INTERCELLULAR COMMUNICATION IN THE LENS

Summary

Principal Investigator: Lisa Ebihara
Abstract: The lens is an avascular, syncytial organ that is dependent on intercellular communication for the maintenance of transparency and tissue homeostasis. Three different connexin proteins (Connexin 43 (Cx43), Connexin 46 (Cx46), Connexin 50 (Cx50)) have been identified in lens fibers. The overall objective of this research proposal is to better understand the role of connexins in the lens. The central hypothesis that will be tested is that both connexin gap junctions and hemichannels play an important role in maintaining lens transparency. There are two specific aims: Aim 1. To understand how structural differences in the N-terminal, first transmembrane spanning domain (M1), and first extracellular domain (E1) contribute to differences in the biophysical properties of wild-type and mutant Cx46 and Cx50 gap junctional channels and hemichannels. We will continue to investigate the functional properties of wild-type and mutant lens connexins expressed in heterologous cell systems. The two connexin specific properties that will be studied are: (1) molecular permeability to larger permeants;(2) hemichannel gating. In addition, the functional and cellular effects of several congenital cataract associated connexin mutations that localize to the N- terminal and E1 domains will be tested. Aim 2. To determine the molecular identity of the nonselective leak conductance in fiber cells that is activated by removal of external calcium. Recently, my laboratory has developed a technique for producing a viable, isolated fiber cell preparation from lenses of adult and neonatal mice. We will use this preparation as well as HeLa cells transfected with different lens connexins to address the following questions: What is the molecular identity of the nonselective leak conductance activated by removal of external calcium?;Can this conductance account for the influx of sodium that occurs in fiber cells under physiological conditions?;Does this conductance mediate the pathological calcium influx that occurs in fiber cells in response to cell swelling? The hypothesis to be tested is that connexin hemichannels are responsible for all of these phenomena. We will also use the isolated fiber cell preparation to study the regulation of gap junctional conductance by a variety of factors that have been previously shown to play an important role in regulating intercellular communication in the intact lens such as phosphorylation, oxidative stress and pHi.
Funding Period: 1994-06-01 - 2014-11-30
more information: NIH RePORT

Top Publications

  1. pmc A novel GJA8 mutation is associated with autosomal dominant lamellar pulverulent cataract: further evidence for gap junction dysfunction in human cataract
    A Arora
    J Med Genet 43:e2. 2006
  2. pmc Properties of two cataract-associated mutations located in the NH2 terminus of connexin 46
    Jun Jie Tong
    Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA
    Am J Physiol Cell Physiol 304:C823-32. 2013
  3. pmc Different consequences of cataract-associated mutations at adjacent positions in the first extracellular boundary of connexin50
    Jun Jie Tong
    Dept of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA
    Am J Physiol Cell Physiol 300:C1055-64. 2011
  4. pmc Properties of connexin 46 hemichannels in dissociated lens fiber cells
    Lisa Ebihara
    Departments of Physiology and Biophysics, Rosalind Franklin School of Medicine and Science, North Chicago, Illinois 60064, USA
    Invest Ophthalmol Vis Sci 52:882-9. 2011
  5. pmc The GJA8 allele encoding CX50I247M is a rare polymorphism, not a cataract-causing mutation
    Jochen Graw
    Helmholtz Center Munich German Research Center for Environmental Health, Institute of Developmental Genetics, D 85764 Neuherberg, Germany
    Mol Vis 15:1881-5. 2009
  6. pmc A mutant connexin50 with enhanced hemichannel function leads to cell death
    Peter J Minogue
    Department of Pediatrics, Section of Hematology Oncology, University of Chicago, Chicago, Illinois 60637, USA
    Invest Ophthalmol Vis Sci 50:5837-45. 2009
  7. pmc A novel connexin50 mutation associated with congenital nuclear pulverulent cataracts
    A Arora
    UCL Institute of Ophthalmology, London, UK
    J Med Genet 45:155-60. 2008
  8. pmc Transgenic overexpression of connexin50 induces cataracts
    June Chung
    Department of Pediatrics, University of Chicago, IL 60637, USA
    Exp Eye Res 84:513-28. 2007
  9. pmc Role of the N-terminus in permeability of chicken connexin45.6 gap junctional channels
    Lixian Dong
    Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA
    J Physiol 576:787-99. 2006
  10. pmc Structural determinants for the differences in voltage gating of chicken Cx56 and Cx45.6 gap-junctional hemichannels
    Jun Jie Tong
    Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science Chicago Medical School, 3333 Green Bay Road North, Chicago, IL 60064, USA
    Biophys J 91:2142-54. 2006

Research Grants

Detail Information

Publications11

  1. pmc A novel GJA8 mutation is associated with autosomal dominant lamellar pulverulent cataract: further evidence for gap junction dysfunction in human cataract
    A Arora
    J Med Genet 43:e2. 2006
    ..To identify the gene responsible for autosomal dominant lamellar pulverulent cataract in a four-generation British family and characterise the functional and cellular consequences of the mutation...
  2. pmc Properties of two cataract-associated mutations located in the NH2 terminus of connexin 46
    Jun Jie Tong
    Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA
    Am J Physiol Cell Physiol 304:C823-32. 2013
    ..These data suggest D3Y and L11S cause cataracts by similar but not identical mechanisms...
  3. pmc Different consequences of cataract-associated mutations at adjacent positions in the first extracellular boundary of connexin50
    Jun Jie Tong
    Dept of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA
    Am J Physiol Cell Physiol 300:C1055-64. 2011
    ....
  4. pmc Properties of connexin 46 hemichannels in dissociated lens fiber cells
    Lisa Ebihara
    Departments of Physiology and Biophysics, Rosalind Franklin School of Medicine and Science, North Chicago, Illinois 60064, USA
    Invest Ophthalmol Vis Sci 52:882-9. 2011
    ..To characterize the properties of connexin 46 hemichannels in differentiating fiber cells isolated from mouse lenses...
  5. pmc The GJA8 allele encoding CX50I247M is a rare polymorphism, not a cataract-causing mutation
    Jochen Graw
    Helmholtz Center Munich German Research Center for Environmental Health, Institute of Developmental Genetics, D 85764 Neuherberg, Germany
    Mol Vis 15:1881-5. 2009
    ..The aim of this study was the genetic, cellular, and physiological characterization of a connexin50 (CX50) variant identified in a child with congenital cataracts...
  6. pmc A mutant connexin50 with enhanced hemichannel function leads to cell death
    Peter J Minogue
    Department of Pediatrics, Section of Hematology Oncology, University of Chicago, Chicago, Illinois 60637, USA
    Invest Ophthalmol Vis Sci 50:5837-45. 2009
    ..To determine the consequences of expression of a novel connexin50 (CX50) mutant identified in a child with congenital total cataracts...
  7. pmc A novel connexin50 mutation associated with congenital nuclear pulverulent cataracts
    A Arora
    UCL Institute of Ophthalmology, London, UK
    J Med Genet 45:155-60. 2008
    ..To screen for mutations of connexin50 (Cx50)/GJA8 in a panel of patients with inherited cataract and to determine the cellular and functional consequences of the identified mutation...
  8. pmc Transgenic overexpression of connexin50 induces cataracts
    June Chung
    Department of Pediatrics, University of Chicago, IL 60637, USA
    Exp Eye Res 84:513-28. 2007
    ....
  9. pmc Role of the N-terminus in permeability of chicken connexin45.6 gap junctional channels
    Lixian Dong
    Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA
    J Physiol 576:787-99. 2006
    ..6. These data suggest that the N-terminus plays a critical role in determining many of biophysical properties of Cx45.6 gap junctional channels, including molecular permeability and voltage gating...
  10. pmc Structural determinants for the differences in voltage gating of chicken Cx56 and Cx45.6 gap-junctional hemichannels
    Jun Jie Tong
    Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science Chicago Medical School, 3333 Green Bay Road North, Chicago, IL 60064, USA
    Biophys J 91:2142-54. 2006
    ..6 and Cx56 hemichannels; the first transmembrane-spanning domain, M1, is an important determinant of macroscopic current magnitude; R9 and E43 are also determinants of single channel conductance and rectification...
  11. pmc Cx46 hemichannels contribute to the sodium leak conductance in lens fiber cells
    Lisa Ebihara
    Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
    Am J Physiol Cell Physiol 306:C506-13. 2014
    ..In conclusion, these results suggest that Cx46 hemichannels may contribute to the sodium leak conductance in lens fiber cells. ..

Research Grants30

  1. Lens intercellular communication connexins and cataract
    Thomas W White; Fiscal Year: 2013
    ..They also will broaden the general paradigm of how an integrated system of intercellular communication contributes to the regulation of development in many tissues. ..