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Connexin Mutations and Hereditary Diseases. Int J Mol Sci 2022; 23:ijms23084255. [PMID: 35457072 PMCID: PMC9027513 DOI: 10.3390/ijms23084255] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 04/04/2022] [Accepted: 04/09/2022] [Indexed: 02/01/2023] Open
Abstract
Inherited diseases caused by connexin mutations are found in multiple organs and include hereditary deafness, congenital cataract, congenital heart diseases, hereditary skin diseases, and X-linked Charcot–Marie–Tooth disease (CMT1X). A large number of knockout and knock-in animal models have been used to study the pathology and pathogenesis of diseases of different organs. Because the structures of different connexins are highly homologous and the functions of gap junctions formed by these connexins are similar, connexin-related hereditary diseases may share the same pathogenic mechanism. Here, we analyze the similarities and differences of the pathology and pathogenesis in animal models and find that connexin mutations in gap junction genes expressed in the ear, eye, heart, skin, and peripheral nerves can affect cellular proliferation and differentiation of corresponding organs. Additionally, some dominant mutations (e.g., Cx43 p.Gly60Ser, Cx32 p.Arg75Trp, Cx32 p.Asn175Asp, and Cx32 p.Arg142Trp) are identified as gain-of-function variants in vivo, which may play a vital role in the onset of dominant inherited diseases. Specifically, patients with these dominant mutations receive no benefits from gene therapy. Finally, the complete loss of gap junctional function or altered channel function including permeability (ions, adenosine triphosphate (ATP), Inositol 1,4,5-trisphosphate (IP3), Ca2+, glucose, miRNA) and electric activity are also identified in vivo or in vitro.
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Minogue PJ, Tong JJ, Wichmann K, Mysliwiec H, Ebihara L, Beyer EC, Berthoud VM. Cataract-linked serine mutations in the gap junction protein connexin50 expose a sorting signal that promotes its lysosomal degradation. J Biol Chem 2022; 298:101673. [PMID: 35120923 PMCID: PMC8927986 DOI: 10.1016/j.jbc.2022.101673] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/21/2022] [Accepted: 01/25/2022] [Indexed: 01/24/2023] Open
Abstract
Many human connexin50 (Cx50) mutants have been linked to cataracts including two carboxyl terminus serine mutants that are known phosphorylation sites in the lens (Cx50S258F and Cx50S259Y). To examine the behavior of these mutants and the role of phosphorylation at these positions, we stably transfected HeLa cells with cataract-linked and phosphorylation-mimicking (Cx50S258D and Cx50S259D) Cx50 mutants. We observed that gap junctional plaques were rarely detected in Cx50S258F- and Cx50S259Y-expressing cells compared with wild-type cells. In addition, gap junction abundance and size were greatly increased for Cx50S258D and Cx50S259D mutants. Cx50S258F and Cx50S259Y supported very low levels of gap junctional coupling, whereas Cx50S258D and Cx50S259D supported extensive intercellular communication. Furthermore, Cx50 levels as detected by immunoblotting were lower in Cx50S258F and Cx50S259Y mutants than in the wild type or the aspartate substitution mutants, and chloroquine or ammonium chloride treatment significantly increased Cx50S258F and Cx50S259Y protein levels, implying participation of the lysosome in their increased degradation. Alanine substitution of amino acids within a predicted tyrosine-based sorting signal in Cx50S258F and Cx50S259Y increased levels of gap junctional plaques and intercellular transfer of Neurobiotin. These results suggest that absence of phosphorylatable serines at these positions exposes a sorting signal leading to lysosomal degradation of Cx50, whereas phosphorylation at these sites conceals this signal and allows targeting of Cx50 to the plasma membrane and stabilization of gap junction plaques. We propose that in the lens degradation of Cx50S258F and Cx50S259Y decreases Cx50 levels at the plasma membrane and consequently Cx50 function, leading to cataracts.
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Affiliation(s)
- Peter J Minogue
- Department of Pediatrics, University of Chicago, Chicago, Illinois, USA
| | - Jun-Jie Tong
- Center of Proteomics and Molecular Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | - Kelly Wichmann
- Department of Pediatrics, University of Chicago, Chicago, Illinois, USA
| | - Hubert Mysliwiec
- Department of Pediatrics, University of Chicago, Chicago, Illinois, USA
| | - Lisa Ebihara
- Center of Proteomics and Molecular Therapeutics/Discipline of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | - Eric C Beyer
- Department of Pediatrics, University of Chicago, Chicago, Illinois, USA
| | - Viviana M Berthoud
- Department of Pediatrics, University of Chicago, Chicago, Illinois, USA.
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Sinyuk M, Mulkearns-Hubert EE, Reizes O, Lathia J. Cancer Connectors: Connexins, Gap Junctions, and Communication. Front Oncol 2018; 8:646. [PMID: 30622930 PMCID: PMC6308394 DOI: 10.3389/fonc.2018.00646] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Accepted: 12/10/2018] [Indexed: 12/21/2022] Open
Abstract
Despite concerted clinical and research efforts, cancer is a leading cause of death worldwide. Surgery, radiation, and chemotherapy have remained the most common standard-of-care strategies against cancer for decades. However, the side effects of these therapies demonstrate the need to investigate adjuvant novel treatment modalities that minimize the harm caused to healthy cells and tissues. Normal and cancerous cells require communication amongst themselves and with their surroundings to proliferate and drive tumor growth. It is vital to understand how intercellular and external communication impacts tumor cell malignancy. To survive and grow, tumor cells, and their normal counterparts utilize cell junction molecules including gap junctions (GJs), tight junctions, and adherens junctions to provide contact points between neighboring cells and the extracellular matrix. GJs are specialized structures composed of a family of connexin proteins that allow the free diffusion of small molecules and ions directly from the cytoplasm of adjacent cells, without encountering the extracellular milieu, which enables rapid, and coordinated cellular responses to internal and external stimuli. Importantly, connexins perform three main cellular functions. They enable direct gap junction intercellular communication (GJIC) between cells, form hemichannels to allow cell communication with the extracellular environment, and serve as a site for protein-protein interactions to regulate signaling pathways. Connexins themselves have been found to promote tumor cell growth and invasiveness, contributing to the overall tumorigenicity and have emerged as attractive anti-tumor targets due to their functional diversity. However, connexins can also serve as tumor suppressors, and therefore, a complete understanding of the roles of the connexins and GJs in physiological and pathophysiological conditions is needed before connexin targeting strategies are applied. Here, we discuss how the three aspects of connexin function, namely GJIC, hemichannel formation, and connexin-protein interactions, function in normal cells, and contribute to tumor cell growth, proliferation, and death. Finally, we discuss the current state of anti-connexin therapies and speculate which role may be most amenable for the development of targeting strategies.
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Affiliation(s)
- Maksim Sinyuk
- Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, OH, United States
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Erin E. Mulkearns-Hubert
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Ofer Reizes
- Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, OH, United States
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
- Cleveland Clinic Lerner College of Medicine, Cleveland Clinic, Cleveland, OH, United States
- Case Comprehensive Cancer Center, Case Western University, Cleveland, OH, United States
| | - Justin Lathia
- Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, OH, United States
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
- Cleveland Clinic Lerner College of Medicine, Cleveland Clinic, Cleveland, OH, United States
- Case Comprehensive Cancer Center, Case Western University, Cleveland, OH, United States
- Rose Ella Burkhardt Brain Tumor and Neuro-Oncology Center, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
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Yao Y, Zheng X, Ge X, Xiu Y, Zhang L, Fang W, Zhao J, Gu F, Zhu Y. Identification of a novel GJA3 mutation in a large Chinese family with congenital cataract using targeted exome sequencing. PLoS One 2017; 12:e0184440. [PMID: 28877251 PMCID: PMC5587237 DOI: 10.1371/journal.pone.0184440] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 08/23/2017] [Indexed: 11/18/2022] Open
Abstract
Autosomal dominant congenital cataract (ADCC) is a clinically and genetically heterogeneous ocular disease in children that results in serious visual impairments or even blindness. Targeted exome sequencing (TES) is an efficient method used for genetic diagnoses of inherited diseases. In the present study, we used a custom-made TES panel to identify the genetic defect of a four-generation Chinese family with bilateral pulverulent nuclear cataracts. A novel heterozygous missense mutation c.443C>T (p. T148I) in GJA3 was identified. The results of the bioinformatic analysis showed that the mutation was deleterious to the structure and hemichannel function of Cx46 encoded by GJA3. Plasmids expressing wild-type and mutant human Cx46 were constructed and ectopically expressed in human lens epithelial cells (HLECs) or human embryonic kidney (HEK-293) cells. Fluorescent images indicated aggregated signals of mutant protein in the cytoplasm, and a higher protein level was also detected in T148I stable cell lines. In summary, we identified a novel mutation in GJA3 for ADCC, which provided molecular insights into the pathogenic mechanism of ADCC.
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Affiliation(s)
- Yihua Yao
- The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian, China
| | - Xuedong Zheng
- The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian, China
| | - Xianglian Ge
- School of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou, Zhejiang, China
| | - Yanghui Xiu
- The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian, China
| | - Liu Zhang
- The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian, China
| | - Weifang Fang
- The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian, China
| | - Junzhao Zhao
- The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Feng Gu
- School of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou, Zhejiang, China
| | - Yihua Zhu
- The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian, China
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Abstract
The lens is an avascular organ composed of an anterior epithelial cell layer and fiber cells that form the bulk of the organ. The lens expresses connexin43 (Cx43), connexin46 (Cx46) and connexin50 (Cx50). Epithelial Cx50 has critical roles in cell proliferation and differentiation, likely involving growth factor-dependent signaling pathways. Both Cx46 and Cx50 are crucial for lens transparency; mutations in their genes have been linked to congenital and age-related cataracts. Congenital cataract-associated connexin mutants can affect protein trafficking, stability and/or function, and the functional effects may differ between gap junction channels and hemichannels. Dominantly inherited cataracts may result from effects of the connexin mutant on its wild type isotype, the other co-expressed wild type connexin and/or its interaction with other cellular components.
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Affiliation(s)
| | - Anaclet Ngezahayo
- Institute of Biophysics, Leibniz University Hannover, Hannover, Germany.
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Identification and functional analysis of two novel connexin 50 mutations associated with autosome dominant congenital cataracts. Sci Rep 2016; 6:26551. [PMID: 27216975 PMCID: PMC4877569 DOI: 10.1038/srep26551] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 05/03/2016] [Indexed: 01/14/2023] Open
Abstract
Autosomal dominant congenital cataracts (ADCC) are clinically and genetically heterogeneous diseases. The present study recruited two Chinese families with bilateral nuclear cataract or zonular pulverulent phenotype. Direct sequencing of candidate genes identified two novel missense mutations of Cx50, Cx50P59A (c.175C > G) and Cx50R76H (c.227G > A), both co-segregated well with all affected individuals. Bioinformatics analysis predicted deleterious for both mutations. Functional and cellular behaviors of wild type and mutant Cx50 examined by stably transfecting recombinant systems revealed similar protein expression levels. Protein distribution pattern by fluorescence microscopy showed that Cx50R76H localized at appositional membranes forming gap junctions with enormous cytoplasmic protein accumulation, whereas the Cx50P59A mutation was found inefficient at forming detectable plaques. Cell growth test by MTT assay showed that induction of Cx50P59A decreased cell viability. Our study constitutes the first report that the Cx50P59A and Cx50R76H mutations are associated with ADCC and expands the mutation spectrum of Cx50 in association with congenital cataracts. The genetic, cellular, and functional data suggest that the altered intercellular communication governed by mutated Cx50 proteins may act as the molecular mechanism underlying ADCC, which further confirms the role of Cx50 in the maintenance of human lens transparency.
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García IE, Prado P, Pupo A, Jara O, Rojas-Gómez D, Mujica P, Flores-Muñoz C, González-Casanova J, Soto-Riveros C, Pinto BI, Retamal MA, González C, Martínez AD. Connexinopathies: a structural and functional glimpse. BMC Cell Biol 2016; 17 Suppl 1:17. [PMID: 27228968 PMCID: PMC4896260 DOI: 10.1186/s12860-016-0092-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Mutations in human connexin (Cx) genes have been related to diseases, which we termed connexinopathies. Such hereditary disorders include nonsyndromic or syndromic deafness (Cx26, Cx30), Charcot Marie Tooth disease (Cx32), occulodentodigital dysplasia and cardiopathies (Cx43), and cataracts (Cx46, Cx50). Despite the clinical phenotypes of connexinopathies have been well documented, their pathogenic molecular determinants remain elusive. The purpose of this work is to identify common/uncommon patterns in channels function among Cx mutations linked to human diseases. To this end, we compiled and discussed the effect of mutations associated to Cx26, Cx32, Cx43, and Cx50 over gap junction channels and hemichannels, highlighting the function of the structural channel domains in which mutations are located and their possible role affecting oligomerization, gating and perm/selectivity processes.
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Affiliation(s)
- Isaac E García
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Pavel Prado
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Oscar Jara
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Diana Rojas-Gómez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Paula Mujica
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Flores-Muñoz
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Jorge González-Casanova
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Soto-Riveros
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Bernardo I Pinto
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
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