Plasma Membrane Cholesterol Content Affects Nitric Oxide Diffusion Dynamics and Signaling*
Journal - Journal of Biological Chemistry
Nitric oxide (NO) signaling is inextricably linked to both itsphysical and chemical properties. Due to its preferentiallyhydrophobic solubility, NO molecules tend to partition fromthe aqueous milieu into biological membranes. We hypothesizedthat plasma membrane ordering provided by cholesterol furthercouples the physics of NO diffusion with cellular signaling.Fluorescence lifetime quenching studies with pyrene liposomepreparations showed that the presence of cholesterol decreasedapparent diffusion coefficients of NO 20–40%, dependingon the phospholipid composition. Electrochemical measurementsindicated that the diffusion rate of NO across artificial bilayermembranes were inversely related to cholesterol content. Steroltransport-defective Niemann-Pick type C1 (NPC1) fibroblastsexhibited increased plasma membrane cholesterol content butdecreased activation of both intracellular soluble guanylylcyclase and vasodilator-stimulated phosphoprotein (VASP) phosphorylationat Ser239 induced by exogenous NO exposure relative to theirnormal human fibroblast (NHF) counterparts. Augmentation ofplasma membrane cholesterol in NHF diminished production ofboth cGMP and VASP phosphorylation elicited by NO to NPC1-comparablelevels. Conversely, decreasing membrane cholesterol in NPC1resulted in the augmentation in both cGMP and VASP phosphorylationto a level similar to those observed in NHF. Increasing plasmamembrane cholesterol contents in NHF, platelets, erythrocytesand tumor cells also resulted in an increased level of extracellulardiaminofluorescein nitrosation following NO exposure. Thesefindings suggest that the impact of cholesterol on membranefluidity and microdomain structure contributes to the spatialheterogeneity of NO diffusion and signaling.* This work was authored, in whole or in part, by National Institutesof Health staff. This work was supported by a National Suborbitaland Educational Research Center (NSERC) Discovery Grant (toM. G. E.) and a Canadian Institutes of Health Research operating(bridging) grant (to B. M.). The costs of publication of thisarticle were defrayed in part by the payment of page charges.This article must therefore be hereby marked "advertisement"inaccordance with 18 U.S.C. Section 1734 solely to indicate thisfact.