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Wu MP, Doyle JR, Barry B, Beauvais A, Rozkalne A, Piao X, Lawlor MW, Kopin AS, Walsh CA, Gussoni E. G-protein coupled receptor 56 promotes myoblast fusion through serum response factor- and nuclear factor of activated T-cell-mediated signalling but is not essential for muscle development in vivo. FEBS J 2013; 280:6097-113. [PMID: 24102982 PMCID: PMC3877849 DOI: 10.1111/febs.12529] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 08/24/2013] [Accepted: 09/04/2013] [Indexed: 12/28/2022]
Abstract
Mammalian muscle cell differentiation is a complex process of multiple steps for which many of the factors involved have not yet been defined. In a screen to identify the regulators of myogenic cell fusion, we found that the gene for G-protein coupled receptor 56 (GPR56) was transiently up-regulated during the early fusion of human myoblasts. Human mutations in the gene for GPR56 cause the disease bilateral frontoparietal polymicrogyria; however, the consequences of receptor dysfunction on muscle development have not been explored. Using knockout mice, we defined the role of GPR56 in skeletal muscle. GPR56(-/-) myoblasts have decreased fusion and smaller myotube sizes in culture. In addition, a loss of GPR56 expression in muscle cells results in decreases or delays in the expression of myogenic differentiation 1, myogenin and nuclear factor of activated T-cell (NFAT)c2. Our data suggest that these abnormalities result from decreased GPR56-mediated serum response element and NFAT signalling. Despite these changes, no overt differences in phenotype were identified in the muscle of GPR56 knockout mice, which presented only a mild but statistically significant elevation of serum creatine kinase compared to wild-type. In agreement with these findings, clinical data from 13 bilateral frontoparietal polymicrogyria patients revealed mild serum creatine kinase increase in only two patients. In summary, targeted disruption of GPR56 in mice results in myoblast abnormalities. The absence of a severe muscle phenotype in GPR56 knockout mice and human patients suggests that other factors may compensate for the lack of this G-protein coupled receptor during muscle development and that the motor delay observed in these patients is likely not a result of primary muscle abnormalities.
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Affiliation(s)
- Melissa P. Wu
- Biological and Biomedical Sciences, Harvard Medical School, Boston MA 02115, USA
- Division of Genetics, Boston Children’s Hospital, Boston MA 02115, USA
| | - Jamie R. Doyle
- Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111, USA
| | - Brenda Barry
- Division of Genetics, Boston Children’s Hospital, Boston MA 02115, USA
- Howard Hughes Medical Institute, Boston Children’s Hospital, Boston MA 02115, USA
| | - Ariane Beauvais
- Division of Genetics, Boston Children’s Hospital, Boston MA 02115, USA
| | - Anete Rozkalne
- Division of Genetics, Boston Children’s Hospital, Boston MA 02115, USA
| | - Xianhua Piao
- Division of Newborn Medicine, Boston Children’s Hospital, Boston MA 02115, USA
| | - Michael W. Lawlor
- Department of Pathology and Laboratory Medicine, Children’s Hospital of Wisconsin and Medical College of Wisconsin, Milwaukee WI 53226, USA
| | - Alan S. Kopin
- Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111, USA
| | - Christopher A. Walsh
- Division of Genetics, Boston Children’s Hospital, Boston MA 02115, USA
- Howard Hughes Medical Institute, Boston Children’s Hospital, Boston MA 02115, USA
| | - Emanuela Gussoni
- Division of Genetics, Boston Children’s Hospital, Boston MA 02115, USA
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52
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Normal muscle regeneration requires tight control of muscle cell fusion by tetraspanins CD9 and CD81. Nat Commun 2013; 4:1674. [PMID: 23575678 DOI: 10.1038/ncomms2675] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 03/01/2013] [Indexed: 12/16/2022] Open
Abstract
Skeletal muscle regeneration after injury follows a remarkable sequence of synchronized events. However, the mechanisms regulating the typical organization of the regenerating muscle at different stages remain largely unknown. Here we show that muscle regeneration in mice lacking either CD9 or CD81 is abnormal and characterized by the formation of discrete giant dystrophic myofibres, which form more quickly in the absence of both tetraspanins. We also show that, in myoblasts, these two tetraspanins associate with the immunoglobulin domain molecule CD9P-1 (EWI-F/FPRP), and that grafting of CD9P-1-depleted myoblasts in regenerating muscles also leads to abnormal regeneration. In vitro myotubes lacking CD9P-1 or both CD9 and CD81 fuse with a higher frequency than normal myotubes. Our study unveils a mechanism preventing inappropriate fusion of myotubes that has an important role in the restitution of normal muscle architecture during muscle regeneration.
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53
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Mukai A, Hashimoto N. Regulation of pre-fusion events: recruitment of M-cadherin to microrafts organized at fusion-competent sites of myogenic cells. BMC Cell Biol 2013; 14:37. [PMID: 23978243 PMCID: PMC3846853 DOI: 10.1186/1471-2121-14-37] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 08/22/2013] [Indexed: 01/16/2023] Open
Abstract
Background Previous research indicates that the membrane ruffles and leading edge of lamellipodia of myogenic cells contain presumptive fusion sites. A micrometer-sized lipid raft (microraft) is organized at the presumptive fusion site of mouse myogenic cells in a cell-contact independent way and serves as a platform tethering adhesion proteins that are relevant to cell fusion. However, the mechanisms underlying recruitment of adhesion proteins to lipid rafts and microraft organization remain unknown. Results Here we show that small G-protein Rac1 was required for microraft organization and subsequent cell fusion. However, Rac1 activity was unnecessary for recruitment of M-cadherin to lipid rafts. We found that p120 catenin (p120) binds to M-cadherin exclusively in lipid rafts of differentiating myogenic cells. The Src kinase inhibitor SU6656 prevented p120 binding to M-cadherin and their recruitment to lipid rafts, then suppressed microraft organization, membrane ruffling, and myogenic cell fusion. Suppression of membrane ruffling in SU6656-treated cells was partially restored by pretreatment with the protein tyrosine phosphatase inhibitor vanadate. The present analyses using an antibody to tyrosine phosphorylated p120 suggest that Src family kinases play a role in binding of p120 to M-cadherin and the recruitment of M-cadherin to lipid rafts through phosphorylation of putative substrates other than p120. Conclusions The present study showed that the procedure establishing fusion-competent sites consists of two sequential events: recruitment of adhesion complexes to lipid rafts and organization of microrafts. The recruitment of M-cadherin to lipid rafts depended on interaction with p120 catenin, whereas the organization of microrafts was controlled by a small G protein, Rac1.
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Affiliation(s)
- Atsushi Mukai
- Department of Regenerative Medicine, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, 35 Gengo, Morioka, Oobu, Aichi 474-8522, Japan.
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Polanco JC, Ho MS, Wang B, Zhou Q, Wolvetang E, Mason E, Wells CA, Kolle G, Grimmond SM, Bertoncello I, O'Brien C, Laslett AL. Identification of Unsafe Human Induced Pluripotent Stem Cell Lines Using a Robust Surrogate Assay for Pluripotency. Stem Cells 2013; 31:1498-510. [DOI: 10.1002/stem.1425] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 04/14/2013] [Indexed: 12/18/2022]
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55
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Kim YH, Kim BJ, Kim BG, Lee YA, Kim KJ, Chung HJ, Hwang S, Woo JS, Park JK, Schmidt JA, Pang MG, Ryu BY. Stage-specific embryonic antigen-1 expression by undifferentiated spermatogonia in the prepubertal boar testis1. J Anim Sci 2013; 91:3143-54. [DOI: 10.2527/jas.2012-6139] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Affiliation(s)
- Y.-H. Kim
- Department of Animal Science & Technology, Chung-Ang University, Anseong, Gyeonggi-do 456-756, Korea
| | - B.-J. Kim
- Department of Animal Science & Technology, Chung-Ang University, Anseong, Gyeonggi-do 456-756, Korea
| | - B.-G. Kim
- Department of Animal Science & Technology, Chung-Ang University, Anseong, Gyeonggi-do 456-756, Korea
| | - Y.-A. Lee
- Department of Animal Science & Technology, Chung-Ang University, Anseong, Gyeonggi-do 456-756, Korea
| | - K.-J. Kim
- Department of Animal Science & Technology, Chung-Ang University, Anseong, Gyeonggi-do 456-756, Korea
| | - H.-J. Chung
- Animal Biotechnology Division, National Institute of Animal Science, RDA, Chuksan-gil 77, Suwon, Gyeonggi-do 441-706, Korea
| | - S. Hwang
- Animal Biotechnology Division, National Institute of Animal Science, RDA, Chuksan-gil 77, Suwon, Gyeonggi-do 441-706, Korea
| | - J.-S. Woo
- Animal Biotechnology Division, National Institute of Animal Science, RDA, Chuksan-gil 77, Suwon, Gyeonggi-do 441-706, Korea
| | - J.-K. Park
- Animal Biotechnology Division, National Institute of Animal Science, RDA, Chuksan-gil 77, Suwon, Gyeonggi-do 441-706, Korea
| | - J. A. Schmidt
- Department of Science, Spokane Community College, 1810 N Greene St., Spokane, WA 99217-5399
| | - M.-G. Pang
- Department of Animal Science & Technology, Chung-Ang University, Anseong, Gyeonggi-do 456-756, Korea
| | - B.-Y. Ryu
- Department of Animal Science & Technology, Chung-Ang University, Anseong, Gyeonggi-do 456-756, Korea
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Rappa G, Mercapide J, Anzanello F, Pope RM, Lorico A. Biochemical and biological characterization of exosomes containing prominin-1/CD133. Mol Cancer 2013; 12:62. [PMID: 23767874 PMCID: PMC3698112 DOI: 10.1186/1476-4598-12-62] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 06/05/2013] [Indexed: 12/14/2022] Open
Abstract
Exosomes can be viewed as complex “messages” packaged to survive trips to other cells in the local microenvironment and, through body fluids, to distant sites. A large body of evidence indicates a pro-metastatic role for certain types of cancer exosomes. We previously reported that prominin-1 had a pro-metastatic role in melanoma cells and that microvesicles released from metastatic melanoma cells expressed high levels of prominin-1. With the goal to explore the mechanisms that govern proteo-lipidic-microRNA sorting in cancer exosomes and their potential contribution(s) to the metastatic phenotype, we here employed prominin-1-based immunomagnetic separation in combination with filtration and ultracentrifugation to purify prominin-1-expressing exosomes (prom1-exo) from melanoma and colon carcinoma cells. Prom1-exo contained 154 proteins, including all of the 14 proteins most frequently expressed in exosomes, and multiple pro-metastatic proteins, including CD44, MAPK4K, GTP-binding proteins, ADAM10 and Annexin A2. Their lipid composition resembled that of raft microdomains, with a great enrichment in lyso-phosphatidylcholine, lyso-phosphatidyl-ethanolamine and sphingomyelin. The abundance of tetraspanins and of tetraspanin-associated proteins, together with the high levels of sphingomyelin, suggests that proteolipidic assemblies, probably tetraspanin webs, might be the essential structural determinant in the release process of prominin-1 of stem and cancer stem cells. Micro-RNA profiling revealed 49 species of micro-RNA present at higher concentrations in prom1-exo than in parental cells, including 20 with cancer-related function. Extensive accumulation of prom1-exo was observed 3 h after their addition to cultures of melanoma and bone marrow-derived stromal cells (MSC). Short-term co-culture of melanoma cells and MSC resulted in heterologous prominin-1 transfer. Exposure of MSC to prom1-exo increased their invasiveness. Our study supports the concept that specific populations of cancer exosomes contain multiple determinants of the metastatic potential of the cells from which they are derived.
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Affiliation(s)
- Germana Rappa
- Cancer Research Center, Roseman University of Health Sciences, Las Vegas, NV 89135, USA
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57
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Caballero JN, Frenette G, Belleannée C, Sullivan R. CD9-positive microvesicles mediate the transfer of molecules to Bovine Spermatozoa during epididymal maturation. PLoS One 2013; 8:e65364. [PMID: 23785420 PMCID: PMC3681974 DOI: 10.1371/journal.pone.0065364] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 04/27/2013] [Indexed: 12/04/2022] Open
Abstract
Acquisition of fertilization ability by spermatozoa during epididymal transit occurs in part by the transfer of molecules from membranous vesicles called epididymosomes. Epididymosomes are heterogeneous in terms of both size and molecular composition. Exosomes and other related small membranous vesicles (30–120 nm) containing tetraspanin proteins on their surface are found in many biological fluids. In this study, we demonstrate that these vesicles are present in bovine cauda epididymal fluid as a subpopulation of epididymosomes. They contain tetraspanin CD9 in addition to other proteins involved in sperm maturation such as P25b, GliPr1L1, and MIF. In order to study the mechanism of protein transfer to sperm, DilC12-labeled unfractionated epididymosomes or CD9-positive microvesicles were coincubated with epididymal spermatozoa, and their transfer was evaluated by flow cytometry. CD9-positive microvesicles from epididymal fluid specifically transferred molecules to spermatozoa, whereas those prepared from blood were unable to do so. The CD9-positive microvesicles transferred molecules to the same sperm regions (acrosome and midpiece) as epididymosomes, with the same kinetics; however, the molecules were preferentially transferred to live sperm and, in contrast to epididymosomes, Zn2+ did not demonstrate potentiated transfer. Tetraspanin CD9 was associated with other proteins on the membrane surface of CD9-positive microvesicles according to coimmunoprecipitation experiments. CD26 cooperated with CD9 in the molecular transfer to sperm since the amount of molecules transferred was significantly reduced in the presence of specific antibodies. In conclusion, CD9-positive microvesicles are present in bovine cauda epididymal fluid and transfer molecules to live maturing sperm in a tissue-specific manner that involves CD9 and CD26.
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Affiliation(s)
- Julieta N. Caballero
- Centre de Recherche du Centre Hospitalier Universitaire de Québec (CRCHU de Québec), Université Laval, Québec, PQ, Canada
| | - Gilles Frenette
- Centre de Recherche du Centre Hospitalier Universitaire de Québec (CRCHU de Québec), Université Laval, Québec, PQ, Canada
| | - Clémence Belleannée
- Centre de Recherche du Centre Hospitalier Universitaire de Québec (CRCHU de Québec), Université Laval, Québec, PQ, Canada
| | - Robert Sullivan
- Centre de Recherche du Centre Hospitalier Universitaire de Québec (CRCHU de Québec), Université Laval, Québec, PQ, Canada
- Centre de Recherche en Biologie de la Reproduction, Département d’Obstétrique, Gynécologie et Reproduction, Université Laval, Québec, PQ, Canada
- * E-mail:
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58
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Spring FA, Griffiths RE, Mankelow TJ, Agnew C, Parsons SF, Chasis JA, Anstee DJ. Tetraspanins CD81 and CD82 facilitate α4β1-mediated adhesion of human erythroblasts to vascular cell adhesion molecule-1. PLoS One 2013; 8:e62654. [PMID: 23704882 PMCID: PMC3660455 DOI: 10.1371/journal.pone.0062654] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 03/25/2013] [Indexed: 11/28/2022] Open
Abstract
The proliferation and terminal differentiation of erythroid progenitors occurs in human bone marrow within erythroblastic islands, specialised structures consisting of a central macrophage surrounded by developing erythroid cells. Many cell-cell and cell-matrix adhesive interactions maintain and regulate the co-ordinated daily production of reticulocytes. Erythroid cells express only one integrin, α4β1, throughout differentiation, and its interactions with both macrophage Vascular Cell Adhesion Molecule-1 and with extracellular matrix fibronectin are critical for erythropoiesis. We observed that proerythroblasts expressed a broad tetraspanin phenotype, and investigated whether any tetraspanin could modulate integrin function. A specific association between α4β1 and CD81, CD82 and CD151 was demonstrated by confocal microscopy and co-immune precipitation. We observed that antibodies to CD81 and CD82 augmented adhesion of proerythroblasts to Vascular Cell Adhesion Molecule-1 but not to the fibronectin spliceoforms FnIII12-IIICS-15 and FnIII12–15. In contrast, different anti-CD151 antibodies augmented or inhibited adhesion of proerythroblasts to Vascular Cell Adhesion Molecule-1 and the fibronectin spliceoform FnIII12-IIICS-15 but not to FnIII12–15. These results strongly suggest that tetraspanins have a functional role in terminal erythropoiesis by modulating interactions of erythroblast α4β1 with both macrophages and extracellular matrix.
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Affiliation(s)
- Frances A Spring
- Bristol Institute for Transfusion Sciences, Bristol, United Kingdom.
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59
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Adhesion proteins--an impact on skeletal myoblast differentiation. PLoS One 2013; 8:e61760. [PMID: 23671573 PMCID: PMC3645998 DOI: 10.1371/journal.pone.0061760] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 03/13/2013] [Indexed: 11/19/2022] Open
Abstract
Formation of mammalian skeletal muscle myofibers, that takes place during embryogenesis, muscle growth or regeneration, requires precise regulation of myoblast adhesion and fusion. There are few evidences showing that adhesion proteins play important role in both processes. To follow the function of these molecules in myoblast differentiation we analysed integrin alpha3, integrin beta1, ADAM12, CD9, CD81, M-cadherin, and VCAM-1 during muscle regeneration. We showed that increase in the expression of these proteins accompanies myoblast fusion and myotube formation in vivo. We also showed that during myoblast fusion in vitro integrin alpha3 associates with integrin beta1 and ADAM12, and also CD9 and CD81, but not with M-cadherin or VCAM-1. Moreover, we documented that experimental modification in the expression of integrin alpha3 lead to the modification of myoblast fusion in vitro. Underexpression of integrin alpha3 decreased myoblasts' ability to fuse. This phenomenon was not related to the modifications in the expression of other adhesion proteins, i.e. integrin beta1, CD9, CD81, ADAM12, M-cadherin, or VCAM-1. Apparently, aberrant expression only of one partner of multiprotein adhesion complexes necessary for myoblast fusion, in this case integrin alpha3, prevents its proper function. Summarizing, we demonstrated the importance of analysed adhesion proteins in myoblast fusion both in vivo and in vitro.
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60
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Mazurov D, Barbashova L, Filatov A. Tetraspanin protein CD9 interacts with metalloprotease CD10 and enhances its release via exosomes. FEBS J 2013; 280:1200-13. [PMID: 23289620 DOI: 10.1111/febs.12110] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 12/27/2012] [Accepted: 01/01/2013] [Indexed: 12/11/2022]
Abstract
Tetraspanins interact with a wide variety of transmembrane and intracellular proteins called molecular partners, and modulate their function. In this article, we describe a new partner of tetraspanin web, membrane metalloprotease CD10, which is selectively associated with CD9. By constructing chimeras between tetraspanins CD9 and CD82 (the latter does not interact with CD10) or by using site-directed mutagenesis, we determined that a portion of the large extracellular loop from the CCG motif to transmembrane domain 4, as well as the C-terminal tail of CD9, are involved in the interaction with CD10. The stable expression of wild-type CD9 in K562 CD10-positive cells enhanced the level of CD10 released with exosomes five-fold. In contrast, the expression of chimeric CD9, which contained the cytoplasmic C-terminal domain from CD82, had little effect on CD10 release. Short hairpin RNA knockdown of CD9 expression in Nalm-6 pre-B cells resulted in a two-fold reduction in the amount of endogenous CD10 released with microvesicles. The peptidase activity of CD10 measured either on cells or on exosomes correlated with the level of CD10 expression, and was not significantly modulated by CD9 expression as such. Our data suggest that the interaction of CD10 with tetraspanin CD9 can play an important role in the redistribution of peptidase activity from the cell surface to outer microenvironments. In bone marrow, where CD10 presumably contributes to the maturation of pre-B cells and migration of B cells to the blood circulation, release of CD10 peptidase activity with exosomes may effectively regulate extracellular matrix microenvironments.
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Affiliation(s)
- Dmitriy Mazurov
- Laboratory of Immunochemistry, Institute of Immunology, Moscow, Russia.
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61
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Wang Y, Grainger DW. RNA therapeutics targeting osteoclast-mediated excessive bone resorption. Adv Drug Deliv Rev 2012; 64:1341-57. [PMID: 21945356 DOI: 10.1016/j.addr.2011.09.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 09/05/2011] [Indexed: 01/13/2023]
Abstract
RNA interference (RNAi) is a sequence-specific post-transcriptional gene silencing technique developed with dramatically increasing utility for both scientific and therapeutic purposes. Short interfering RNA (siRNA) is currently exploited to regulate protein expression relevant to many therapeutic applications, and commonly used as a tool for elucidating disease-associated genes. Osteoporosis and their associated osteoporotic fragility fractures in both men and women are rapidly becoming a global healthcare crisis as average life expectancy increases worldwide. New therapeutics are needed for this increasing patient population. This review describes the diversity of molecular targets suitable for RNAi-based gene knock down in osteoclasts to control osteoclast-mediated excessive bone resorption. We identify strategies for developing targeted siRNA delivery and efficient gene silencing, and describe opportunities and challenges of introducing siRNA as a therapeutic approach to hard and connective tissue disorders.
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62
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Zohni K, Zhang X, Tan SL, Chan P, Nagano M. CD9 Is Expressed on Human Male Germ Cells That Have a Long-Term Repopulation Potential after Transplantation into Mouse Testes1. Biol Reprod 2012; 87:27. [DOI: 10.1095/biolreprod.112.098913] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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63
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Liu QC, Zha XH, Faralli H, Yin H, Louis-Jeune C, Perdiguero E, Pranckeviciene E, Muñoz-Cànoves P, Rudnicki MA, Brand M, Perez-Iratxeta C, Dilworth FJ. Comparative expression profiling identifies differential roles for Myogenin and p38α MAPK signaling in myogenesis. J Mol Cell Biol 2012; 4:386-97. [PMID: 22847234 DOI: 10.1093/jmcb/mjs045] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Skeletal muscle differentiation is mediated by a complex gene expression program requiring both the muscle-specific transcription factor Myogenin (Myog) and p38α MAPK (p38α) signaling. However, the relative contribution of Myog and p38α to the formation of mature myotubes remains unknown. Here, we have uncoupled the activity of Myog from that of p38α to gain insight into the individual roles of these proteins in myogenesis. Comparative expression profiling confirmed that Myog activates the expression of genes involved in muscle function. Furthermore, we found that in the absence of p38α signaling, Myog expression leads to the down-regulation of genes involved in cell cycle progression. Consistent with this, the expression of Myog is sufficient to induce cell cycle exit. Interestingly, p38α-defective, Myog-expressing myoblasts fail to form multinucleated myotubes, suggesting an important role for p38α in cell fusion. Through the analysis of p38α up-regulated genes, the tetraspanin CD53 was identified as a candidate fusion protein, a role confirmed both ex vivo in primary myoblasts, and in vivo during myofiber regeneration in mice. Thus, our study has revealed an unexpected role for Myog in mediating cell cycle exit and has identified an essential role for p38α in cell fusion through the up-regulation of CD53.
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Affiliation(s)
- Qi-Cai Liu
- Sprott Center for Stem Cell Research, Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada K1H 8L6
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Carloni V, Mazzocca A, Mello T, Galli A, Capaccioli S. Cell fusion promotes chemoresistance in metastatic colon carcinoma. Oncogene 2012; 32:2649-60. [PMID: 22751128 DOI: 10.1038/onc.2012.268] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chemoresistance is an important concern in the treatment of metastatic colon cancer. It may emerge through selection of clones that are inherently resistant from the outset or through mechanisms acquired during treatment. Cell fusion represents an efficient means of rapid phenotypic evolution that make cells with new properties at a rate exceeding that achievable by random mutagenesis. Here, we first identified a number of proteins involved in cell fusion using a shotgun proteomics approach, then we investigated the role of these proteins namely tetraspanin CD81/CD9, ADAM10, GTP-binding protein α13, radixin, myosin regulatory light chain and RhoA in the regulation of colon cancer cell fusion. We also found a previously unrecognized role of ADAM10, Gα13 and RhoA in promoting cell fusion. Finally, we show that the occurrence of cell fusion in a metastatic model of colon carcinoma causes the appearance of cells resistant to both 5-fluorouracil and oxaliplatin. These findings highlight the importance of cell fusion in cancer progression and raise significant implications for overcoming chemoresistance in metastatic colon cancer.
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Affiliation(s)
- V Carloni
- Department of Internal Medicine, Center for Research, Transfer and High Education, DENOthe, University of Florence, Florence, Italy.
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65
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IgSF8: a developmentally and functionally regulated cell adhesion molecule in olfactory sensory neuron axons and synapses. Mol Cell Neurosci 2012; 50:238-49. [PMID: 22687584 DOI: 10.1016/j.mcn.2012.05.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 05/10/2012] [Accepted: 05/28/2012] [Indexed: 01/08/2023] Open
Abstract
Here, we investigated an Immunoglobulin (Ig) superfamily protein IgSF8 which is abundantly expressed in olfactory sensory neuron (OSN) axons and their developing synapses. We demonstrate that expression of IgSF8 within synaptic neuropil is transitory, limited to the period of glomerular formation. Glomerular expression decreases after synaptic maturation and compartmental glomerular organization is achieved, although expression is maintained at high levels within the olfactory nerve layer (ONL). Immunoprecipitations indicate that IgSF8 interacts with tetraspanin CD9 in the olfactory bulb (OB). CD9 is a component of tetraspanin-enriched microdomains (TEMs), specialized microdomains of the plasma membrane known to regulate cell morphology, motility, invasion, fusion and signaling, in both the nervous and immune systems, as well as in tumors. In vitro, both IgSF8 and CD9 localize to puncta within axons and growth cones of OSNs, consistent with TEM localization. When the olfactory epithelium (OE) was lesioned, forcing OSN regeneration en masse, IgSF8 was once again able to be detected in OSN axon terminals as synapses were reestablished. Finally, we halted synaptic maturation within glomeruli by unilaterally blocking functional activity and found that IgSF8 did not undergo exclusion from this subcellular compartment and instead continued to be detected in adult glomeruli. These data support the hypothesis that IgSF8 facilitates OSN synapse formation.
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Köberle M, Kaesler S, Kempf W, Wölbing F, Biedermann T. Tetraspanins in mast cells. Front Immunol 2012; 3:106. [PMID: 22783251 PMCID: PMC3346162 DOI: 10.3389/fimmu.2012.00106] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 04/17/2012] [Indexed: 01/01/2023] Open
Abstract
Mast cells (MC) are key mediators of the immune system, most prominently known for their role in eliciting harmful allergic reactions. Mast cell mediator release (e.g. by degranulation) is triggered by FcεRI recognition of antigen – IgE complexes. Until today no therapeutic targeting of this and other mast cell activation pathways is established. Among possible new candidates there are tetraspanins that have been described on MC already several years ago. Tetraspanins are transmembrane proteins acting as scaffolds, mediating local clustering of their interaction partners, and thus amplify their activities. More recently, tetraspanins were also found to exert intrinsic receptor functions. Tetraspanins have been found to be crucial components of fundamental biological processes like cell motility and adhesion. In immune cells, they not only boost the effectiveness of antigen presentation by clustering MHC molecules, they are also key players in all kinds of degranulation events and immune receptor clustering. This review focuses on the contribution of tetraspanins clustered with FcεRI or residing in granule membranes to classical MC functions but also undertakes an outlook on the possible contribution of tetraspanins to newly described mast cell functions and discusses possible targets for drug development.
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Affiliation(s)
- Martin Köberle
- Department of Dermatology, Eberhard Karls University Tübingen Tübingen, Germany
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67
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Kooijmans SAA, Vader P, van Dommelen SM, van Solinge WW, Schiffelers RM. Exosome mimetics: a novel class of drug delivery systems. Int J Nanomedicine 2012; 7:1525-41. [PMID: 22619510 PMCID: PMC3356169 DOI: 10.2147/ijn.s29661] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The identification of extracellular phospholipid vesicles as conveyors of cellular information has created excitement in the field of drug delivery. Biological therapeutics, including short interfering RNA and recombinant proteins, are prone to degradation, have limited ability to cross biological membranes, and may elicit immune responses. Therefore, delivery systems for such drugs are under intensive investigation. Exploiting extracellular vesicles as carriers for biological therapeutics is a promising strategy to overcome these issues and to achieve efficient delivery to the cytosol of target cells. Exosomes are a well studied class of extracellular vesicles known to carry proteins and nucleic acids, making them especially suitable for such strategies. However, the considerable complexity and the related high chance of off-target effects of these carriers are major barriers for translation to the clinic. Given that it is well possible that not all components of exosomes are required for their proper functioning, an alternative strategy would be to mimic these vesicles synthetically. By assembly of liposomes harboring only crucial components of natural exosomes, functional exosome mimetics may be created. The low complexity and use of well characterized components strongly increase the pharmaceutical acceptability of such systems. However, exosomal components that would be required for the assembly of functional exosome mimetics remain to be identified. This review provides insights into the composition and functional properties of exosomes, and focuses on components which could be used to enhance the drug delivery properties of exosome mimetics.
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Affiliation(s)
- Sander A A Kooijmans
- Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht, The Netherlands
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68
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Kaul G, Kumar S, Kumari S. Enrichment of CD9<sup>+</sup> spermatogonial stem cells from goat (<i>Capra aegagrus hircus</i>) testis using magnetic microbeads. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/scd.2012.23014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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69
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Abstract
Dendritic cells (DCs) are the most potent APCs. Whereas immature DCs down-regulate T-cell responses to induce/maintain immunologic tolerance, mature DCs promote immunity. To amplify their functions, DCs communicate with neighboring DCs through soluble mediators, cell-to-cell contact, and vesicle exchange. Transfer of nanovesicles (< 100 nm) derived from the endocytic pathway (termed exosomes) represents a novel mechanism of DC-to-DC communication. The facts that exosomes contain exosome-shuttle miRNAs and DC functions can be regulated by exogenous miRNAs, suggest that DC-to-DC interactions could be mediated through exosome-shuttle miRNAs, a hypothesis that remains to be tested. Importantly, the mechanism of transfer of exosome-shuttle miRNAs from the exosome lumen to the cytosol of target cells is unknown. Here, we demonstrate that DCs release exosomes with different miRNAs depending on the maturation of the DCs. By visualizing spontaneous transfer of exosomes between DCs, we demonstrate that exosomes fused with the target DCs, the latter followed by release of the exosome content into the DC cytosol. Importantly, exosome-shuttle miRNAs are functional, because they repress target mRNAs of acceptor DCs. Our findings unveil a mechanism of transfer of exosome-shuttle miRNAs between DCs and its role as a means of communication and posttranscriptional regulation between DCs.
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Molecular and cellular mechanisms of mammalian cell fusion. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 713:33-64. [PMID: 21432013 DOI: 10.1007/978-94-007-0763-4_4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The fusion of one cell with another occurs in development, injury and disease. Despite the diversity of fusion events, five steps in sequence appear common. These steps include programming fusion-competent status, chemotaxis, membrane adhesion, membrane fusion, and post-fusion resetting. Recent advances in the field start to reveal the molecules involved in each step. This review focuses on some key molecules and cellular events of cell fusion in mammals. Increasing evidence demonstrates that membrane lipid rafts, adhesion proteins and actin rearrangement are critical in the final step of membrane fusion. Here we propose a new model for the formation and expansion of membrane fusion pores based on recent observations on myotube formation. In this model, membrane lipid rafts first recruit adhesion molecules and align with opposing membranes, with the help of a cortical actin "wall" as a rigid supportive platform. Second, the membrane adhesion proteins interact with each other and trigger actin rearrangement, which leads to rapid dispersion of lipid rafts and flow of a highly fluidic phospholipid bilayer into the site. Finally, the opposing phospholipid bilayers are then pushed into direct contact leading to the formation of fusion pores by the force generated through actin polymerization. The actin polymerization generated force also drives the expansion of the fusion pores. However, several key questions about the process of cell fusion still remain to be explored. The understanding of the mechanisms of cell fusion may provide new opportunities in correcting development disorders or regenerating damaged tissues by inhibiting or promoting molecular events associated with fusion.
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Wang HX, Kolesnikova TV, Denison C, Gygi SP, Hemler ME. The C-terminal tail of tetraspanin protein CD9 contributes to its function and molecular organization. J Cell Sci 2011; 124:2702-10. [PMID: 21771881 DOI: 10.1242/jcs.085449] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Tetraspanin protein CD9 supports sperm-egg fusion, and regulates cell adhesion, motility, metastasis, proliferation and signaling. The large extracellular loop and transmembrane domains of CD9 engage in functionally important interactions with partner proteins. However, neither functional nor biochemical roles have been shown for the CD9 C-terminal tail, despite it being highly conserved throughout vertebrate species. To gain new insight into the CD9 tail, three C-terminal amino acids (Glu-Met-Val) were replaced with residues corresponding to C-terminal amino acids from tetraspanin protein CD82 (Pro-Lys-Tyr). Wild-type and mutant CD9 were then stably expressed in MOLT-4, K562, U937, RD and HT1080 cells. Whereas wild-type CD9 inhibited cell adhesion and spreading on fibronectin, mutant CD9 did not. Wild-type CD9 also promoted homotypic cell-cell aggregation and microvilli formation, whereas mutant CD9 did not. Protein interactions of wild-type and mutant CD9 were compared quantitatively using stable isotope labeling with amino acids in cell culture (SILAC) in conjunction with liquid-chromatography-tandem mass spectrometry (LC-MS/MS) technology. SILAC results showed that, despite wild-type and mutant CD9 having identical expression levels, mutant CD9 and its major transmembrane interacting partners were recovered in substantially reduced amounts from 1% Brij 96 lysates. Immunoprecipitation experiments confirmed that mutant CD9 recovery was decreased in Brij 96, but not in more stringent Triton X-100 detergent. Additionally, compared with wild-type CD9 complexes, mutant CD9 complexes were larger and more oligomerized in Brij 96 detergent, consistent with decreased Brij 96 solubility, perhaps due to more membrane domains packing more tightly together. In conclusion, multiple CD9 functions depend on its C-terminal tail, which affects the molecular organization of CD9 complexes, as manifested by their altered solubilization in Brij 96 and organization on the cell surface.
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Affiliation(s)
- Hong-Xing Wang
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute and Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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Singethan K, Schneider-Schaulies J. Tetraspanins: Small transmembrane proteins with big impact on membrane microdomain structures. Commun Integr Biol 2011; 1:11-3. [PMID: 19704780 DOI: 10.4161/cib.1.1.6406] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Accepted: 06/10/2008] [Indexed: 01/15/2023] Open
Abstract
Members of the tetraspanin family of transmembrane proteins including CD9, CD37, CD53, CD63, CD81, CD82, CD151, etc., contribute to the structural organization of the plasma membrane by forming microdomain structures, influencing cell fusion and regulating cell motility. Interestingly, K41, a CD9-specific monoclonal antibody (mAb), inhibits the release of human immunodeficiency virus (HIV-1), and the canine distemper virus (CDV)-, but not measles virus (MV)-induced cell-cell fusion. This mAb, which recognizes a conformational epitope on the large extracellular loop (LEL) of CD9, induced rapid relocation and clustering of CD9 in net-like structures at cell-cell contact areas.1 High-resolution analyses revealed that CD9 clustering is accompanied by the formation of microvilli that protrude from either side of adjacent cell surfaces, thus forming structures like microvilli zippers. While the cellular CD9-associated proteins beta1-integrin and EWI-F were co-clustered with CD9 at cell-cell interfaces, viral proteins in infected cells were differentially affected. MV envelope proteins were detected within, whereas CDV proteins were excluded from CD9 clusters, and thus, the tetraspanin CD9 can regulate cell-cell fusion by controlling the access of the viral fusion machinery to cell contact areas.
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Affiliation(s)
- Katrin Singethan
- Institute for Virology and Immunobiology; University of Würzburg; Würzburg, Germany
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Abstract
Membrane fusion underlies such important biological processes as virus entry into host cells, intracellular protein trafficking, fertilization, formation of muscle fibres and bone resorption. In addition, pathologies such as osteoporosis and implant rejection have been attributed to aberrant fusion. Members of the tetraspanin protein superfamily have been ascribed multiple roles in membrane biology, forming extensive lateral associations and regulating the function of effector molecules by clustering them in specific areas of the membrane. The present review aims to summarize the experimental evidence for tetraspanin function in different fusion events and highlight common themes.
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Comparison of satellite cell-derived myoblasts and C2C12 differentiation in two- and three-dimensional cultures: changes in adhesion protein expression. Cell Biol Int 2011; 35:125-33. [PMID: 20836763 DOI: 10.1042/cbi20090335] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Changes in the expression of adhesion proteins involved in myoblast differentiation were investigated in monolayer (two-dimensional) and 3D (three-dimensional) cell cultures. The expression of integrin alpha3 subunit, integrin beta1 subunit, ADAM12 (a disintegrin and metalloproteinase 12), tetraspanins CD9 and CD81 and M-cadherin were examined in the murine myoblast cell line C2C12 and in a primary culture of rat satellite cells. Myoblasts in monolayer and 3D cultures showed significant differences in their morphology and cytoskeletal organization. All of the studied proteins participated in myoblast fusion in each culture examined, but differences in their levels of expression were observed. Satellite cell-derived myoblasts exhibited higher expression of adhesion protein mRNAs than C2C12 cells. Also, C2C12 cells from a 3D culture showed slightly higher expression of adhesion protein transcripts than the same cells cultured as a monolayer. Significantly, the levels of adhesion protein mRNAs were found to change in parallel in all cell culture types. Despite this finding, it is important that differences between satellite cell-derived myoblasts and cell line C2C12 grown in monolayer and 3D cultures are taken into account when studying processes of myoblast differentiation in vitro.
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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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Cailleteau L, Estrach S, Thyss R, Boyer L, Doye A, Domange B, Johnsson N, Rubinstein E, Boucheix C, Ebrahimian T, Silvestre JS, Lemichez E, Meneguzzi G, Mettouchi A. alpha2beta1 integrin controls association of Rac with the membrane and triggers quiescence of endothelial cells. J Cell Sci 2010; 123:2491-501. [PMID: 20592186 DOI: 10.1242/jcs.058875] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integrin receptors and their extracellular matrix ligands provide cues to cell proliferation, survival, differentiation and migration. Here, we show that alpha2beta1 integrin, when ligated to the basement membrane component laminin-1, triggers a proliferation arrest in primary endothelial cells. Indeed, in the presence of strong growth signals supplied by growth factors and fibronectin, alpha2beta1 engagement alters assembly of mature focal adhesions by alpha5beta1 and leads to impairment of downstream signaling and cell-cycle arrest in the G1 phase. Although the capacity of alpha5beta1 to signal for GTP loading of Rac is preserved, the joint engagement of alpha2beta1 interferes with membrane anchorage of Rac. Adapting the 'split-ubiquitin' sensor to screen for membrane-proximal alpha2 integrin partners, we identified the CD9 tetraspanin and further establish its requirement for destabilization of focal adhesions, control of Rac subcellular localization and growth arrest induced by alpha2beta1 integrin. Altogether, our data establish that alpha2beta1 integrin controls endothelial cell commitment towards quiescence by triggering a CD9-dependent dominant signaling.
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Affiliation(s)
- Laurence Cailleteau
- INSERM, U634, Faculté de Médecine, 27 Avenue de Valombrose, Nice, F-06107, France
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Oursler MJ. Recent advances in understanding the mechanisms of osteoclast precursor fusion. J Cell Biochem 2010; 110:1058-62. [PMID: 20564220 DOI: 10.1002/jcb.22640] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Bone marrow macrophages fuse on the bone surface to form multinucleated osteoclasts that then organize to efficiently resorb bone. Many, if not all, of the stages of macrophage fusion involve cytoskeletal components that reorganize the cells. Recruitment may involve chemotactic responses to bone matrix protein and calcium ion gradients and/or chemokine production by bone forming osteoblasts. The roles of integrins vary, depending on the particular subunits with some interfering with fusion and others having a participatory role. RANKL is essential for fusion and many identified modulators of fusion influence RANKL signaling pathways. Tetraspanins have been implicated in fusion of macrophages and myoblasts, but differences in impacts exist between these two cell types. Macrophage recruitment to apoptotic cells prior to their engulfment is driven by the exposed phospholipids on the external surface of the apoptotic cells and there is evidence that this same identification mechanism is employed in macrophage fusion. Because loss of cadherin or ADAM family members suppresses macrophage fusion, a crucial role for these membrane glycoproteins is evident. The Ig membrane glycoprotein superfamily members CD200 and MFR/SIRPalpha are involved in macrophage fusion, although their influences are unresolved. Differential screenings have identified the structurally related membrane proteins DC-STAMP and OC-STAMP as required components for fusion and the contributions to fusion remain active areas of investigation. While many of the key components involved in these processes have been identified, a great deal of work remains in resolving the precise processes involved and the interactions between key contributors to multinucleated osteoclast formation.
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Affiliation(s)
- Merry Jo Oursler
- Robert and Arlene Kogod Center on Aging, Endocrine Research Unit, Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA.
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Fragments of antigen-loaded dendritic cells (DC) and DC-derived exosomes induce protective immunity against Leishmania major. Vaccine 2010; 28:5785-93. [DOI: 10.1016/j.vaccine.2010.06.077] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 06/19/2010] [Accepted: 06/24/2010] [Indexed: 11/20/2022]
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Hassuna N, Monk PN, Moseley GW, Partridge LJ. Strategies for targeting tetraspanin proteins: potential therapeutic applications in microbial infections. BioDrugs 2010; 23:341-59. [PMID: 19894777 PMCID: PMC7100176 DOI: 10.2165/11315650-000000000-00000] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The identification of novel targets and strategies for therapy of microbial infections is an area of intensive research due to the failure of conventional vaccines or antibiotics to combat both newly emerging diseases (e.g. viruses such as severe acute respiratory syndrome (SARS) and new influenza strains, and antibiotic-resistant bacteria) and entrenched, pandemic diseases exemplified by HIV. One clear approach to this problem is to target processes of the host organism rather than the microbe. Recent data have indicated that members of the tetraspanin superfamily, proteins with a widespread distribution in eukaryotic organisms and 33 members in humans, may provide such an approach. Tetraspanins traverse the membrane four times, but are distinguished from other four-pass membrane proteins by the presence of conserved charged residues in the transmembrane domains and a defining ‘signature’ motif in the larger of the two extracellular domains (the EC2). They characteristically form promiscuous associations with one another and with other membrane proteins and lipids to generate a specialized type of microdomain: the tetraspanin-enriched microdomain (TEM). TEMs are integral to the main role of tetraspanins as ‘molecular organizers’ involved in functions such as membrane trafficking, cell-cell fusion, motility, and signaling. Increasing evidence demonstrates that tetraspanins are used by intracellular pathogens as a means of entering and replicating within human cells. Although previous investigations focused mainly on viruses such as hepatitis C and HIV, it is now becoming clear that other microbes associate with tetraspanins, using TEMs as a ‘gateway’ to infection. In this article we review the properties and functions of tetraspanins/TEMs that are relevant to infective processes and discuss the accumulating evidence that shows how different pathogens exploit these properties in infection and in the pathogenesis of disease. We then investigate the novel and exciting possibilities of targeting tetraspanins for the treatment of infectious disease, using specific antibodies, recombinant EC2 domains, small-molecule mimetics, and small interfering RNA. Such therapies, directed at host-cell molecules, may provide alternative options for combating fast-mutating or newly emerging pathogens, where conventional approaches face difficulties.
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Affiliation(s)
- Noha Hassuna
- Department of Molecular Biology and Biotechnology, Krebs Institute, University of Sheffield, Sheffield, UK
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80
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Systematic analysis of cis-elements in unstable mRNAs demonstrates that CUGBP1 is a key regulator of mRNA decay in muscle cells. PLoS One 2010; 5:e11201. [PMID: 20574513 PMCID: PMC2888570 DOI: 10.1371/journal.pone.0011201] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 05/27/2010] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Dramatic changes in gene expression occur in response to extracellular stimuli and during differentiation. Although transcriptional effects are important, alterations in mRNA decay also play a major role in achieving rapid and massive changes in mRNA abundance. Moreover, just as transcription factor activity varies between different cell types, the factors influencing mRNA decay are also cell-type specific. PRINCIPAL FINDINGS We have established the rates of decay for over 7000 transcripts expressed in mouse C2C12 myoblasts. We found that GU-rich (GRE) and AU-rich (ARE) elements are over-represented in the 3'UTRs of short-lived mRNAs and that these mRNAs tend to encode factors involved in cell cycle and transcription regulation. Stabilizing elements were also identified. By comparing mRNA decay rates in C2C12 cells with those previously measured for pluripotent and differentiating embryonic stem (ES) cells, we identified several groups of transcripts that exhibit cell-type specific decay rates. Further, whereas in C2C12 cells the impact of GREs on mRNA decay appears to be greater than that of AREs, AREs are more significant in ES cells, supporting the idea that cis elements make a cell-specific contribution to mRNA stability. GREs are recognized by CUGBP1, an RNA-binding protein and instability factor whose function is affected in several neuromuscular diseases. We therefore utilized RNA immunoprecipitation followed by microarray (RIP-Chip) to identify CUGBP1-associated transcripts. These mRNAs also showed dramatic enrichment of GREs in their 3'UTRs and encode proteins linked with cell cycle, and intracellular transport. Interestingly several CUGBP1 substrate mRNAs, including those encoding the myogenic transcription factors Myod1 and Myog, are also bound by the stabilizing factor HuR in C2C12 cells. Finally, we show that several CUGBP1-associated mRNAs containing 3'UTR GREs, including Myod1, are stabilized in cells depleted of CUGBP1, consistent with the role of CUGBP1 as a destabilizing factor. CONCLUSIONS Taken together, our results systematically establish cis-acting determinants of mRNA decay rates in C2C12 myoblast cells and demonstrate that CUGBP1 associates with GREs to regulate decay of a wide range of mRNAs including several that are critical for muscle development.
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Boyd M, Hansen M, Jensen TGK, Perearnau A, Olsen AK, Bram LL, Bak M, Tommerup N, Olsen J, Troelsen JT. Genome-wide analysis of CDX2 binding in intestinal epithelial cells (Caco-2). J Biol Chem 2010; 285:25115-25. [PMID: 20551321 DOI: 10.1074/jbc.m109.089516] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The CDX2 transcription factor is known to play a crucial role in inhibiting proliferation, promoting differentiation and the expression of intestinal specific genes in intestinal cells. The overall effect of CDX2 in intestinal cells has previously been investigated in conditional knock-out mice, revealing a critical role of CDX2 in the formation of the normal intestinal identity. The identification of direct targets of transcription factors is a key problem in the study of gene regulatory networks. The ChIP-seq technique combines chromatin immunoprecipitation (ChIP) with next generation sequencing resulting in a high throughput experimental method of identifying direct targets of specific transcription factors. The method was applied to CDX2, leading to the identification of the direct binding of CDX2 to several known and novel target genes in the intestinal cell. Examination of the transcript levels of selected genes verified the regulatory role of CDX2 binding. The results place CDX2 as a key node in a transcription factor network controlling the proliferation and differentiation of intestinal cells.
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Affiliation(s)
- Mette Boyd
- Department of Cellular and Molecular Medicine, Panum Institute, Building 6.4, University of Copenhagen, Blegdamsvej 3. 2200 Copenhagen N, Denmark
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Abstract
Tetraspanins are small integral membrane proteins that are known to control a variety of cellular processes, including signaling, migration and cell-cell fusion. Research over the past few years established that they are also regulators of various steps in the HIV-1 replication cycle, but the mechanisms through which these proteins either enhance or repress virus spread remain largely unknown.
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Affiliation(s)
- Markus Thali
- Department of Microbiology and Molecular Genetics, College of Medicine and CALS, University of Vermont, 318 Stafford Hall, 95 Carrigan Drive, Burlington, VT 05405-0084, USA.
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83
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Is HAP2-GCS1 an ancestral gamete fusogen? Trends Cell Biol 2010; 20:134-41. [DOI: 10.1016/j.tcb.2009.12.007] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 12/17/2009] [Accepted: 12/17/2009] [Indexed: 12/31/2022]
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84
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EBNA1 regulates cellular gene expression by binding cellular promoters. Proc Natl Acad Sci U S A 2009; 106:22421-6. [PMID: 20080792 DOI: 10.1073/pnas.0911676106] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Epstein-Barr virus (EBV) is associated with several types of lymphomas and epithelial tumors including Burkitt's lymphoma (BL), HIV-associated lymphoma, posttransplant lymphoproliferative disorder, and nasopharyngeal carcinoma. EBV nuclear antigen 1 (EBNA1) is expressed in all EBV associated tumors and is required for latency and transformation. EBNA1 initiates latent viral replication in B cells, maintains the viral genome copy number, and regulates transcription of other EBV-encoded latent genes. These activities are mediated through the ability of EBNA1 to bind viral-DNA. To further elucidate the role of EBNA1 in the host cell, we have examined the effect of EBNA1 on cellular gene expression by microarray analysis using the B cell BJAB and the epithelial 293 cell lines transfected with EBNA1. Analysis of the data revealed distinct profiles of cellular gene changes in BJAB and 293 cell lines. Subsequently, chromatin immune-precipitation revealed a direct binding of EBNA1 to cellular promoters. We have correlated EBNA1 bound promoters with changes in gene expression. Sequence analysis of the 100 promoters most enriched revealed a DNA motif that differs from the EBNA1 binding site in the EBV genome.
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85
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Bassnett S, Wilmarth PA, David LL. The membrane proteome of the mouse lens fiber cell. Mol Vis 2009; 15:2448-63. [PMID: 19956408 PMCID: PMC2786885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 11/18/2009] [Indexed: 11/16/2022] Open
Abstract
PURPOSE Fiber cells of the ocular lens are bounded by a highly specialized plasma membrane. Despite the pivotal role that membrane proteins play in the physiology and pathophysiology of the lens, our knowledge of the structure and composition of the fiber cell plasma membrane remains fragmentary. In the current study, we utilized mass spectrometry-based shotgun proteomics to provide a comprehensive survey of the mouse lens fiber cell membrane proteome. METHODS Membranes were purified from young mouse lenses and subjected to MudPIT (Multidimensional protein identification technology) analysis. The resulting proteomic data were analyzed further by reference to publically available microarray databases. RESULTS More than 200 membrane proteins were identified by MudPIT, including Type I, Type II, Type III (multi-pass), lipid-anchored, and GPI-anchored membrane proteins, in addition to membrane-associated cytoskeletal elements and extracellular matrix components. The membrane proteins of highest apparent abundance included Mip, Lim2, and the lens-specific connexin proteins Gja3, Gja8, and Gje1. Significantly, many proteins previously unsuspected in the lens were also detected, including proteins with roles in cell adhesion, solute transport, and cell signaling. CONCLUSIONS The MudPIT technique constitutes a powerful technique for the analysis of the lens membrane proteome and provides valuable insights into the composition of the lens fiber cell unit membrane.
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Affiliation(s)
- Steven Bassnett
- Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, MO
| | - Phillip A. Wilmarth
- Biochemistry & Molecular Biology, Oregon Health & Science University, Portland, OR
| | - Larry L. David
- Biochemistry & Molecular Biology, Oregon Health & Science University, Portland, OR
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86
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Helming L, Gordon S. Molecular mediators of macrophage fusion. Trends Cell Biol 2009; 19:514-22. [PMID: 19733078 DOI: 10.1016/j.tcb.2009.07.005] [Citation(s) in RCA: 238] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 07/01/2009] [Accepted: 07/07/2009] [Indexed: 12/13/2022]
Abstract
Fusion of macrophages leads to the formation of osteoclasts in bone and of multinucleated giant cells in granulomas. The precise function of granuloma-associated multinucleates giant cells is not clear but substantial progress has recently been made in identifying the molecular machinery involved in macrophage fusion. Signaling processes mediated by DAP12 and STAT6 induce a fusion-competent status. Chemotaxis through CCL2, cell-cell adhesion mediated by E-cadherin, exposure of phosphatidylserine, lipid recognition by CD36 and cytoskeletal rearrangements depending on RAC1 are prerequisites for successful macrophage fusion. We review current knowledge on the molecular mediators of giant cell formation, compare giant cells with osteoclasts and highlight key target areas for future research and medical relevance.
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Affiliation(s)
- Laura Helming
- Institute for Medical Microbiology, Immunology, and Hygiene, Technische Universität München, Munich, Germany.
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87
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O'Donnell CD, Shukla D. A novel function of heparan sulfate in the regulation of cell-cell fusion. J Biol Chem 2009; 284:29654-65. [PMID: 19726670 DOI: 10.1074/jbc.m109.037960] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Despite the important contribution of cell-cell fusion in the development and physiology of eukaryotes, little is known about the mechanisms that regulate this process. Our study shows that glycosaminoglycans and more specifically heparan sulfate (HS) expressed on the cell surface and extracellular matrix may act as negative regulator of cell-cell fusion. Using herpes simplex virus type-1 as a tool to enhance cell-cell fusion, we demonstrate that the absence of HS expression on the cell surface results in a significant increase in cell-cell fusion. An identical phenomenon was observed when other viruses or polyethylene glycol was used as fusion enhancer. Cells deficient in HS biosynthesis showed increased activity of two Rho GTPases, RhoA and Cdc42, both of which showed a correlation between increased activity and increased cell-cell fusion. This could serve as a possible explanation as to why HS-deficient cells showed significantly enhanced cell-cell fusion and suggests that HS could regulate fusion via fine tuning of RhoA and Cdc42 activities.
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Affiliation(s)
- Christopher D O'Donnell
- Department of Ophthalmology and Visual Sciences and the Department of Microbiology and Immunology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA
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88
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Muroi Y, Sakurai T, Hanashi A, Kubota K, Nagaoka K, Imakawa K. CD9 regulates transcription factor GCM1 and ERVWE1 expression through the cAMP/protein kinase A signaling pathway. Reproduction 2009; 138:945-51. [PMID: 19692500 DOI: 10.1530/rep-09-0082] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
ERVWE1 (SYNCYTIN-1), a membrane protein originating from the envelope gene of human endogenous retrovirus-W (HERV-W), mediates the fusion of mononucleated cytotrophoblasts into multinucleated syncytiotrophoblast. Though ERVWE1 has been characterized since its discovery, regulatory mechanisms associated with ERVWE1 expression have not been firmly established. We hypothesized that membrane protein CD9, involved in cell-cell fusion of fertilization and myogenesis, could be involved in the regulation of ERVWE1 gene expression. In this study, regulatory mechanisms of ERVWE1 expression were studied using human choriocarcinoma BeWo cells. Forskolin is an activator of adenylate cyclase, which increased CD9 and ERVWE1 expression. The increase in CD9 expression was inhibited by a protein kinase A (PKA) inhibitor, Rp-cAMPS. These results indicate that CD9 expression is regulated by the cAMP/PKA signaling pathway. Overexpression of CD9 increased expression levels of ERVWE1 as well as GCM1 (hGCMa), which is a transcription factor known to activate ERVWE1 gene transcription. However, high ERVWE1 expression induced by CD9 overexpression did not result in the increase in chorionic gonadotropin, beta polypeptide production. Moreover, CD9-induced increase in ERVWE1 and GCM1 expressions were inhibited by Rp-cAMPS. These results suggest that CD9 increases GCM1 expression via the cAMP/PKA signaling pathway, resulting in the increase in ERVWE1 expression.
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Affiliation(s)
- Yoshikage Muroi
- Laboratory of Animal Breeding, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, 113-8657 Tokyo, Japan
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89
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Coffey GP, Rajapaksa R, Liu R, Sharpe O, Kuo CC, Krauss SW, Sagi Y, Davis RE, Staudt LM, Sharman JP, Robinson WH, Levy S. Engagement of CD81 induces ezrin tyrosine phosphorylation and its cellular redistribution with filamentous actin. J Cell Sci 2009; 122:3137-44. [PMID: 19654214 DOI: 10.1242/jcs.045658] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CD81 is a tetraspanin family member involved in diverse cellular interactions in the immune and nervous systems and in cell fusion events. However, the mechanism of action of CD81 and of other tetraspanins has not been defined. We reasoned that identifying signaling molecules downstream of CD81 would provide mechanistic clues. We engaged CD81 on the surface of B-lymphocytes and identified the induced tyrosine-phosphorylated proteins by mass spectrometry. This analysis showed that the most prominent tyrosine phosphorylated protein was ezrin, an actin-binding protein and a member of the ezrin-radixin-moesin family. We also found that CD81 engagement induces spleen tyrosine kinase (Syk) and that Syk was involved in tyrosine phosphorylation of ezrin. After engagement of CD81, it colocalized with ezrin and F-actin, and this association was disrupted when Syk activation was blocked. Taken together, these studies suggest a model in which CD81 interfaces between the plasma membrane and the cytoskeleton by activating Syk, mobilizing ezrin, and recruiting F-actin to facilitate cytoskeletal reorganization and cell signaling. This mechanism might explain the pleiotropic effects induced in response to stimulation of cells by anti-CD81 antibodies or by the hepatitis C virus, which uses this molecule as its key receptor.
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Affiliation(s)
- Greg P Coffey
- Stanford University, School of Medicine, Division of Oncology, Stanford, CA 94305, USA
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90
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Parthasarathy V, Martin F, Higginbottom A, Murray H, Moseley GW, Read RC, Mal G, Hulme R, Monk PN, Partridge LJ. Distinct roles for tetraspanins CD9, CD63 and CD81 in the formation of multinucleated giant cells. Immunology 2009; 127:237-48. [PMID: 19489128 DOI: 10.1111/j.1365-2567.2008.02945.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Members of the tetraspanin superfamily of proteins are implicated in a variety of complex cell processes including cell fusion. However, the contribution of individual tetraspanins to these processes has proved difficult to define. Here we report the use of recombinant extracellular regions of tetraspanins to investigate the role of specific members of this family in the fusion of monocytes to form multinucleated giant cells (MGC). In contrast to their positive requirement in sperm-egg fusion, previous studies using antibodies and knockout mice have indicated a negative regulatory role for tetraspanins CD9 and CD81 in this process. In an in vitro model of fusion using human monocytes, we have confirmed observations that antibodies to CD9 and CD81 enhance MGC formation; however, in contrast to previous investigations, we found that all members of a panel of antibodies to CD63 inhibited fusion. Moreover, recombinant proteins corresponding to the large extracellular domains (EC2s) of CD63 and CD9 inhibited MGC formation, whereas the EC2s of CD81 and CD151 had no effect. The potent inhibition of fusion and binding of labelled CD63 EC2 to monocytes under fusogenic conditions suggest a direct interaction with a membrane component required for fusion. Our findings indicate that the tetraspanins CD9, CD63 and CD81 are all involved in MGC formation, but play distinct roles.
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91
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Dynamic clustering and dispersion of lipid rafts contribute to fusion competence of myogenic cells. Exp Cell Res 2009; 315:3052-63. [PMID: 19615358 DOI: 10.1016/j.yexcr.2009.07.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 06/22/2009] [Accepted: 07/08/2009] [Indexed: 11/21/2022]
Abstract
Recent research indicates that the leading edge of lamellipodia of myogenic cells (myoblasts and myotubes) contains presumptive fusion sites, yet the mechanisms that render the plasma membrane fusion-competent remain largely unknown. Here we show that dynamic clustering and dispersion of lipid rafts contribute to both cell adhesion and plasma membrane union during myogenic cell fusion. Adhesion-complex proteins including M-cadherin, beta-catenin, and p120-catenin accumulated at the leading edge of lamellipodia, which contains the presumptive fusion sites of the plasma membrane, in a lipid raft-dependent fashion prior to cell contact. In addition, disruption of lipid rafts by cholesterol depletion directly prevented the membrane union of myogenic cell fusion. Time-lapse recording showed that lipid rafts were laterally dispersed from the center of the lamellipodia prior to membrane fusion. Adhesion proteins that had accumulated at lipid rafts were also removed from the presumptive fusion sites when lipid rafts were laterally dispersed. The resultant lipid raft- and adhesion complex-free area at the leading edge fused with the opposing plasma membrane. These results demonstrate a key role for dynamic clustering/dispersion of lipid rafts in establishing fusion-competent sites of the myogenic cell membrane, providing a novel mechanistic insight into the regulation of myogenic cell fusion.
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92
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Gorjup E, Danner S, Rotter N, Habermann J, Brassat U, Brummendorf TH, Wien S, Meyerhans A, Wollenberg B, Kruse C, von Briesen H. Glandular tissue from human pancreas and salivary gland yields similar stem cell populations. Eur J Cell Biol 2009; 88:409-21. [DOI: 10.1016/j.ejcb.2009.02.187] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2007] [Revised: 01/23/2009] [Accepted: 02/25/2009] [Indexed: 01/04/2023] Open
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93
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Quach NL, Biressi S, Reichardt LF, Keller C, Rando TA. Focal adhesion kinase signaling regulates the expression of caveolin 3 and beta1 integrin, genes essential for normal myoblast fusion. Mol Biol Cell 2009; 20:3422-35. [PMID: 19458188 DOI: 10.1091/mbc.e09-02-0175] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
An essential phase of skeletal myogenesis is the fusion of mononucleated myoblasts to form multinucleated myotubes. Many cell adhesion proteins, including integrins, have been shown to be important for myoblast fusion in vertebrates, but the mechanisms by which these proteins regulate cell fusion remain mostly unknown. Here, we focused on the role of focal adhesion kinase (FAK), an important nonreceptor protein tyrosine kinase involved in integrin signaling, as a potential mediator by which integrins may regulate myoblast fusion. To test this hypothesis in vivo, we generated mice in which the Fak gene was disrupted specifically in muscle stem cells ("satellite cells") and we found that this resulted in impaired myotube formation during muscle regeneration after injury. To examine the role of FAK in the fusion of myogenic cells, we examined the expression of FAK and the effects of FAK deletion on the differentiation of myoblasts in vitro. Differentiation of mouse primary myoblasts was accompanied by a rapid and transient increase of phosphorylated FAK. To investigate the requirement of FAK in myoblast fusion, we used two loss-of-function approaches (a dominant-negative inhibitor of FAK and FAK small interfering RNA [siRNA]). Inhibition of FAK resulted in markedly impaired fusion but did not inhibit other biochemical measures of myogenic differentiation, suggesting a specific role of FAK in the morphological changes of cell fusion as part of the differentiation program. To examine the mechanisms by which FAK may be regulating fusion, we used microarray analysis to identify the genes that failed to be normally regulated in cells that were fusion defective due to FAK inhibition. Several genes that have been implicated in myoblast fusion were aberrantly regulated during differentiation when FAK was inhibited. Intriguingly, the normal increases in the transcript of caveolin 3 as well as an integrin subunit, the beta1D isoform, were suppressed by FAK inhibition. We confirmed this also at the protein level and show that direct inhibition of beta1D subunit expression by siRNA inhibited myotube formation with a prominent effect on secondary fusion. These data suggest that FAK regulation of profusion genes, including caveolin 3 and the beta1D integrin subunit, is essential for morphological muscle differentiation.
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Affiliation(s)
- Navaline L Quach
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
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94
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Formation of syncytia is repressed by tetraspanins in human immunodeficiency virus type 1-producing cells. J Virol 2009; 83:7467-74. [PMID: 19458002 DOI: 10.1128/jvi.00163-09] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In vitro propagation studies have established that human immunodeficiency virus type 1 (HIV-1) is most efficiently transmitted at the virological synapse that forms between producer and target cells. Despite the presence of the viral envelope glycoprotein (Env) and CD4 and chemokine receptors at the respective surfaces, producer and target cells usually do not fuse with each other but disengage after the viral particles have been delivered, consistent with the idea that syncytia, at least in vitro, are not required for HIV-1 spread. Here, we tested whether tetraspanins, which are well known regulators of cellular membrane fusion processes that are enriched at HIV-1 exit sites, regulate syncytium formation. We found that overexpression of tetraspanins in producer cells leads to reduced syncytium formation, while downregulation has the opposite effect. Further, we document that repression of Env-induced cell-cell fusion by tetraspanins depends on the presence of viral Gag, and we demonstrate that fusion repression requires the recruitment of Env by Gag to tetraspanin-enriched microdomains (TEMs). However, sensitivity to fusion repression by tetraspanins varied for different viral strains, despite comparable recruitment of their Envs to TEMs. Overall, these data establish tetraspanins as negative regulators of HIV-1-induced cell-cell fusion, and they start delineating the requirements for this regulation.
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95
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Abstract
Despite high expression levels at the plasma membrane or in intracellular vesicles, tetraspanins remain among the most mysterious transmembrane molecules 20 years after their discovery. Several genetic studies in mammals and invertebrates have demonstrated key physiological roles for some of these tetraspanins, in particular in the immune response, sperm-egg fusion, photoreceptor function and the normal function of certain epithelia. Other studies have highlighted their ability to modulate cell migration and metastasis formation. Their role in the propagation of infectious agents has drawn recent attention, with evidence for HIV budding in tetraspanin-enriched plasma membrane domains. Infection of hepatocytic cells by two major pathogens, the hepatitis C virus and the malaria parasite, also requires the tetraspanin CD81. The function of tetraspanins is thought to be linked to their ability to associate with one another and a wealth of other integral proteins, thereby building up an interacting network or 'tetraspanin web'. On the basis of the biochemical dissection of the tetraspanin web and recent analysis of the dynamics of some of its constituents, we propose that tetraspanins tightly regulate transient interactions between a variety of molecules and as such favour the efficient assembly of specialized structures upon proper stimulation.
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96
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Functional relevance of tetraspanin CD9 in vascular smooth muscle cell injury phenotypes: A novel target for the prevention of neointimal hyperplasia. Atherosclerosis 2009; 203:377-86. [DOI: 10.1016/j.atherosclerosis.2008.07.036] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Revised: 06/18/2008] [Accepted: 07/22/2008] [Indexed: 11/18/2022]
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97
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Hemler ME. Targeting of tetraspanin proteins--potential benefits and strategies. Nat Rev Drug Discov 2009; 7:747-58. [PMID: 18758472 DOI: 10.1038/nrd2659] [Citation(s) in RCA: 258] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The tetraspanin transmembrane proteins have emerged as key players in malignancy, the immune system, during fertilization and infectious disease processes. Tetraspanins engage in a wide range of specific molecular interactions, occurring through the formation of tetraspanin-enriched microdomains (TEMs). TEMs therefore serve as a starting point for understanding how tetraspanins affect cell signalling, adhesion, morphology, motility, fusion and virus infection. An abundance of recent evidence suggests that targeting tetraspanins, for example, by monoclonal antibodies, soluble large-loop proteins or RNAi technology, should be therapeutically beneficial.
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Affiliation(s)
- Martin E Hemler
- Dana-Farber Cancer Institute, 44 Binney Street, Boston, Massachussetts 02115, USA.
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98
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Abstract
Myoblasts in vitro form characteristic arrays of bipolar-shaped cells prior to fusion. We have shown that the actin cytoskeleton re-organizes in these fusing cells and that the interaction of non-muscle myosin 2A with actin at the plasma membrane helps to generate the bipolar shape of myoblasts, which is key for fusion. Here we discuss how fusion occurs, and in particular how the actin cytoskeleton is involved. Myoblast fusion is essential to form the multi-nucleated muscle fibres that make up the skeletal muscle. Skeletal muscle fibres contain many nuclei, roughly one nucleus to every 15 sarcomeres (35 microm) in adult muscle, although this varies with muscle type (Bruusgaard et al., 2006). Thus a muscle fibre 30 cm long contains about 8000 nuclei and is formed by the fusion of about 8000 cells during development. The formation of multi-nucleated myotubes has been intensively studied for many years using a number of different systems. Many different proteins have been identified using Drosophila as a model system (e.g. see reviews by Taylor, 2000, 2002) that have given an insight into what happens in mammals. However, the process of fusion of mammalian cells is less well understood, and this paper will cover some of the aspects of mammalian myoblast fusion, with a particular focus on the role of the actin cytoskeleton.
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Affiliation(s)
- M Peckham
- Institute of Cellular and Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
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99
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Shibota Y, Kaneko Y, Kuroda M, Nishikawa A. Larval-to-adult conversion of a myogenic system in the frog, Xenopus laevis, by larval-type myoblast-specific control of cell division, cell differentiation, and programmed cell death by triiodo-L-thyronine. Differentiation 2008. [DOI: 10.1111/j.1432-0436.2000.660409.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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100
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Singethan K, Müller N, Schubert S, Lüttge D, Krementsov DN, Khurana SR, Krohne G, Schneider-Schaulies S, Thali M, Schneider-Schaulies J. CD9 clustering and formation of microvilli zippers between contacting cells regulates virus-induced cell fusion. Traffic 2008; 9:924-35. [PMID: 18363777 PMCID: PMC2992846 DOI: 10.1111/j.1600-0854.2008.00737.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Members of the tetraspanin family including CD9 contribute to the structural organization and plasticity of the plasma membrane. K41, a CD9-specific monoclonal antibody, inhibits the release of HIV-1 and canine distemper virus (CDV)- but not measles virus (MV)-induced cell-cell fusion. We now report that K41, which recognizes a conformational epitope on the large extracellular loop of CD9, induces rapid relocation and clustering of CD9 in net-like structures at cell-cell contact areas. High-resolution analyses revealed that CD9 clustering is accompanied by the formation of microvilli that protrude from either side of adjacent cell surfaces, thus forming structures like microvilli zippers. While the cellular CD9-associated proteins beta(1)-integrin and EWI-F were co-clustered with CD9 at cell-cell interfaces, viral proteins in infected cells were differentially affected. MV envelope proteins were detected within CD9 clusters, whereas CDV proteins were excluded from CD9 clusters. Thus, the tetraspanin CD9 can regulate cell-cell fusion by controlling the access of the fusion machinery to cell contact areas.
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MESH Headings
- Animals
- Antibodies, Monoclonal/immunology
- Antibodies, Monoclonal/metabolism
- Antibodies, Monoclonal/ultrastructure
- Antibodies, Viral/immunology
- Antibodies, Viral/ultrastructure
- Antigens, CD/immunology
- Antigens, CD/metabolism
- Antigens, CD/ultrastructure
- CHO Cells
- Cell Communication
- Cell Fusion
- Cells, Cultured
- Chlorocebus aethiops
- Cricetinae
- Cricetulus
- Distemper Virus, Canine/genetics
- Distemper Virus, Canine/pathogenicity
- Dogs
- Endothelial Cells/immunology
- Endothelial Cells/ultrastructure
- Endothelial Cells/virology
- Endothelium, Vascular/cytology
- Fluorescent Antibody Technique, Indirect
- HeLa Cells
- Humans
- Kinetics
- Measles virus/genetics
- Measles virus/pathogenicity
- Membrane Glycoproteins/immunology
- Membrane Glycoproteins/metabolism
- Membrane Glycoproteins/ultrastructure
- Microvilli/metabolism
- Microvilli/ultrastructure
- Tetraspanin 29
- Transfection
- Umbilical Veins/cytology
- Vero Cells
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Affiliation(s)
- Katrin Singethan
- Institute for Virology and Immunobiology, University of Würzburg, Versbacher Str. 7, D-97078 Würzburg, Germany
| | - Nora Müller
- Institute for Virology and Immunobiology, University of Würzburg, Versbacher Str. 7, D-97078 Würzburg, Germany
| | - Sabine Schubert
- Institute for Virology and Immunobiology, University of Würzburg, Versbacher Str. 7, D-97078 Würzburg, Germany
| | - Doreen Lüttge
- Institute for Virology and Immunobiology, University of Würzburg, Versbacher Str. 7, D-97078 Würzburg, Germany
| | - Dimitry N Krementsov
- College of Medicine and CALS, University of Vermont, Department of Microbiology and Molecular Genetics, Burlington, VT 05405-0084, USA
| | - Sandhya R Khurana
- College of Medicine and CALS, University of Vermont, Department of Microbiology and Molecular Genetics, Burlington, VT 05405-0084, USA
| | - Georg Krohne
- Division of Electron Microscopy, Biocenter, University of Würzburg, Am Hubland, D-97070 Würzburg, Germany
| | - Sibylle Schneider-Schaulies
- Institute for Virology and Immunobiology, University of Würzburg, Versbacher Str. 7, D-97078 Würzburg, Germany
| | - Markus Thali
- College of Medicine and CALS, University of Vermont, Department of Microbiology and Molecular Genetics, Burlington, VT 05405-0084, USA
| | - Jürgen Schneider-Schaulies
- Institute for Virology and Immunobiology, University of Würzburg, Versbacher Str. 7, D-97078 Würzburg, Germany
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