Submitted on November 13, 2006
Revised on March 15, 2007
Accepted on March 26, 2007
Fc
RI and Thy-1 domains have unique protein and lipid compositions
Zurab Surviladze, Kathleen A. Harrison, Robert C. Murphy, and Bridget S. Wilson
Dept of Pathology, University of New Mexico, Albuquerque, NM 87131
Corresponding Author: bwilson{at}salud.unm.edu
Receptor activation leads to the dynamic remodeling of the plasma membrane. Previous work using immunoelectron microscopy showed that aggregated Fc
RI and aggregated Thy-1, a GPI-anchored protein, occupy distinct membrane distributions. We now report lipidomics analysis of FceRI and Thy-1 enriched vesicles obtained by magnetic bead isolation in the absence of detergent. Protein analyses show that FceRI domains are enriched in receptors and associated signaling molecules, while Thy-1 domains are devoid of FceRI subunits. Positive and negative ion electrospray mass spectrometry demonstrated that both domains retained a complex mixture of phospholipid classes and molecular species, predominately glycerophosphocholine (GPC), glycerophosphoethanolamine (GPE), and sphingomyelin (SM) as well as glycerophosphoserine (GPS) and glycerophosphoinositol (GPI) lipids. Analysis of total acyl groups show <50% of fatty acids in these domains are fully saturated, inconsistent with recruitment of aggregated receptors or GPI-anchored proteins to liquid ordered domains. However, further analysis showed that FceRI domains contain 2 times more sphingomyelin and a high ratio of cholesterol to total fatty acid content, compared to Thy 1-enriched domains. Remarkably, plasmenylglycerophosphoethanolamine phospholipids (plasmalogen GPE) were also 2.5-3 times more abundant in FceRI domains than in the Thy-1 microdomains, while most diacyl GPE molecular species were equally abundant in the two domains.
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