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The gating effect of calmodulin and calcium on the connexin50 hemichannel

  • Xianrong Zhang , Tingting Zou , Yingle Liu and Yipeng Qi
Published/Copyright: June 1, 2006
Biological Chemistry
From the journal Volume 387 Issue 5

Abstract

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 μg/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 μg/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.

Keywords: calcium; calmodulin; connexin50; gap junction; hemichannel; patch clamp
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Published Online: 2006-06-01
Published in Print: 2006-05-01

©2006 by Walter de Gruyter Berlin New York

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https://doi.org/10.1515/BC.2006.076
Keywords for this article
calcium; calmodulin; connexin50; gap junction; hemichannel; patch clamp

Articles in the same Issue

  1. Protein aggregation in crowded environments
  2. Nitrite, a naturally occurring precursor of nitric oxide that acts like a ‘prodrug’
  3. Functional studies of the small subunit of EcoHK31I DNA methyltransferase
  4. Functional analysis of amino acid residues at the dimerisation interface of KpnI DNA methyltransferase
  5. Conformation and stability of the Streptococcus pyogenes pSM19035-encoded site-specific β recombinase, and identification of a folding intermediate
  6. Tyr-48, a conserved residue in ribotoxins, is involved in the RNA-degrading activity of α-sarcin
  7. Pathogenicity of catalytic antibodies: catalytic activity of Bence Jones proteins from myeloma patients with renal impairment can elicit cytotoxic effects
  8. Transgenic expression of gallerimycin, a novel antifungal insect defensin from the greater wax moth Galleria mellonella, confers resistance to pathogenic fungi in tobacco
  9. Catalytic pathways of Euphorbia characias peroxidase reacting with hydrogen peroxide
  10. Biochemical and pharmacological characterization of the human bradykinin subtype 2 receptor produced in mammalian cells using the Semliki Forest virus system
  11. A spectroscopic analysis of the interaction between the human regulatory proteins RACK1 and Ki-1/57
  12. Subcellular localisation of human inositol 1,4,5-trisphosphate 3-kinase C: species-specific use of alternative export sites for nucleo-cytoplasmic shuttling indicates divergent roles of the catalytic and N-terminal domains
  13. The gating effect of calmodulin and calcium on the connexin50 hemichannel
  14. C-Terminal fusion of eGFP to the bradykinin B2 receptor strongly affects down-regulation but not receptor internalization or signaling
  15. Angiotensin I-converting enzyme inhibitor peptides derived from the endostatin-containing NC1 fragment of human collagen XVIII
  16. μ-Calpain binds to lipid bilayers via the exposed hydrophobic surface of its Ca2+-activated conformation
  17. Cathepsin L splice variants in human breast cell lines
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