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.
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.
|Slavi, Nefeli; Wang, Zhen; Harvey, Lucas et al. (2016) Identification and Functional Assessment of Age-Dependent Truncations to Cx46 and Cx50 in the Human Lens. Invest Ophthalmol Vis Sci 57:5714-5722|
|Sanchez, Helmuth A; Slavi, Nefeli; Srinivas, Miduturu et al. (2016) Syndromic deafness mutations at Asn 14 differentially alter the open stability of Cx26 hemichannels. J Gen Physiol 148:25-42|
|Slavi, Nefeli; Rubinos, Clio; Li, Leping et al. (2014) Connexin 46 (cx46) gap junctions provide a pathway for the delivery of glutathione to the lens nucleus. J Biol Chem 289:32694-702|
|Srinivas, Miduturu (2014) Delivery of glutathione to the lens nucleus. J Ophthalmic Vis Res 9:148-9|
|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|
|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; 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; SÃ¡nchez, 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|
|Kronengold, Jack; Srinivas, Miduturu; Verselis, Vytas K (2012) The N-terminal half of the connexin protein contains the core elements of the pore and voltage gates. J Membr Biol 245:453-63|
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