title: Lipid-binding hSH3 domains in immune cell adapter proteins.
abstract: SH3 domains represent versatile scaffolds within eukaryotic cells by targeting proline-rich sequences within intracellular proteins. More recently, binding of SH3 domains to unusual peptide motifs, folded proteins or lipids has been reported. Here we show that the newly defined hSH3 domains of immune cell adapter proteins bind lipid membranes with distinct affinities. The interaction of the hSH3 domains of adhesion and degranulation promoting adapter protein (ADAP) and PRAM-1 (Promyelocytic-Retinoic acid receptor alpha target gene encoding an Adaptor Molecule-1), with phosphatidylcholine-containing liposomes is observed upon incorporation of phosphatidylserine (PS) or phosphoinositides (PIs) into the membrane bilayer. Mechanistically we show that stable association of the N-terminal, amphipathic helix with the beta-sheet scaffold favours lipid binding and that the interaction with PI(4,5)P(2)-containing liposomes is consistent with a single-site, non-cooperative binding mechanism. Functional investigations indicate that deletion of both amphipathic helices of the hSH3 domains reduces the ability of ADAP to enhance adhesion and migration in stimulated T cells.
authors.affiliation: Protein Engineering Group, Leibniz Institute of Molecular Pharmacology and Freie Universität Berlin, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Heuer
authors.forename: Marc
authors.initials: M
authors.lastname: Sylvester
authors.forename: Stefanie
authors.initials: S
authors.lastname: Kliche
authors.forename: Rico
authors.initials: R
authors.lastname: Pusch
authors.forename: Katharina
authors.initials: K
authors.lastname: Thiemke
authors.forename: Burkhart
authors.initials: B
authors.lastname: Schraven
authors.forename: Christian
authors.initials: C
authors.lastname: Freund
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D017951:Antigen Presentation; D002448:Cell Adhesion / Q000276:immunology; D002465:Cell Movement / Q000276:immunology; D006801:Humans; D019169:Jurkat Cells; D050356:Lipid Metabolism / Q000276:immunology*; D011506:Proteins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism*; D018909:src Homology Domains / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C106957:FYB1 protein, human; C430907:PRAM1 protein, human; D011506:Proteins