You are here: Home :: Area NEM :: Life sciences :: Biochemistry

Xianrong Zhang, Tingting Zou, Yingle Liu, Yipeng Qi

The gating effect of calmodulin and calcium on the connexin50 hemichannel

Keywords: calcium, calmodulin, connexin50, gap junction, hemichannel, patch clamp

Gap junction channels formed by connexin50 (Cx50) are critical for the maintenance of eye lens transparency, which is sensitive to pH and external Ca²⁺ concentration, but the mechanism is still not clear. In this study we performed dye uptake-leakage assays, patch clamping and confocal co-localization experiments to confirm the function of calmodulin (CaM) and Ca²⁺ in the Cx50 hemichannel. Below pH 7.4, lucifer yellow (LY)-preloaded Cx50-HeLa cells allow dye to leak out when washed with Ca²⁺-free solution or incubated in solution containing 50 ?g/ml W7 (CaM inhibitor) first, then washed in solution containing 2 mM Ca²⁺, whereas little or no dye leakage was observed when LY-preloaded Cx50-HeLa cells were incubated in solution containing 2 mM Ca²⁺. Moreover, in the absence of Ca²⁺, polarizing pulses applied to Cx50-HeLa activated outward transmembrane currents, which were inhibited by 2 mM external Ca²⁺. When Cx50-HeLa cells were incubated with 2 mM Ca²⁺and 50 ?g/ml W7, the transmembrane currents were activated again. This indicates that Ca²⁺ and CaM play a gating role in Cx50 hemichannels. Either the chelation of Ca²⁺ or the inhibition of CaM increased the permeability of Cx50 hemichannels. The same phenomena were observed below pH 6.5. Furthermore, CaM could be localized in gap junctions formed by Cx50 below pH 6.5. Our results demonstrate that CaM and Ca²⁺ can cooperate in the gating control of Cx50 hemichannels.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 387, 05/2006
Pages: 595 - 601

Show full article (external site)

Show all available items of this journal

 

Area NEM