulin-stimulated glucose uptake signaling in adipocytes.
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Affiliation(s)
- Nobuyuki Takenaka
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Japan
| | - Mika Nakao
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Japan
| | - Kiko Hasegawa
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Japan
| | - Man Piu Chan
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Japan
| | - Takaya Satoh
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Japan
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9
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Møller LLV, Jaurji M, Kjøbsted R, Joseph GA, Madsen AB, Knudsen JR, Lundsgaard AM, Andersen NR, Schjerling P, Jensen TE, Krauss RS, Richter EA, Sylow L. Insulin-stimulated glucose uptake partly relies on p21-activated kinase (PAK)2, but not PAK1, in mouse skeletal muscle. J Physiol 2020; 598:5351-5377. [PMID: 32844438 DOI: 10.1113/jp280294] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 08/24/2020] [Indexed: 12/28/2022] Open
Abstract
KEY POINTS Muscle-specific genetic ablation of p21-activated kinase (PAK)2, but not whole-body PAK1 knockout, impairs glucose tolerance in mice. Insulin-stimulated glucose uptake partly relies on PAK2 in glycolytic extensor digitorum longus muscle By contrast to previous reports, PAK1 is dispensable for insulin-stimulated glucose uptake in mouse muscle. ABSTRACT The group I p21-activated kinase (PAK) isoforms PAK1 and PAK2 are activated in response to insulin in skeletal muscle and PAK1/2 signalling is impaired in insulin-resistant mouse and human skeletal muscle. Interestingly, PAK1 has been suggested to be required for insulin-stimulated glucose transporter 4 translocation in mouse skeletal muscle. Therefore, the present study aimed to examine the role of PAK1 in insulin-stimulated muscle glucose uptake. The pharmacological inhibitor of group I PAKs, IPA-3 partially reduced (-20%) insulin-stimulated glucose uptake in isolated mouse soleus muscle (P < 0.001). However, because there was no phenotype with genetic ablation of PAK1 alone, consequently, the relative requirement for PAK1 and PAK2 in whole-body glucose homeostasis and insulin-stimulated muscle glucose uptake was investigated. Whole-body respiratory exchange ratio was largely unaffected in whole-body PAK1 knockout (KO), muscle-specific PAK2 KO and in mice with combined whole-body PAK1 KO and muscle-specific PAK2 KO. By contrast, glucose tolerance was mildly impaired in mice lacking PAK2 specifically in muscle, but not PAK1 KO mice. Moreover, while PAK1 KO muscles displayed normal insulin-stimulated glucose uptake in vivo and in isolated muscle, insulin-stimulated glucose uptake was slightly reduced in isolated glycolytic extensor digitorum longus muscle lacking PAK2 alone (-18%) or in combination with PAK1 KO (-12%) (P < 0.05). In conclusion, glucose tolerance and insulin-stimulated glucose uptake partly rely on PAK2 in glycolytic mouse muscle, whereas PAK1 is dispensable for whole-body glucose homeostasis and insulin-stimulated muscle glucose uptake.
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Affiliation(s)
- Lisbeth L V Møller
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Merna Jaurji
- 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
| | - Giselle A Joseph
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mount Sinai, NY, USA
| | - Agnete B Madsen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Jonas R Knudsen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.,Microsystems Laboratory 2, Institute of Microengineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Anne-Marie Lundsgaard
- 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
| | - Peter Schjerling
- Institute of Sports Medicine, Department of Orthopaedic Surgery M, Bispebjerg Hospital, Copenhagen, Denmark.,Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Thomas E Jensen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Robert S Krauss
- Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mount Sinai, NY, USA
| | - Erik A Richter
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Lykke Sylow
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
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10
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Satoh T, Takenaka N. A critical role for the small GTPase Rac1 in insulin signaling that regulates glucose uptake in skeletal muscle. RESEARCH ON CHEMICAL INTERMEDIATES 2019. [DOI: 10.1007/s11164-019-03976-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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11
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A Crucial Role for the Small GTPase Rac1 Downstream of the Protein Kinase Akt2 in Insulin Signaling that Regulates Glucose Uptake in Mouse Adipocytes. Int J Mol Sci 2019; 20:ijms20215443. [PMID: 31683681 PMCID: PMC6861951 DOI: 10.3390/ijms20215443] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 10/29/2019] [Indexed: 01/10/2023] Open
Abstract
Insulin-stimulated glucose uptake is mediated by translocation of the glucose transporter GLUT4 to the plasma membrane in adipocytes and skeletal muscle cells. In both types of cells, phosphoinositide 3-kinase and the protein kinase Akt2 have been implicated as critical regulators. In skeletal muscle, the small GTPase Rac1 plays an important role downstream of Akt2 in the regulation of insulin-stimulated glucose uptake. However, the role for Rac1 in adipocytes remains controversial. Here, we show that Rac1 is required for insulin-dependent GLUT4 translocation also in adipocytes. A Rac1-specific inhibitor almost completely suppressed GLUT4 translocation induced by insulin or a constitutively activated mutant of phosphoinositide 3-kinase or Akt2. Constitutively activated Rac1 also enhanced GLUT4 translocation. Insulin-induced, but not constitutively activated Rac1-induced, GLUT4 translocation was abrogated by inhibition of phosphoinositide 3-kinase or Akt2. On the other hand, constitutively activated Akt2 caused Rac1 activation, and insulin-induced Rac1 activation was suppressed by an Akt2-specific inhibitor. Moreover, GLUT4 translocation induced by a constitutively activated mutant of Akt2 or Rac1 was diminished by knockdown of another small GTPase RalA. RalA was activated by a constitutively activated mutant of Akt2 or Rac1, and insulin-induced RalA activation was suppressed by an Akt2- or Rac1-specific inhibitor. Collectively, these results suggest that Rac1 plays an important role in the regulation of insulin-dependent GLUT4 translocation downstream of Akt2, leading to RalA activation in adipocytes.
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12
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Chi B, Fan X, Li Z, Liu G, Zhang G, Xu H, Li Z, Lian Q, Xing L, Tian F. Identification of Gli1-interacting proteins during simvastatin-stimulated osteogenic differentiation of bone marrow mesenchymal stem cells. J Cell Biochem 2019; 120:18979-18994. [PMID: 31245876 DOI: 10.1002/jcb.29221] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 05/31/2019] [Accepted: 05/31/2019] [Indexed: 01/20/2023]
Abstract
Simvastatin has been shown to promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Our study aimed to illuminate the underlying mechanism, with a specific focus on the role of Hedgehog signaling in this process. BMSCs cultured with or without 10-7 mol/L simvastatin were subjected to evaluation of osteogenic differentiation capacity. Osteogenic markers such as type 1 collagen (COL1) and osteocalcin (OCN), as well as key molecules of Hedgehog signaling molecules, were examined by Western blot and real-time polymerase chain reaction (PCR). Co-immunoprecipitation and mass spectrometry assays were applied to screen for Gli1-interacting proteins. Cyclopamine (Cpn) was used as a Hedgehog signaling inhibitor. Our results indicated that simvastatin increased alkaline phosphatase (ALP) activity; mineralization of extracellular matrix; mRNA expression of ALP, COL1, and OCN; and expression and nuclear translocation of Gli1. Contrasting effects were observed in Cpn-exposed groups, but were partially rescued by the simvastatin treatment. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses indicated that Gli1-interacting proteins were primarily associated with mitogen-activated protein kinase (MAPK) (P = 7.04E-04 ), hippo, insulin, and glucagon signaling. Further, hub genes identified by protein-protein interaction network analysis included Gli1-interacting proteins such as Ppp2r1a, Rac1, Etf1, and XPO1/CRM1. In summary, the current study showed that the mechanism by which simvastatin stimulates osteogenic differentiation of BMSCs involves activation of Hedgehog signaling, as indicated by interactions with Gli1 and, most notably, the MAPK signaling pathway.
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Affiliation(s)
- Bojing Chi
- Medical Research Center, North China University of Science and Technology, Tangshan, China.,Department of Geriatrics, Affiliated Hospital of North China University of Science and Technology, Tangshan, China
| | - Xinhao Fan
- Department of Stomatology, Kailuan General Hospital, Tangshan, China
| | - Zhengxiao Li
- Department of Dermatology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Guangyuan Liu
- Medical Research Center, North China University of Science and Technology, Tangshan, China
| | - Guobin Zhang
- Medical Research Center, North China University of Science and Technology, Tangshan, China
| | - Hong Xu
- Medical Research Center, North China University of Science and Technology, Tangshan, China
| | - Zhiguo Li
- Medical Research Center, North China University of Science and Technology, Tangshan, China
| | - Qiangqiang Lian
- Medical Research Center, North China University of Science and Technology, Tangshan, China
| | - Lei Xing
- Department of Geriatrics, Affiliated Hospital of North China University of Science and Technology, Tangshan, China
| | - Faming Tian
- Medical Research Center, North China University of Science and Technology, Tangshan, China
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13
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Takenaka N, Araki N, Satoh T. Involvement of the protein kinase Akt2 in insulin-stimulated Rac1 activation leading to glucose uptake in mouse skeletal muscle. PLoS One 2019; 14:e0212219. [PMID: 30735546 PMCID: PMC6368313 DOI: 10.1371/journal.pone.0212219] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 01/29/2019] [Indexed: 11/27/2022] Open
Abstract
Translocation of the glucose transporter GLUT4 to the sarcolemma accounts for glucose uptake in skeletal muscle following insulin administration. The protein kinase Akt2 and the small GTPase Rac1 have been implicated as essential regulators of insulin-stimulated GLUT4 translocation. Several lines of evidence suggest that Rac1 is modulated downstream of Akt2, and indeed the guanine nucleotide exchange factor FLJ00068 has been identified as an activator of Rac1. On the other hand, the mechanisms whereby Akt2 and Rac1 are regulated in parallel downstream of phosphoinositide 3-kinase are also proposed. Herein, we aimed to provide additional evidence that support a critical role for Akt2 in insulin regulation of Rac1 in mouse skeletal muscle. Knockdown of Akt2 by RNA interference abolished Rac1 activation following intravenous administration of insulin or ectopic expression of a constitutively activated phosphoinositide 3-kinase mutant. The activation of another small GTPase RalA and GLUT4 translocation to the sarcolemma following insulin administration or ectopic expression of a constitutively activated form of phosphoinositide 3-kinase, but not Rac1, were also diminished by downregulation of Akt2 expression. Collectively, these results strongly support the notion that Rac1 acts downstream of Akt2 leading to the activation of RalA and GLUT4 translocation to the sarcolemma in skeletal muscle.
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Affiliation(s)
- Nobuyuki Takenaka
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Natsumi Araki
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Takaya Satoh
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan
- * E-mail:
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14
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In situ detection of the activation of Rac1 and RalA small GTPases in mouse adipocytes by immunofluorescent microscopy following in vivo and ex vivo insulin stimulation. Cell Signal 2017; 39:108-117. [PMID: 28821441 DOI: 10.1016/j.cellsig.2017.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 07/15/2017] [Accepted: 08/14/2017] [Indexed: 01/01/2023]
Abstract
Rac1 has been implicated in insulin-dependent glucose uptake by mechanisms involving plasma membrane translocation of the glucose transporter GLUT4 in skeletal muscle. Although the uptake of glucose is also stimulated by insulin in adipose tissue, the role for Rac1 in adipocyte insulin signaling remains controversial. As a step to reveal the role for Rac1 in adipocytes, we aimed to establish immunofluorescent microscopy to detect the intracellular distribution of activated Rac1. The epitope-tagged Rac1-binding domain of a Rac1-specific target was utilized as a probe that specifically recognizes the activated form of Rac1. Rac1 activation in response to ex vivo and in vivo insulin stimulations in primary adipocyte culture and mouse white adipose tissue, respectively, was successfully observed by immunofluorescent microscopy. These Rac1 activations were mediated by phosphoinositide 3-kinase. Another small GTPase RalA has also been implicated in insulin-stimulated glucose uptake in skeletal muscle and adipose tissue. Similarly to Rac1, immunofluorescent microscopy using an activated RalA-specific polypeptide probe allowed us to detect intracellular distribution of insulin-activated RalA in adipocytes. These novel approaches to visualize the activation status of small GTPases in adipocytes will largely contribute to the understanding of signal transduction mechanisms particularly for insulin action.
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15
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Sylow L, Kleinert M, Richter EA, Jensen TE. Exercise-stimulated glucose uptake - regulation and implications for glycaemic control. Nat Rev Endocrinol 2017; 13:133-148. [PMID: 27739515 DOI: 10.1038/nrendo.2016.162] [Citation(s) in RCA: 257] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Skeletal muscle extracts glucose from the blood to maintain demand for carbohydrates as an energy source during exercise. Such uptake involves complex molecular signalling processes that are distinct from those activated by insulin. Exercise-stimulated glucose uptake is preserved in insulin-resistant muscle, emphasizing exercise as a therapeutic cornerstone among patients with metabolic diseases such as diabetes mellitus. Exercise increases uptake of glucose by up to 50-fold through the simultaneous stimulation of three key steps: delivery, transport across the muscle membrane and intracellular flux through metabolic processes (glycolysis and glucose oxidation). The available data suggest that no single signal transduction pathway can fully account for the regulation of any of these key steps, owing to redundancy in the signalling pathways that mediate glucose uptake to ensure maintenance of muscle energy supply during physical activity. Here, we review the molecular mechanisms that regulate the movement of glucose from the capillary bed into the muscle cell and discuss what is known about their integrated regulation during exercise. Novel developments within the field of mass spectrometry-based proteomics indicate that the known regulators of glucose uptake are only the tip of the iceberg. Consequently, many exciting discoveries clearly lie ahead.
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Affiliation(s)
- Lykke Sylow
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Maximilian Kleinert
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Erik A Richter
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Thomas E Jensen
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
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16
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Varshney P, Dey CS. P21-activated kinase 2 (PAK2) regulates glucose uptake and insulin sensitivity in neuronal cells. Mol Cell Endocrinol 2016; 429:50-61. [PMID: 27040307 DOI: 10.1016/j.mce.2016.03.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 03/25/2016] [Accepted: 03/29/2016] [Indexed: 12/15/2022]
Abstract
P21-activated kinases (PAKs) are recently reported as important players of insulin signaling and glucose homeostasis in tissues like muscle, pancreas and liver. However, their role in neuronal insulin signaling is still unknown. Present study reports the involvement of PAK2 in neuronal insulin signaling, glucose uptake and insulin resistance. Irrespective of insulin sensitivity, insulin stimulation decreased PAK2 activity. PAK2 downregulation displayed marked enhancement of GLUT4 translocation with increase in glucose uptake whereas PAK2 over-expression showed its reduction. Treatment with Akti-1/2 and wortmannin suggested that Akt and PI3K are mediators of insulin effect on PAK2 and glucose uptake. Rac1 inhibition demonstrated decreased PAK2 activity while inhibition of PP2A resulted in increased PAK2 activity, with corresponding changes in glucose uptake. Taken together, present study demonstrates an inhibitory role of insulin signaling (via PI3K-Akt) and PP2A on PAK2 activity and establishes PAK2 as a Rac1-dependent negative regulator of neuronal glucose uptake and insulin sensitivity.
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Affiliation(s)
- Pallavi Varshney
- Kusuma School of Biological Sciences, Indian Institute of Technology-Delhi, Hauz Khas, New Delhi 110016, India
| | - Chinmoy Sankar Dey
- Kusuma School of Biological Sciences, Indian Institute of Technology-Delhi, Hauz Khas, New Delhi 110016, India.
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17
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Takenaka N, Nihata Y, Satoh T. Rac1 Activation Caused by Membrane Translocation of a Guanine Nucleotide Exchange Factor in Akt2-Mediated Insulin Signaling in Mouse Skeletal Muscle. PLoS One 2016; 11:e0155292. [PMID: 27163697 PMCID: PMC4862641 DOI: 10.1371/journal.pone.0155292] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 04/27/2016] [Indexed: 11/25/2022] Open
Abstract
Insulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4, which is translocated to the plasma membrane following insulin stimulation. Several lines of evidence suggested that the protein kinase Akt2 plays a key role in this insulin action. The small GTPase Rac1 has also been implicated as a regulator of insulin-stimulated GLUT4 translocation, acting downstream of Akt2. However, the mechanisms whereby Akt2 regulates Rac1 activity remain obscure. The guanine nucleotide exchange factor FLJ00068 has been identified as a direct regulator of Rac1 in Akt2-mediated signaling, but its characterization was performed mostly in cultured myoblasts. Here, we provide in vivo evidence that FLJ00068 indeed acts downstream of Akt2 as a Rac1 regulator by using mouse skeletal muscle. Small interfering RNA knockdown of FLJ00068 markedly diminished GLUT4 translocation to the sarcolemma following insulin administration or ectopic expression of a constitutively activated mutant of either phosphoinositide 3-kinase or Akt2. Additionally, insulin and these constitutively activated mutants caused the activation of Rac1 as shown by immunofluorescent microscopy using a polypeptide probe specific to activated Rac1 in isolated gastrocnemius muscle fibers and frozen sections of gastrocnemius muscle. This Rac1 activation was also abrogated by FLJ00068 knockdown. Furthermore, we observed translocation of FLJ00068 to the cell periphery following insulin stimulation in cultured myoblasts. Localization of FLJ00068 in the plasma membrane in insulin-stimulated, but not unstimulated, myoblasts and mouse gastrocnemius muscle was further affirmed by subcellular fractionation and subsequent immunoblotting. Collectively, these results strongly support a critical role of FLJ00068 in Akt2-mediated Rac1 activation in mouse skeletal muscle insulin signaling.
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Affiliation(s)
- Nobuyuki Takenaka
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Yuma Nihata
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan
| | - Takaya Satoh
- Laboratory of Cell Biology, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan
- * E-mail:
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18
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Cartee GD. Mechanisms for greater insulin-stimulated glucose uptake in normal and insulin-resistant skeletal muscle after acute exercise. Am J Physiol Endocrinol Metab 2015; 309:E949-59. [PMID: 26487009 PMCID: PMC4816200 DOI: 10.1152/ajpendo.00416.2015] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 10/14/2015] [Indexed: 02/08/2023]
Abstract
Enhanced skeletal muscle and whole body insulin sensitivity can persist for up to 24-48 h after one exercise session. This review focuses on potential mechanisms for greater postexercise and insulin-stimulated glucose uptake (ISGU) by muscle in individuals with normal or reduced insulin sensitivity. A model is proposed for the processes underlying this improvement; i.e., triggers initiate events that activate subsequent memory elements, which store information that is relayed to mediators, which translate memory into action by controlling an end effector that directly executes increased insulin-stimulated glucose transport. Several candidates are potential triggers or memory elements, but none have been conclusively verified. Regarding potential mediators in both normal and insulin-resistant individuals, elevated postexercise ISGU with a physiological insulin dose coincides with greater Akt substrate of 160 kDa (AS160) phosphorylation without improved proximal insulin signaling at steps from insulin receptor binding to Akt activity. Causality remains to be established between greater AS160 phosphorylation and improved ISGU. The end effector for normal individuals is increased GLUT4 translocation, but this remains untested for insulin-resistant individuals postexercise. Following exercise, insulin-resistant individuals can attain ISGU values similar to nonexercising healthy controls, but after a comparable exercise protocol performed by both groups, ISGU for the insulin-resistant group has been consistently reported to be below postexercise values for the healthy group. Further research is required to fully understand the mechanisms underlying the improved postexercise ISGU in individuals with normal or subnormal insulin sensitivity and to explain the disparity between these groups after similar exercise.
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Affiliation(s)
- Gregory D Cartee
- Muscle Biology Laboratory, School of Kinesiology, Department of Molecular and Integrative Physiology, and Institute of Gerontology, University of Michigan, Ann Arbor, Michigan
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