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James CC, Zeitz MJ, Calhoun PJ, Lamouille S, Smyth JW. Altered translation initiation of Gja1 limits gap junction formation during epithelial-mesenchymal transition. Mol Biol Cell 2018; 29:797-808. [PMID: 29467255 PMCID: PMC5905293 DOI: 10.1091/mbc.e17-06-0406] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Epithelial-mesenchymal transition (EMT) is activated during development, wound healing, and pathologies including fibrosis and cancer metastasis. Hallmarks of EMT are remodeling of intercellular junctions and adhesion proteins, including gap junctions. The GJA1 mRNA transcript encoding the gap junction protein connexin43 (Cx43) has been demonstrated to undergo internal translation initiation, yielding truncated isoforms that modulate gap junctions. The PI3K/Akt/mTOR pathway is central to translation regulation and is activated during EMT, leading us to hypothesize that altered translation initiation would contribute to gap junction loss. Using TGF-β-induced EMT as a model, we find reductions in Cx43 gap junctions despite increased transcription and stabilization of Cx43 protein. Biochemical experiments reveal suppression of the internally translated Cx43 isoform, GJA1-20k in a Smad3 and ERK-dependent manner. Ectopic expression of GJA1-20k does not halt EMT, but is sufficient to rescue gap junction formation. GJA1-20k localizes to the Golgi apparatus, and using superresolution localization microscopy we find retention of GJA1-43k at the Golgi in mesenchymal cells lacking GJA1-20k. NativePAGE demonstrates that levels of GJA1-20k regulate GJA1-43k hexamer oligomerization, a limiting step in Cx43 trafficking. These findings reveal alterations in translation initiation as an unexplored mechanism by which the cell regulates Cx43 gap junction formation during EMT.
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Affiliation(s)
- Carissa C James
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016.,Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Michael J Zeitz
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016
| | - Patrick J Calhoun
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016.,Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Samy Lamouille
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016
| | - James W Smyth
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016.,Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
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Gago-Fuentes R, Bechberger JF, Varela-Eirin M, Varela-Vazquez A, Acea B, Fonseca E, Naus CC, Mayan MD. The C-terminal domain of connexin43 modulates cartilage structure via chondrocyte phenotypic changes. Oncotarget 2018; 7:73055-73067. [PMID: 27682878 PMCID: PMC5341963 DOI: 10.18632/oncotarget.12197] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 09/16/2016] [Indexed: 12/13/2022] Open
Abstract
Chondrocytes in cartilage and bone cells population express connexin43 (Cx43) and gap junction intercellular communication (GJIC) is essential to synchronize cells for coordinated electrical, mechanical, metabolic and chemical communication in both tissues. Reduced Cx43 connectivity decreases chondrocyte differentiation and defective Cx43 causes skeletal defects. The carboxy terminal domain (CTD) of Cx43 is located in the cytoplasmic side and is key for protein functions. Here we demonstrated that chondrocytes from the CTD-deficient mice, K258stop/Cx43KO and K258stop/K258stop, have reduced GJIC, increased rates of proliferation and reduced expression of collagen type II and proteoglycans. We observed that CTD-truncated mice were significantly smaller in size. Together these results demonstrated that the deletion of the CTD negatively impacts cartilage structure and normal chondrocyte phenotype. These findings suggest that the proteolytic cleavage of the CTD under pathological conditions, such as under the activation of metalloproteinases during tissue injury or inflammation, may account for the deleterious effects of Cx43 in cartilage and bone disorders such as osteoarthritis.
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Affiliation(s)
- Raquel Gago-Fuentes
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - John F Bechberger
- Department of Cellular and Physiological Sciences, The Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3
| | - Marta Varela-Eirin
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - Adrian Varela-Vazquez
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - Benigno Acea
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - Eduardo Fonseca
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
| | - Christian C Naus
- Department of Cellular and Physiological Sciences, The Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3
| | - Maria D Mayan
- CellCOM-SB Research Group, Instituto de Investigación Biomédica de A Coruña (INIBIC), CH-Universitario A Coruña (XXIAC), University of A Coruña, Servizo Galego de Saúde (SERGAS), Xubias de Arriba, 84 15006 A Coruña, Spain
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Fu Y, Zhang SS, Xiao S, Basheer WA, Baum R, Epifantseva I, Hong T, Shaw RM. Cx43 Isoform GJA1-20k Promotes Microtubule Dependent Mitochondrial Transport. Front Physiol 2017; 8:905. [PMID: 29163229 PMCID: PMC5682029 DOI: 10.3389/fphys.2017.00905] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 10/25/2017] [Indexed: 01/26/2023] Open
Abstract
Connexin 43 (Cx43, encoded by GJA1) is a cell-cell communication gap junction protein expressed in all organ systems. It was recently found that GJA1 mRNA undergoes alternative translation to generate N-terminal truncated isoforms, of which GJA1-20k is the most abundant. Here we report a surprising finding that, unlike full length GJA1-43k, GJA1-20k has a strong tropism for mitochondria. Exploring function, we found that GJA1-20k appears to be an organelle chaperone and that overexpression of GJA1-20k is sufficient to rescue mitochondrial localization to the cell periphery upon exposure to hydrogen peroxide, which effectively limits the network fragmentation that occurs with oxidative stress. By high-resolution fluorescent imaging and electron microscopy, we determined that GJA1-20k is enriched at the interface between mitochondria and microtubules, appearing to load organelles for transport. Mutagenesis experiments revealed that although the microtubule-binding domain (MTBD) in GJA1-20k is not necessary for protein localization to mitochondria, the MTBD is essential for GJA1-20k to facilitate mitochondrial transport and maintain mitochondrial localization at the periphery. These results reveal an unexpected role for the alternatively translated isoform of the Cx43 gap junction protein, GJA1-20k, which is to facilitate microtubule-based mitochondrial transport and to maintain mitochondrial network integrity during cellular stress.
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Affiliation(s)
- Ying Fu
- Cedars-Sinai Medical Center, Cedars-Sinai Heart Institute, Los Angeles, CA, United States
| | - Shan-Shan Zhang
- Cedars-Sinai Medical Center, Cedars-Sinai Heart Institute, Los Angeles, CA, United States
| | - Shaohua Xiao
- Cedars-Sinai Medical Center, Cedars-Sinai Heart Institute, Los Angeles, CA, United States
| | - Wassim A Basheer
- Cedars-Sinai Medical Center, Cedars-Sinai Heart Institute, Los Angeles, CA, United States
| | - Rachel Baum
- Cedars-Sinai Medical Center, Cedars-Sinai Heart Institute, Los Angeles, CA, United States
| | - Irina Epifantseva
- Cedars-Sinai Medical Center, Cedars-Sinai Heart Institute, Los Angeles, CA, United States
| | - TingTing Hong
- Cedars-Sinai Medical Center, Cedars-Sinai Heart Institute, Los Angeles, CA, United States.,Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Robin M Shaw
- Cedars-Sinai Medical Center, Cedars-Sinai Heart Institute, Los Angeles, CA, United States.,Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
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Basheer WA, Xiao S, Epifantseva I, Fu Y, Kleber AG, Hong T, Shaw RM. GJA1-20k Arranges Actin to Guide Cx43 Delivery to Cardiac Intercalated Discs. Circ Res 2017; 121:1069-1080. [PMID: 28923791 DOI: 10.1161/circresaha.117.311955] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Revised: 09/14/2017] [Accepted: 09/15/2017] [Indexed: 01/21/2023]
Abstract
RATIONALE Delivery of Cx43 (connexin 43) to the intercalated disc is a continuous and rapid process critical for intercellular coupling. By a pathway of targeted delivery involving microtubule highways, vesicles of Cx43 hemichannels are efficiently trafficked to adherens junctions at intercalated discs. It has also been identified that actin provides rest stops for Cx43 forward trafficking and that Cx43 has a 20 kDa internally translated small C terminus isoform, GJA1-20k (Gap Junction Protein Alpha 1- 20 kDa), which is required for full-length Cx43 trafficking, but by an unknown mechanism. OBJECTIVE We explored the mechanism by which the GJA1-20k isoform is required for full-length Cx43 forward trafficking to intercalated discs. METHODS AND RESULTS Using an in vivo Adeno-associated virus serotype 9-mediated gene transfer system, we confirmed in whole animal that GJA1-20k markedly increases endogenous myocardial Cx43 gap junction plaque size at the intercalated discs. In micropatterned cell pairing systems, we found that exogenous GJA1-20k expression stabilizes filamentous actin without affecting actin protein expression and that GJA1-20k complexes with both actin and tubulin. We also found that filamentous actin regulates microtubule organization as inhibition of actin polymerization with a low dose of latrunculin A disrupts the targeting of microtubules to cell-cell junctions. GJA1-20k protects actin filament from latrunculin A disruption, preserving microtubule trajectory to the cell-cell border. For therapeutic implications, we found that prior in vivo Adeno-associated virus serotype 9-mediated gene delivery of GJA1-20k to the heart protects Cx43 localization to the intercalated discs against acute ischemic injury. CONCLUSIONS The internally translated GJA1-20k isoform stabilizes actin filaments, which guides growth trajectories of the Cx43 microtubule trafficking machinery, increasing delivery of Cx43 hemichannels to cardiac intercalated discs. Exogenous GJA1-20k helps to maintain cell-cell coupling in instances of anticipated myocardial ischemia.
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Affiliation(s)
- Wassim A Basheer
- From the Cedars-Sinai Heart Institute (W.A.B., S.X., I.E., Y.F., T.H., R.M.S.) and Department of Medicine (T.H., R.M.S.), Cedars-Sinai Medical Center and UCLA, Los Angeles, CA; and Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (A.G.K.)
| | - Shaohua Xiao
- From the Cedars-Sinai Heart Institute (W.A.B., S.X., I.E., Y.F., T.H., R.M.S.) and Department of Medicine (T.H., R.M.S.), Cedars-Sinai Medical Center and UCLA, Los Angeles, CA; and Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (A.G.K.)
| | - Irina Epifantseva
- From the Cedars-Sinai Heart Institute (W.A.B., S.X., I.E., Y.F., T.H., R.M.S.) and Department of Medicine (T.H., R.M.S.), Cedars-Sinai Medical Center and UCLA, Los Angeles, CA; and Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (A.G.K.)
| | - Ying Fu
- From the Cedars-Sinai Heart Institute (W.A.B., S.X., I.E., Y.F., T.H., R.M.S.) and Department of Medicine (T.H., R.M.S.), Cedars-Sinai Medical Center and UCLA, Los Angeles, CA; and Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (A.G.K.)
| | - Andre G Kleber
- From the Cedars-Sinai Heart Institute (W.A.B., S.X., I.E., Y.F., T.H., R.M.S.) and Department of Medicine (T.H., R.M.S.), Cedars-Sinai Medical Center and UCLA, Los Angeles, CA; and Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (A.G.K.)
| | - TingTing Hong
- From the Cedars-Sinai Heart Institute (W.A.B., S.X., I.E., Y.F., T.H., R.M.S.) and Department of Medicine (T.H., R.M.S.), Cedars-Sinai Medical Center and UCLA, Los Angeles, CA; and Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (A.G.K.)
| | - Robin M Shaw
- From the Cedars-Sinai Heart Institute (W.A.B., S.X., I.E., Y.F., T.H., R.M.S.) and Department of Medicine (T.H., R.M.S.), Cedars-Sinai Medical Center and UCLA, Los Angeles, CA; and Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (A.G.K.).
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55
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Connexin 43 is required for the maintenance of mitochondrial integrity in brown adipose tissue. Sci Rep 2017; 7:7159. [PMID: 28769076 PMCID: PMC5540980 DOI: 10.1038/s41598-017-07658-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 06/30/2017] [Indexed: 11/09/2022] Open
Abstract
We investigated the role of connexin 43 (Cx43) in maintaining the integrity of mitochondria in brown adipose tissue (BAT). The functional effects of Cx43 were evaluated using inducible, adipocyte-specific Cx43 knockout in mice (Gja1adipoqKO) and by overexpression and knockdown of Cx43 in cultured adipocytes. Mitochondrial morphology was evaluated by electron microscopy and mitochondrial function and autophagy were assessed by immunoblotting, immunohistochemistry, and qPCR. The metabolic effects of adipocyte-specific knockout of Cx43 were assessed during cold stress and following high fat diet feeding. Cx43 expression was higher in BAT compared to white adipose tissue. Treatment with the β3-adrenergic receptor agonist CL316,243 increased Cx43 expression and mitochondrial localization. Gja1adipoqKO mice reduced mitochondrial density and increased the presence of damaged mitochondria in BAT. Moreover, metabolic activation with CL316,243 further reduced mitochondrial integrity and upregulated autophagy in the BAT of Gja1adipoqKO mice. Inhibition of Cx43 in cultured adipocytes increased the generation of reactive oxygen species and induction of autophagy during β-adrenergic stimulation. Gja1adipoqKO mice were cold intolerant, expended less energy in response to β3-adrenergic receptor activation, and were more insulin resistant after a high-fat diet challenge. Collectively, our data demonstrate that Cx43 is required for maintaining the mitochondrial integrity and metabolic activity of BAT.
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Mesnil M, Aasen T, Boucher J, Chépied A, Cronier L, Defamie N, Kameritsch P, Laird DW, Lampe PD, Lathia JD, Leithe E, Mehta PP, Monvoisin A, Pogoda K, Sin WC, Tabernero A, Yamasaki H, Yeh ES, Dagli MLZ, Naus CC. An update on minding the gap in cancer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:237-243. [PMID: 28655619 DOI: 10.1016/j.bbamem.2017.06.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 06/22/2017] [Accepted: 06/23/2017] [Indexed: 01/08/2023]
Abstract
This article is a report of the "International Colloquium on Gap junctions: 50Years of Impact on Cancer" that was held 8-9 September 2016, at the Amphitheater "Pôle Biologie Santé" of the University of Poitiers (Poitiers, France). The colloquium was organized by M Mesnil (Université de Poitiers, Poitiers, France) and C Naus (University of British Columbia, Vancouver, Canada) to celebrate the 50th anniversary of the seminal work published in 1966 by Loewenstein and Kanno [Intercellular communication and the control of tissue growth: lack of communication between cancer cells, Nature, 116 (1966) 1248-1249] which initiated studies on the involvement of gap junctions in carcinogenesis. During the colloquium, 15 participants presented reviews or research updates in the field which are summarized below.
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Affiliation(s)
- Marc Mesnil
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences Fondamentales et Appliquées, Université de Poitiers, Poitiers 86073, cedex 09, France.
| | - Trond Aasen
- Translational Molecular Pathology, Vall d'Hebron Institute of Research (VHIR), Autonomous University of Barcelona, CIBERONC, 08035 Barcelona, Spain
| | - Jonathan Boucher
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences Fondamentales et Appliquées, Université de Poitiers, Poitiers 86073, cedex 09, France
| | - Amandine Chépied
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences Fondamentales et Appliquées, Université de Poitiers, Poitiers 86073, cedex 09, France
| | - Laurent Cronier
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences Fondamentales et Appliquées, Université de Poitiers, Poitiers 86073, cedex 09, France
| | - Norah Defamie
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences Fondamentales et Appliquées, Université de Poitiers, Poitiers 86073, cedex 09, France
| | - Petra Kameritsch
- Walter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-Universität München and Munich University Hospital, München, Germany
| | - Dale W Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario N6A 5C1, Canada
| | - Paul D Lampe
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Justin D Lathia
- Cleveland Clinic, Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
| | - Edward Leithe
- Department of Molecular Oncology, Institute for Cancer Research, Oslo University Hospital, and Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, NO-0424 Oslo, Norway
| | - Parmender P Mehta
- Department of Biochemistry and Molecular Biology, University of Nebraska, Medical Center, Omaha, NE 68198, USA
| | - Arnaud Monvoisin
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences Fondamentales et Appliquées, Université de Poitiers, Poitiers 86073, cedex 09, France
| | - Kristin Pogoda
- Walter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-Universität München and Munich University Hospital, München, Germany
| | - Wun-Chey Sin
- Department of Cellular & Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Arantxa Tabernero
- Departamento de Bioquímica y Biología Molecular, Instituto de Neurociencias de Castilla y León (INCYL), Universidad de Salamanca, Salamanca 37007, Spain
| | | | - Elizabeth S Yeh
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, SC 29412, USA
| | - Maria Lucia Zaidan Dagli
- Laboratory of Experimental and Comparative Oncology, School of Veterinary Medicine and Animal Science of the University of São Paulo, São Paulo, SP CEP 05508-900, Brazil
| | - Christian C Naus
- Department of Cellular & Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
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Epifantseva I, Shaw RM. Intracellular trafficking pathways of Cx43 gap junction channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:40-47. [PMID: 28576298 DOI: 10.1016/j.bbamem.2017.05.018] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 05/19/2017] [Accepted: 05/25/2017] [Indexed: 12/11/2022]
Abstract
Gap Junction (GJ) channels, including the most common Connexin 43 (Cx43), have fundamental roles in excitable tissues by facilitating rapid transmission of action potentials between adjacent cells. For instance, synchronization during each heartbeat is regulated by these ion channels at the cardiomyocyte cell-cell border. Cx43 protein has a short half-life, and rapid synthesis and timely delivery of those proteins to particular subdomains are crucial for the cellular organization of gap junctions and maintenance of intracellular coupling. Impairment in gap junction trafficking contributes to dangerous complications in diseased hearts such as the arrhythmias of sudden cardiac death. Of recent interest are the protein-protein interactions with the Cx43 carboxy-terminus. These interactions have significant impact on the full length Cx43 lifecycle and also contribute to trafficking of Cx43 as well as possibly other functions. We are learning that many of the known non-canonical roles of Cx43 can be attributed to the recently identified six endogenous Cx43 truncated isoforms which are produced by internal translation. In general, alternative translation is a new leading edge for proteome expansion and therapeutic drug development. This review highlights recent mechanisms identified in the trafficking of gap junction channels, involvement of other proteins contributing to the delivery of channels to the cell-cell border, and understanding of possible roles of the newly discovered alternatively translated isoforms in Cx43 biology. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Irina Epifantseva
- Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Robin M Shaw
- Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.; Department of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA..
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Leithe E, Mesnil M, Aasen T. The connexin 43 C-terminus: A tail of many tales. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:48-64. [PMID: 28526583 DOI: 10.1016/j.bbamem.2017.05.008] [Citation(s) in RCA: 137] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 05/10/2017] [Accepted: 05/12/2017] [Indexed: 10/19/2022]
Abstract
Connexins are chordate gap junction channel proteins that, by enabling direct communication between the cytosols of adjacent cells, create a unique cell signalling network. Gap junctional intercellular communication (GJIC) has important roles in controlling cell growth and differentiation and in tissue development and homeostasis. Moreover, several non-canonical connexin functions unrelated to GJIC have been discovered. Of the 21 members of the human connexin family, connexin 43 (Cx43) is the most widely expressed and studied. The long cytosolic C-terminus (CT) of Cx43 is subject to extensive post-translational modifications that modulate its intracellular trafficking and gap junction channel gating. Moreover, the Cx43 CT contains multiple domains involved in protein interactions that permit crosstalk between Cx43 and cytoskeletal and regulatory proteins. These domains endow Cx43 with the capacity to affect cell growth and differentiation independently of GJIC. Here, we review the current understanding of the regulation and unique functions of the Cx43 CT, both as an essential component of full-length Cx43 and as an independent signalling hub. We highlight the complex regulatory and signalling networks controlled by the Cx43 CT, including the extensive protein interactome that underlies both gap junction channel-dependent and -independent functions. We discuss these data in relation to the recent discovery of the direct translation of specific truncated forms of Cx43. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Edward Leithe
- Department of Molecular Oncology, Institute for Cancer Research, University of Oslo, NO-0424 Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, NO-0424 Oslo, Norway
| | - Marc Mesnil
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences Fondamentales et Appliquées, Université de Poitiers, Poitiers 86073, France
| | - Trond Aasen
- Translational Molecular Pathology, Vall d'Hebron Institute of Research (VHIR), Autonomous University of Barcelona, CIBERONC, 08035 Barcelona, Spain.
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Kitazawa M, Hida S, Fujii C, Taniguchi S, Ito K, Matsumura T, Okada N, Sakaizawa T, Kobayashi A, Takeoka M, Miyagawa SI. ASC Induces Apoptosis via Activation of Caspase-9 by Enhancing Gap Junction-Mediated Intercellular Communication. PLoS One 2017; 12:e0169340. [PMID: 28056049 PMCID: PMC5215782 DOI: 10.1371/journal.pone.0169340] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 12/15/2016] [Indexed: 12/20/2022] Open
Abstract
ASC (apoptosis-associated speck-like protein containing a CARD) is a key adaptor molecule of inflammasomes that mediates inflammatory and apoptotic signals. Aberrant methylation-induced silencing of ASC has been observed in a variety of cancer cells, thus implicating ASC in tumor suppression, although this role remains incompletely defined especially in the context of closely neighboring cell proliferation. As ASC has been confirmed to be silenced by abnormal methylation in HT1080 fibrosarcoma cells as well, this cell line was investigated to characterize the precise role and mechanism of ASC in tumor progression. The effects of ASC were examined using in vitro cell cultures based on comparisons between low and high cell density conditions as well as in a xenograft murine model. ASC overexpression was established by insertion of the ASC gene into pcDNA3 and pMX-IRES-GFP vectors, the latter being packed into a retrovirus and subjected to reproducible competitive assays using parental cells as an internal control, for evaluation of cell viability. p21 and p53 were silenced using shRNA. Cell viability was suppressed in ASC-expressing transfectants as compared with control cells at high cell density conditions in in vitro culture and colony formation assays and in in vivo ectopic tumor formation trials. This suppression was not detected in low cell density conditions. Furthermore, remarkable progression of apoptosis was observed in ASC-introduced cells at a high cell density, but not at a low one. ASC-dependent apoptosis was mediated not by p21, p53, or caspase-1, but rather by cleavage of caspase-9 as well as by suppression of the NF-κB-related X-linked inhibitor-of-apoptosis protein. Caspase-9 cleavage was observed to be dependent on gap junction formation. The remarkable effect of ASC on the induction of apoptosis through caspase-9 and gap junctions revealed in this study may lead to promising new approaches in anticancer therapy.
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Affiliation(s)
- Masato Kitazawa
- Department of Surgery, Shinshu University School of Medicine, Matsumoto, Japan
- Department of Molecular Oncology, Shinshu University Graduate School of Medicine, Matsumoto, Japan
- * E-mail:
| | - Shigeaki Hida
- Department of Molecular and Cellular Health Science, Nagoya City University Graduate School of Pharmaceutical Sciences, Mizuho-ku, Nagoya, Japan
| | - Chifumi Fujii
- Department of Molecular Oncology, Shinshu University Graduate School of Medicine, Matsumoto, Japan
| | - Shun’ichiro Taniguchi
- Department of Molecular Oncology, Shinshu University Graduate School of Medicine, Matsumoto, Japan
| | - Kensuke Ito
- Department of Molecular Oncology, Shinshu University Graduate School of Medicine, Matsumoto, Japan
| | - Tomio Matsumura
- Department of Molecular Oncology, Shinshu University Graduate School of Medicine, Matsumoto, Japan
| | - Nagisa Okada
- Department of Molecular Oncology, Shinshu University Graduate School of Medicine, Matsumoto, Japan
| | - Takashi Sakaizawa
- Department of Surgery, Shinshu University School of Medicine, Matsumoto, Japan
| | - Akira Kobayashi
- Department of Surgery, Shinshu University School of Medicine, Matsumoto, Japan
| | - Michiko Takeoka
- Department of Surgery, Shinshu University School of Medicine, Matsumoto, Japan
| | - Shin-ichi Miyagawa
- Department of Surgery, Shinshu University School of Medicine, Matsumoto, Japan
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Karginov TA, Pastor DPH, Semler BL, Gomez CM. Mammalian Polycistronic mRNAs and Disease. Trends Genet 2016; 33:129-142. [PMID: 28012572 DOI: 10.1016/j.tig.2016.11.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 11/22/2016] [Accepted: 11/28/2016] [Indexed: 01/08/2023]
Abstract
Our understanding of gene expression has come far since the 'one-gene one-polypeptide' hypothesis proposed by Beadle and Tatum. In this review, we address the gradual recognition that a growing number of polycistronic genes, originally discovered in viruses, are being identified within the mammalian genome, and that these may provide new insights into disease mechanisms and treatment. We carried out a systematic literature review identifying 13 mammalian genes for which there is evidence for polycistronic expression via translation through an internal ribosome entry site (IRES). Although the canonical mechanism of translation initiation has been studied extensively, here we highlight a process of noncanonical translation, IRES-mediated translation, that is a growing source for understanding complex inheritance, the elucidation of disease mechanisms, and the discovery of novel therapeutic targets. Identification of additional polycistronic genes may provide new insights into disease therapy and allow for new discoveries of both translational and disease mechanisms.
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Affiliation(s)
| | | | - Bert L Semler
- Department of Microbiology & Molecular Genetics, School of Medicine, University of California, Irvine, CA, USA
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Abstract
Fifty years ago, tumour cells were found to lack electrical coupling, leading to the hypothesis that loss of direct intercellular communication is commonly associated with cancer onset and progression. Subsequent studies linked this phenomenon to gap junctions composed of connexin proteins. Although many studies support the notion that connexins are tumour suppressors, recent evidence suggests that, in some tumour types, they may facilitate specific stages of tumour progression through both junctional and non-junctional signalling pathways. This Timeline article highlights the milestones connecting gap junctions to cancer, and underscores important unanswered questions, controversies and therapeutic opportunities in the field.
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Affiliation(s)
- Trond Aasen
- (Co-corresponding authors) Correspondence to
T.A. () and D.W.L.
()
| | - Marc Mesnil
- STIM Laboratory ERL 7368 CNRS - Faculté des Sciences
Fondamentales et Appliquées, Université de Poitiers, Poitiers,
France
| | - Christian C. Naus
- Department of Cellular and Physiological Sciences, The Life
Sciences Institute, University of British Columbia, Vancouver, British
Columbia, Canada
| | - Paul D. Lampe
- Translational Research Program, Fred Hutchinson Cancer Research
Center, Seattle, United States
| | - Dale W. Laird
- (Co-corresponding authors) Correspondence to
T.A. () and D.W.L.
()
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62
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Gu R, Xu J, Lin Y, Zhang J, Wang H, Sheng W, Ma D, Ma X, Huang G. Liganded retinoic acid X receptor α represses connexin 43 through a potential retinoic acid response element in the promoter region. Pediatr Res 2016; 80:159-68. [PMID: 26991262 DOI: 10.1038/pr.2016.47] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 09/28/2015] [Indexed: 11/10/2022]
Abstract
INTRODUCTION Retinoic acid X receptor alpha (RXRα) and Connexin 43 (Cx43) both play a crucial role in cardiogenesis. However, little is known about the interplay mechanism between the RXRα and Cx43. METHODS The activations of retinoic acid response element (RARE) in Cx43 were measured by luciferase transfection assay. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) was performed to prove that RXRα can directly bind to the RARE sequence. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to analyze the RXRα and Cx43 mRNA level and protein level in cells. RESULTS In this study, we confirmed the negative association of the gene expression between the RXRα and Cx43 in the cell level. Interestingly, a functional RARE was detected in the region from -1,426 to -314 base pairs upstream from the transcriptional start site of Cx43. Moreover, we also prove that RXRα can directly bind to this RARE sequence in vitro and in vivo. CONCLUSIONS RXRα negatively regulates the transcription and expression by directly binding to the RARE in the promoter of Cx43. The RARE-like sequence harbored in the Cx43 promoter region may serve as a functional RARE in the retinoic acid (RA) signaling pathway.
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Affiliation(s)
- Ruoyi Gu
- Children's Hospital of Fudan University, Shanghai, China
| | - Jun Xu
- Children's Hospital of Fudan University, Shanghai, China
| | - Yixiang Lin
- Children's Hospital of Fudan University, Shanghai, China
| | - Jing Zhang
- Children's Hospital of Fudan University, Shanghai, China.,Present address: Department of Pediatrics, Chengdu Women and Children's Medical Center, Sichuan, China
| | - Huijun Wang
- Children's Hospital of Fudan University, Shanghai, China.,Shanghai Key Laboratory of Birth Defects, Shanghai, China
| | - Wei Sheng
- Children's Hospital of Fudan University, Shanghai, China.,Shanghai Key Laboratory of Birth Defects, Shanghai, China
| | - Duan Ma
- Shanghai Key Laboratory of Birth Defects, Shanghai, China.,Key Laboratory of Molecular Medicine, Ministry of Education, Shanghai Medical College, Fudan University, Shanghai, China
| | - Xiaojing Ma
- Children's Hospital of Fudan University, Shanghai, China.,Shanghai Key Laboratory of Birth Defects, Shanghai, China
| | - Guoying Huang
- Children's Hospital of Fudan University, Shanghai, China.,Shanghai Key Laboratory of Birth Defects, Shanghai, China
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63
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Esseltine JL, Laird DW. Next-Generation Connexin and Pannexin Cell Biology. Trends Cell Biol 2016; 26:944-955. [PMID: 27339936 DOI: 10.1016/j.tcb.2016.06.003] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 06/02/2016] [Accepted: 06/06/2016] [Indexed: 01/17/2023]
Abstract
Connexins and pannexins are two families of large-pore channel forming proteins that are capable of passing small signaling molecules. While connexins serve the seminal task of direct gap junctional intercellular communication, pannexins are far less understood but function primarily as single membrane channels in autocrine and paracrine signaling. Advancements in connexin and pannexin biology in recent years has revealed that in addition to well-described classical functions at the plasma membrane, exciting new evidence suggests that connexins and pannexins participate in alternative pathways involving multiple intracellular compartments. Here we briefly highlight classical functions of connexins and pannexins but focus our attention mostly on the transformative findings that suggest that these channel-forming proteins may serve roles far beyond our current understandings.
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Affiliation(s)
- Jessica L Esseltine
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
| | - Dale W Laird
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada.
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64
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Basheer W, Shaw R. The "tail" of Connexin43: An unexpected journey from alternative translation to trafficking. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:1848-56. [PMID: 26526689 DOI: 10.1016/j.bbamcr.2015.10.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 10/13/2015] [Accepted: 10/20/2015] [Indexed: 12/23/2022]
Abstract
With each heartbeat, Connexin43 (Cx43) cell-cell communication gap junctions are needed to rapidly spread and coordinate excitation signals for an effective heart contraction. The correct formation and delivery of channels to their respective membrane subdomain is referred to as protein trafficking. Altered Cx43 trafficking is a dangerous complication of diseased myocardium which contributes to the arrhythmias of sudden cardiac death. Cx43 has also been found to regulate many other cellular processes that cannot be explained by cell-cell communication. We recently identified the existence of up to six endogenous internally translated Cx43 N-terminal truncated isoforms from the same full-length mRNA molecule. This is the first evidence that alternative translation is possible for human ion channels and in human heart. Interestingly, we found that these internally translated isoforms, more specifically the 20 kDa isoform (GJA1-20k), is important for delivery of Cx43 to its respective membrane subdomain. This review covers recent advances in Cx43 trafficking and potential importance of alternatively translated Cx43 truncated isoforms. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.
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Affiliation(s)
- Wassim Basheer
- Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Robin Shaw
- Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA; Department of Medicine, University of California Los Angeles, Los Angeles, CA, USA.
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Intracellular Cleavage of the Cx43 C-Terminal Domain by Matrix-Metalloproteases: A Novel Contributor to Inflammation? Mediators Inflamm 2015; 2015:257471. [PMID: 26424967 PMCID: PMC4573893 DOI: 10.1155/2015/257471] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Accepted: 08/13/2015] [Indexed: 01/11/2023] Open
Abstract
The coordination of tissue function is mediated by gap junctions (GJs) that enable direct cell-cell transfer of metabolic and electric signals. GJs are formed by connexin (Cx) proteins of which Cx43 is most widespread in the human body. Beyond its role in direct intercellular communication, Cx43 also forms nonjunctional hemichannels (HCs) in the plasma membrane that mediate the release of paracrine signaling molecules in the extracellular environment. Both HC and GJ channel function are regulated by protein-protein interactions and posttranslational modifications that predominantly take place in the C-terminal domain of Cx43. Matrix metalloproteases (MMPs) are a major group of zinc-dependent proteases, known to regulate not only extracellular matrix remodeling, but also processing of intracellular proteins. Together with Cx43 channels, both GJs and HCs, MMPs contribute to acute inflammation and a small number of studies reports on an MMP-Cx43 link. Here, we build further on these reports and present a novel hypothesis that describes proteolytic cleavage of the Cx43 C-terminal domain by MMPs and explores possibilities of how such cleavage events may affect Cx43 channel function. Finally, we set out how aberrant channel function resulting from cleavage can contribute to the acute inflammatory response during tissue injury.
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Abstract
Gap junctions allow intercellular communication. Their structural subunits are four-transmembrane proteins named connexins (Cxs), which can be post-transcriptionally regulated by developmental and cellular signalling cues. Cx translation and mRNA stability is regulated by miRNAs and RNA-binding proteins (RBPs) such as human antigen R (HuR). In addition, several Cxs have also been suggested to contain 5′ internal ribosome entry site (IRES) elements that are thought to allow cap-independent translation in situations such as mitosis, stress and senescence. Furthermore, several recent reports have documented internal translation of Cx mRNAs that result in N-terminally truncated protein isoforms that may have unique gap junction-independent functions [Ul-Hussain et al. (2008) BMC Mol. Biol. 9, 52; Smyth and Shaw (2013) Cell Rep. 5, 611–618; Salat-Canela et al. (2014) Cell Commun. Signal. 12, 31; Ul-Hussain et al. (2014) J. Biol. Chem. 289, 20979–20990]. This review covers the emerging field of the post-transcriptional regulation of Cxs, with particular focus on the translational control of Cx 43 and its possible functional consequences.
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67
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Aasen T. Connexins: junctional and non-junctional modulators of proliferation. Cell Tissue Res 2014; 360:685-99. [PMID: 25547217 DOI: 10.1007/s00441-014-2078-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2014] [Accepted: 11/14/2014] [Indexed: 12/11/2022]
Abstract
Mounting evidence indicates that dysregulation of gap junctions and their structural subunits-connexins-often occurs in, and sometimes causes, a variety of proliferative disorders, including cancer. Connexin-mediated regulation of cell proliferation is complex and may involve modulation of gap junction intercellular communication (GJIC), hemichannel signalling, or gap junction-independent paths. However, the exact mechanisms linking connexins to proliferation remain poorly defined and a number of contradictory studies report both pro- and anti-proliferative effects, effects that often depend on the cell or tissue type or the microenvironment. The present review covers junctional and non-junctional regulation of proliferation by connexins, with a particular emphasis on their association with cancer.
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Affiliation(s)
- Trond Aasen
- Molecular Pathology Group, Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Passeig Vall d'Hebron 119-129, Barcelona, 08035, Spain,
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68
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Connexins in migration during development and cancer. Dev Biol 2014; 401:143-51. [PMID: 25553982 DOI: 10.1016/j.ydbio.2014.12.023] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 12/17/2014] [Accepted: 12/18/2014] [Indexed: 12/12/2022]
Abstract
Connexins, the gap junction proteins, through their multitude of actions are implicated in a variety of cell processes during animal development and cancer. They allow direct or paracrine/autocrine cell communication through their channel and hemi-channel functions. They enable adhesion and interact with a plethora of signalling molecules. Here, we review the common themes in developmental and pathological processes and we focus in their involvement in cell migration in four different systems: neurons, astrocytes, neural crest and cancer.
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69
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Xiao S, Shaw RM. Cardiomyocyte protein trafficking: Relevance to heart disease and opportunities for therapeutic intervention. Trends Cardiovasc Med 2014; 25:379-89. [PMID: 25649302 DOI: 10.1016/j.tcm.2014.12.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 12/18/2014] [Accepted: 12/20/2014] [Indexed: 11/30/2022]
Abstract
Cardiomyocytes, the individual contractile units of heart muscle, are long-lived and robust. Given the longevity of these cells, it can be easy to overlook their dynamic intracellular environment that contain rapid protein movements and frequent protein turnover. Critical gene transcription and protein translation occur continuously, as well as trafficking and localization of proteins to specific functional zones of cell membrane. As heart failure becomes an increasingly important clinical entity, growing numbers of investigative teams are examining the cell biology of healthy and diseased cardiomyocytes. In this review, we introduce the major architectural structures and types of protein movements within cardiac cells, and then review recent studies that explore the regulation of such movements. We conclude by introducing current translational directions of the basic studies with a focus on novel areas of therapeutic development.
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Affiliation(s)
- Shaohua Xiao
- Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Robin M Shaw
- Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA; Department of Medicine, University of California Los Angeles, Los Angeles, CA.
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