Phosphatidic Acid and Phosphatidylserine Have Distinct Structural and Functional Interactions with the Nicotinic Acetylcholine Receptor

daCosta, Corrie J.B.; Wagg, Ian D.; McKay, Marlene E.; Baenziger, John E.

doi:10.1074/jbc.m310037200

Cited by 59 publications

(52 citation statements)

References 22 publications

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“…Hence, the lipid ordering is unlikely a dominant factor that affects the protein functions. The requirement of the presence of both PA and CHOL for fully functional nAChR 9,11 implies the importance of potential interplay between PA and CHOL. Although it is impossible to assess synergetic effects of POPA and CHOL on nAChR in a system without the presence of nAChR, the close interactions of POPA and CHOL observed in our current system implicated the possibility for producing their synergetic effects and the necessity for further investigation along the line.…”

Section: Lipid Orderingmentioning

confidence: 99%

“…The anionic lipid phosphatidic acid (PA) and cholesterol (CHOL) are proved to be critical components to restore nAChR's full functionality, including ligand binding and ion translocation, in reconstitution lipid mixtures [6][7][8][9][10] . Other anionic lipids, such as phosphatidylserine (PS) and phosphatidylinositol (PI), showed lower efficacy than PA in stabilizing nAChR in the resting state, though they are much more abundant in native Torpedo membranes 10,11 .…”

Section: Introductionmentioning

confidence: 99%

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Molecular Dynamics Simulations of Ternary Membrane Mixture: Phosphatidylcholine, Phosphatidic Acid, and Cholesterol

et al. 2007

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A ternary mixture of 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC), 1-palmitoyl-2-oleoyl phosphatidic acid (POPA), and cholesterol (CHOL) works effectively for a functional conformation of nicotinic acetylcholine receptor (nAChR) that can undergo agonist-induced conformation changes, but POPC alone can stabilize only a desensitized state of nAChR. To gain insights into the lipid mixture that have strong impact to nAChR functions, we performed more than 50-ns all atom molecular dynamic (MD) simulations at 303 K on a fully hydrated bilayer consisting of 240 POPC, 80 POPA, and 80 CHOL (3:1:1). The MD simulation revealed various interactions between different types of molecular pairs that ultimately regulated lipid organization. The heterogeneous interactions among three different constituents resulted in a broad spectrum of lipid properties, including extensive distribution of average area per lipids and varied lipid ordering as a function of lipid closeness to CHOL. Higher percentage of POPA than POPC had close association with CHOL, which coincided with relatively higher ordering of POPA molecules in their acyl chains near lipid head groups. Lower fraction of gauche dihedrals was also found in the same region of POPA. Although the CHOL molecules had the effects on the enhancement of surrounding lipid order, relatively low lipid order parameters and high fraction of gauche bonds were observed in the ternary mixture. Collectively, these results suggest that the dynamical structure of the ternary system could be determinant for a functional nAChR.

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Section: Lipid Orderingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of Ternary Membrane Mixture: Phosphatidylcholine, Phosphatidic Acid, and Cholesterol

et al. 2007

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“…However, inclusion of both cholesterol (CH) and phosphatidic acid (PA) with PC membranes (PC/PA/CH) completely restores nAChR functionality (7,9,10). Membranes containing PA or CH alone, that is PC/PA or PC/CH, are able to stabilize differing proportions of nAChRs in the resting state, though clearly the presence of both lipids is required for full functionality (9,11). The amount of PA present in native Torpedo membranes is relatively low (∼0.3 mol% on a molar basis; in Ref.…”

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confidence: 99%

Assessing the Lipid Requirements of theTorpedo californicaNicotinic Acetylcholine Receptor

et al. 2006

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The lipid requirements of the Torpedo californica nicotinic acetylcholine receptor (nAChR) were assessed by reconstituting purified receptors into lipid vesicles of defined composition and by using photolabeling with 3-trifluoromethyl-3-(m-[ 125 I]iodophenyl) diazirine ([ 125 I]TID) to determine functionality. Earlier studies demonstrated that nAChRs reconstituted into membranes containing phosphatidylcholine (PC), the anionic lipid phosphatidic acid (PA) and cholesterol (CH) are particularly effective at stabilizing the nAChR in the resting (closed) state that is capable of undergoing agonist-induced conformational transitions (i.e. functionality). The present studies demonstrate that: (1) there is no obligatory requirement for PC; (2) that increasing the CH content serves to increase the degree to which nAChRs are stabilized in the resting state, this effect saturates at ∼ 35 mol% (molar lipid percentage); (3) the effect of increasing levels of PA saturates at ∼12 mol % and in the absence of PA nAChRs are stabilized in the desensitized state (i.e. nonfunctional). Native Torpedo membranes contain ∼35 mol% CH but less than 1 mol% PA, suggesting that other anionic lipid may substitute for PA. We report that: (4) phosphatidylserine (PS) and phosphatidylinositol (PI), anionic lipids that are abundant in native Torpedo membranes, also stabilize the receptor in the resting state although with reduced efficacy (∼50-60%) compared to PA; (5) For nAChRs reconstituted into PA/CH membranes at different lipid-protein molar ratios, receptor functionality decreases rapidly below ∼65 lipids per receptor. Collectively, these results are consistent with a functional requirement of a single shell of lipids surrounding the nAChR and specific anionic lipid-and sterol-(CH) protein interactions.The agonist-induced conformational transitions that underlie the function of the Torpedo nicotinic acetylcholine receptor (nAChR) have been shown to be highly dependent on the surrounding lipid environment, providing a model system for understanding lipid-protein interactions (1-3). The nAChR is the best characterized member of a superfamily of ligandgated ion channels (LGIC) that includes muscle-and neuronal-type nAChRs, serotonin 5-HT 3 receptors, gamma-amino butyric acid type A receptors (GABA A ), and glycine receptors (4,5). The Torpedo (muscle-type) nAChR is a pentameric multispanning transmembrane protein comprised of four homologous subunits with a subunit stoichiometry of 2α:β:γ:δ that are arranged pseudosymetrically around a central axis forming an ion-conducting channel. In

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“…The AChR was purified by affinity chromatography in the presence of synthetic lipids (45,46). Briefly, the affinity column was prepared by coupling cystamine to Affi-Gel 10, reduction with dithiothreitol, and final modification with bromoacetylcholine bromide.…”

Section: Methodsmentioning

confidence: 99%

Modulation of Nicotinic Acetylcholine Receptor Conformational State by Free Fatty Acids and Steroids

Nievas

Barrantes

Antollini

2008

Journal of Biological Chemistry

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Steroids and free fatty acids (FFA) are noncompetitive antagonists of the nicotinic acetylcholine receptor (AChR). Their site of action is purportedly located at the lipid-AChR interface, but their exact mechanism of action is still unknown. Here we studied the effect of structurally different FFA and steroids on the conformational equilibrium of the AChR in Torpedo californica receptor-rich membranes. We took advantage of the higher affinity of the fluorescent AChR open channel blocker, crystal violet, for the desensitized state than for the resting state. Increasing concentrations of steroids and FFA decreased the K D of crystal violet in the absence of agonist; however, only cisunsaturated FFA caused an increase in K D in the presence of agonist. This latter effect was also observed with treatments that caused the opposite effects on membrane polarity, such as phospholipase A 2 treatment or temperature increase (decreasing or increasing membrane polarity, respectively). Quenching by spin-labeled fatty acids of pyrene-labeled AChR reconstituted into model membranes, with the label located at the ␥M4 transmembrane segment, disclosed the occurrence of conformational changes induced by steroids and cis-unsaturated FFA. The present work is a step forward in understanding the mechanism of action of this type of molecules, suggesting that the direct contact between exogenous lipids and the AChR transmembrane segments removes the AChR from its resting state and that membrane polarity modulates the AChR activation equilibrium by an independent mechanism.

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Phosphatidic Acid and Phosphatidylserine Have Distinct Structural and Functional Interactions with the Nicotinic Acetylcholine Receptor

Cited by 59 publications

References 22 publications

Molecular Dynamics Simulations of Ternary Membrane Mixture: Phosphatidylcholine, Phosphatidic Acid, and Cholesterol

Molecular Dynamics Simulations of Ternary Membrane Mixture: Phosphatidylcholine, Phosphatidic Acid, and Cholesterol

Assessing the Lipid Requirements of theTorpedo californicaNicotinic Acetylcholine Receptor

Modulation of Nicotinic Acetylcholine Receptor Conformational State by Free Fatty Acids and Steroids

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