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Hua R, Gu S, Jiang JX. Connexin 43 Hemichannels Regulate Osteoblast to Osteocyte Differentiation. Front Cell Dev Biol 2022; 10:892229. [PMID: 35693933 PMCID: PMC9184820 DOI: 10.3389/fcell.2022.892229] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 04/18/2022] [Indexed: 11/13/2022] Open
Abstract
Connexin 43 (Cx43) is the predominant connexin subtype expressed in osteocytes. Osteocytes, accounting for 90%–95% of total bone cells, function as orchestrators coordinating balanced activity between bone-resorbing osteoclasts and bone-forming osteoblasts. In this study, two newly developed osteocytic cell lines, OCY454 and IDG-SW3, were used to determine the role of Cx43 gap junctions and hemichannels (HCs) in the regulation of osteoblast to osteocyte differentiation. We found that the Cx43 level was substantially increased during the differentiation of IDG-SW3 cells and is also much higher than that of OCY454 cells. We knocked down Cx43 expression using the lentiviral CRISPR/Cas9 approach and inhibition of Cx43 HCs using Cx43 (E2) antibody in IDG-SW3 cells. Cx43 knockdown (KD) or Cx43 HC inhibition decreased gene expression for osteoblast and osteocyte markers, including alkaline phosphatase, type I collagen, dentin matrix protein 1, sclerostin, and fibroblast growth factor 23, whereas increasing the osteoclastogenesis indicator and the receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG) ratio at early and late differentiation stages. Moreover, mineralization was remarkably attenuated in differentiated Cx43-deficient IDG-SW3 cells compared to ROSA26 control. The conditioned medium collected from fully differentiated IDG-SW3 cells with Cx43 KD promoted osteoclastogenesis of RAW264.7 osteoclast precursors. Our results demonstrated that Cx43 HCs play critical roles in osteoblast to osteocyte differentiation process and regulate osteoclast differentiation via secreted factors.
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Applicability of Scrape Loading-Dye Transfer Assay for Non-Genotoxic Carcinogen Testing. Int J Mol Sci 2021; 22:ijms22168977. [PMID: 34445682 PMCID: PMC8396440 DOI: 10.3390/ijms22168977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/30/2021] [Accepted: 07/31/2021] [Indexed: 12/27/2022] Open
Abstract
Dysregulation of gap junction intercellular communication (GJIC) is recognized as one of the key hallmarks for identifying non-genotoxic carcinogens (NGTxC). Currently, there is a demand for in vitro assays addressing the gap junction hallmark, which would have the potential to eventually become an integral part of an integrated approach to the testing and assessment (IATA) of NGTxC. The scrape loading-dye transfer (SL-DT) technique is a simple assay for the functional evaluation of GJIC in various in vitro cultured mammalian cells and represents an interesting candidate assay. Out of the various techniques for evaluating GJIC, the SL-DT assay has been used frequently to assess the effects of various chemicals on GJIC in toxicological and tumor promotion research. In this review, we systematically searched the existing literature to gather papers assessing GJIC using the SL-DT assay in a rat liver epithelial cell line, WB-F344, after treating with chemicals, especially environmental and food toxicants, drugs, reproductive-, cardio- and neuro-toxicants and chemical tumor promoters. We discuss findings derived from the SL-DT assay with the known knowledge about the tumor-promoting activity and carcinogenicity of the assessed chemicals to evaluate the predictive capacity of the SL-DT assay in terms of its sensitivity, specificity and accuracy for identifying carcinogens. These data represent important information with respect to the applicability of the SL-DT assay for the testing of NGTxC within the IATA framework.
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Wang J, Li G, Li Y, Zhao Y, Manthari RK, Wang J. The Effects of Fluoride on the Gap-Junctional Intercellular Communication of Rats' Osteoblast. Biol Trace Elem Res 2020; 193:195-203. [PMID: 30887282 DOI: 10.1007/s12011-019-01692-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/06/2019] [Indexed: 12/18/2022]
Abstract
The gap junction protein plays an important role in the bone formation and alteration of these proteins leading to cause bone development. Aim to determine the effects of different concentration of fluoride on gap-junctional intercellular communication (GJIC) related genes and proteins in the rats' osteoblast cells. We treated the osteoblast cells with various concentrations (0, 0.01, 0.1, 0.5, and 1.0 mM) NaF for 24 and 72 h. We used the scrape loading and dye transfer technique to research the intracellular connectivity. Moreover, the mRNA expression levels of connexin 43 (Cx43), connexin45 (Cx45), collagen I, and osteocalcin (OCN) were analyzed by qRT-PCR, the protein expression levels of connexin43 (Cx43) were analyzed by western blotting and immunofluorescence. Our results suggested that the osteoblast proliferations were decreased in the 0.5 and 1 mM NaF groups, after 24 and 72 treatments. The scrape loading and dye transfer experiment showed that the GJIC were increased in the 0.01 mM NaF group and decreased in the 0.5 and 1 mM NaF groups. In addition, the mRNA expressions of Cx43, Cx45, and OCN, and the protein expressions of Cx43 were increased in the 0.01 mM NaF group and decreased in the 0.5 and 1 mM NaF groups. In summary, these results suggest that the low concentration NaF is good for the GJIC, but the high concentration NaF damages the GJIC.
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Affiliation(s)
- Jinming Wang
- Shanxi Key Laboratory of Environmental Veterinary Medicine, Shanxi Agricultural University, Jinzhong, Shanxi, China
| | - Guangsheng Li
- Shanxi Key Laboratory of Environmental Veterinary Medicine, Shanxi Agricultural University, Jinzhong, Shanxi, China
| | - Yanyan Li
- Shanxi Key Laboratory of Environmental Veterinary Medicine, Shanxi Agricultural University, Jinzhong, Shanxi, China
| | - Yangfei Zhao
- Shanxi Key Laboratory of Environmental Veterinary Medicine, Shanxi Agricultural University, Jinzhong, Shanxi, China
| | - Ram Kumar Manthari
- Shanxi Key Laboratory of Environmental Veterinary Medicine, Shanxi Agricultural University, Jinzhong, Shanxi, China
| | - Jundong Wang
- Shanxi Key Laboratory of Environmental Veterinary Medicine, Shanxi Agricultural University, Jinzhong, Shanxi, China.
- Shanxi Key Laboratory of Ecological Animal Science and Environmental Veterinary Medicine, Shanxi Agricultural University, Taigu, 030801, Shanxi, China.
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Liu XY, Li X, Bai MR, Chen X, Wang CL, Xie J, Ye L. FGF-7 Dictates Osteocyte Cell Processes Through Beta-Catenin Transduction. Sci Rep 2018; 8:14792. [PMID: 30287900 PMCID: PMC6172271 DOI: 10.1038/s41598-018-33247-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 09/26/2018] [Indexed: 02/05/2023] Open
Abstract
It is well recognized that osteocytes communicate with each other via gap junctions and that connxin43 (Cx43) shows its great potential in gap junction for the contribution enabling transmission of small molecules and operating in an autocrine/a paracrine manner. Fibroblast growth factors (FGFs) play significant roles in new bone formation and adult bone remodeling, and FGF signaling is regulated by the precise spatiotemporal approaches. However, the influence of FGF7 on osteocyte cell processes is not well elucidated. In this study, we aimed to examine the impact of FGF7 on osteocyte cell processes by characterizing the expression of Cx43 and to reveal the underlying mechanism regulating this cell process. We first found that the mRNA level of FGF7 was higher relative to other FGF family members both in osteocytes cell line (MLO-Y4) and bone tissue. We then demonstrated that FGF7 could increase the expression of Cx43 in osteocytes and promote the cell processes in the form of gap junctions between osteocytes. This modulation was due to the FGF7-induced cytoplasmic accumulation and resultant nuclear translocation of β-catenin. Our results could help us to further understand the importance of FGF7 on bone cell behavior and bone physiology and even pathology.
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Affiliation(s)
- Xiao-Yu Liu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xin Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Ming-Ru Bai
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xia Chen
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Cheng-Lin Wang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jing Xie
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
| | - Ling Ye
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
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Chen Y, Xu J, Liao H, Ma Z, Zhang Y, Chen H, Huang Z, Hu J. Prostaglandin E2 and Connexin 43 crosstalk in the osteogenesis induced by extracorporeal shockwave. Med Hypotheses 2016; 94:123-5. [PMID: 27515217 DOI: 10.1016/j.mehy.2016.07.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 07/12/2016] [Accepted: 07/18/2016] [Indexed: 02/05/2023]
Abstract
As a type of mechanical stimulation, extracorporeal shockwave (ESW) has been widely used in the clinic to treat bone fracture delayed union and non-unions. A large number of studies have shown beneficial effects of ESW in promoting fracture healing by inducing bone regeneration; however, the underlying mechanisms remain unclear. ESW has been shown to induce the production of prostaglandin E2 (PGE2), which is essential for gap junction intercellular communication in response to mechanical stress. Among the 19 known gap junction subunits, connexin43 (Cx43) is the most prevalent for mediating the response of mechanical stress. However, to our knowledge, the effect of ESW on Cx43 expression has not been reported before. Herein, we propose that a crosstalk between PGE2 and Cx43 is involved in the enhancement of osteogenesis induced by ESW. We review the currently available data to propose an unrevealed, but important mechanism via which ESW treatment affects osteogenic differentiation of bone marrow stromal cells.
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Affiliation(s)
- Youbin Chen
- Department of Orthopedics, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China
| | - Jiankun Xu
- Department of Orthopedics, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China; Department of Orthopedics and Traumatology, Faculty of Medicine, the Chinese University of Hong Kong, Hong Kong Special Administrative Region
| | - Haojie Liao
- Department of Orthopedics, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China
| | - Zebin Ma
- Department of Orthopedics, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China
| | - Yuantao Zhang
- Department of Orthopedics, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China
| | - Hongjiang Chen
- Department of Orthopedics, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China
| | - Zhonglian Huang
- Department of Orthopedics, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China
| | - Jun Hu
- Department of Orthopedics, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China.
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Hashida Y, Nakahama KI, Shimizu K, Akiyama M, Harada K, Morita I. Communication-dependent mineralization of osteoblasts via gap junctions. Bone 2014; 61:19-26. [PMID: 24389413 DOI: 10.1016/j.bone.2013.12.031] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 12/06/2013] [Accepted: 12/25/2013] [Indexed: 10/25/2022]
Abstract
Connexin43 (Cx43) is a major gap junction (GJ) protein in bone and plays a critical role in osteoblast differentiation. Several studies show that osteoblast differentiation is delayed by Cx43 ablation. However, the precise mechanism underlying the role of Cx43 in osteoblast differentiation is not fully understood. Firstly, we analyzed the phenotype of a conditional knockout mouse, which was generated by mating of an osterix promoter-driven Cre expressing mouse with a Cx43-floxed mouse. As expected, delayed ossification was observed. Secondly, we demonstrated that the cell communication via gap junctions played an important role in osteoblast differentiation using a tamoxifen-inducible knockout system in vitro. Genetic ablation of Cx43 resulted in both the disruption of cell-communications and the attenuation of osteoblast mineralization induced by BMP-2, but not by ascorbic acid. Moreover, restoring full-length Cx43 (382aa) expression rescued the impairment of osteoblast cell-communication and osteoblast mineralization; however, the expression of the Cx43 N-terminal mutant (382aaG2V) did not rescue either of them. Comparing the gene expression profiles, the genes directly regulated by BMP-2 were attenuated by Cx43 gene ablation. These results suggested that the cell-communication mediated by gap junctions was indispensable for normal differentiation of osteoblast induced by BMP-2.
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Affiliation(s)
- Yukihiko Hashida
- Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan; Section of Maxillofacial Surgery, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan; Global Center of Excellence (GCOE) Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Japan
| | - Ken-ichi Nakahama
- Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan.
| | - Kaori Shimizu
- Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan; Section of Oral Implantology and Regenerative Dental Medicine, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan
| | - Masako Akiyama
- Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan
| | - Kiyoshi Harada
- Section of Maxillofacial Surgery, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan
| | - Ikuo Morita
- Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan; Global Center of Excellence (GCOE) Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Japan
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7
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Lloyd SA, Loiselle AE, Zhang Y, Donahue HJ. Shifting paradigms on the role of connexin43 in the skeletal response to mechanical load. J Bone Miner Res 2014; 29:275-86. [PMID: 24588015 PMCID: PMC5949871 DOI: 10.1002/jbmr.2165] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Gap junctions (GJs) are membrane-spanning channels that allow for the movement of small molecules across cell membranes. Connexin43 (Cx43) is the predominant GJ protein in bone. In vitro studies suggest that gap junctional intercellular communication (GJIC) sensitizes bone cells to mechanical signals. Additionally, mechanical signals detected by osteocytes are communicated to osteoblasts via GJIC, and osteocytic Cx43 hemichannels release anabolic factors, such as PGE2 and ATP, in response to mechanical load. These findings and others have led to near consensus among researchers in the field that GJIC, hemichannels or connexins facilitate the anabolic response of bone to mechanical load and, in their absence, bone would be less sensitive to load. However, recent in vivo evidence suggests the opposite is true. Studies from our laboratory and others demonstrate that Cx43-deficient mice have an increased anabolic response to mechanical load and are protected against the catabolic effects of mechanical unloading. These developments suggest a paradigm shift in our understanding of connexins, GJIC, and mechanotransduction in bone. That is, inhibiting bone cell Cx43 expression or GJIC has a beneficial effect on bone's response to its mechanical environment, preserving bone during unloading and enhancing its formation during loading. Here, we review literature in support of this hypothesis and suggest a mechanism by which Cx43, through interaction with WNT/β-catenin signaling, moderates both arms of bone remodeling.
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Affiliation(s)
- Shane A Lloyd
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation; Penn State College of Medicine; Hershey PA USA
| | - Alayna E Loiselle
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation; Penn State College of Medicine; Hershey PA USA
| | - Yue Zhang
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation; Penn State College of Medicine; Hershey PA USA
| | - Henry J Donahue
- Division of Musculoskeletal Sciences, Department of Orthopaedics and Rehabilitation; Penn State College of Medicine; Hershey PA USA
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Talhouk RS, Khalil AA, Bajjani R, Rahme GJ, El-Sabban ME. Gap junctions mediate STAT5-independent β-casein expression in CID-9 mammary epithelial cells. ACTA ACUST UNITED AC 2011; 18:104-16. [DOI: 10.3109/15419061.2011.639468] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Rabih S. Talhouk
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Antoine A. Khalil
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Rachid Bajjani
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Gilbert J. Rahme
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Marwan E. El-Sabban
- Department of Human Morphology, American University of Beirut, Beirut, Lebanon
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9
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Inhibition of osteoblastic differentiation by warfarin and 18-α-glycyrrhetinic acid. Arch Pharm Res 2011; 34:1381-7. [PMID: 21910061 DOI: 10.1007/s12272-011-0819-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 05/30/2011] [Accepted: 05/30/2011] [Indexed: 10/17/2022]
Abstract
Anticoagulation therapy with vitamin K antagonists such as warfarin is widely used to prevent and treat stroke in patients with chronic atrial fibrillation or mechanical heart valves. Because vitamin K is an essential factor for ggg-carboxylation of osteocalcin, vitamin K antagonists might cause bone loss. Although the association between warfarin use and bone metabolism is still controversial, several studies show that bone mineral density is decreased and fracture risk is increased with warfarin therapy. Meanwhile, attenuation of gap junctional communication (GJC) by warfarin is reported in rat liver epithelial cells. However, the effect of warfarin on osteoblasts, in which GJC is important for osteoblastic differentiation, remains unknown. Here we investigated whether warfarin has an inhibitory effect on osteoblastic differentiation using an osteoblastic cell line (C2C12). Warfarin and 18-α-glycyrrhetinic acid (AGA), which is known as a nontoxic reversible GJC inhibitor, had the same effect on osteoblastic differentiation. Warfarin and AGA inhibited the bone morphogenetic protein (BMP)2-induced mRNA levels of alkaline phosphatase (ALP), collagen I α1, osteocalcin (OC) and osterix, which are specific markers for osteoblastic differentiation, in a dose-dependent manner. Moreover, the activities of OC- and ALP-luciferase reporters, which are induced by BMP2, and the transcriptional activity of Runx2 on OC and ALP promoters were inhibited by warfarin and AGA. The amount and activity of ALP induced by BMP2 were also decreased by warfarin and AGA. These results suggest that warfarin and AGA, a GJC inhibitor, have an inhibitory effect on osteoblastic differentiation.
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Kang KS, Trosko JE. Stem cells in toxicology: fundamental biology and practical considerations. Toxicol Sci 2010; 120 Suppl 1:S269-89. [PMID: 21163910 DOI: 10.1093/toxsci/kfq370] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
This "Commentary" has examined the use of human stem cells for detection of toxicities of physical, chemical, and biological toxins/toxicants in response to the challenge posed by the NRC Report, "Toxicity Testing in the 21st Century: A vision and Strategy." Before widespread application of the use of human embryonic, pluripotent, "iPS," or adult stem cells be considered, the basic characterization of stem cell biology should be undertaken. Because no in vitro system can mimic all factors that influence cells in vivo (individual genetic, gender, developmental, immunological and diurnal states; niche conditions; complex intercellular interactions between stem, progenitor, terminal differentiated cells, and the signaling from extracellular matrices, oxygen tensions, etc.), attempts should be made to use both embryonic and adult stem cells, grown in three dimension under "niche-like" conditions. Because many toxins and toxicants work by "epigenetic" mechanisms and that epigenetic mechanisms play important roles in regulating gene expression and in the pathogenesis of many human diseases, epigenetic toxicity must be incorporated in toxicity testing. Because modulation of gap junctional intercellular communication by epigenetic agents plays a major role in homeostatic regulation of both stem and progenitor cells in normal tissues, the modulation of this biological process by both endogenous and endogenous chemicals should be incorporated as an end point to monitor for potential toxicities or chemo-preventive attributes. In addition, modulation of quantity, as well as the quality, of stem cells should be considered as potential source of a chemical's toxic potential in affecting any stem cell-based pathology, such as cancer.
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Affiliation(s)
- Kyung-Sun Kang
- Adult Stem Cell Research Center, Laboratory for Stem Cell and Tumor Biology, Department of Veterinary Public Health, College of Veterinary Medicine, Seoul National University, Sillim-Dong, Seoul 151-742, Korea
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Morel S, Burnier L, Roatti A, Chassot A, Roth I, Sutter E, Galan K, Pfenniger A, Chanson M, Kwak BR. Unexpected role for the human Cx37 C1019T polymorphism in tumour cell proliferation. Carcinogenesis 2010; 31:1922-31. [PMID: 20705954 DOI: 10.1093/carcin/bgq170] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Connexins are a large family of proteins that form gap junction channels allowing exchange of ions and small metabolites between neighboring cells. They have been implicated in pathological processes such as tumourigenesis in which they may act as tumour suppressors. A polymorphism in the human connexin37 (Cx37) gene (C1019T), resulting in a non-conservative amino acid change in the regulatory C-terminus (CT) of the Cx37 protein (P319S) has been suggested to be implicated in predisposition to angiosarcomas. In this study, we have used communication-deficient HeLa and SK-HEP-1 cells transfected with Cx37-319S, Cx37-319P or empty vector. We showed that the expression of Cx37-319P limited proliferation of HeLa and SK-HEP-1 cells, whereas Cx37-319S expression was without effect. Using an in vitro kinase assay, we demonstrated phosphorylation of Cx37 CT by glycogen synthase kinase-3 (GSK-3), a kinase known to be implicated in cell proliferation and cancer. GSK-3-induced phosphorylation was associated with reduced gap junctional intercellular communication (GJIC) as measured by microinjection of the tracer neurobiotin. Inhibition of GSK-3 by LiCl or SB415286 reduced phosphorylation of Cx37-319P and increased GJIC. This latter effect on GJIC involved the beta and not the alpha isoform of GSK-3. In contrast, GSK-3 inhibitors were without effect on HeLa cells expressing Cx37-319S. In conclusion, our data indicate functional effects of the Cx37 C1019T polymorphism on GJIC that might contribute to tumour cell growth.
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Affiliation(s)
- Sandrine Morel
- Department of Pathology and Immunology, University of Geneva, 64 avenue de la Roseraie, Geneva, Switzerland.
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Geneau G, Lamiche C, Niger C, Strale PO, Clarhaut J, Defamie N, Debiais F, Mesnil M, Cronier L. Effect of endothelin-1 on osteoblastic differentiation is modified by the level of connexin43: comparative study on calvarial osteoblastic cells isolated from Cx43+/- and Cx43+/+ mice. Cell Tissue Res 2010; 340:103-15. [PMID: 20195637 DOI: 10.1007/s00441-009-0924-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 12/18/2009] [Indexed: 01/04/2023]
Abstract
Bone is a dynamic tissue that undergoes a precise remodeling process involving resorptive osteoclastic cells and bone-forming osteoblastic (OB) cells. The functional imbalance of either of these cell types can lead to severe skeletal diseases. The proliferation and differentiation of OB cells play a major role in bone development and turnover. These cellular processes are coordinated by connexin43 (Cx43)-based gap-junctional intercellular communication (GJIC) and by soluble factors such as endothelin-1 (ET-1). We have used the Cx43 heterozygous (Cx43(+/-)) murine model to study the possible cross-talk between Cx43 and ET-1 in cultured calvarial OB cells. On microcomputed tomographic analysis of 3-day-old pups, Cx43(+/-) mice showed hypomineralized calvaria in comparison with their Cx43(+/+) littermates. Characterization of cultured OB cells clearly demonstrated the effect of the partial deletion of the Cx43 gene on its expression, on GJIC, and subsequently on OB differentiation. In this model, ET-1 (10(-8) M) lost its mitogenic action in Cx43(+/-) OB cells compared with Cx43(+/+) cells. Moreover, a correlation between the inhibition of cell differentiation by ET-1 and the decreased amount and function of Cx43 was found in Cx43(+/+) OB cells but not in their Cx43(+/-) counterparts. Thus, as Cx43 is linked to OB differentiation, our data indicate that this mitogenic ET-1 peptide has pronounced effects on fully differentiated OB cells. With respect to roles in mechanotransduction and OB differentiation, Cx43 might modulate osteoblastic sensitivity to soluble factors.
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Affiliation(s)
- Graziello Geneau
- Institut de Physiologie et Biologie Cellulaires, University of Poitiers, CNRS UMR 6187, 86022, Poitiers Cedex, France
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13
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Lima F, Niger C, Hebert C, Stains JP. Connexin43 potentiates osteoblast responsiveness to fibroblast growth factor 2 via a protein kinase C-delta/Runx2-dependent mechanism. Mol Biol Cell 2009; 20:2697-708. [PMID: 19339281 PMCID: PMC2688549 DOI: 10.1091/mbc.e08-10-1079] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 03/20/2009] [Accepted: 03/24/2009] [Indexed: 12/13/2022] Open
Abstract
In this study, we examine the role of the gap junction protein, connexin43 (Cx43), in the transcriptional response of osteocalcin to fibroblast growth factor 2 (FGF2) in MC3T3 osteoblasts. By luciferase reporter assays, we identify that the osteocalcin transcriptional response to FGF2 is markedly increased by overexpression of Cx43, an effect that is mediated by Runx2 via its OSE2 cognate element, but not by a previously identified connexin-responsive Sp1/Sp3-binding element. Furthermore, disruption of Cx43 function with Cx43 siRNAs or overexpression of connexin45 markedly attenuates the response to FGF2. Inhibition of protein kinase C delta (PKCdelta) with rottlerin or siRNA-mediated knockdown abrogates the osteocalcin response to FGF2. Additionally, we show that upon treatment with FGF2, PKCdelta translocates to the nucleus, PKCdelta and Runx2 are phosphorylated and these events are enhanced by Cx43 overexpression, suggesting that the degree of activation is enhanced by increased Cx43 levels. Indeed, chromatin immunoprecipitations of the osteocalcin proximal promoter with antibodies against Runx2 demonstrate that the recruitment of Runx2 to the osteocalcin promoter in response to FGF2 treatment is dramatically enhanced by Cx43 overexpression. Thus, Cx43 plays a critical role in regulating the ability of osteoblasts to respond to FGF2 by impacting PKCdelta and Runx2 function.
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Affiliation(s)
- Florence Lima
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201
| | - Corinne Niger
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201
| | - Carla Hebert
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201
| | - Joseph P. Stains
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD 21201
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Cronier L, Crespin S, Strale PO, Defamie N, Mesnil M. Gap junctions and cancer: new functions for an old story. Antioxid Redox Signal 2009; 11:323-38. [PMID: 18834328 DOI: 10.1089/ars.2008.2153] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Cancer was one of the first pathologies to be associated with gap-junction defect. Despite the evidence accumulated over the last 40-year period, the molecular involvement of gap junctions and their structural proteins (connexins) in cancer has not been elucidated. The lack of a satisfying explanation may come from the complexity of the disease, evolving through various stages during tumor progression, with cancer cells exhibiting different phenotypes. Here, the question of the involvement of gap junctions has been readdressed by considering the connexin expression/function level at different fundamental stages of carcinogenesis (cell proliferation, cell invasion, and cancer cell dissemination). By performing this analysis, it becomes clear that gap junctions are probably differently involved, depending on the stage of the cancer progression considered. In particular, the most recent data suggest that connexins may act on cell growth by controlling gene expression through a variety of processes (independent of or dependent on the gap-junctional communication capacity). During invasion, connexins have been demonstrated to enhance adherence of cancer cells to the stroma, migration, and probably their dissemination by establishing communication with the endothelial barrier. All these data present a complex picture of connexins in various functions, depending on the cell phenotype.
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Affiliation(s)
- Laurent Cronier
- Institute of Cellular Physiology and Biology, University of Poitiers/CNRS, Poitiers, France
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Tacheau C, Fontaine J, Loy J, Mauviel A, Verrecchia F. TGF-β induces connexin43 gene expression in normal murine mammary gland epithelial cells via activation of p38 and PI3K/AKT signaling pathways. J Cell Physiol 2008; 217:759-68. [DOI: 10.1002/jcp.21551] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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ODDD-linked Cx43 mutants reduce endogenous Cx43 expression and function in osteoblasts and inhibit late stage differentiation. J Bone Miner Res 2008; 23:928-38. [PMID: 18269311 DOI: 10.1359/jbmr.080217] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
INTRODUCTION Bone development and modeling requires precise gap junctional intercellular communication (GJIC). Oculodentodigital dysplasia (ODDD) is an autosomal dominant human disease caused by mutations in the gene (GJA1) encoding the gap junction protein, connexin43 (Cx43). The disease is characterized by craniofacial bone deformities and limb abnormalities. It is our hypothesis that Cx43 mutation causes osteoblast dysfunction, which may contribute to the bone phenotype of ODDD. MATERIALS AND METHODS We expressed human and mouse ODDD-linked Cx43 mutants in MC3T3-E1 cells and primary mouse osteoblasts by retroviral infection and evaluated their in vitro differentiation as an index of osteoblast function. We compared these findings to the differentiation of osteoblasts isolated from a mouse model of ODDD that harbors a germ line Cx43 mutation and exhibits craniofacial and limb defects mimicking human ODDD. We determined the differentiation status of osteoblasts by analyzing alkaline phosphatase activity and the expression levels of osteoblast markers including bone sialoprotein and osteocalcin. RESULTS We showed that ODDD-linked Cx43 mutants are loss-of-function and dominant-negative to co-expressed Cx43 and, furthermore, greatly inhibit functional GJIC in osteoblasts. Surprisingly, the mutants had only a minor effect on osteoblast differentiation when introduced into lineage committed cells. In contrast, osteoblasts isolated from the ODDD mouse model exhibited impaired late stage differentiation. CONCLUSIONS Expression of human and mouse ODDD-linked Cx43 mutants failed to significantly impair differentiation in cells predisposed to the osteoblast lineage; however, germ line reduction of Cx43-based GJIC leads to impaired osteoblast differentiation, which may account for the bone phenotypes observed in ODDD patients.
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Civitelli R. Cell-cell communication in the osteoblast/osteocyte lineage. Arch Biochem Biophys 2008; 473:188-92. [PMID: 18424255 PMCID: PMC2441851 DOI: 10.1016/j.abb.2008.04.005] [Citation(s) in RCA: 178] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 04/04/2008] [Accepted: 04/07/2008] [Indexed: 11/17/2022]
Abstract
Skeletal development (bone modeling) and its maintenance in post-natal life in response to local and systemic stimuli (bone remodeling) require coordinated activity among osteoblasts (bone forming cells), osteocytes (cells embedded in bone) and osteoclasts (bone resorbing cells), in order to meet the needs of structural integrity, mechanical competence and maintenance of mineral homeostasis. One mechanism of cell-cell interaction is via direct cell-cell communication via gap junctions. These are transmembrane channels that allow continuity of cytoplasms between communicating cells. The biologic importance of connexin43 (Cx43), the most abundant gap junction protein in the skeleton is demonstrated by the skeletal malformations present in oculodentodigital dysplasia (ODDD), a disease linked to Cx43 gene (GJA1) mutations, and by the low bone mass and osteoblast dysfunction in Gja1 ablated mice. The presence of Cx43 is required for osteoblast differentiation and function, and by forming either gap junctions or "hemichannels" Cx43 allows participation of cell networks to responses to extracellular stimuli, via propagation of specific signals converging upon connexin sensitive transcriptional units. Hence, Cx43 is involved in skeletal responsiveness to anabolic signals, as those provided by parathyroid hormone and physical load, the latter function probably involving osteocyte-osteoblast communication.
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Affiliation(s)
- Roberto Civitelli
- Washington University in St. Louis, Department of Internal Medicine, Division of Bone and Mineral Diseases, 660 S. Euclid Avenue, P.O. Box 8301, St. Louis, MO 63110, USA.
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Geneau G, Defamie N, Mesnil M, Cronier L. Endothelin1-induced Ca(2+) mobilization is altered in calvarial osteoblastic cells of Cx43(+/- ) mice. J Membr Biol 2007; 217:71-81. [PMID: 17568972 DOI: 10.1007/s00232-007-9024-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2007] [Accepted: 04/04/2007] [Indexed: 10/23/2022]
Abstract
During bone remodeling, osteoblastic (OB) cells have a central role leading to the production of extracellular matrix and its subsequent mineralization. As revealed by human physiopathologies, the OB differentiation process is essential for the control of calcium metabolism and normal bone formation. Moreover, accumulating data in the field of bone development suggest that connexin 43 (Cx43)-mediated gap junctional communication plays an important role in OB differentiation and function. Since Ca(2+) has a central role in OB physiology, the aim of the present study was to investigate the hypothetical involvement of Cx43 in OB calcium homeostasis. We performed measurements of intracellular calcium activity ([Ca(2+)]( i )) by a cytofluorimetric method using Fluo-4 as a calcium indicator and endothelin-1 (ET-1) as a physiological calcium-mobilizing factor on cultured OB cells isolated from calvaria of Cx43(+/-) and Cx43(+/+) mice. Partial deletion of the Cx43 gene induced a significant decrease in the [Ca(2+)]( i ) rise elicited by ET-1. This reduction was not correlated to a decrease or a modification of ET receptor subtype expression as assessed by real-time reverse-transcription polymerase chain reaction. Pharmacological investigations led us to demonstrate that the significant difference in [Ca(2+)]( i ) peak amplitude during the ET-1 action was associated with decreased calcium influx involving L-type voltage-sensitive calcium channels, whereas calcium release from intracellular stores and implication of phospholipase C were not affected by the reduced expression of Cx43. In conclusion, our data demonstrate for the first time that the Cx43 level of expression and/or function is able to modulate the [Ca(2+)]( i ) mobilization in OB cells.
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Affiliation(s)
- Graziello Geneau
- Institut de Physiologie et de Biologie Cellulaires, CNRS UMR6187, Université de Poitiers, 40 avenue du recteur Pineau, 86022, Poitiers, France
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Kizana E, Chang CY, Cingolani E, Ramirez-Correa GA, Sekar RB, Abraham MR, Ginn SL, Tung L, Alexander IE, Marbán E. Gene Transfer of Connexin43 Mutants Attenuates Coupling in Cardiomyocytes. Circ Res 2007; 100:1597-604. [PMID: 17495226 DOI: 10.1161/circresaha.106.144956] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Modification of electrical conduction would be a useful principle to recruit in preventing or treating certain arrhythmias, notably ventricular tachycardia (VT). Here we pursue a novel gene transfer approach to modulate electrical conduction by reducing gap junctional intercellular communication (GJIC) and hence potentially modify the arrhythmia substrate. The ultimate goal is to develop a nondestructive approach to uncouple zones of slow conduction by focal gene transfer. Lentiviral vectors encoding connexin43 (Cx43) internal loop mutants were produced and studied in vitro. Transduction of neonatal rat ventricular myocytes (NRVMs) revealed the expected subcellular localization of the mutant gene product. Fluorescent dye transfer studies showed a significant reduction of GJIC in NRVMs that had been genetically modified. Additionally, adjacent mutant gene-modified NRVMs displayed delayed calcium transients, indicative of electrical uncoupling. Multi-site optical mapping of action potential (AP) propagation in gene-modified NRVM monolayers revealed a 3-fold slowing of conduction velocity (CV) relative to nontransduced NRVMs. In conclusion, lentiviral vector–mediated gene transfer of Cx43 mutants reduced GJIC in NRVMs. Electrical charge transfer was also reduced as evidenced by delayed calcium transients in adjacent NRVMs and reduced CV in NRVM monolayers. These data validate a molecular tool that opens the prospect for gene transfer targeting gap junctions as an approach to modulate cardiac conduction.
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Affiliation(s)
- Eddy Kizana
- Gene Therapy Research Unit, The Children's Hospital at Westmead and Children's Medical Research Institute, Westmead, Australia
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20
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McLachlan E, Manias JL, Gong XQ, Lounsbury CS, Shao Q, Bernier SM, Bai D, Laird DW. Functional characterization of oculodentodigital dysplasia-associated Cx43 mutants. ACTA ACUST UNITED AC 2007; 12:279-92. [PMID: 16531323 DOI: 10.1080/15419060500514143] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Oculodentodigital dysplasia (ODDD) is associated with at least 28 connexin43 (Cx43) mutations. We characterized four of these mutants; Q49K, L90V, R202H, and V216L. Populations of these GFP-tagged mutants were transported to the cell surface in Cx43-negative HeLa cells and Cx43-positive NRK cells. Dual patch-clamp functional analysis in N2A cells demonstrated that channels formed by each mutant have dramatically reduced conductance. Dye-coupling analysis revealed that each mutant exhibits a dominant-negative effect on wild-type Cx43. Since ODDD patients display skeletal abnormalities, we examined the effect of three other Cx43 mutants previously shown to exert dominant-negative effects on wild-type Cx43 (G21R, G138R, and G60S) in neonatal calvarial osteoblasts. Differentiation was unaltered by expression of these mutants as alkaline phosphatase activity and extent of culture mineralization were unchanged. This suggests that loss-of-function Cx43 mutants are insufficient to deter committed osteoblasts from their normal function in vitro. Thus, we hypothesize that the bone phenotype of ODDD patients may result from disrupted gap junctional intercellular communication earlier in development or during bone remodeling.
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Affiliation(s)
- Elizabeth McLachlan
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario, Canada
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21
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Niger C, Geneau G, Fiorini C, Defamie N, Pointis G, Mesnil M, Cronier L. Endothelin-1 inhibits human osteoblastic cell differentiation: Influence of connexin-43 expression level. J Cell Biochem 2007; 103:110-22. [PMID: 17486593 DOI: 10.1002/jcb.21390] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Gap junctional intercellular communication (GJIC) permits coordinated cellular activities during developmental and differentiation processes. In bone, the involvement of the gap junctional protein, connexin-43 (Cx43), and of GJIC in osteoblastic differentiation and mineralization of the extracellular matrix has been previously demonstrated. Former studies have shown that endothelin-1 (ET-1) was also implicated in the control of osteoblastic proliferation and differentiation. However, depending on the cellular models, ET-1 has been shown to decrease or increase osteoblastic differentiation markers. As no data were available on the ET-1 effect on GJIC and Cx43 expression in osteoblastic cells, we analyzed here the possible crosstalk between Cx43 and ET-1 in a human cell line (hFOB 1.19) which displays different Cx43 expression levels and phenotypes when cultured at 33.5 or 39 degrees C. The presence of ET-1 (10(-8) M) for 2-12 days of culture did not significantly alter the proliferation rate of hFOB cells whatever their phenotype. In contrast, ET-1 induced a differential inhibitory effect on the biochemical differentiation markers (alkaline phosphatase activity and osteocalcin expression) with a significant reduction in the differentiated phenotype at 39 degrees C, whereas no effects were measured at 33.5 degrees C. The inhibitory effect was linked to a decrease of GJIC and of Cx43 both at transcriptional and protein levels. Altogether, our results suggest that Cx43 expression level could influence the action of ET-1 on human osteoblastic cell differentiation. Our data also indicate that the gap junctional protein could play a pivotal role in the response of osteoblasts to mitogenic factors implicated in bone pathologies.
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Affiliation(s)
- Corinne Niger
- Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, USA
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22
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Waggett AD, Benjamin M, Ralphs JR. Connexin 32 and 43 gap junctions differentially modulate tenocyte response to cyclic mechanical load. Eur J Cell Biol 2006; 85:1145-54. [PMID: 16859807 DOI: 10.1016/j.ejcb.2006.06.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Revised: 06/07/2006] [Accepted: 06/12/2006] [Indexed: 12/11/2022] Open
Abstract
Gap junctions allow rapid exchange of ions and small metabolites between cells. They can occur between connective tissue cells, and in tendons there are two prominent types, composed of connexin 32 or 43. These form distinct networks - tenocyte rows are linked by both longitudinally, but only by connexin 43 laterally. We hypothesised that the junctions had different roles in cell response to mechanical loading, and measured the effects of inhibitors of gap junction function on secretion of collagen by tenocyte cultures exposed to mechanical strain. Chicken tendon fibroblasts were exposed to cyclic tensile loading in the presence or absence of general gap junction inhibitors (halothane or the biomimetic peptide gap27), or antisense oligonucleotides to chicken connexin 32 or 43. Untreated cultures increased collagen secretion by around 25% under load. Halothane eliminated this response but caused cell damage. Gap27 peptide reduced secretion but maintained loading effects - strained cultures secreting more collagen than unstrained. Antisense downregulation showed major differences between connexins: antisense 32 reduced, and antisense 43 increased, collagen secretion. In both cases loading effects were maintained. This shows that (i) gap junctional integration of signals is important in load response of tenocyte populations - mechanotransduction occurs in individual cells but integration of signals markedly enhances it and (ii) communication via connexin 32 and 43 have differential effects on the load response, with connexin 32 being stimulatory and connexin 43 being inhibitory. Cells coordinate and control their response to mechanical signals at least in part by differential actions of these two types of gap junction.
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Affiliation(s)
- Andrew D Waggett
- Connective Tissue Biology Laboratory, School of Biosciences, Cardiff University, Biomedical Sciences Building, Museum Avenue, PO Box 911, Cardiff CF10 3US, UK
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23
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Squecco R, Sassoli C, Nuti F, Martinesi M, Chellini F, Nosi D, Zecchi-Orlandini S, Francini F, Formigli L, Meacci E. Sphingosine 1-phosphate induces myoblast differentiation through Cx43 protein expression: a role for a gap junction-dependent and -independent function. Mol Biol Cell 2006; 17:4896-910. [PMID: 16957055 PMCID: PMC1635397 DOI: 10.1091/mbc.e06-03-0243] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Although sphingosine 1-phosphate (S1P) has been considered a potent regulator of skeletal muscle biology, acting as a physiological anti-mitogenic and prodifferentiating agent, its downstream effectors are poorly known. In the present study, we provide experimental evidence for a novel mechanism by which S1P regulates skeletal muscle differentiation through the regulation of gap junctional protein connexin (Cx) 43. Indeed, the treatment with S1P greatly enhanced Cx43 expression and gap junctional intercellular communication during the early phases of myoblast differentiation, whereas the down-regulation of Cx43 by transfection with short interfering RNA blocked myogenesis elicited by S1P. Moreover, calcium and p38 MAPK-dependent pathways were required for S1P-induced increase in Cx43 expression. Interestingly, enforced expression of mutated Cx43(Delta130-136) reduced gap junction communication and totally inhibited S1P-induced expression of the myogenic markers, myogenin, myosin heavy chain, caveolin-3, and myotube formation. Notably, in S1P-stimulated myoblasts, endogenous or wild-type Cx43 protein, but not the mutated form, coimmunoprecipitated and colocalized with F-actin and cortactin in a p38 MAPK-dependent manner. These data, together with the known role of actin remodeling in cell differentiation, strongly support the important contribution of gap junctional communication, Cx43 expression and Cx43/cytoskeleton interaction in skeletal myogenesis elicited by S1P.
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Affiliation(s)
- R Squecco
- Departments of Biochemical Sciences, University of Florence, Interuniversity Institute of Myology, Florence I-50134, Italy
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24
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Watanabe M, Iwashita M, Ishii M, Kurachi Y, Kawakami A, Kondo S, Okada N. Spot pattern of leopard Danio is caused by mutation in the zebrafish connexin41.8 gene. EMBO Rep 2006; 7:893-7. [PMID: 16845369 PMCID: PMC1559663 DOI: 10.1038/sj.embor.7400757] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 06/20/2006] [Accepted: 06/20/2006] [Indexed: 11/08/2022] Open
Abstract
Leopard, a well-known zebrafish mutant that has a spotted skin pattern instead of stripes, is a model for the study of pigment patterning. To understand the mechanisms underlying stripe formation, as well as the spot variation observed in leopard, we sought to identify the gene responsible for this phenotype. Using positional cloning, we identified the leopard gene as an orthologue of the mammalian connexin 40 gene. A variety of different leopard alleles, such as leo(t1), leo(tq270) and leo(tw28), show different skin-pattern phenotypes. In this manuscript we show that the mutation in allele leo(t1) is a nonsense mutation, whereas alleles leo(tq270) and leo(tw28) contain the missense mutations I202F and I31F, respectively. Patch-clamp experiments of connexin hemichannels demonstrated that the I202F substitution in allele leo(tq270) disrupted the channel function of connexin41.8. These results demonstrate that mutations in this gene lead to a variety of leopard spot patterns.
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Affiliation(s)
- Masakatsu Watanabe
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B21, Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
| | - Motoko Iwashita
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B21, Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
- Center of Developmental Biology, Riken, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0077, Japan
| | - Masaru Ishii
- Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Yoshihisa Kurachi
- Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Atsushi Kawakami
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B21, Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
- Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shigeru Kondo
- Center of Developmental Biology, Riken, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0077, Japan
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Norihiro Okada
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B21, Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
- National Institute for Basic Biology, Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
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Muller-Borer BJ, Cascio WE, Esch GL, Grisham JW, Anderson PAW, Malouf NN. Acquired cell-to-cell coupling and "cardiac-like" calcium oscillations in adult stem cells in a cardiomyocyte microenvironment. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2006; 2006:576-579. [PMID: 17946843 DOI: 10.1109/iembs.2006.260737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Adult-derived stem cells have recently been found to respond in vivo to inductive signals from the microenvironment and to differentiate into a phenotype that is characteristic of cells in that microenvironment. We examined the differentiation potential of an adult liver stem cell line (WBF344) in a cardiac microenvironment in vitro. WBF344 cells were established from a single cloned non-parenchymal epithelial cell isolated from a normal male adult rat liver. Genetically modified, WBF344 cells that express beta-galactosidase, green fluorescent protein (GFP) or mitochondrial red fluorescent protein (DsRed) were co-cultured with rat neonatal cardiac cells. After 4-14 days, we identified WBF344-derived cardiomyocytes that were elongated, binucleated and expressed the cardiac specific proteins cardiac troponin T, cardiac troponin I and N cadherin. These WBF344-derived cardiomyocytes also exhibited myofibrils, sarcomeres, and a nascent sarcoplasmic reticulum. Furthermore, rhythmically beating WBF344-derived cardiomyocytes displayed "cardiac-like" calcium transients similar to the surrounding neonatal cardiomyocytes. Fluorescent recovery after photobleaching demonstrated that WBF344-derived cardiomyocytes were electrically coupled with adjacent neonatal cardiomyocytes through gap junctions (GJs). Collectively, these results support the conclusion that these adult-derived liver stem cells respond to signals generated in a cardiac microenvironment in vitro acquiring a cardiomyocyte phenotype and function. The identification of micro-environmental signals that appear to cross germ layer and species specificities should prove valuable in understanding the regulation of normal development and stem cell differentiation in vivo.
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Trosko JE, Chang CC, Upham BL, Tai MH. The role of human adult stem cells and cell-cell communication in cancer chemoprevention and chemotherapy strategies. Mutat Res 2005; 591:187-97. [PMID: 16084532 DOI: 10.1016/j.mrfmmm.2005.01.034] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2004] [Revised: 12/29/2004] [Accepted: 01/12/2005] [Indexed: 05/03/2023]
Abstract
Since carcinogenesis is a multi-stage, multi-mechanism process, involving mutagenic, cell death and epigenetic mechanisms, during the "initiation/promotion/and progression" phases, chemoprevention must be based on understanding the underlying mechanism(s) of each phase, In principle, prevention of each of these phases could reduce the risk to cancer. However, because reducing the mutagenic/initiation phase to a zero level is impossible, the most efficacious intervention would be at the promotion phase that requires a sustained exposure to promoting conditions/agents. In addition, assuming the "target" cells for carcinogenesis are the pluri-potent stem cells and their early progenitor or transit cells, chemoprevention strategies for inhibiting the promotion of these two types of pre-malignant "initiated" cells will require different kinds of agents. A hypothesis will be proposed that involves adult stem cells, which express Oct-4 gene and lack gap junctional intercellular communication (GJIC-) or the early progenitor cells which express GJIC+ and are partially-differentiated, if initiated, will be promoted by agents that either inhibit secreted negative growth regulators or by inhibitors of GJIC. Consequently, anti-tumor promoting chemopreventing agents to each of these two types of initiated cells must have different mechanisms of action and work on different target cells. Assuming stem cells are target cells for carcinogenesis, an alternative method of chemoprevention would be to reduce the stem cell pool. Many classes of anti-tumor promoter chemopreventive agents, such as green tea components, resveratrol, caffeic acid phenethylene ester, either up-regulate GJIC in stem cells or prevent the down regulation of GJIC by tumor promoters in early progenitor cells.
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Affiliation(s)
- James E Trosko
- 246 National Food Safety Toxicology Center, Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University, East Lansing, MI 48824, USA.
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Stains JP, Civitelli R. Gap junctions in skeletal development and function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1719:69-81. [PMID: 16359941 DOI: 10.1016/j.bbamem.2005.10.012] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Revised: 10/26/2005] [Accepted: 10/28/2005] [Indexed: 11/29/2022]
Abstract
Gap junctions play a critical role in the coordinated function and activity of nearly all of the skeletal cells. This is not surprising, given the elaborate orchestration of skeletal patterning, bone modeling and subsequent remodeling, as well as the mechanical stresses, strains and adaptive responses that the skeleton must accommodate. Much remains to be learned regarding the role of gap junctions and hemichannels in these processes. A common theme is that without connexins none of the cells of bone function properly. Thus, connexins play an important role in skeletal form and function.
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Affiliation(s)
- Joseph P Stains
- University of Maryland School of Medicine, Department of Orthopaedics, Baltimore, MD 21201, USA
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28
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Li Z, Zhou Z, Saunders MM, Donahue HJ. Modulation of connexin43 alters expression of osteoblastic differentiation markers. Am J Physiol Cell Physiol 2005; 290:C1248-55. [PMID: 16319124 DOI: 10.1152/ajpcell.00428.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Gap junctional channels between cells provide a pathway for exchange of regulatory ions and small molecules. We previously demonstrated that expression of connexins and cell-to-cell communication parallel osteoblastic differentiation and that nonspecific pharmacological inhibitors of gap junctional communication inhibit alkaline phosphatase activity. In this study, we stably transfected connexin (Cx)43 antisense cDNA into the immortalized human fetal osteoblastic cell line hFOB 1.19 (hFOB/Cx43(-)). hFOB/Cx43(-) cells express lower levels of Cx43 protein and mRNA and display a 50% decrease in gap junctional intercellular communication relative to control [hFOB/plasmid vector control (pvc)]. This suggests that other connexins, such as Cx45, which is expressed to a similar degree in hFOB/Cx43(-) cells and hFOB/pvc cells, contribute to cell-to-cell communication in hFOB 1.19 cells. We observed almost total inhibition of alkaline phosphatase activity in hFOB/Cx43(-) cells despite only a 50% decrease in cell-to-cell communication. This suggests the intriguing possibility that Cx43 expression per se, independent of cell-to-cell communication, influences alkaline phosphatase activity and perhaps bone cell differentiation. Quantitative real-time RT-PCR revealed that mRNA levels for osteocalcin and core binding factor alpha1 (Cbfa1) increased as a function of time in hFOB/pvc but were inhibited in hFOB/Cx43(-). Osteopontin mRNA levels were increased in hFOB/Cx43(-) relative to hFOB/pvc and decreased as a function of time in both hFOB/Cx43(-) and hFOB/pvc. Transfection with Cx43 antisense did not affect expression of type I collagen in hFOB 1.19 cells. These results suggest that gap junctional intercellular communication and expression of Cx43 contribute to alkaline phosphatase activity, as well as osteocalcin, osteopontin, and Cbfa1 expression in osteoblastic cells.
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Affiliation(s)
- Zhongyong Li
- Division of Musculoskeletal Sciences, Department of Orthopaedics & Rehabilitation, Pennsylvania State University College of Medicine 500 University Dr., Hershey, 17033, USA.
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Wang M, Martínez AD, Berthoud VM, Seul KH, Gemel J, Valiunas V, Kumari S, Brink PR, Beyer EC. Connexin43 with a cytoplasmic loop deletion inhibits the function of several connexins. Biochem Biophys Res Commun 2005; 333:1185-93. [PMID: 15979566 PMCID: PMC2751629 DOI: 10.1016/j.bbrc.2005.05.201] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Accepted: 05/31/2005] [Indexed: 11/24/2022]
Abstract
Connexins (Cx) form gap junction channels mediating direct intercellular communication. To study the role of amino acids within the cytoplasmic loop, we produced a recombinant adenovirus containing Cx43 with a deletion of amino acids 130-136 (Cx43del(130-136)). Cx43del(130-136) expressed alone in HeLa cells localized within the cytoplasm and did not allow transfer of ions, neurobiotin or Lucifer yellow. When co-expressed with wild type Cx43, Cx43del(130-136) blocked electrical coupling and transfer of neurobiotin or Lucifer yellow. Cx43del(130-136) and Cx43 co-localized by immunofluorescence and were co-purified from Triton X-100-solubilized cell extracts. Intercellular transfer mediated by Cx37 and Cx45 (but not Cx26 or Cx40) was inhibited when co-expressed with Cx43del(130-136). Cx43del(130-136) co-localized with Cx37, Cx40, or Cx45, but not Cx26. These data suggest that Cx43del(130-136) produces connexin-specific inhibition of intercellular communication through formation of heteromeric connexons that are non-functional and/or retained in the cytoplasm.
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Affiliation(s)
- Min Wang
- Department of Pediatrics, Section of Hematology/Oncology and Stem Cell Transplantation, University of Chicago, Chicago, IL, USA
| | - Agustín D. Martínez
- Department of Pediatrics, Section of Hematology/Oncology and Stem Cell Transplantation, University of Chicago, Chicago, IL, USA
| | - Viviana M. Berthoud
- Department of Pediatrics, Section of Hematology/Oncology and Stem Cell Transplantation, University of Chicago, Chicago, IL, USA
| | - Kyung H. Seul
- Department of Pediatrics, Section of Hematology/Oncology and Stem Cell Transplantation, University of Chicago, Chicago, IL, USA
| | - Joanna Gemel
- Department of Pediatrics, Section of Hematology/Oncology and Stem Cell Transplantation, University of Chicago, Chicago, IL, USA
| | - Virginijus Valiunas
- Department of Physiology and Biophysics, State University of New York, Stony Brook, NY, USA
| | - Sindhu Kumari
- Department of Physiology and Biophysics, State University of New York, Stony Brook, NY, USA
| | - Peter R. Brink
- Department of Physiology and Biophysics, State University of New York, Stony Brook, NY, USA
| | - Eric C. Beyer
- Department of Pediatrics, Section of Hematology/Oncology and Stem Cell Transplantation, University of Chicago, Chicago, IL, USA
- Corresponding author. Fax: +1 773 702 9881. (E.C. Beyer)
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Muller-Borer BJ, Cascio WE, Anderson PAW, Snowwaert JN, Frye JR, Desai N, Esch GL, Brackham JA, Bagnell CR, Coleman WB, Grisham JW, Malouf NN. Adult-derived liver stem cells acquire a cardiomyocyte structural and functional phenotype ex vivo. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 165:135-45. [PMID: 15215169 PMCID: PMC1618549 DOI: 10.1016/s0002-9440(10)63282-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We examined the differentiation potential of an adult liver stem cell line (WB F344) in a cardiac microenvironment, ex vivo. WB F344 cells were established from a single cloned nonparenchymal epithelial cell isolated from a normal male adult rat liver. Genetically modified, WB F344 cells that express beta-galactosidase and green fluorescent protein or only beta-galactosidase were co-cultured with dissociated rat or mouse neonatal cardiac cells. After 4 to 14 days, WB F344-derived cardiomyocytes expressed cardiac-specific proteins and exhibited myofibrils, sarcomeres, and a nascent sarcoplasmic reticulum. Further, rhythmically beating WB F344-derived cardiomyocytes displayed calcium transients. Fluorescent recovery after photobleaching demonstrated that WB F344-derived cardiomyocytes were coupled with adjacent neonatal cardiomyocytes and other WB F344-derived cardiomyocytes. Fluorescence in situ hybridization experiments suggested that fusion between WB F344 cells and neonatal mouse cardiomyocytes did not take place. Collectively, these results support the conclusion that these adult-derived liver stem cells respond to signals generated in a cardiac microenvironment ex vivo acquiring a cardiomyocyte phenotype and function. The identification ex vivo of microenvironmental signals that appear to cross germ layer and species specificities should prove valuable in understanding the molecular basis of adult stem cell differentiation and phenotypic plasticity.
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Affiliation(s)
- Barbara J Muller-Borer
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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