Connexins are now known to have dual functions, serving both as intercellular (cell-cell) channels that mediate direct signaling between neighboring cells, and as membrane channels (hemichannels) that mediate signaling across the plasma membrane. The functional significance of connexins is now widely recognized from studies of targeted gene disruptions and a number of human hereditary diseases shown linked to mutations in connexin genes. Tissue- and cell-specific patterns of connexin expression are linked to functional properties that principally include regulation of channel opening, i.e. gating, conductance and permeability. In this proposal, we use combined molecular and biophysical approaches to identify the pore- lining and regulatory elements of connexin channels and hemichannels using Cx46 and Cx50 isoforms. Cystein-substitution accessibility will be used at the level of single hemichannels to map pore-lining residues, which should provide a fundamental basis for understanding what biological signals are selected for transmission. Parallel studies will address correspondence between hemichannels and cell-cell channels. Both voltage and extracellular Ca2+ play important roles in regulating hemichannel opening and we examine underlying mechanisms of action. We also present a novel form of regulation, mediated by extracellular monovalent cations, that strongly modulates hemichannel opening. This form of regulation is particularly robust for the Cx50 isoform and is a physiologically viable mechanism for regulated hemichannel opening. We will examine the underlying mechanism of action and use the sequence similarities of Cx46 and Cx50 to localize molecular determinants. Finally, mutations in Cx46 have been shown to cause congenital cataracts in humans. A number of mutations have been recently reported that map to areas important in gating and permeability and we will undertake functional analyses to examine possible mechanisms of disease associated with Cx46 dysfunction.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Biophysics of Neural Systems Study Section (BPNS)
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Rivera-Rentas, Alberto L
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Albert Einstein College of Medicine
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Srinivas, Miduturu; Verselis, Vytas K; White, Thomas W (2018) Human diseases associated with connexin mutations. Biochim Biophys Acta Biomembr 1860:192-201
Verselis, Vytas K (2017) Connexin hemichannels and cochlear function. Neurosci Lett :
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
Sanchez, Helmuth A; Verselis, Vytas K (2014) Aberrant Cx26 hemichannels and keratitis-ichthyosis-deafness syndrome: insights into syndromic hearing loss. Front Cell Neurosci 8:354
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
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
Rubinos, Clio; Sánchez, 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
Sánchez, Helmuth A; Mese, Gülistan; Srinivas, Miduturu et al. (2010) Differentially altered Ca2+ regulation and Ca2+ permeability in Cx26 hemichannels formed by the A40V and G45E mutations that cause keratitis ichthyosis deafness syndrome. J Gen Physiol 136:47-62

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