کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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2132368 | 1086686 | 2009 | 8 صفحه PDF | دانلود رایگان |
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 A2A receptor-activated transepithelial short circuit current (Isc), 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 Isc. Cholesterol depletion had a major effect on the functional selectivity of A2A receptors. Under control conditions, adenosine activated Isc more potently than the specific A2A agonist, CGS-21680, and the current was inhibited by XE991, an inhibitor of cAMP-dependent K+ channels. Following cholesterol depletion, CGS-21680 activated Isc more potently than adenosine, and the current was inhibited by clotrimazole, an inhibitor of Ca2+-activated K+ (IK1) channels. Co-immunoprecipitation experiments revealed that A2A 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.
Journal: Experimental Cell Research - Volume 315, Issue 17, 15 October 2009, Pages 3028–3035