Mechanism for modulation of gating of connexin26-containing channels by taurine

Darren Locke, Fabien Kieken, Liang Tao, Paul L. Sorgen, Andrew L. Harris

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The mechanisms of action of endogenous modulatory ligands of connexin channels are largely unknown. Previous work showed that protonated aminosulfonates (AS), notably taurine, directly and reversibly inhibit homomeric and heteromeric channels that contain Cx26, a widely distributed connexin, but not homomeric Cx32 channels. The present study investigated the molecular mechanisms of connexin channel modulation by taurine, using hemichannels and junctional channels composed of Cx26 (homomeric) and Cx26/Cx32 (heteromeric). The addition of a 28-amino acid "tag" to the carboxyl-terminal domain (CT) of Cx26 (Cx26T) eliminated taurine sensitivity of homomeric and heteromeric hemichannels in cells and liposomes. Cleavage of all but four residues of the tag (Cx26Tc) resulted in taurine-induced pore narrowing in homomeric hemichannels, and restored taurine inhibition of heteromeric hemichannels (Cx26Tc/Cx32). Taurine actions on junctional channels were fully consistent with those on hemichannels. Taurine-induced inhibition of Cx26/Cx32T and nontagged Cx26 junctional channels was blocked by extracellular HEPES, a blocker of the taurine transporter, confirming that the taurine-sensitive site of Cx26 is cytoplasmic. Nuclear magnetic resonance of peptides corresponding to Cx26 cytoplasmic domains showed that taurine binds to the cytoplasmic loop (CL) and not the CT, and that the CT and CL directly interact. ELISA showed that taurine disrupts a pH-dependent interaction between the CT and the CT-proximal half of the CL. These studies reveal that AS disrupt a pH-driven cytoplasmic interdomain interaction in Cx26-containing channels, causing closure, and that the Cx26CT has a modulatory role in Cx26 function.

Original languageEnglish (US)
Pages (from-to)321-339
Number of pages19
JournalJournal of General Physiology
Volume138
Issue number3
DOIs
StatePublished - Sep 2011
Externally publishedYes

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Taurine
Connexins
HEPES
Liposomes
Magnetic Resonance Spectroscopy
Enzyme-Linked Immunosorbent Assay
Ligands
Amino Acids
Peptides

ASJC Scopus subject areas

  • Physiology

Cite this

Mechanism for modulation of gating of connexin26-containing channels by taurine. / Locke, Darren; Kieken, Fabien; Tao, Liang; Sorgen, Paul L.; Harris, Andrew L.

In: Journal of General Physiology, Vol. 138, No. 3, 09.2011, p. 321-339.

Research output: Contribution to journalArticle

Locke, Darren ; Kieken, Fabien ; Tao, Liang ; Sorgen, Paul L. ; Harris, Andrew L. / Mechanism for modulation of gating of connexin26-containing channels by taurine. In: Journal of General Physiology. 2011 ; Vol. 138, No. 3. pp. 321-339.
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