Cholesterol-dependent regulation of adenosine A_2A receptor-mediated anion secretion in colon epithelial cells

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• 作者：Rebecca S. Lam ; Drew Nahirney ; Marek Duszyk
• 关键词：Anion secretion ; Short-circuit current ; Colonic epithelia ; Co-immunoprecipitation
• 刊名：Experimental Cell Research
• 出版年：2009
• 出版时间：15 October 2009
• 年：2009
• 卷：315
• 期：17
• 页码：3028-3035
• 全文大小：479 K

文摘

Cholesterol affects diverse biological processes, in many cases by modulating the function of integral membrane proteins. In this study we have investigated the role of cholesterol in the adenosine-dependent regulation of ion transport in colonic epithelial cells. We observed that methyl-β-cyclodextrin (MβCD), a cholesterol-sequestering molecule, enhanced adenosine A_2A receptor-activated transepithelial short circuit current (I_sc), but only from the basolateral side. Cholesterol is a major constituent of membrane microdomains, called lipid rafts that also contain sphingolipids. However, studies with the sphingomyelin-degrading enzyme, sphingomyelinase, and the cholesterol-binding agent, filipin, indicated that the change in the level of cholesterol alone was sufficient to control the adenosine-modulated I_sc. Cholesterol depletion had a major effect on the functional selectivity of A_2A receptors. Under control conditions, adenosine activated I_sc more potently than the specific A_2A agonist, CGS-21680, and the current was inhibited by XE991, an inhibitor of cAMP-dependent K⁺ channels. Following cholesterol depletion, CGS-21680 activated I_sc more potently than adenosine, and the current was inhibited by clotrimazole, an inhibitor of Ca²⁺-activated K⁺ (IK1) channels. Co-immunoprecipitation experiments revealed that A_2A receptors associate with IK1 channels following cholesterol depletion. These results suggest that cholesterol content in colonic epithelia affects adenosine-mediated anion secretion by controlling agonist-selective signaling.