Gap junctional communication provided by connexin channels is required for postnatal lens growth and transparency. Targeted deletions of genes encoding Cx46 and Cx50 lead to cataracts in mice. Similarly, mutations in both Cx50 and Cx46 genes cause a variety of cataract types in both humans and mice. Alterations in coupling have been suggested to underlie cataracts that occur with diabetes and with age, but there are few studies directly linking gap junctional coupling to these pathophysiological conditions. More recently, we found that there are differences in the molecular permeability through channels made of Cx46, Cx50 and Cx43. In this proposal, we will continue to pursue electrophysiological studies to understand how the diversity in channel types formed by connexin proteins influences lens function and how their alteration leads to congenital and age-related cataracts by pursuing the following two Aims.
In Aim 1, we will determine the importance of coupling provided by Cx46 and Cx50 gap junctions in the lens in the maintenance of adequate concentrations of important metabolites in inner fiber cells. We will use electrophysiological and biochemical assays to study the permeation of molecules in vitro and in vivo. We will also determine whether Cx50 and Cx46 mutations that cause congenital cataracts have alterations in molecular permeability. Second, we will determine whether coupling conductance and/or permeability is altered with aging and oxidative stress. Mass spectrometric methods will be employed to identify modifications to connexins with aging and during cataractogenesis. The effect of modifications on conductance and permeability of gap junctions will be assessed using electrophysiological methods.

Public Health Relevance

Communication between cells is mediated by proteins called connexins. Mutations in these connexin proteins are responsible for a number of diseases in humans, including cataracts, the leading cause of blindness in the world. Our studies are aimed at understanding the importance of these proteins in both age-onset and congenital cataracts.

National Institute of Health (NIH)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Araj, Houmam H
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State College of Optometry
Schools of Optometry/Opht Tech
New York
United States
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Rubinos, Clio; Villone, Krista; Mhaske, Pallavi V et al. (2014) Functional effects of Cx50 mutations associated with congenital cataracts. Am J Physiol Cell Physiol 306:C212-20
Sanchez, Helmuth A; Bienkowski, Rick; Slavi, Nefeli et al. (2014) Altered inhibition of Cx26 hemichannels by pH and Zn2+ in the A40V mutation associated with keratitis-ichthyosis-deafness syndrome. J Biol Chem 289:21519-32
Sanchez, Helmuth A; Villone, Krista; Srinivas, Miduturu et al. (2013) The D50N mutation and syndromic deafness: altered Cx26 hemichannel properties caused by effects on the pore and intersubunit interactions. J Gen Physiol 142:3-22
Verselis, Vytas K; Srinivas, Miduturu (2013) Connexin channel modulators and their mechanisms of action. Neuropharmacology 75:517-24
Rubinos, Clio; Sanchez, Helmuth A; Verselis, Vytas K et al. (2012) Mechanism of inhibition of connexin channels by the quinine derivative N-benzylquininium. J Gen Physiol 139:69-82
Verselis, Vytas K; Trelles, Maria P; Rubinos, Clio et al. (2009) Loop gating of connexin hemichannels involves movement of pore-lining residues in the first extracellular loop domain. J Biol Chem 284:4484-93
Shakespeare, Teresa I; Sellitto, Caterina; Li, Leping et al. (2009) Interaction between Connexin50 and mitogen-activated protein kinase signaling in lens homeostasis. Mol Biol Cell 20:2582-92
Verselis, Vytas K; Srinivas, Miduturu (2008) Divalent cations regulate connexin hemichannels by modulating intrinsic voltage-dependent gating. J Gen Physiol 132:315-27
White, Thomas W; Gao, Yang; Li, Leping et al. (2007) Optimal lens epithelial cell proliferation is dependent on the connexin isoform providing gap junctional coupling. Invest Ophthalmol Vis Sci 48:5630-7
Bai, Donglin; del Corsso, Cristiane; Srinivas, Miduturu et al. (2006) Block of specific gap junction channel subtypes by 2-aminoethoxydiphenyl borate (2-APB). J Pharmacol Exp Ther 319:1452-8

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