A synthetic channel-forming peptide induces Cl⁻ secretion: modulation by Ca²⁺-dependent K⁺ channels

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• 作者：Wallace ; Darren P. ; Tomich ; John M. ; Eppler ; Jason W. ; Iwamoto ; Takeo ; Grantham ; Jared J. ; et. al.
• 关键词：Chloride channel ; Cystic fibrosis ; Calcium-activated potassium channel
• 刊名：Biochimica et Biophysica Acta (BBA)/Biomembranes
• 出版年：2000
• 出版时间：March 15, 2000
• 年：2000
• 卷：1464
• 期：1
• 页码：69-82
• 全文大小：318 K

文摘

A synthetic Cl⁻ channel-forming peptide, C-K4-M2GlyR, applied to the apical membrane of human epithelial cell monolayers induces transepithelial Cl⁻ and fluid secretion. The sequence of the core peptide, M2GlyR, corresponds to the second membrane-spanning region of the glycine receptor, a domain thought to line the pore of the ligand-gated Cl⁻ channel. Using a pharmacological approach, we show that the flux of Cl⁻ through the artificial Cl⁻ channel can be regulated by modulating basolateral K⁺ efflux through Ca²⁺-dependent K⁺ channels. Application of C-K4-M2GlyR to the apical surface of monolayers composed of human colonic cells of the T84 cell line generated a sustained increase in short-circuit current (I_SC) and caused net fluid secretion. The current was inhibited by the application of clotrimazole, a non-specific inhibitor of K⁺ channels, and charybdotoxin, a potent inhibitor of Ca²⁺-dependent K⁺ channels. Direct activation of these channels with 1-ethyl-2-benzimidazolinone (1-EBIO) greatly amplified the Cl⁻ secretory current induced by C-K4-M2GlyR. The effect of the combination of C-K4-M2GlyR and 1-EBIO on I_SC was significantly greater than the sum of the individual effects of the two compounds and was independent of cAMP. Treatment with 1-EBIO also increased the magnitude of fluid secretion induced by the peptide. The cooperative action of C-K4-M2GlyR and 1-EBIO on I_SC was attenuated by Cl⁻ transport inhibitors, by removing Cl⁻ from the bathing solution and by basolateral treatment with K⁺ channel blockers. These results indicate that apical membrane insertion of Cl⁻ channel-forming peptides such as C-K4-M2GlyR and direct activation of basolateral K⁺ channels with benzimidazolones may coordinate the apical Cl⁻ conductance and the basolateral K⁺ conductance, thereby providing a pharmacological approach to modulating Cl⁻ and fluid secretion by human epithelia deficient in cystic fibrosis transmembrane conductance regulator Cl⁻ channels.