Novel Acid-Activated Fluorophores Reveal a Dynamic Wave of Protons in the Intestine of Caenorhabditis elegans

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• 作者：Aaron Bender ; Zachary R. Woydziak ; Liqiang Fu ; Michael Branden ; Zhenguo Zhou ; Brian D. Ackley ; Blake R. Peterson
• 刊名：ACS Chemical Biology
• 出版年：2013
• 出版时间：March 15, 2013
• 年：2013
• 卷：8
• 期：3
• 页码：636-642
• 全文大小：570K
• 年卷期：v.8,no.3(March 15, 2013)
• ISSN：1554-8937

文摘

Unlike the digestive systems of vertebrate animals, the lumen of the alimentary canal of Caenorhabditis elegans is unsegmented and weakly acidic (pH 4.4), with ultradian fluctuations to pH > 6 every 45鈥?0 s. To probe the dynamics of this acidity, we synthesized novel acid-activated fluorophores termed Kansas Reds. These dicationic derivatives of rhodamine B become concentrated in the lumen of the intestine of living C. elegans and exhibit tunable pK_a values (2.3鈥?.4), controlled by the extent of fluorination of an alkylamine substituent, that allow imaging of a range of acidic fluids in vivo. Fluorescence video microscopy of animals freely feeding on these fluorophores revealed that acidity in the C. elegans intestine is discontinuous; the posterior intestine contains a large acidic segment flanked by a smaller region of higher pH at the posterior-most end. Remarkably, during the defecation motor program, this hot spot of acidity rapidly moves from the posterior intestine to the anterior-most intestine where it becomes localized for up to 7 s every 45鈥?0 s. Studies of pH-insensitive and base-activated fluorophores as well as mutant and transgenic animals revealed that this dynamic wave of acidity requires the proton exchanger PBO-4, does not involve substantial movement of fluid, and likely involves the sequential activation of proton transporters on the apical surface of intestinal cells. Lacking a specific organ that sequesters low pH, C. elegans compartmentalizes acidity by producing of a dynamic hot spot of protons that rhythmically migrates from the posterior to anterior intestine.