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Whitlock JM. Muscle Progenitor Cell Fusion in the Maintenance of Skeletal Muscle. Results Probl Cell Differ 2024; 71:257-279. [PMID: 37996682 DOI: 10.1007/978-3-031-37936-9_13] [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] [Indexed: 11/25/2023]
Abstract
Skeletal muscle possesses a resident, multipotent stem cell population that is essential for its repair and maintenance throughout life. Here I highlight the role of this stem cell population in muscle repair and regeneration and review the genetic control of the process; the mechanistic steps of activation, migration, recognition, adhesion, and fusion of these cells; and discuss the novel recognition of the membrane signaling that coordinates myogenic cell-cell fusion, as well as the identification of a two-part fusogen system that facilitates it.
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Affiliation(s)
- Jarred M Whitlock
- Section on Membrane Biology, Eunice Kennedy Shrive National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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Nguyen MT, Ly QK, Kim HJ, Lee W. FLII Modulates the Myogenic Differentiation of Progenitor Cells via Actin Remodeling-Mediated YAP1 Regulation. Int J Mol Sci 2023; 24:14335. [PMID: 37762638 PMCID: PMC10531566 DOI: 10.3390/ijms241814335] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 09/16/2023] [Accepted: 09/19/2023] [Indexed: 09/29/2023] Open
Abstract
The dynamic rearrangement of the actin cytoskeleton plays an essential role in myogenesis, which is regulated by diverse mechanisms, such as mechanotransduction, modulation of the Hippo signaling pathway, control of cell proliferation, and the influence of morphological changes. Despite the recognized importance of actin-binding protein Flightless-1 (FLII) during actin remodeling, the role played by FLII in the differentiation of myogenic progenitor cells has not been explored. Here, we investigated the roles of FLII in the proliferation and differentiation of myoblasts. FLII was found to be enriched in C2C12 myoblasts, and its expression was stable during the early stages of differentiation but down-regulated in fully differentiated myotubes. Knockdown of FLII in C2C12 myoblasts resulted in filamentous actin (F-actin) accumulation and inhibited Yes-associated protein 1 (YAP1) phosphorylation, which triggers its nuclear translocation from the cytoplasm. Consequently, the expressions of YAP1 target genes, including PCNA, CCNB1, and CCND1, were induced, and the cell cycle and proliferation of myoblasts were promoted. Moreover, FLII knockdown significantly inhibited the expression of myogenic regulatory factors, i.e., MyoD and MyoG, thereby impairing myoblast differentiation, fusion, and myotube formation. Thus, our findings demonstrate that FLII is crucial for the differentiation of myoblasts via modulation of the F-actin/YAP1 axis and suggest that FLII is a putative novel therapeutic target for muscle wasting.
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Affiliation(s)
- Mai Thi Nguyen
- Department of Biochemistry, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea; (M.T.N.); (Q.K.L.); (H.-J.K.)
| | - Quoc Kiet Ly
- Department of Biochemistry, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea; (M.T.N.); (Q.K.L.); (H.-J.K.)
| | - Hyun-Jung Kim
- Department of Biochemistry, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea; (M.T.N.); (Q.K.L.); (H.-J.K.)
| | - Wan Lee
- Department of Biochemistry, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea; (M.T.N.); (Q.K.L.); (H.-J.K.)
- Channelopathy Research Center, Dongguk University College of Medicine, 32 Dongguk-ro, Goyang 10326, Republic of Korea
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Nguyen MT, Lee W. Induction of miR-665-3p Impairs the Differentiation of Myogenic Progenitor Cells by Regulating the TWF1-YAP1 Axis. Cells 2023; 12:cells12081114. [PMID: 37190023 DOI: 10.3390/cells12081114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 04/03/2023] [Accepted: 04/06/2023] [Indexed: 05/17/2023] Open
Abstract
Actin dynamics are known to orchestrate various myogenic processes in progenitor cells. Twinfilin-1 (TWF1) is an actin-depolymerizing factor that plays a crucial role in the differentiation of myogenic progenitor cells. However, little is known about the mechanisms underlying the epigenetic regulation of TWF1 expression and impaired myogenic differentiation in the background of muscle wasting. This study investigated how miR-665-3p affects TWF1 expression, actin filaments' modulation, proliferation, and myogenic differentiation in progenitor cells. Palmitic acid, the most prevalent saturated fatty acid (SFA) in food, suppressed TWF1 expression and inhibited the myogenic differentiation of C2C12 cells while increasing the level of miR-665-3p expression. Interestingly, miR-665-3p inhibited TWF1 expression by targeting TWF1 3'UTR directly. In addition, miR-665-3p accumulated filamentous actin (F-actin) and enhanced the nuclear translocation of Yes-associated protein 1 (YAP1), consequently promoting cell cycle progression and proliferation. Furthermore, miR-665-3p suppressed the expressions of myogenic factors, i.e., MyoD, MyoG, and MyHC, and consequently impaired myoblast differentiation. In conclusion, this study suggests that SFA-inducible miR-665-3p suppresses TWF1 expression epigenetically and inhibits myogenic differentiation by facilitating myoblast proliferation via the F-actin/YAP1 axis.
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Affiliation(s)
- Mai Thi Nguyen
- Department of Biochemistry, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea
| | - Wan Lee
- Department of Biochemistry, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea
- Channelopathy Research Center, Dongguk University College of Medicine, 32 Dongguk-ro, Ilsan Dong-gu, Goyang 10326, Republic of Korea
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Nguyen MT, Lee W. Mir-302a/TWF1 Axis Impairs the Myogenic Differentiation of Progenitor Cells through F-Actin-Mediated YAP1 Activation. Int J Mol Sci 2023; 24:ijms24076341. [PMID: 37047312 PMCID: PMC10094299 DOI: 10.3390/ijms24076341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 03/17/2023] [Accepted: 03/21/2023] [Indexed: 03/30/2023] Open
Abstract
Actin cytoskeleton dynamics have been found to regulate myogenesis in various progenitor cells, and twinfilin-1 (TWF1), an actin-depolymerizing factor, plays a vital role in actin dynamics and myoblast differentiation. Nevertheless, the molecular mechanisms underlying the epigenetic regulation and biological significance of TWF1 in obesity and muscle wasting have not been explored. Here, we investigated the roles of miR-302a in TWF1 expression, actin filament modulation, proliferation, and myogenic differentiation in C2C12 progenitor cells. Palmitic acid, the most prevalent saturated fatty acid (SFA) in the diet, decreased the expression of TWF1 and impeded myogenic differentiation while increasing the miR-302a levels in C2C12 myoblasts. Interestingly, miR-302a inhibited TWF1 expression directly by targeting its 3′UTR. Furthermore, ectopic expression of miR-302a promoted cell cycle progression and proliferation by increasing the filamentous actin (F-actin) accumulation, which facilitated the nuclear translocation of Yes-associated protein 1 (YAP1). Consequently, by suppressing the expressions of myogenic factors, i.e., MyoD, MyoG, and MyHC, miR-302a impaired myoblast differentiation. Hence, this study demonstrated that SFA-inducible miR-302a suppresses TWF1 expression epigenetically and impairs myogenic differentiation by facilitating myoblast proliferation via F-actin-mediated YAP1 activation.
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Affiliation(s)
- Mai Thi Nguyen
- Department of Biochemistry, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea
| | - Wan Lee
- Department of Biochemistry, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju 38066, Republic of Korea
- Channelopathy Research Center, Dongguk University College of Medicine, 32 Dongguk-ro, Ilsan Dong-gu, Goyang 10326, Republic of Korea
- Correspondence: ; Tel.: +82-54-770-2409
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Ali R, Mir HA, Hamid R, Bhat B, Shah RA, Khanday FA, Bhat SS. Actin Modulation Regulates the Alpha-1-Syntrophin/p66Shc Mediated Redox Signaling Contributing to the RhoA GTPase Protein Activation in Breast Cancer Cells. Front Oncol 2022; 12:841303. [PMID: 35273919 PMCID: PMC8904154 DOI: 10.3389/fonc.2022.841303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 01/25/2022] [Indexed: 11/13/2022] Open
Abstract
SNTA1 signaling axis plays an essential role in cytoskeletal organization and is also implicated in breast cancers. In this study, we aimed to investigate the involvement of actin cytoskeleton in the propagation of SNTA1/p66shc mediated pro-metastatic cascade in breast cancer cells.The effect of actin filament depolymerization on SNTA1-p66Shc interaction and the trimeric complex formation was analyzed using co-immunoprecipitation assays. Immunofluorescence and RhoA activation assays were used to show the involvement of SNTA1-p66Shc interaction in RhoA activation and F-actin organization. Cellular proliferation and ROS levels were assessed using MTT assay and Amplex red catalase assay. The migratory potential was evaluated using transwell migration assay and wound healing assay.We found that cytochalasin D mediated actin depolymerization significantly declines endogenous interaction between SNTA1 and p66Shc protein in MDA-MB-231 cells. Results indicate that SNTA1 and p66Shc interact with RhoA protein under physiological conditions. The ROS generation and RhoA activation were substantially enhanced in cells overexpressing SNTA1 and p66Shc, promoting proliferation and migration in these cells. In addition, we found that loss of SNTA1-p66Shc interaction impaired actin organization, proliferation, and migration in breast cancer cells. Our results demonstrate a novel reciprocal regulatory mechanism between actin modulation and SNTA1/p66Shc/RhoA signaling cascade in human metastatic breast cancer cells.
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Affiliation(s)
- Roshia Ali
- Department of Biotechnology, University of Kashmir, Srinagar, India.,Department of Biochemistry, University of Kashmir, Srinagar, India
| | - Hilal Ahmad Mir
- Department of Biotechnology, University of Kashmir, Srinagar, India
| | - Rabia Hamid
- Department of Nanotechnology, University of Kashmir, Srinagar, India
| | - Basharat Bhat
- National Agricultural Higher Education Project (NAHEP) Sher-e-Kashmir University of Agricultural Sciences and Technology-Kashmir, Srinagar, India
| | - Riaz A Shah
- Division of Animal Biotechnology, Sher-e-Kashmir University of Agricultural Sciences and Technology-Kashmir, Faculty of Veterinary Sciences and Animal Husbandry, Srinagar, India
| | | | - Sahar Saleem Bhat
- Division of Animal Biotechnology, Sher-e-Kashmir University of Agricultural Sciences and Technology-Kashmir, Faculty of Veterinary Sciences and Animal Husbandry, Srinagar, India
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Dowling P, Gargan S, Murphy S, Zweyer M, Sabir H, Swandulla D, Ohlendieck K. The Dystrophin Node as Integrator of Cytoskeletal Organization, Lateral Force Transmission, Fiber Stability and Cellular Signaling in Skeletal Muscle. Proteomes 2021; 9:9. [PMID: 33540575 PMCID: PMC7931087 DOI: 10.3390/proteomes9010009] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 01/22/2021] [Accepted: 01/27/2021] [Indexed: 12/13/2022] Open
Abstract
The systematic bioanalytical characterization of the protein product of the DMD gene, which is defective in the pediatric disorder Duchenne muscular dystrophy, led to the discovery of the membrane cytoskeletal protein dystrophin. Its full-length muscle isoform Dp427-M is tightly linked to a sarcolemma-associated complex consisting of dystroglycans, sarcoglyans, sarcospan, dystrobrevins and syntrophins. Besides these core members of the dystrophin-glycoprotein complex, the wider dystrophin-associated network includes key proteins belonging to the intracellular cytoskeleton and microtubular assembly, the basal lamina and extracellular matrix, various plasma membrane proteins and cytosolic components. Here, we review the central role of the dystrophin complex as a master node in muscle fibers that integrates cytoskeletal organization and cellular signaling at the muscle periphery, as well as providing sarcolemmal stabilization and contractile force transmission to the extracellular region. The combination of optimized tissue extraction, subcellular fractionation, advanced protein co-purification strategies, immunoprecipitation, liquid chromatography and two-dimensional gel electrophoresis with modern mass spectrometry-based proteomics has confirmed the composition of the core dystrophin complex at the sarcolemma membrane. Importantly, these biochemical and mass spectrometric surveys have identified additional members of the wider dystrophin network including biglycan, cavin, synemin, desmoglein, tubulin, plakoglobin, cytokeratin and a variety of signaling proteins and ion channels.
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Affiliation(s)
- Paul Dowling
- Department of Biology, Maynooth University, National University of Ireland, W23F2H6 Maynooth, Co. Kildare, Ireland; (P.D.); (S.G.)
- Kathleen Lonsdale Institute for Human Health Research, Maynooth University, W23F2H6 Maynooth, Co. Kildare, Ireland
| | - Stephen Gargan
- Department of Biology, Maynooth University, National University of Ireland, W23F2H6 Maynooth, Co. Kildare, Ireland; (P.D.); (S.G.)
- Kathleen Lonsdale Institute for Human Health Research, Maynooth University, W23F2H6 Maynooth, Co. Kildare, Ireland
| | - Sandra Murphy
- Newcastle Fibrosis Research Group, Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE24HH, UK;
| | - Margit Zweyer
- Department of Neonatology and Paediatric Intensive Care, Children’s Hospital, University of Bonn, D53113 Bonn, Germany; (M.Z.); (H.S.)
| | - Hemmen Sabir
- Department of Neonatology and Paediatric Intensive Care, Children’s Hospital, University of Bonn, D53113 Bonn, Germany; (M.Z.); (H.S.)
| | - Dieter Swandulla
- Institute of Physiology II, University of Bonn, D53115 Bonn, Germany;
| | - Kay Ohlendieck
- Department of Biology, Maynooth University, National University of Ireland, W23F2H6 Maynooth, Co. Kildare, Ireland; (P.D.); (S.G.)
- Kathleen Lonsdale Institute for Human Health Research, Maynooth University, W23F2H6 Maynooth, Co. Kildare, Ireland
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7
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Ali R, Mir HA, Hamid R, Shah RA, Khanday FA, Bhat SS. Jasplakinolide Attenuates Cell Migration by Impeding Alpha-1-syntrophin Protein Phosphorylation in Breast Cancer Cells. Protein J 2021; 40:234-244. [PMID: 33515365 DOI: 10.1007/s10930-021-09963-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/2021] [Indexed: 01/01/2023]
Abstract
BACKGROUND Alpha-1-syntrophin (SNTA1) is emerging as a novel modulator of the actin cytoskeleton. SNTA1 binds to F-actin and regulates intracellular localization and activity of various actin organizing signaling molecules. Aberration in syntrophin signaling has been closely linked with deregulated growth connected to tumor development/metastasis and its abnormal over expression has been observed in breast cancer. In the present work the effect of jasplakinolide, an actin-binding cyclodepsipeptide, on the SNTA1 protein activity and SNTA1 mediated downstream cellular events was studied in MDA-MB-231 breast cancer cell line. METHODS SNTA1 protein levels and phosphorylation status were determined in MDA-MB-231 cells post jasplakinolide exposure using western blotting and immunoprecipitation techniques respectively. MDA-MB-231 cells were transfected with WT SNTA1 and DM SNTA1 (Y215/229 phospho mutant) and simultaneously treated with jasplakinolide. The effect of jasplakinolide and SNTA1 protein on cell migration was determined using the boyden chamber assay. RESULTS Jasplakinolide treatment decreases proliferation of MDA-MB-231 cells in both dose and time dependent manner. Results suggest that subtoxic doses of jasplakinolide induce morphological changes in MDA-MB-231 cells from flat spindle shape adherent cells to round weakly adherent forms. Mechanistically, jasplakinolide treatment was found to decrease SNTA1 protein levels and its tyrosine phosphorylation status. Moreover, migratory potential of jasplakinolide treated cells was significantly inhibited in comparison to control cells. CONCLUSION Our results demonstrate that jasplakinolide inhibits cell migration by impairing SNTA1 functioning in breast cancer cells.
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Affiliation(s)
- Roshia Ali
- Department of Biotechnology, University of Kashmir, Hazratbal, Srinagar, J&K, 190006, India
- Department of Biochemistry, University of Kashmir, Srinagar, J&K, 190006, India
| | - Hilal Ahmad Mir
- Department of Biotechnology, University of Kashmir, Hazratbal, Srinagar, J&K, 190006, India
| | - Rabia Hamid
- Department of Nanotechnology, University of Kashmir, Srinagar, J&K, 190006, India
| | - Riaz A Shah
- Division of Biotechnology, FVSc & AH, SKUAST-K, Shuhama, Srinagar, J&K, India
| | - Firdous A Khanday
- Department of Biotechnology, University of Kashmir, Hazratbal, Srinagar, J&K, 190006, India.
| | - Sahar Saleem Bhat
- Division of Biotechnology, FVSc & AH, SKUAST-K, Shuhama, Srinagar, J&K, India.
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Chen B, You W, Wang Y, Shan T. The regulatory role of Myomaker and Myomixer-Myomerger-Minion in muscle development and regeneration. Cell Mol Life Sci 2020; 77:1551-1569. [PMID: 31642939 PMCID: PMC11105057 DOI: 10.1007/s00018-019-03341-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 10/07/2019] [Accepted: 10/10/2019] [Indexed: 12/12/2022]
Abstract
Skeletal muscle plays essential roles in motor function, energy, and glucose metabolism. Skeletal muscle formation occurs through a process called myogenesis, in which a crucial step is the fusion of mononucleated myoblasts to form multinucleated myofibers. The myoblast/myocyte fusion is triggered and coordinated in a muscle-specific way that is essential for muscle development and post-natal muscle regeneration. Many molecules and proteins have been found and demonstrated to have the capacity to regulate the fusion of myoblast/myocytes. Interestingly, two newly discovered muscle-specific membrane proteins, Myomaker and Myomixer (also called Myomerger and Minion), have been identified as fusogenic regulators in vertebrates. Both Myomaker and Myomixer-Myomerger-Minion have the capacity to directly control the myogenic fusion process. Here, we review and discuss the latest studies related to these two proteins, including the discovery, structure, expression pattern, functions, and regulation of Myomaker and Myomixer-Myomerger-Minion. We also emphasize and discuss the interaction between Myomaker and Myomixer-Myomerger-Minion, as well as their cooperative regulatory roles in cell-cell fusion. Moreover, we highlight the areas for exploration of Myomaker and Myomixer-Myomerger-Minion in future studies and consider their potential application to control cell fusion for cell-therapy purposes.
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Affiliation(s)
- Bide Chen
- College of Animal Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China
- The Key Laboratory of Molecular Animal Nutrition, Ministry of Education, Hangzhou, China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition, Hangzhou, China
| | - Wenjing You
- College of Animal Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China
- The Key Laboratory of Molecular Animal Nutrition, Ministry of Education, Hangzhou, China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition, Hangzhou, China
| | - Yizhen Wang
- College of Animal Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China
- The Key Laboratory of Molecular Animal Nutrition, Ministry of Education, Hangzhou, China
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition, Hangzhou, China
| | - Tizhong Shan
- College of Animal Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, China.
- The Key Laboratory of Molecular Animal Nutrition, Ministry of Education, Hangzhou, China.
- Zhejiang Provincial Laboratory of Feed and Animal Nutrition, Hangzhou, China.
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Pizza FX, Martin RA, Springer EM, Leffler MS, Woelmer BR, Recker IJ, Leaman DW. Intercellular adhesion molecule-1 augments myoblast adhesion and fusion through homophilic trans-interactions. Sci Rep 2017; 7:5094. [PMID: 28698658 PMCID: PMC5506053 DOI: 10.1038/s41598-017-05283-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 05/25/2017] [Indexed: 01/01/2023] Open
Abstract
The overall objective of the study was to identify mechanisms through which intercellular adhesion molecule-1 (ICAM-1) augments the adhesive and fusogenic properties of myogenic cells. Hypotheses were tested using cultured myoblasts and fibroblasts, which do not constitutively express ICAM-1, and myoblasts and fibroblasts forced to express full length ICAM-1 or a truncated form lacking the cytoplasmic domain of ICAM-1. ICAM-1 mediated myoblast adhesion and fusion were quantified using novel assays and cell mixing experiments. We report that ICAM-1 augments myoblast adhesion to myoblasts and myotubes through homophilic trans-interactions. Such adhesive interactions enhanced levels of active Rac in adherent and fusing myoblasts, as well as triggered lamellipodia, spreading, and fusion of myoblasts through the signaling function of the cytoplasmic domain of ICAM-1. Rac inhibition negated ICAM-1 mediated lamellipodia, spreading, and fusion of myoblasts. The fusogenic property of ICAM-1-ICAM-1 interactions was restricted to myogenic cells, as forced expression of ICAM-1 by fibroblasts did not augment their fusion to ICAM-1+ myoblasts/myotubes. We conclude that ICAM-1 augments myoblast adhesion and fusion through its ability to self-associate and initiate Rac-mediated remodeling of the actin cytoskeleton.
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Affiliation(s)
- Francis X Pizza
- School of Exercise and Rehabilitation Sciences, University of Toledo, Toledo, Ohio, USA.
| | - Ryan A Martin
- School of Exercise and Rehabilitation Sciences, University of Toledo, Toledo, Ohio, USA
| | - Evan M Springer
- School of Exercise and Rehabilitation Sciences, University of Toledo, Toledo, Ohio, USA
| | - Maxwell S Leffler
- School of Exercise and Rehabilitation Sciences, University of Toledo, Toledo, Ohio, USA
| | - Bryce R Woelmer
- School of Exercise and Rehabilitation Sciences, University of Toledo, Toledo, Ohio, USA
| | - Isaac J Recker
- School of Exercise and Rehabilitation Sciences, University of Toledo, Toledo, Ohio, USA
| | - Douglas W Leaman
- Department of Biological Sciences, University of Toledo, Toledo, Ohio, USA.,Wright State University, 4035 Colonel Glenn Hwy., Suite 300, Beavercreek, OH, 45431, USA
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Regulation of Skeletal Myoblast Differentiation by Drebrin. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1006:361-373. [DOI: 10.1007/978-4-431-56550-5_22] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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11
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Allen DG, Whitehead NP, Froehner SC. Absence of Dystrophin Disrupts Skeletal Muscle Signaling: Roles of Ca2+, Reactive Oxygen Species, and Nitric Oxide in the Development of Muscular Dystrophy. Physiol Rev 2016; 96:253-305. [PMID: 26676145 DOI: 10.1152/physrev.00007.2015] [Citation(s) in RCA: 272] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Dystrophin is a long rod-shaped protein that connects the subsarcolemmal cytoskeleton to a complex of proteins in the surface membrane (dystrophin protein complex, DPC), with further connections via laminin to other extracellular matrix proteins. Initially considered a structural complex that protected the sarcolemma from mechanical damage, the DPC is now known to serve as a scaffold for numerous signaling proteins. Absence or reduced expression of dystrophin or many of the DPC components cause the muscular dystrophies, a group of inherited diseases in which repeated bouts of muscle damage lead to atrophy and fibrosis, and eventually muscle degeneration. The normal function of dystrophin is poorly defined. In its absence a complex series of changes occur with multiple muscle proteins showing reduced or increased expression or being modified in various ways. In this review, we will consider the various proteins whose expression and function is changed in muscular dystrophies, focusing on Ca(2+)-permeable channels, nitric oxide synthase, NADPH oxidase, and caveolins. Excessive Ca(2+) entry, increased membrane permeability, disordered caveolar function, and increased levels of reactive oxygen species are early changes in the disease, and the hypotheses for these phenomena will be critically considered. The aim of the review is to define the early damage pathways in muscular dystrophy which might be appropriate targets for therapy designed to minimize the muscle degeneration and slow the progression of the disease.
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Affiliation(s)
- David G Allen
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
| | - Nicholas P Whitehead
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
| | - Stanley C Froehner
- Sydney Medical School & Bosch Institute, University of Sydney, New South Wales, Australia; and Department of Physiology & Biophysics, University of Washington, Seattle, Washington
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Abstract
Mammalian life begins with a cell-cell fusion event, i.e. the fusion of the spermatozoid with the oocyte and needs further cell-cell fusion processes for the development, growth, and maintenance of tissues and organs over the whole life span. Furthermore, cellular fusion plays a role in infection, cancer, and stem cell-dependent regeneration as well as including an expanded meaning of partial cellular fusion, nanotube formation, and microparticle-cell fusion. The cellular fusion process is highly regulated by proteins which carry the information to organize and regulate membranes allowing the merge of two separate lipid bilayers into one. The regulation of this genetically and epigenetically controlled process is achieved by different kinds of signals leading to communication of fusing cells. The local cellular and extracellular environment additionally initiates specific cell signaling necessary for the induction of the cell-cell fusion process. Common motifs exist in distinct cell-cell fusion processes and their regulation. However, there is specific regulation of different cell-cell fusion processes, e.g. myoblast, placental, osteoclast, and stem cell fusion. Hence, specialized fusion events vary between cell types and species. Molecular mechanisms remain largely unknown, especially limited knowledge is present for cancer and stem cell fusion mechanisms and regulation. More research is necessary for the understanding of cellular fusion processes which can lead to development of new therapeutic strategies grounding on cellular fusion regulation.
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Affiliation(s)
- Lena Willkomm
- Department of Molecular and Cellular Sport Medicine, Institute of Cardiovascular Research and Sport Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany
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13
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Ard R, Mulatz K, Pomoransky JL, Parks RJ, Trinkle-Mulcahy L, Bell JC, Gee SH. Regulation of Macropinocytosis by Diacylglycerol Kinase ζ. PLoS One 2015; 10:e0144942. [PMID: 26701304 PMCID: PMC4689489 DOI: 10.1371/journal.pone.0144942] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 11/25/2015] [Indexed: 12/02/2022] Open
Abstract
Macropinosomes arise from the closure of plasma membrane ruffles to bring about the non-selective uptake of nutrients and solutes into cells. The morphological changes underlying ruffle formation and macropinosome biogenesis are driven by actin cytoskeleton rearrangements under the control of the Rho GTPase Rac1. We showed previously that Rac1 is activated by diacylglycerol kinase ζ (DGKζ), which phosphorylates diacylglycerol to yield phosphatidic acid. Here, we show DGKζ is required for optimal macropinocytosis induced by growth factor stimulation of mouse embryonic fibroblasts. Time-lapse imaging of live cells and quantitative analysis revealed DGKζ was associated with membrane ruffles and nascent macropinosomes. Macropinocytosis was attenuated in DGKζ-null cells, as determined by live imaging and vaccinia virus uptake experiments. Moreover, macropinosomes that did form in DGKζ-null cells were smaller than those found in wild type cells. Rescue of this defect required DGKζ catalytic activity, consistent with it also being required for Rac1 activation. A constitutively membrane bound DGKζ mutant substantially increased the size of macropinosomes and potentiated the effect of a constitutively active Rac1 mutant on macropinocytosis. Collectively, our results suggest DGKζ functions in concert with Rac1 to regulate macropinocytosis.
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Affiliation(s)
- Ryan Ard
- Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON, K1H 8M5, Canada
- Centre for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
| | - Kirk Mulatz
- Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON, K1H 8M5, Canada
- Centre for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
| | - Julia L. Pomoransky
- Centre for Innovative Cancer Research, Ottawa Hospital Research Institute, 503 Smyth Road, 3rd floor ORCC, Ottawa, ON, K1H 1C4, Canada
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada
| | - Robin J. Parks
- Centre for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, ON, K1H 8L6, Canada
| | - Laura Trinkle-Mulcahy
- Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON, K1H 8M5, Canada
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON, Canada
| | - John C. Bell
- Centre for Innovative Cancer Research, Ottawa Hospital Research Institute, 503 Smyth Road, 3rd floor ORCC, Ottawa, ON, K1H 1C4, Canada
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada
| | - Stephen H. Gee
- Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON, K1H 8M5, Canada
- Centre for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
- * E-mail:
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14
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Xie S, Naslavsky N, Caplan S. Diacylglycerol kinases in membrane trafficking. CELLULAR LOGISTICS 2015; 5:e1078431. [PMID: 27057419 DOI: 10.1080/21592799.2015.1078431] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 07/22/2015] [Accepted: 07/24/2015] [Indexed: 10/23/2022]
Abstract
Diacylglycerol kinases (DGKs) belong to a family of cytosolic kinases that regulate the phosphorylation of diacylglycerol (DAG), converting it into phosphatidic acid (PA). There are 10 known mammalian DGK isoforms, each with a different tissue distribution and substrate specificity. These differences allow regulation of cellular responses by fine-tuning the delicate balance of cellular DAG and PA. DGK isoforms are best characterized as mediators of signal transduction and immune function. However, since recent studies reveal that DAG and PA are also involved in the regulation of endocytic trafficking, it is therefore anticipated that DGKs also plays an important role in membrane trafficking. In this review, we summarize the literature discussing the role of DGK isoforms at different stages of endocytic trafficking, including endocytosis, exocytosis, endocytic recycling, and transport from/to the Golgi apparatus. Overall, these studies contribute to our understanding of the involvement of PA and DAG in endocytic trafficking, an area of research that is drawing increasing attention in recent years.
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Affiliation(s)
- Shuwei Xie
- Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center; University of Nebraska Medical Center ; Omaha, NE USA
| | - Naava Naslavsky
- Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center; University of Nebraska Medical Center ; Omaha, NE USA
| | - Steve Caplan
- Department of Biochemistry and Molecular Biology and the Fred and Pamela Buffett Cancer Center; University of Nebraska Medical Center ; Omaha, NE USA
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15
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Simionescu-Bankston A, Pichavant C, Canner JP, Apponi LH, Wang Y, Steeds C, Olthoff JT, Belanto JJ, Ervasti JM, Pavlath GK. Creatine kinase B is necessary to limit myoblast fusion during myogenesis. Am J Physiol Cell Physiol 2015; 308:C919-31. [PMID: 25810257 DOI: 10.1152/ajpcell.00029.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 03/19/2015] [Indexed: 11/22/2022]
Abstract
Myoblast fusion is critical for proper muscle growth and regeneration. During myoblast fusion, the localization of some molecules is spatially restricted; however, the exact reason for such localization is unknown. Creatine kinase B (CKB), which replenishes local ATP pools, localizes near the ends of cultured primary mouse myotubes. To gain insights into the function of CKB, we performed a yeast two-hybrid screen to identify CKB-interacting proteins. We identified molecules with a broad diversity of roles, including actin polymerization, intracellular protein trafficking, and alternative splicing, as well as sarcomeric components. In-depth studies of α-skeletal actin and α-cardiac actin, two predominant muscle actin isoforms, demonstrated their biochemical interaction and partial colocalization with CKB near the ends of myotubes in vitro. In contrast to other cell types, specific knockdown of CKB did not grossly affect actin polymerization in myotubes, suggesting other muscle-specific roles for CKB. Interestingly, knockdown of CKB resulted in significantly increased myoblast fusion and myotube size in vitro, whereas knockdown of creatine kinase M had no effect on these myogenic parameters. Our results suggest that localized CKB plays a key role in myotube formation by limiting myoblast fusion during myogenesis.
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Affiliation(s)
- Adriana Simionescu-Bankston
- Graduate Program in Biochemistry, Cell and Developmental Biology, Emory University School of Medicine, Atlanta, Georgia; Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - Christophe Pichavant
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - James P Canner
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - Luciano H Apponi
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - Yanru Wang
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - Craig Steeds
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - John T Olthoff
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Joseph J Belanto
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - James M Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Grace K Pavlath
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
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16
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Wu M, Yang G, Chen Y, Zhou X, Chen H, Li M, Yu K, Zhang X, Xie S, Zhang Y, Chu G, Mo D. CEP2 attenuates myoblast differentiation but does not affect proliferation. Int J Biol Sci 2015; 11:99-108. [PMID: 25552934 PMCID: PMC4278259 DOI: 10.7150/ijbs.8621] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 03/11/2014] [Indexed: 12/30/2022] Open
Abstract
CEP2 (CDC42EP2) is a member of the CDC42 subfamily that belongs to the Rho family. The Rho family plays an important role in a variety of cellular processes including skeletal myogenesis. Here, we find the expression of CEP2 increased significantly during C2C12 myogenesis. Overexpression of CEP2 could attenuate myoblast differentiation, while knockdown of CEP2 by siRNA results in enhancing myogenesis. Furthermore, we demonstrate for the first time that CEP2 attenuates myoblast differentiation via suppression of muscle regulatory factors (MRFs) rather than influencing myoblast proliferation. These results indicate that CEP2 acts as a repressor during myogenesis, which provides new insights into the role of CEP2 in muscle development.
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Affiliation(s)
- Ming Wu
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Gongshe Yang
- 2. Laboratory of Animal Fat Deposition and Muscle Development, College of Animal Science and Technology, Northwest A&F University, Yangling, China
| | - Yaosheng Chen
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Xingyu Zhou
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Hu Chen
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Mingsen Li
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Kaifan Yu
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Xumeng Zhang
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Shuihua Xie
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Ying Zhang
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Guiyan Chu
- 2. Laboratory of Animal Fat Deposition and Muscle Development, College of Animal Science and Technology, Northwest A&F University, Yangling, China
| | - Delin Mo
- 1. State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
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Poliakova K, Adebola A, Leung CL, Favre B, Liem RKH, Schepens I, Borradori L. BPAG1a and b associate with EB1 and EB3 and modulate vesicular transport, Golgi apparatus structure, and cell migration in C2.7 myoblasts. PLoS One 2014; 9:e107535. [PMID: 25244344 PMCID: PMC4171495 DOI: 10.1371/journal.pone.0107535] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 08/18/2014] [Indexed: 11/19/2022] Open
Abstract
BPAG1a and BPAG1b (BPAG1a/b) constitute two major isoforms encoded by the dystonin (Dst) gene and show homology with MACF1a and MACF1b. These proteins are members of the plakin family, giant multi-modular proteins able to connect the intermediate filament, microtubule and microfilament cytoskeletal networks with each other and to distinct cell membrane sites. They also serve as scaffolds for signaling proteins that modulate cytoskeletal dynamics. To gain better insights into the functions of BPAG1a/b, we further characterized their C-terminal region important for their interaction with microtubules and assessed the role of these isoforms in the cytoskeletal organization of C2.7 myoblast cells. Our results show that alternative splicing does not only occur at the 5′ end of Dst and Macf1 pre-mRNAs, as previously reported, but also at their 3′ end, resulting in expression of additional four mRNA variants of BPAG1 and MACF1. These isoform-specific C-tails were able to bundle microtubules and bound to both EB1 and EB3, two microtubule plus end proteins. In the C2.7 cell line, knockdown of BPAG1a/b had no major effect on the organization of the microtubule and microfilament networks, but negatively affected endocytosis and maintenance of the Golgi apparatus structure, which became dispersed. Finally, knockdown of BPAG1a/b caused a specific decrease in the directness of cell migration, but did not impair initial cell adhesion. These data provide novel insights into the complexity of alternative splicing of Dst pre-mRNAs and into the role of BPAG1a/b in vesicular transport, Golgi apparatus structure as well as in migration in C2.7 myoblasts.
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Affiliation(s)
- Kseniia Poliakova
- Department of Clinical Research, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
- Department of Dermatology, Inselspital, Bern University Hospital, Bern, Switzerland
- * E-mail:
| | - Adijat Adebola
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Conrad L. Leung
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Bertrand Favre
- Department of Clinical Research, University of Bern, Bern, Switzerland
- Department of Dermatology, Inselspital, Bern University Hospital, Bern, Switzerland
| | - Ronald K. H. Liem
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Isabelle Schepens
- Department of Clinical Research, University of Bern, Bern, Switzerland
| | - Luca Borradori
- Department of Clinical Research, University of Bern, Bern, Switzerland
- Department of Dermatology, Inselspital, Bern University Hospital, Bern, Switzerland
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18
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You JS, Lincoln HC, Kim CR, Frey JW, Goodman CA, Zhong XP, Hornberger TA. The role of diacylglycerol kinase ζ and phosphatidic acid in the mechanical activation of mammalian target of rapamycin (mTOR) signaling and skeletal muscle hypertrophy. J Biol Chem 2013; 289:1551-63. [PMID: 24302719 DOI: 10.1074/jbc.m113.531392] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The activation of mTOR signaling is essential for mechanically induced changes in skeletal muscle mass, and previous studies have suggested that mechanical stimuli activate mTOR (mammalian target of rapamycin) signaling through a phospholipase D (PLD)-dependent increase in the concentration of phosphatidic acid (PA). Consistent with this conclusion, we obtained evidence which further suggests that mechanical stimuli utilize PA as a direct upstream activator of mTOR signaling. Unexpectedly though, we found that the activation of PLD is not necessary for the mechanically induced increases in PA or mTOR signaling. Motivated by this observation, we performed experiments that were aimed at identifying the enzyme(s) that promotes the increase in PA. These experiments revealed that mechanical stimulation increases the concentration of diacylglycerol (DAG) and the activity of DAG kinases (DGKs) in membranous structures. Furthermore, using knock-out mice, we determined that the ζ isoform of DGK (DGKζ) is necessary for the mechanically induced increase in PA. We also determined that DGKζ significantly contributes to the mechanical activation of mTOR signaling, and this is likely driven by an enhanced binding of PA to mTOR. Last, we found that the overexpression of DGKζ is sufficient to induce muscle fiber hypertrophy through an mTOR-dependent mechanism, and this event requires DGKζ kinase activity (i.e. the synthesis of PA). Combined, these results indicate that DGKζ, but not PLD, plays an important role in mechanically induced increases in PA and mTOR signaling. Furthermore, this study suggests that DGKζ could be a fundamental component of the mechanism(s) through which mechanical stimuli regulate skeletal muscle mass.
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Affiliation(s)
- Jae-Sung You
- From the Program in Cellular and Molecular Biology and
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19
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Simionescu-Bankston A, Leoni G, Wang Y, Pham PP, Ramalingam A, DuHadaway JB, Faundez V, Nusrat A, Prendergast GC, Pavlath GK. The N-BAR domain protein, Bin3, regulates Rac1- and Cdc42-dependent processes in myogenesis. Dev Biol 2013; 382:160-71. [PMID: 23872330 DOI: 10.1016/j.ydbio.2013.07.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 07/01/2013] [Accepted: 07/05/2013] [Indexed: 11/28/2022]
Abstract
Actin dynamics are necessary at multiple steps in the formation of multinucleated muscle cells. BAR domain proteins can regulate actin dynamics in several cell types, but have been little studied in skeletal muscle. Here, we identify novel functions for the N-BAR domain protein, Bridging integrator 3 (Bin3), during myogenesis in mice. Bin3 plays an important role in regulating myofiber size in vitro and in vivo. During early myogenesis, Bin3 promotes migration of differentiated muscle cells, where it colocalizes with F-actin in lamellipodia. In addition, Bin3 forms a complex with Rac1 and Cdc42, Rho GTPases involved in actin polymerization, which are known to be essential for myotube formation. Importantly, a Bin3-dependent pathway is a major regulator of Rac1 and Cdc42 activity in differentiated muscle cells. Overall, these data classify N-BAR domain proteins as novel regulators of actin-dependent processes in myogenesis, and further implicate BAR domain proteins in muscle growth and repair.
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Affiliation(s)
- Adriana Simionescu-Bankston
- Graduate Program in Biochemistry, Cell and Developmental Biology, Emory University School of Medicine, Atlanta, GA 30322, USA; Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
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20
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Joshi RP, Koretzky GA. Diacylglycerol kinases: regulated controllers of T cell activation, function, and development. Int J Mol Sci 2013; 14:6649-73. [PMID: 23531532 PMCID: PMC3645659 DOI: 10.3390/ijms14046649] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 03/07/2013] [Accepted: 03/14/2013] [Indexed: 01/22/2023] Open
Abstract
Diacylglycerol kinases (DGKs) are a diverse family of enzymes that catalyze the conversion of diacylglycerol (DAG), a crucial second messenger of receptor-mediated signaling, to phosphatidic acid (PA). Both DAG and PA are bioactive molecules that regulate a wide set of intracellular signaling proteins involved in innate and adaptive immunity. Clear evidence points to a critical role for DGKs in modulating T cell activation, function, and development. More recently, studies have elucidated factors that control DGK function, suggesting an added complexity to how DGKs act during signaling. This review summarizes the available knowledge of the function and regulation of DGK isoforms in signal transduction with a particular focus on T lymphocytes.
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Affiliation(s)
- Rohan P. Joshi
- Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, PA 19104, USA; E-Mail:
| | - Gary A. Koretzky
- Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, PA 19104, USA; E-Mail:
- Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-215-746-5522; Fax: +1-215-746-5525
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21
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Kocić J, Santibañez JF, Krstić A, Mojsilović S, Ilić V, Bugarski D. Interleukin-17 modulates myoblast cell migration by inhibiting urokinase type plasminogen activator expression through p38 mitogen-activated protein kinase. Int J Biochem Cell Biol 2012. [PMID: 23183001 DOI: 10.1016/j.biocel.2012.11.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Interleukin-17 belongs to a family of pro-inflammatory cytokines with pleiotropic effects, which can be associated with several inflammatory diseases of the muscle tissue. Although elevated levels of interleukin-17 have been described in inflammatory myopathies, its role in muscle homeostasis remains to be elucidated. The requirement of the urokinase type plasminogen activator in skeletal myogenesis was recently demonstrated in vivo and in vitro, suggesting its involvement in the regulation of extracellular matrix remodeling, cell migration and myoblast fusion. Our previous results have demonstrated that interleukin-17 inhibits myogenic differentiation of C2C12 myoblasts in vitro concomitantly with the inhibition of cell migration. However, the involvement of urokinase type plasminogen activator in interleukin-17-inhibited myogenesis and migration remained to be analyzed. Therefore, the effect of interleukin-17 on the production of urokinase type plasminogen activator by C2C12 myoblasts was determined in the present study. Our results demonstrated that interleukin-17 strongly inhibits urokinase type plasminogen activator expression during myogenic differentiation. This reduction of urokinase type plasminogen activator production corresponded with the inhibition of cell migration by interleukin-17. Activation of p38 signaling pathway elicited by interleukin-17 mediated the inhibition of both urokinase type plasminogen activator expression and cell migration. Additionally, IL-17 inhibited C2C12 cells migration by causing the cells to reorganize their cytoskeleton and lose polarity. Therefore, our results suggest a novel mechanism by which interleukin-17 regulates myogenic differentiation through the inhibition of urokinase type plasminogen activator expression and cell migration. Accordingly, interleukin-17 may represent a potential clinical target worth investigating for the treatment of inflammatory muscle diseases.
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Affiliation(s)
- Jelena Kocić
- Laboratory for Experimental Hematology and Stem Cells, Institute for Medical Research, University of Belgrade, Dr Subotića 4, 11129 Belgrade, Serbia
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22
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Ladiwala U, Basu H, Mathur D. Assembling neurospheres: dynamics of neural progenitor/stem cell aggregation probed using an optical trap. PLoS One 2012; 7:e38613. [PMID: 22693648 PMCID: PMC3367915 DOI: 10.1371/journal.pone.0038613] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Accepted: 05/07/2012] [Indexed: 11/18/2022] Open
Abstract
Optical trapping (tweezing) has been used in conjunction with fluid flow technology to dissect the mechanics and spatio-temporal dynamics of how neural progenitor/stem cells (NSCs) adhere and aggregate. Hitherto unavailable information has been obtained on the most probable minimum time (∼5 s) and most probable minimum distance of approach (4–6 µm) required for irreversible adhesion of proximate cells to occur. Our experiments also allow us to study and quantify the spatial characteristics of filopodial- and membrane-mediated adhesion, and to probe the functional dynamics of NSCs to quantify a lower limit of the adhesive force by which NSCs aggregate (∼18 pN). Our findings, which we also validate by computational modeling, have important implications for the neurosphere assay: once aggregated, neurospheres cannot disassemble merely by being subjected to shaking or by thermal effects. Our findings provide quantitative affirmation to the notion that the neurosphere assay may not be a valid measure of clonality and “stemness”. Post-adhesion dynamics were also studied and oscillatory motion in filopodia-mediated adhesion was observed. Furthermore, we have also explored the effect of the removal of calcium ions: both filopodia-mediated as well as membrane-membrane adhesion were inhibited. On the other hand, F-actin disrupted the dynamics of such adhesion events such that filopodia-mediated adhesion was inhibited but not membrane-membrane adhesion.
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Affiliation(s)
- Uma Ladiwala
- UM-DAE Centre for Excellence in Basic Science, University of Mumbai, Kalina Campus, Mumbai, India
- * E-mail: (UL); (DM)
| | - Himanish Basu
- Tata Institute of Fundamental Research, Mumbai, India
| | - Deepak Mathur
- Tata Institute of Fundamental Research, Mumbai, India
- * E-mail: (UL); (DM)
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23
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Abstract
The fusion of myoblasts into multinucleate syncytia plays a fundamental role in muscle function, as it supports the formation of extended sarcomeric arrays, or myofibrils, within a large volume of cytoplasm. Principles learned from the study of myoblast fusion not only enhance our understanding of myogenesis, but also contribute to our perspectives on membrane fusion and cell-cell fusion in a wide array of model organisms and experimental systems. Recent studies have advanced our views of the cell biological processes and crucial proteins that drive myoblast fusion. Here, we provide an overview of myoblast fusion in three model systems that have contributed much to our understanding of these events: the Drosophila embryo; developing and regenerating mouse muscle; and cultured rodent muscle cells.
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Affiliation(s)
- Susan M Abmayr
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
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24
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Rincón E, Gharbi SI, Santos-Mendoza T, Mérida I. Diacylglycerol kinase ζ: At the crossroads of lipid signaling and protein complex organization. Prog Lipid Res 2012; 51:1-10. [DOI: 10.1016/j.plipres.2011.10.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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25
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Mancini A, Sirabella D, Zhang W, Yamazaki H, Shirao T, Krauss RS. Regulation of myotube formation by the actin-binding factor drebrin. Skelet Muscle 2011; 1:36. [PMID: 22152295 PMCID: PMC3251523 DOI: 10.1186/2044-5040-1-36] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 12/08/2011] [Indexed: 11/15/2022] Open
Abstract
Background Myogenic differentiation involves cell-cycle arrest, activation of the muscle-specific transcriptome, and elongation, alignment and fusion of myoblasts into multinucleated myotubes. This process is controlled by promyogenic transcription factors and regulated by signaling pathways in response to extracellular cues. The p38 mitogen-activated protein kinase (p38 MAPK) pathway promotes the activity of several such transcription factors, including MyoD and MEF2, thereby controlling the muscle-specific transcription program. However, few p38-regulated genes that play a role in the regulation of myogenesis have been identified. Methods RNA interference (RNAi), chemical inhibition and immunofluorescence approaches were used to assess the role of drebrin in differentiation of primary mouse myoblasts and C2C12 cells. Results In a search for p38-regulated genes that promote myogenic differentiation, we identified Dbn1, which encodes the actin-binding protein drebrin. Drebrin is an F-actin side-binding protein that remodels actin to facilitate the change of filopodia into dendritic spines during synaptogenesis in developing neurons. Dbn1 mRNA and protein are induced during differentiation of primary mouse and C2C12 myoblasts, and induction is substantially reduced by the p38 MAPK inhibitor SB203580. Primary myoblasts and C2C12 cells depleted of drebrin by RNAi display reduced levels of myogenin and myosin heavy chain and form multinucleated myotubes very inefficiently. Treatment of myoblasts with BTP2, a small-molecule inhibitor of drebrin, produces a phenotype similar to that produced by knockdown of drebrin, and the inhibitory effects of BTP2 are rescued by expression of a mutant form of drebrin that is unable to bind BTP2. Drebrin in myoblasts is enriched in cellular projections and cell cortices and at regions of cell-cell contact, all sites where F-actin, too, was concentrated. Conclusions Our findings reveal that Dbn1 expression is a target of p38 MAPK signaling during myogenesis and that drebrin promotes myoblast differentiation.
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Affiliation(s)
- Annalisa Mancini
- Department of Developmental and Regenerative Biology, Mount Sinai School of Medicine, One Gustave L, Levy Place, New York, NY 10029, USA.
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26
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Baldanzi G, Pietronave S, Locarno D, Merlin S, Porporato P, Chianale F, Filigheddu N, Cantelmo AR, Albini A, Graziani A, Prat M. Diacylglycerol kinases are essential for hepatocyte growth factor-dependent proliferation and motility of Kaposi's sarcoma cells. Cancer Sci 2011; 102:1329-36. [PMID: 21477072 DOI: 10.1111/j.1349-7006.2011.01953.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Hepatocyte growth factor (HGF) is involved in the pathogenesis of Kaposi's sarcoma (KS), the most frequent neoplasia in patients with AIDS, characterized by proliferating spindle cells, infiltrating inflammatory cells, angiogenesis, edema, and invasiveness. In vitro, this factor sustains the biological behavior of KS derived cells, after activation of its receptor and the downstream MAPK and AKT signals. In other cell types, namely endothelial and epithelial cells, movement, proliferation, and survival stimulated by HGF and other growth factors and cytokines depend on diacylglycerol kinases (DGK). In an effort to identify new intracellular transducers operative in KS cells, which could represent therapeutic targets, we investigated the role of DGK in KS cell movement and proliferation by treating cells with the DGK pharmacological inhibitor R59949. We report that R59949 strongly inhibits HGF-induced KS motility, proliferation, and anchorage-independent growth with only a partial effect on cell adhesion and spreading. R59949 does not affect cell survival, HGF receptor activation, or the classical MAPK and AKT signalling pathways. Furthermore, we carried out an siRNA screen to characterize the DGK isoforms involved in KS motility and anchorage independent growth. Our data indicate a strong involvement of DGK-δ in KS motility and of DGK-ι in anchorage-independent growth. These results indicate that DGK inhibition is sufficient to impair in vitro KS cell proliferation and movement and suggest that selected DGK represent new pharmacological targets to interfere with the malignant properties of KS, independently from the well-known RAS/MAPK and PI3K/AKT pathways.
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Affiliation(s)
- Gianluca Baldanzi
- Department of Experimental and Clinical Medicine, Università del Piemonte Orientale Amedeo Avogadro, Novara IRCCS Multimedica, Milan, Italy
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Hes6 is required for actin cytoskeletal organization in differentiating C2C12 myoblasts. Exp Cell Res 2011; 317:1590-602. [PMID: 21501606 DOI: 10.1016/j.yexcr.2011.03.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 03/29/2011] [Accepted: 03/31/2011] [Indexed: 11/23/2022]
Abstract
Hes6 is a member of the hairy-enhancer-of-split family of transcription factors that regulate proliferating cell fate in development and is known to be expressed in developing muscle. Here we investigate its function in myogenesis in vitro. We show that Hes6 is a direct transcriptional target of the myogenic transcription factors MyoD and Myf5, indicating that it is integral to the myogenic transcriptional program. The localization of Hes6 protein changes during differentiation, becoming predominantly nuclear. Knockdown of Hes6 mRNA levels by siRNA has no effect on cell cycle exit or induction of myosin heavy chain expression in differentiating C2C12 myoblasts, but F-actin filament formation is disrupted and both cell motility and myoblast fusion are reduced. The knockdown phenotype is rescued by expression of Hes6 cDNA resistant to siRNA. These results define a novel role for Hes6 in actin cytoskeletal dynamics in post mitotic myoblasts.
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Molecular mechanisms of myoblast fusion across species. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 713:113-35. [PMID: 21432017 DOI: 10.1007/978-94-007-0763-4_8] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Skeletal muscle development, growth and regeneration depend on the ability of progenitor myoblasts to fuse to one another in a series of ordered steps. Whereas the cellular steps leading to the formation of a multinucleated myofiber are conserved in several model organisms, the molecular regulatory factors may vary. Understanding the common and divergent mechanisms regulating myoblast fusion in Drosophila melanogaster (fruit fly), Danio rerio (zebrafish) and Mus musculus (mouse) provides a better insight into the process of myoblast fusion than any of these models could provide alone. Deciphering the mechanisms of myoblast fusion from simpler to more complex organisms is of fundamental interest to skeletal muscle biology and may provide therapeutic avenues for various diseases that affect muscle.
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Pavlath GK. Spatial and functional restriction of regulatory molecules during mammalian myoblast fusion. Exp Cell Res 2010; 316:3067-72. [PMID: 20553712 DOI: 10.1016/j.yexcr.2010.05.025] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 05/21/2010] [Accepted: 05/21/2010] [Indexed: 10/19/2022]
Abstract
Myoblast fusion is a highly regulated process that is key for forming skeletal muscle during development and regeneration in mammals. Much remains to be understood about the molecular regulation of myoblast fusion. Some molecules that influence mammalian muscle fusion display specific cellular localization during myogenesis. Such molecules can be localized to the contact region between two fusing cells either in both cells or only in one of the cells. How distinct localization of molecules contributes to fusion is not clear. Further complexity exists as other molecules are functionally restricted to myoblasts at later stages of myogenesis to regulate their fusion with multinucleated myotubes. This review examines these three categories of molecules and discusses how spatial and functional restriction may contribute to the formation of a multinucleated cell. Understanding how and why molecules become restricted in location or function is likely to provide further insights into the mechanisms regulating mammalian muscle fusion.
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Affiliation(s)
- Grace K Pavlath
- Department of Pharmacology, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA.
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30
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Rochlin K, Yu S, Roy S, Baylies MK. Myoblast fusion: when it takes more to make one. Dev Biol 2009; 341:66-83. [PMID: 19932206 DOI: 10.1016/j.ydbio.2009.10.024] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Revised: 10/14/2009] [Accepted: 10/14/2009] [Indexed: 01/09/2023]
Abstract
Cell-cell fusion is a crucial and highly regulated event in the genesis of both form and function of many tissues. One particular type of cell fusion, myoblast fusion, is a key cellular process that shapes the formation and repair of muscle. Despite its importance for human health, the mechanisms underlying this process are still not well understood. The purpose of this review is to highlight the recent literature pertaining to myoblast fusion and to focus on a comparison of these studies across several model systems, particularly the fly, zebrafish and mouse. Advances in technical analysis and imaging have allowed identification of new fusion genes and propelled further characterization of previously identified genes in each of these systems. Among the cellular steps identified as critical for myoblast fusion are migration, recognition, adhesion, membrane alignment and membrane pore formation and resolution. Importantly, striking new evidence indicates that orthologous genes govern several of these steps across these species. Taken together, comparisons across three model systems are illuminating a once elusive process, providing exciting new insights and a useful framework of genes and mechanisms.
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Affiliation(s)
- Kate Rochlin
- Program in Developmental Biology, Sloan-Kettering Institute, New York, NY 10065, USA
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31
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Nowak SJ, Nahirney PC, Hadjantonakis AK, Baylies MK. Nap1-mediated actin remodeling is essential for mammalian myoblast fusion. J Cell Sci 2009; 122:3282-93. [PMID: 19706686 DOI: 10.1242/jcs.047597] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Myoblast fusion is crucial for the formation, growth, maintenance and regeneration of healthy skeletal muscle. Unfortunately, the molecular machinery, cell behaviors, and membrane and cytoskeletal remodeling events that govern fusion and myofiber formation remain poorly understood. Using time-lapse imaging approaches on mouse C2C12 myoblasts, we identify discrete and specific molecular events at myoblast membranes during fusion and myotube formation. These events include rearrangement of cell shape from fibroblast to spindle-like morphologies, changes in lamellipodial and filopodial extensions during different periods of differentiation, and changes in membrane alignment and organization during fusion. We find that actin-cytoskeleton remodeling is crucial for these events: pharmacological inhibition of F-actin polymerization leads to decreased lamellipodial and filopodial extensions and to reduced myoblast fusion. Additionally, shRNA-mediated inhibition of Nap1, a member of the WAVE actin-remodeling complex, results in accumulations of F-actin structures at the plasma membrane that are concomitant with a decrease in myoblast fusion. Our data highlight distinct and essential roles for actin cytoskeleton remodeling during mammalian myoblast fusion, provide a platform for cellular and molecular dissection of the fusion process, and suggest a functional conservation of Nap1-regulated actin-cytoskeleton remodeling during myoblast fusion between mammals and Drosophila.
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Affiliation(s)
- Scott J Nowak
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, USA
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Abramovici H, Mojtabaie P, Parks RJ, Zhong XP, Koretzky GA, Topham MK, Gee SH. Diacylglycerol kinase zeta regulates actin cytoskeleton reorganization through dissociation of Rac1 from RhoGDI. Mol Biol Cell 2009; 20:2049-59. [PMID: 19211846 DOI: 10.1091/mbc.e07-12-1248] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Activation of Rac1 GTPase signaling is stimulated by phosphorylation and release of RhoGDI by the effector p21-activated kinase 1 (PAK1), but it is unclear what initiates this potential feed-forward mechanism for regulation of Rac activity. Phosphatidic acid (PA), which is produced from the lipid second messenger diacylglycerol (DAG) by the action of DAG kinases (DGKs), is known to activate PAK1. Here, we investigated whether PA produced by DGKzeta initiates RhoGDI release and Rac1 activation. In DGKzeta-deficient fibroblasts PAK1 phosphorylation and Rac1-RhoGDI dissociation were attenuated, leading to reduced Rac1 activation after platelet-derived growth factor stimulation. The cells were defective in Rac1-regulated behaviors, including lamellipodia formation, membrane ruffling, migration, and spreading. Wild-type DGKzeta, but not a kinase-dead mutant, or addition of exogenous PA rescued Rac activation. DGKzeta stably associated with PAK1 and RhoGDI, suggesting these proteins form a complex that functions as a Rac1-selective RhoGDI dissociation factor. These results define a pathway that links diacylglycerol, DGKzeta, and PA to the activation of Rac1: the PA generated by DGKzeta activates PAK1, which dissociates RhoGDI from Rac1 leading to changes in actin dynamics that facilitate the changes necessary for cell motility.
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Affiliation(s)
- Hanan Abramovici
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
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Zhong XP, Guo R, Zhou H, Liu C, Wan CK. Diacylglycerol kinases in immune cell function and self-tolerance. Immunol Rev 2008; 224:249-64. [PMID: 18759932 DOI: 10.1111/j.1600-065x.2008.00647.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Both diacylglycerol (DAG) and phosphatidic acid (PA) are important second messengers involved in signal transduction from many immune cell receptors and can be generated and metabolized through multiple mechanisms. Recent studies indicate that diacylglycerol kinases (DGKs), the enzymes that catalyze phosphorylation of DAG to produce PA, play critical roles in regulating the functions of multiple immune cell lineages. In T cells, two DGK isoforms, alpha and zeta, inhibit DAG-mediated signaling following T-cell receptor engagement and prevent T-cell hyperactivation. DGK alpha and zeta synergistically promote T-cell anergy and are critical for T-cell tolerance. In mast cells, DGKzeta plays differential roles in their activation by promoting degranulation but attenuating cytokine production following engagement of the high affinity receptor for immunoglobulin E. In dendritic cells and macrophages, DGKzeta positively regulates Toll-like receptor-induced proinflammatory cytokine production through its product PA and is critical for host defense against Toxoplasma gondii infection. These studies demonstrate pivotal roles of DGKs in regulating immune cell function by acting both as signal terminator and initiator.
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Affiliation(s)
- Xiao-Ping Zhong
- Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA.
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Richardson BE, Nowak SJ, Baylies MK. Myoblast fusion in fly and vertebrates: new genes, new processes and new perspectives. Traffic 2008; 9:1050-9. [PMID: 18435820 DOI: 10.1111/j.1600-0854.2008.00756.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Muscle formation and repair depends critically on the fusion of myoblasts. Despite the importance of this process, little is known about the cellular and molecular mechanisms regulating fusion. Forward genetic screens in Drosophila melanogaster have uncovered genes that, when mutated, prevent myoblast fusion. Analyses of these gene products have indicated that the actin cytoskeleton and its regulation play a central role in the fusion process. In this review, we discuss recent advances in the field, including new imaging approaches to analyze fusion as well as a description of novel genes required for fusion. In particular, we highlight what has been learned about the requirement of a specific actin structure at the site of fusion. We also place these findings from Drosophila within the context of myoblast fusion in vertebrates.
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Affiliation(s)
- Brian E Richardson
- Sloan-Kettering Institute, Weill Graduate School of Medical Sciences, Cornell University, New York, NY 10021, USA
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