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Papers In Press, published online ahead of print June 1, 2007
J. Lipid Res., doi:10.1194/jlr.M600485-JLR200

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Journal of Lipid Research, Vol. 48, 1325-1335, June 2007
Copyright © 2007 by American Society for Biochemistry and Molecular Biology

FcRI and Thy-1 domains have unique protein and lipid compositions

Zurab Surviladze^*, Kathleen A. Harrison, Robert C. Murphy and Bridget S. Wilson^1,*

^* Department of Pathology, University of New Mexico, Albuquerque, NM
Department of Pharmacology, University of Colorado at Denver and Health Sciences Center, Aurora, CO

The online version of this article (available at http://www.jlr.org) contains supplementary data in the form of three figures and two tables.

Published, JLR Papers in Press, March 26, 2007.

¹ To whom correspondence should be addressed. e-mail: bwilson{at}salud.unm.edu

Receptor activation leads to the dynamic remodeling of the plasma membrane. Previous work using immunoelectron microscopy showed that aggregated high-affinity receptor for immunoglobulin E (FcRI) and aggregated Thy-1, a glycerophosphoinositol (GPI)-anchored protein, have distinct membrane distributions. We now report lipidomics analysis of FcRI- and Thy-1-enriched vesicles obtained by magnetic bead isolation in the absence of detergent. Protein analyses show that FcRI domains are enriched in receptors and associated signaling molecules, whereas Thy-1 domains are devoid of FcRI subunits. Positive and negative ion electrospray mass spectrometry demonstrated that both domains retained a complex mixture of phospholipid classes and molecular species, predominantly glycerophosphocholine, glycerophosphoethanolamine (GPE), and sphingomyelin as well as glycerophosphoserine and GPI lipids. Analysis of total acyl groups showed that <50% of fatty acids in these domains are fully saturated, inconsistent with the recruitment of aggregated receptors or GPI-anchored proteins to liquid ordered domains. However, further analysis showed that FcRI domains contain two times more sphingomyelin and a high ratio of cholesterol to total fatty acid content compared with Thy 1-enriched domains. Remarkably, plasmenyl glycerophosphoethanolamine phospholipids (plasmalogen GPE) were also 2.5–3 times more abundant in FcRI domains than in the Thy-1 microdomains, whereas most diacyl GPE molecular species were equally abundant in the two domains.

Supplementary key words lipidomics • membrane microdomains • lipid rafts • immunoglobulin E receptor • glycerophosphoinositol-anchored proteins

Abbreviations: DRM, detergent-resistant membrane; ESI, electrospray ionization; FcRI, high-affinity receptor for immunoglobulin E; GPC, glycerophosphocholine; GPE, glycerophosphoethanolamine; GPI, glycerophosphoinositol; GPS, glycerophosphoserine; MßCD, methyl-ß-cyclodextrin; MS/MS, tandem mass spectrometry

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