Electrical signaling constitutes one of the primary means of communication in the central nervous system with the voltage-dependent sodium channels being responsible for initiating electrical impulses. Na+ channels exist in three functional states depending on transmembrane voltage: closed, open and inactivated. Mutations of Na+ channels that lead to incomplete inactivation has been linked to various disease conditions including congenital long QT syndrome, generalized epilepsy and muscle myotonia. Local anesthetics are a class of open channel blockers that are used to treat some channel-associated conditions and are believed to stabilize the channel in the inactivated state. The long term goal of my laboratory is to use structural approaches to understand the physical basis of gating of Na+ channels and their modulation. In this study, we propose to address a fundamental question: How do molecules like local anesthetics that bind to the channel pore modify the voltage-dependent gating behavior of ion channels. We will use fluorescence recordings of site-specific labels along with electrophysiological measurements to study the effect of local anesthetic on the conformational changes associated with voltage-sensing S4 segments of Na+ channels. We propose to study a) the effect of local anesthetic on the dynamics of individual S4 segments, b) the effect of local anesthetic on structure of the individual S4 segments, c) determine the molecular basis of coupling between S4 segments and local anesthetic binding at the pore, and d) determine if stabilizing the channel in the inactivated state favors local anesthetic binding. These experiments will be interpreted in light of the recently elucidated structure of a prototypical voltage-gated ion channel (Kv 1.2) to understand the structural basis of Na+ channel gating and its modulation by local anesthetics.

Public Health Relevance

In order to develop better drugs to treat ion channel associated disease conditions, it becomes necessary to understand the structural underpinnings of ion channel function. The research proposed here utilizes a relatively novel structural approach to study the dynamics of the Na+ channel and its modulation by local anesthetics. This research will advance human health and well-being by contributing to the development of next generation of ion channel drugs that will modulate the channel function in a specified manner.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM084140-03
Application #
7860272
Study Section
Biophysics of Neural Systems Study Section (BPNS)
Program Officer
Cole, Alison E
Project Start
2008-08-01
Project End
2013-05-31
Budget Start
2010-06-01
Budget End
2011-05-31
Support Year
3
Fiscal Year
2010
Total Cost
$426,344
Indirect Cost
Name
University of Wisconsin Madison
Department
Physiology
Type
Schools of Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
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Goldschen-Ohm, Marcel P; Klenchin, Vadim A; White, David S et al. (2016) Structure and dynamics underlying elementary ligand binding events in human pacemaking channels. Elife 5:
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Oelstrom, Kevin; Chanda, Baron (2016) Congruent pattern of accessibility identifies minimal pore gate in a non-symmetric voltage-gated sodium channel. Nat Commun 7:11608
Bao, Huan; Goldschen-Ohm, Marcel; Jeggle, Pia et al. (2016) Exocytotic fusion pores are composed of both lipids and proteins. Nat Struct Mol Biol 23:67-73
Goldschen-Ohm, Marcel P; Chanda, Baron (2015) How to open a proton pore-more than S4? Nat Struct Mol Biol 22:277-8
Goldschen-Ohm, Marcel P; Chanda, Baron (2014) Probing gating mechanisms of sodium channels using pore blockers. Handb Exp Pharmacol 221:183-201
Chowdhury, Sandipan; Haehnel, Benjamin M; Chanda, Baron (2014) A self-consistent approach for determining pairwise interactions that underlie channel activation. J Gen Physiol 144:441-55
Oelstrom, Kevin; Goldschen-Ohm, Marcel P; Holmgren, Miguel et al. (2014) Evolutionarily conserved intracellular gate of voltage-dependent sodium channels. Nat Commun 5:3420

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