Clustering and lateral concentration of raft lipids by the MAL protein

Lee Goldstein Magal, Yakey Yaffe, Jeanne Shepshelovich, Juan Francisco Aranda, Maria Del Carmen De Marco, Katharina Gaus, Miguel Angel Alonso, Koret Hirschberg

Research output: Contribution to journalArticlepeer-review

Abstract

MAL, a compact hydrophobic, four-transmembrane-domain apical protein that copurifies with detergent-resistant membranes is obligatory for the machinery that sorts glycophosphatidylinositol (GPI)-anchored proteins and others to the apical membrane in epithelia. The mechanism of MAL function in lipid-raft-mediated apical sorting is unknown. We report that MAL clusters formed by two independent procedures - spontaneous clustering of MAL tagged with the tandem dimer DiHcRED (DiHcRED-MAL) in the plasma membrane of COS7 cells and antibody-mediated cross-linking of FLAG-tagged MAL - laterally concentrate markers of sphingolipid rafts and exclude a fluorescent analogue of phosphatidylethanolamine. Site-directed mutagenesis and bimolecular fluorescence complementation analysis demonstrate that MAL forms oligomers via φxxφ intramembrane protein-protein binding motifs. Furthermore, results from membrane modulation by using exogenously added cholesterol or ceramides support the hypothesis that MAL-mediated association with raft lipids is driven at least in part by positive hydrophobic mismatch between the lengths of the transmembrane helices of MAL and membrane lipids. These data place MAL as a key component in the organization of membrane domains that could potentially serve as membrane sorting platforms.

Original languageEnglish
Pages (from-to)3751-3762
Number of pages12
JournalMolecular Biology of the Cell
Volume20
Issue number16
DOIs
StatePublished - 15 Aug 2009

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