Gap junctions formed by Cx26 and Cx32 differ in molecular permeability and in sensitivity to transjunctional voltage. These differences will be exploited to define the molecular mechanisms that underlie voltage dependence and ionic fluxes of intercellular and membrane channels formed by proteins of the connexin gene family. In the long term, integration of data from biophysical, molecular genetic, NMR and computer modeling studies will lead to understanding of how conformational changes in this membrane protein and others dynamically relate to their function and how fixed charges modulate ion flux. In the proposed studies the pore-lining sequence of the Cx32 channel will be further defined and the atomic structure of the amino terminus of wild type and mutated Cx32 will be solved by high resolution NMR. The position of the voltage sensor and its relation to the transjunctional electric field will be explored. Studies are proposed to test the hypothesis that the conformational flexibility of a proline kink motif underlies the conformational changes required for voltage dependent gating. Studies are also proposed to distinguish between concerted and individual subunit gating models. Data from molecular and electrophysiological studies of ionic flux will be examined using the electrodiffusive model of Chen and Eisenberg to further define the roles of charged amino acids in determining permeation and selectivity of gap junction channels. X-linked Charcot-Marie-Tooth disease (CMTX) is caused by mutations of human Cx32, and nonsyndromic deafness by mutations of Cx26. Biophysical and molecular studies have shown that changes in permeability of Cx32 are likely to underlie the etiology of CMTX. The proposed studies will advance the basic scientific knowledge required to define the molecular basis of this and other connexin-related diseases, and the biological role of gap junctions.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM046889-09A1
Application #
6266215
Study Section
Special Emphasis Panel (ZRG1-MDCN-3 (01))
Program Officer
Shapiro, Bert I
Project Start
1992-02-01
Project End
2004-07-31
Budget Start
2000-12-19
Budget End
2001-11-30
Support Year
9
Fiscal Year
2001
Total Cost
$377,775
Indirect Cost
Name
Albert Einstein College of Medicine
Department
Neurosciences
Type
Schools of Medicine
DUNS #
009095365
City
Bronx
State
NY
Country
United States
Zip Code
10461
Bargiello, Thaddeus A; Oh, Seunghoon; Tang, Qingxiu et al. (2018) Gating of Connexin Channels by transjunctional-voltage: Conformations and models of open and closed states. Biochim Biophys Acta Biomembr 1860:22-39
Oh, Seunghoon; Bargiello, Thaddeus A (2015) Voltage regulation of connexin channel conductance. Yonsei Med J 56:1-15
Kwon, Taekyung; Tang, Qingxiu; Bargiello, Thaddeus A (2013) Voltage-dependent gating of the Cx32*43E1 hemichannel: conformational changes at the channel entrances. J Gen Physiol 141:243-59
Kwon, Taekyung; Roux, BenoƮt; Jo, Sunhwan et al. (2012) Molecular dynamics simulations of the Cx26 hemichannel: insights into voltage-dependent loop-gating. Biophys J 102:1341-51
Kalmatsky, B D; Batir, Y; Bargiello, T A et al. (2012) Structural studies of N-terminal mutants of connexin 32 using (1)H NMR spectroscopy. Arch Biochem Biophys 526:1-8
Bargiello, Thaddeus A; Tang, Qingxiu; Oh, Seunghoon et al. (2012) Voltage-dependent conformational changes in connexin channels. Biochim Biophys Acta 1818:1807-22
Kwon, Taekyung; Harris, Andrew L; Rossi, Angelo et al. (2011) Molecular dynamics simulations of the Cx26 hemichannel: evaluation of structural models with Brownian dynamics. J Gen Physiol 138:475-93
Freidin, Mona; Asche, Samantha; Bargiello, Thaddeus A et al. (2009) Connexin 32 increases the proliferative response of Schwann cells to neuregulin-1 (Nrg1). Proc Natl Acad Sci U S A 106:3567-72
Tang, Qingxiu; Dowd, Terry L; Verselis, Vytas K et al. (2009) Conformational changes in a pore-forming region underlie voltage-dependent ""loop gating"" of an unapposed connexin hemichannel. J Gen Physiol 133:555-70
Kalmatsky, B D; Bhagan, S; Tang, Q et al. (2009) Structural studies of the N-terminus of Connexin 32 using 1H NMR spectroscopy. Arch Biochem Biophys 490:9-16

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