A conserved pore-lining glutamate as a voltage- and chloride-dependent gate in the CIC-2 chloride channel

Niemeyer, MI; Cid, LP; Zuniga, L; Catalán M.; Sepulveda, FV

Abstract

ClC-2 is a ubiquitously expressed, two-pore homodimeric Cl- channel opened by hyperpolarisation. Little is known about its gating mechanisms. Crystallographic and functional studies in other ClC channels suggest that a conserved glutamate residue carboxylate side-chain can close protopores by interacting with a Cl--binding site in the pore. Competition for this site is thought to provide the molecular basis for gating by extracellular Cl-. We now show that ClC-2 gating depends upon intra- but not extracellular Cl- and that neutralisation of E217, the homologous pore glutamate, leads to loss of sensitivity to intracellular Cl- and voltage. Experiments testing for transient activation by extracellular protons demonstrate that E217 is not available for protonation in the closed channel state but becomes so after opening by hyperpolarisation. The results suggest that E217 is a hyperpolarisation-dependent protopore gate in ClC-2 and that access of intracellular Cl- to a site normally occupied by its side-chain in the pore stabilises the open state. A remaining hyperpolarisation-dependent gate might correspond to that closing both pores simultaneously in other ClC channels.

Más información

Título según WOS: A conserved pore-lining glutamate as a voltage- and chloride-dependent gate in the CIC-2 chloride channel
Título según SCOPUS: A conserved pore-lining glutamate as a voltage- and chloride-dependent gate in the ClC-2 chloride channel
Título de la Revista: JOURNAL OF PHYSIOLOGY-LONDON
Volumen: 553
Número: 3
Editorial: Wiley
Fecha de publicación: 2003
Página de inicio: 873
Página final: 879
Idioma: English
URL: http://www.jphysiol.org/cgi/doi/10.1113/jphysiol.2003.055988
DOI:

10.1113/jphysiol.2003.055988

Notas: ISI, SCOPUS