1
|
Leighton SE, Wong RS, Lucaciu SA, Hauser A, Johnston D, Stathopulos PB, Bai D, Penuela S, Laird DW. Cx31.1 can selectively intermix with co-expressed connexins to facilitate its assembly into gap junctions. J Cell Sci 2024; 137:jcs261631. [PMID: 38533727 PMCID: PMC11058089 DOI: 10.1242/jcs.261631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 03/05/2024] [Indexed: 03/28/2024] Open
Abstract
Connexins are channel-forming proteins that function to facilitate gap junctional intercellular communication. Here, we use dual cell voltage clamp and dye transfer studies to corroborate past findings showing that Cx31.1 (encoded by GJB5) is defective in gap junction channel formation, illustrating that Cx31.1 alone does not form functional gap junction channels in connexin-deficient mammalian cells. Rather Cx31.1 transiently localizes to the secretory pathway with a subpopulation reaching the cell surface, which is rarely seen in puncta reminiscent of gap junctions. Intracellular retained Cx31.1 was subject to degradation as Cx31.1 accumulated in the presence of proteasomal inhibition, had a faster turnover when Cx43 was present and ultimately reached lysosomes. Although intracellularly retained Cx31.1 was found to interact with Cx43, this interaction did not rescue its delivery to the cell surface. Conversely, the co-expression of Cx31 dramatically rescued the assembly of Cx31.1 into gap junctions where gap junction-mediated dye transfer was enhanced. Collectively, our results indicate that the localization and functional status of Cx31.1 is altered through selective interplay with co-expressed connexins, perhaps suggesting Cx31.1 is a key regulator of intercellular signaling in keratinocytes.
Collapse
Affiliation(s)
- Stephanie E. Leighton
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Robert S. Wong
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Sergiu A. Lucaciu
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Alexandra Hauser
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Danielle Johnston
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Peter B. Stathopulos
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Silvia Penuela
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
- Western's Bone and Joint Institute, The Dr. Sandy Kirkley Centre for Musculoskeletal Research, University Hospital, London, ON N6A 5B9, Canada
- Division of Experimental Oncology, Department of Oncology, University of Western Ontario, London, ON N6A 5W9, Canada
| | - Dale W. Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
| |
Collapse
|
2
|
Lucaciu SA, Figliuzzi R, Neumann R, Nazarali S, Del Sordo L, Leighton SE, Hauser A, Shao Q, Johnston D, Bai D, Laird DW. GJB4 variants linked to skin disease exhibit a trafficking deficiency en route to gap junction formation that can be restored by co-expression of select connexins. Front Cell Dev Biol 2023; 11:1073805. [PMID: 36861039 PMCID: PMC9968944 DOI: 10.3389/fcell.2023.1073805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 02/01/2023] [Indexed: 02/15/2023] Open
Abstract
Epidermal keratinocytes are enriched with at least nine connexins that are key regulators of epidermal homeostasis. The role of Cx30.3 in keratinocytes and epidermal health became evident when fourteen autosomal dominant mutations in the Cx30.3-encoding GJB4 gene were linked to a rare and incurable skin disorder called erythrokeratodermia variabilis et progressiva (EKVP). While these variants are linked to EKVP, they remain largely uncharacterized hindering therapeutic options. In this study, we characterize the expression and functional status of three EKVP-linked Cx30.3 mutants (G12D, T85P, and F189Y) in tissue-relevant and differentiation-competent rat epidermal keratinocytes. We found that GFP-tagged Cx30.3 mutants were non-functional likely due to their impaired trafficking and primary entrapment within the endoplasmic reticulum (ER). However, all mutants failed to increase BiP/GRP78 levels suggesting they were not inducing an unfolded protein response. FLAG-tagged Cx30.3 mutants were also trafficking impaired yet occasionally exhibited some capacity to assemble into gap junctions. The pathological impact of these mutants may extend beyond their trafficking deficiencies as keratinocytes expressing FLAG-tagged Cx30.3 mutants exhibited increased propidium iodide uptake in the absence of divalent cations. Attempts to rescue the delivery of trafficking impaired GFP-tagged Cx30.3 mutants into gap junctions by chemical chaperone treatment were ineffective. However, co-expression of wild type Cx30.3 greatly enhanced the assembly of Cx30.3 mutants into gap junctions, although endogenous levels of Cx30.3 do not appear to prevent the skin pathology found in patients harboring these autosomal dominant mutations. In addition, a spectrum of connexin isoforms (Cx26, Cx30, and Cx43) exhibited the differential ability to trans-dominantly rescue the assembly of GFP-tagged Cx30.3 mutants into gap junctions suggesting a broad range of connexins found in keratinocytes may favourably interact with Cx30.3 mutants. We conclude that selective upregulation of compatible wild type connexins in keratinocytes may have potential therapeutic value in rescuing epidermal defects invoked by Cx30.3 EKVP-linked mutants.
Collapse
Affiliation(s)
- Sergiu A. Lucaciu
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada,Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
| | - Rhett Figliuzzi
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Ruth Neumann
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Samina Nazarali
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Luigi Del Sordo
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada,Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
| | - Stephanie E. Leighton
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Alexandra Hauser
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Qing Shao
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Danielle Johnston
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
| | - Dale W. Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada,Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada,*Correspondence: Dale W. Laird,
| |
Collapse
|
3
|
van der Sande E, Haarman AEG, Quint WH, Tadema KCD, Meester-Smoor MA, Kamermans M, De Zeeuw CI, Klaver CCW, Winkelman BHJ, Iglesias AI. The Role of GJD2(Cx36) in Refractive Error Development. Invest Ophthalmol Vis Sci 2022; 63:5. [PMID: 35262731 PMCID: PMC8934558 DOI: 10.1167/iovs.63.3.5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 02/16/2022] [Indexed: 02/06/2023] Open
Abstract
Refractive errors are common eye disorders characterized by a mismatch between the focal power of the eye and its axial length. An increased axial length is a common cause of the refractive error myopia (nearsightedness). The substantial increase in myopia prevalence over the last decades has raised public health concerns because myopia can lead to severe ocular complications later in life. Genomewide association studies (GWAS) have made considerable contributions to the understanding of the genetic architecture of refractive errors. Among the hundreds of genetic variants identified, common variants near the gap junction delta-2 (GJD2) gene have consistently been reported as one of the top hits. GJD2 encodes the connexin 36 (Cx36) protein, which forms gap junction channels and is highly expressed in the neural retina. In this review, we provide current evidence that links GJD2(Cx36) to the development of myopia. We summarize the gap junctional communication in the eye and the specific role of GJD2(Cx36) in retinal processing of visual signals. Finally, we discuss the pathways involving dopamine and gap junction phosphorylation and coupling as potential mechanisms that may explain the role of GJD2(Cx36) in refractive error development.
Collapse
Affiliation(s)
- Emilie van der Sande
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
| | - Annechien E. G. Haarman
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Wim H. Quint
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Kirke C. D. Tadema
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Magda A. Meester-Smoor
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Maarten Kamermans
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Biomedical Physics and Biomedical Photonics, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Chris I. De Zeeuw
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Caroline C. W. Klaver
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
- Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland
| | - Beerend H. J. Winkelman
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
- Netherlands Institute for Neuroscience (NIN), Royal Dutch Academy of Art & Science (KNAW), Amsterdam, The Netherlands
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Adriana I. Iglesias
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| |
Collapse
|
4
|
Shi W, Meng Z, Luo J. Connexin 43 (Cx43) regulates high-glucose-induced retinal endothelial cell angiogenesis and retinal neovascularization. Front Endocrinol (Lausanne) 2022; 13:909207. [PMID: 36120455 PMCID: PMC9478119 DOI: 10.3389/fendo.2022.909207] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 07/06/2022] [Indexed: 11/13/2022] Open
Abstract
Diabetic retinopathy (DR) is an important microvascular complication of type 1 and type 2 diabetes mellitus (DM) and a major cause of blindness. Retinal neovascularization plays a critical role in the proliferative DR. In this study, high glucose-induced connexin 43 (Cx43) expression in human retinal endothelial cells (hRECs) in a dose-dependent manner. Compared with hRECs under normal culture conditions, high-glucose (HG)-stimulated hRECs showed promoted tubule formation, increased ROS release, and elevated levels of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), vascular endothelial growth factor A (VEGFA), and intercellular adhesion molecule 1 (ICAM-1) in the culture medium. HG-induced alterations were further magnified after Cx43 overexpression, whereas partially eliminated after Cx43 knockdown. Finally, in the DR mouse model, impaired retinal structure, increased CD31 expression, and elevated mRNA levels of TNF-α, IL-1β, VEGFA, and ICAM-1 were observed; in-vivo Cx43 knockdown partially reversed these phenomena. Conclusively, Cx43 knockdown could inhibit hREC angiogenesis, therefore improving DR in the mouse model.
Collapse
Affiliation(s)
- Wen Shi
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, China
- Department of Ophthalmology, Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, China
| | - Zhishang Meng
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, China
- Department of Ophthalmology, Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, China
| | - Jing Luo
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, China
- Department of Ophthalmology, Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, China
- *Correspondence: Jing Luo,
| |
Collapse
|
5
|
Cell transdifferentiation in ocular disease: Potential role for connexin channels. Exp Cell Res 2021; 407:112823. [PMID: 34506760 DOI: 10.1016/j.yexcr.2021.112823] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/02/2021] [Accepted: 09/05/2021] [Indexed: 11/22/2022]
Abstract
Cell transdifferentiation is the conversion of a cell type to another without requiring passage through a pluripotent cell state, and encompasses epithelial- and endothelial-mesenchymal transition (EMT and EndMT). EMT and EndMT are well defined processes characterized by a loss of epithelial/endothelial phenotype and gain in mesenchymal spindle shaped morphology, which results in increased cell migration and decreased apoptosis and cellular senescence. Such cells often develop invasive properties. Physiologically, these processes may occur during embryonic development and can resurface, for example, to promote wound healing in later life. However, they can also be a pathological process. In the eye, EMT, EndMT and cell transdifferentiation have all been implicated in development, homeostasis, and multiple diseases affecting different parts of the eye. Connexins, constituents of connexin hemichannels and intercellular gap junctions, have been implicated in many of these processes. In this review, we firstly provide an overview of the molecular mechanisms induced by transdifferentiation (including EMT and EndMT) and its involvement in eye diseases. We then review the literature for the role of connexins in transdifferentiation in the eye and eye diseases. The evidence presented in this review supports the need for more studies into the therapeutic potential for connexin modulators in prevention and treatment of transdifferentiation related eye diseases, but does indicate that connexin channel modulation may be an upstream and unifying approach for regulating these otherwise complex processes.
Collapse
|
6
|
Ligocki AJ, Fury W, Gutierrez C, Adler C, Yang T, Ni M, Bai Y, Wei Y, Lehmann GL, Romano C. Molecular characteristics and spatial distribution of adult human corneal cell subtypes. Sci Rep 2021; 11:16323. [PMID: 34381080 PMCID: PMC8357950 DOI: 10.1038/s41598-021-94933-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 07/19/2021] [Indexed: 12/13/2022] Open
Abstract
Bulk RNA sequencing of a tissue captures the gene expression profile from all cell types combined. Single-cell RNA sequencing identifies discrete cell-signatures based on transcriptomic identities. Six adult human corneas were processed for single-cell RNAseq and 16 cell clusters were bioinformatically identified. Based on their transcriptomic signatures and RNAscope results using representative cluster marker genes on human cornea cross-sections, these clusters were confirmed to be stromal keratocytes, endothelium, several subtypes of corneal epithelium, conjunctival epithelium, and supportive cells in the limbal stem cell niche. The complexity of the epithelial cell layer was captured by eight distinct corneal clusters and three conjunctival clusters. These were further characterized by enriched biological pathways and molecular characteristics which revealed novel groupings related to development, function, and location within the epithelial layer. Moreover, epithelial subtypes were found to reflect their initial generation in the limbal region, differentiation, and migration through to mature epithelial cells. The single-cell map of the human cornea deepens the knowledge of the cellular subsets of the cornea on a whole genome transcriptional level. This information can be applied to better understand normal corneal biology, serve as a reference to understand corneal disease pathology, and provide potential insights into therapeutic approaches.
Collapse
Affiliation(s)
- Ann J Ligocki
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | - Wen Fury
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | | | | | - Tao Yang
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | - Min Ni
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | - Yu Bai
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | - Yi Wei
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA
| | | | - Carmelo Romano
- Regeneron Pharmaceuticals, Inc., Tarrytown, NY, 10591, USA.
| |
Collapse
|
7
|
Zheng XS, Zheng H, Xu D, Liu PP, Li B, Cao ZM, Liu Y, Liu Y. Effect of zymosan on the expression and function of the gap-junction protein connexin 43 in human corneal fibroblasts. Int J Ophthalmol 2021; 14:341-348. [PMID: 33747807 DOI: 10.18240/ijo.2021.03.02] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 11/17/2020] [Indexed: 12/27/2022] Open
Abstract
AIM To study the effect of zymosan, a ligand found on the surface of fungi, on gap junctional intercellular communication (GJIC) in cultured human corneal fibroblasts (HCFs). METHODS Zymosan was added to the medium of cultured HCFs with or without the administration of mitogen-activated protein kinase (MAPK) inhibitors or the inhibitor kappa B kinase 2 (IKK2) inhibitor IV. The protein and mRNA levels of connexin 43 (Cx43) in HCFs were measured by Western blot, immunofluorescence, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses. The GJIC activity was tested using a dye-coupling assay. RESULTS The reduction of Cx43 protein and mRNA levels as well as a significant decrease in GJIC activity were observed in cultured HCFs when zymosan was added into the culture medium. Compared with controls (no zymosan), the protein level of Cx43 was reduced by 45% and 54% in the presence of zymosan at 200 and 600 µg/mL, respectively (P<0.05); and it was reduced by 45%, 48%, and 75% in the presence of zymosan (600 µg/mL) for 24, 36, and 48h, respectively (P<0.05). The mRNA expression of Cx43 was reduced by 98% in the presence of zymosan (P<0.05). The effects of zymosan on Cx43 expression and GJIC activity were attenuated by the administration of PD98059 [an extracellular signal-regulated kinase (ERK) signaling inhibitor] (P<0.05), c-Jun NH2-terminal kinase (JNK) inhibitor II (P<0.05), and IKK2 inhibitor IV (P<0.05). CONCLUSION Zymosan inhibits the activity of GJIC in cultured HCFs. This effect is likely regulated via the nuclear factor-κB (NF-κB), MAPK/ERK, and JNK signaling pathways. The inhibitory effects of zymosan on Cx43 expression and GJIC activity in HCFs may induce damage of corneal stroma during corneal fungal infection.
Collapse
Affiliation(s)
- Xiao-Shuo Zheng
- Department of Ophthalmology, the Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai 519000, Guangzhou Province, China
| | - Hui Zheng
- Department of Ophthalmology, the Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai 519000, Guangzhou Province, China
| | - Dan Xu
- Institute of Environmental Systems Biology, Environmental Science and Engineering College, Dalian Maritime University, Dalian 116027, Liaoning Province, China
| | - Ping-Ping Liu
- Department of Ophthalmology, the Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai 519000, Guangzhou Province, China
| | - Bing Li
- Department of Ophthalmology, the Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai 519000, Guangzhou Province, China
| | - Zi-Mu Cao
- Institute of Environmental Systems Biology, Environmental Science and Engineering College, Dalian Maritime University, Dalian 116027, Liaoning Province, China
| | - Yang Liu
- Department of Ophthalmology, the Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai 519000, Guangzhou Province, China
| | - Ye Liu
- Department of Pathology, the Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai 519000, Guangzhou Province, China
| |
Collapse
|
8
|
Garcia-Vega L, O’Shaughnessy EM, Albuloushi A, Martin PE. Connexins and the Epithelial Tissue Barrier: A Focus on Connexin 26. BIOLOGY 2021; 10:biology10010059. [PMID: 33466954 PMCID: PMC7829877 DOI: 10.3390/biology10010059] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/11/2021] [Accepted: 01/12/2021] [Indexed: 12/15/2022]
Abstract
Simple Summary Tissues that face the external environment are known as ‘epithelial tissue’ and form barriers between different body compartments. This includes the outer layer of the skin, linings of the intestine and airways that project into the lumen connecting with the external environment, and the cornea of the eye. These tissues do not have a direct blood supply and are dependent on exchange of regulatory molecules between cells to ensure co-ordination of tissue events. Proteins known as connexins form channels linking cells directly and permit exchange of small regulatory signals. A range of environmental stimuli can dysregulate the level of connexin proteins and or protein function within the epithelia, leading to pathologies including non-healing wounds. Mutations in these proteins are linked with hearing loss, skin and eye disorders of differing severity. As such, connexins emerge as prime therapeutic targets with several agents currently in clinical trials. This review outlines the role of connexins in epithelial tissue and how their dysregulation contributes to pathological pathways. Abstract Epithelial tissue responds rapidly to environmental triggers and is constantly renewed. This tissue is also highly accessible for therapeutic targeting. This review highlights the role of connexin mediated communication in avascular epithelial tissue. These proteins form communication conduits with the extracellular space (hemichannels) and between neighboring cells (gap junctions). Regulated exchange of small metabolites less than 1kDa aide the co-ordination of cellular activities and in spatial communication compartments segregating tissue networks. Dysregulation of connexin expression and function has profound impact on physiological processes in epithelial tissue including wound healing. Connexin 26, one of the smallest connexins, is expressed in diverse epithelial tissue and mutations in this protein are associated with hearing loss, skin and eye conditions of differing severity. The functional consequences of dysregulated connexin activity is discussed and the development of connexin targeted therapeutic strategies highlighted.
Collapse
|
9
|
Zheng H, Liu Y, Xu D, Liu P, Yang X, Li B, Cao Z, Liu Y, Zheng X. Inhibition of Gap Junction-Mediated Intercellular Communication by Poly(I:C) in Cultured Human Corneal Fibroblasts. Curr Eye Res 2020; 45:1043-1050. [PMID: 32078434 DOI: 10.1080/02713683.2020.1716986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
PURPOSE/AIM Corneal stromal fibroblasts are connected to each other via gap junctions, which contribute to maintenance of corneal homeostasis. Viral infection of the corneal stroma can result in inflammation and scarring. The effects of polyinosinic-polycytidylic acid [poly(I:C)], an analog of viral double-stranded RNA, on gap junctional intercellular communication (GJIC) in cultured human corneal fibroblasts (HCFs) were examined. MATERIALS AND METHODS Cultured HCFs were exposed to poly(I:C) in the absence or presence of inhibitors of mitogen-activated protein kinase (MAPK) signaling or the antioxidant N-acetyl-L-cysteine (NAC). Expression of the gap junction protein connexin 43 (Cx43) was examined by immunoblot and immunofluorescence analyses. The level of Cx43 mRNA or microRNA-21 or -130a was determined by quantitative reverse transcription-polymerase chain reaction analysis. GJIC was measured with a dye coupling assay. The amount of malondialdehyde and the activity of superoxide dismutase (SOD) were measured with assay kits. RESULTS Exposure of HCFs to poly(I:C) resulted in down-regulation of Cx43 expression and GJIC activity as well as in up-regulation of microRNA-21 expression. Poly(I:C) increased the amount of malondialdehyde and reduced the activity of SOD in the cells, and these effects were prevented by NAC. The inhibitory effects of poly(I:C) on both Cx43 expression and GJIC activity were attenuated by NAC and by c-Jun NH2-terminal kinase (JNK) inhibitor II. CONCLUSIONS Poly(I:C) inhibited Cx43 expression and GJIC in cultured HCFs, possibly as a result of the associated up-regulation of microRNA-21. Poly(I:C) also increased oxidative stress in these cells, and such stress together with signaling by the MAPK JNK was implicated in the effects of poly(I:C) on Cx43 expression and GJIC activity. Down-regulation of GJIC activity among corneal fibroblasts by double-stranded RNA may thus contribute to the disruption of stromal homeostasis during viral infection of the cornea.
Collapse
Affiliation(s)
- Hui Zheng
- Department of Ophthalmology, Fifth Affiliated Hospital, Sun Yat-sen University , Zhuhai, PR China
| | - Ye Liu
- Department of Pathology, Fifth Affiliated Hospital, Sun Yat-sen University , Zhuhai, PR China
| | - Dan Xu
- Institute of Environmental Systems Biology, Environmental Science and Engineering College, Dalian Maritime University , Dalian, PR China
| | - Pingping Liu
- Department of Ophthalmology, Fifth Affiliated Hospital, Sun Yat-sen University , Zhuhai, PR China
| | - Xiuxia Yang
- Department of Ophthalmology, Fifth Affiliated Hospital, Sun Yat-sen University , Zhuhai, PR China
| | - Bing Li
- Department of Ophthalmology, Fifth Affiliated Hospital, Sun Yat-sen University , Zhuhai, PR China
| | - Zimu Cao
- Institute of Environmental Systems Biology, Environmental Science and Engineering College, Dalian Maritime University , Dalian, PR China
| | - Yang Liu
- Department of Ophthalmology, Fifth Affiliated Hospital, Sun Yat-sen University , Zhuhai, PR China
| | - Xiaoshuo Zheng
- Department of Ophthalmology, Fifth Affiliated Hospital, Sun Yat-sen University , Zhuhai, PR China
| |
Collapse
|
10
|
Lu X, Chen Z, Vick S, Watsky MA. Vitamin D receptor and metabolite effects on corneal epithelial cell gap junction proteins. Exp Eye Res 2019; 187:107776. [PMID: 31465769 DOI: 10.1016/j.exer.2019.107776] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/12/2019] [Accepted: 08/23/2019] [Indexed: 12/29/2022]
Abstract
Vitamin D is a fat-soluble prohormone that can be activated both systemically and within individual tissues. Our lab has previously demonstrated that the corneal epithelium can activate vitamin D and that the vitamin D metabolites 1,25(OH)2D3 and 24R,25(OH)2D3 can affect corneal epithelial migration, proliferation, and tight and gap junction function. These vitamin D-derived metabolites signal through the vitamin D receptor (VDR). The purpose of this study was to specifically determine the effects of 1,25(OH)2D3 and 24R,25(OH)2D3 on corneal epithelial cell gap junction proteins. Connexin (Cx) 26, 30 and 43 protein expression was detected in a human corneal epithelial cell line (HCEC), wild type and vitamin D receptor knockout (VDR-/-) mouse corneas, and cultured mouse primary epithelial cells (MPCEC). In vitro gap junction function was assessed using the scrape loading/dye transfer assay. HCEC and MPCEC were treated with 1,25(OH)2D3 or 24R,25(OH)2D3. Western blotting was used to detect gap junction proteins. Vitamin D3 effects on epithelial intracellular Ca++ (Ca++i) were determined using the dye Cal-520. Cx26 and Cx43 protein levels were significantly increased in HCEC and MPCEC treated with both 1,25(OH)2D3 and 24R,25(OH)2D3. Cx30 and Cx43 protein levels were also significantly increased in VDR-/- MPCEC. In vitro gap junction connectivity was significanlty enhanced in HCEC and MPCEC cultured with 24R,25(OH)2D3 and 1,25(OH)2D3. Ca++i was not affected by 1,25(OH)2D3 or 24R,25(OH)2D3 in HCEC or MPCEC. We conclude that both 1,25(OH)2D3 and 24R,25(OH)2D3 are positive regulators of connexin proteins and gap junction communication in the corneal epithelium. These vitamin D metabolites appear to signal through both VDR-dependent and -independent pathways. The effects of vitamin D on corneal epithelial gap junctions do not seem to be dependent on Ca++i.
Collapse
Affiliation(s)
- Xiaowen Lu
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Zhong Chen
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Sarah Vick
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Mitchell A Watsky
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA; The Graduate School, Augusta University, Augusta, GA, USA.
| |
Collapse
|
11
|
The Role of Connexin-43 in the Inflammatory Process: A New Potential Therapy to Influence Keratitis. J Ophthalmol 2019; 2019:9312827. [PMID: 30805212 PMCID: PMC6360563 DOI: 10.1155/2019/9312827] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 11/12/2018] [Accepted: 11/19/2018] [Indexed: 12/22/2022] Open
Abstract
The studies outlined in this review highlight the relationship between inflammatory signaling molecules and connexin-43 (Cx43). Gap junction (GJ) channels and hemichannels (HCs) participate in the metabolic activity between intra- and extracellular space. Some ions and small molecules are exchanged from cell to cell or cell to extracellular space to affect the process of inflammation via GJ. We analyzed the effects of signaling molecules, such as innate immunity messengers, transcription factors, LPS, cytokine, inflammatory chemokines, and MMPs, on Cx43 expression during the inflammatory process. At the same time, we found that these signaling molecules play a critical role in the pathogenesis of keratitis. Thus, we assessed the function of Cx43 during inflammatory corneal disease. Corneal healing plays an essential role in the late stage of keratitis. We found that Cx43 is involved in wound healing. Studies have shown that the decrease of Cx43 can decrease the time of healing. We also report several Cx43 mimic peptides which can inhibit the activity of Cx43 Hc to mediate the releasing of adenosine triphosphate (ATP), which may in turn influence the inflammatory process.
Collapse
|
12
|
Li SKL, Shan SW, Li HL, Cheng AKW, Pan F, Yip SP, Civan MM, To CH, Do CW. Characterization and Regulation of Gap Junctions in Porcine Ciliary Epithelium. ACTA ACUST UNITED AC 2018; 59:3461-3468. [DOI: 10.1167/iovs.18-24682] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Stanley Ka-Lok Li
- School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Sze-Wan Shan
- School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Hoi-Lam Li
- School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Angela King-Wah Cheng
- School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Feng Pan
- School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Shea-Ping Yip
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Mortimer M. Civan
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Chi-Ho To
- School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Chi-Wai Do
- School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| |
Collapse
|
13
|
Wong P, Tan T, Chan C, Laxton V, Chan YWF, Liu T, Wong WT, Tse G. The Role of Connexins in Wound Healing and Repair: Novel Therapeutic Approaches. Front Physiol 2016; 7:596. [PMID: 27999549 PMCID: PMC5138227 DOI: 10.3389/fphys.2016.00596] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 11/16/2016] [Indexed: 12/26/2022] Open
Abstract
Gap junctions are intercellular proteins responsible for mediating both electrical and biochemical coupling through the exchange of ions, second messengers and small metabolites. They consist of two connexons, with (one) connexon supplied by each cell. A connexon is a hexamer of connexins and currently more than 20 connexin isoforms have been described in the literature thus far. Connexins have a short half-life, and therefore gap junction remodeling constantly occurs with a high turnover rate. Post-translational modification, such as phosphorylation, can modify their channel activities. In this article, the roles of connexins in wound healing and repair are reviewed. Novel strategies for modulating the function or expression of connexins, such as the use of antisense technology, synthetic mimetic peptides and bioactive materials for the treatment of skin wounds, diabetic and pressure ulcers as well as cornea wounds, are considered.
Collapse
Affiliation(s)
- Pui Wong
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong Kong Hong Kong, Hong Kong
| | - Teresa Tan
- Department of Surgery, Faculty of Medicine, Chinese University of Hong Kong Hong Kong, Hong Kong
| | - Catherine Chan
- Department of Surgery, Faculty of Medicine, Chinese University of Hong Kong Hong Kong, Hong Kong
| | - Victoria Laxton
- Intensive Care Department, Royal Brompton and Harefield NHS Foundation Trust London, UK
| | - Yin Wah Fiona Chan
- Department of Psychology, School of Biological Sciences, University of Cambridge Cambridge, UK
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University Tianjin, China
| | - Wing Tak Wong
- School of Life Sciences, Chinese University of Hong Kong Hong Kong, Hong Kong
| | - Gary Tse
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong KongHong Kong, Hong Kong; Faculty of Medicine, Li Ka Shing Institute of Health Sciences, Chinese University of Hong KongHong Kong, Hong Kong
| |
Collapse
|
14
|
Takamiya M, Weger BD, Schindler S, Beil T, Yang L, Armant O, Ferg M, Schlunck G, Reinhard T, Dickmeis T, Rastegar S, Strähle U. Molecular description of eye defects in the zebrafish Pax6b mutant, sunrise, reveals a Pax6b-dependent genetic network in the developing anterior chamber. PLoS One 2015; 10:e0117645. [PMID: 25692557 PMCID: PMC4334901 DOI: 10.1371/journal.pone.0117645] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 12/29/2014] [Indexed: 11/19/2022] Open
Abstract
The cornea is a central component of the camera eye of vertebrates and even slight corneal disturbances severely affect vision. The transcription factor PAX6 is required for normal eye development, namely the proper separation of the lens from the developing cornea and the formation of the iris and anterior chamber. Human PAX6 mutations are associated with severe ocular disorders such as aniridia, Peters anomaly and chronic limbal stem cell insufficiency. To develop the zebrafish as a model for corneal disease, we first performed transcriptome and in situ expression analysis to identify marker genes to characterise the cornea in normal and pathological conditions. We show that, at 7 days post fertilisation (dpf), the zebrafish cornea expresses the majority of marker genes (67/84 tested genes) found also expressed in the cornea of juvenile and adult stages. We also characterised homozygous pax6b mutants. Mutant embryos have a thick cornea, iris hypoplasia, a shallow anterior chamber and a small lens. Ultrastructure analysis revealed a disrupted corneal endothelium. pax6b mutants show loss of corneal epithelial gene expression including regulatory genes (sox3, tfap2a, foxc1a and pitx2). In contrast, several genes (pitx2, ctnnb2, dcn and fabp7a) were ectopically expressed in the malformed corneal endothelium. Lack of pax6b function leads to severe disturbance of the corneal gene regulatory programme.
Collapse
Affiliation(s)
- Masanari Takamiya
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Benjamin D. Weger
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Simone Schindler
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Tanja Beil
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Lixin Yang
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Olivier Armant
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Marco Ferg
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Günther Schlunck
- Eye Center, Freiburg University Medical Center, Killianstr. 5, 79106 Freiburg, Germany
| | - Thomas Reinhard
- Eye Center, Freiburg University Medical Center, Killianstr. 5, 79106 Freiburg, Germany
| | - Thomas Dickmeis
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Sepand Rastegar
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
| | - Uwe Strähle
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany
- * E-mail:
| |
Collapse
|