title: Interaction of actin with carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) receptor in liposomes is Ca2+- and phospholipid-dependent.
abstract: The regulation of binding of G-actin to cytoplasmic domains of cell surface receptors is a common mechanism to control diverse biological processes. To model the regulation of G-actin binding to a cell surface receptor we used the cell-cell adhesion molecule carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1-S) in which G-actin binds to its short cytoplasmic domain (12 amino acids; Chen, C. J., Kirshner, J., Sherman, M. A., Hu, W., Nguyen, T., and Shively, J. E. (2007) J. Biol. Chem. 282, 5749-5760). A liposome model system demonstrates that G-actin binds to the cytosolic domain peptide of CEACAM1-S in the presence of negatively charged palmitoyl-oleoyl phosphatidylserine (POPS) liposomes and Ca(2+). In contrast, no binding of G-actin was observed in palmitoyl-oleoyl phosphatidylcholine (POPC) liposomes or when a key residue in the peptide, Phe-454, is replaced with Ala. Molecular Dynamics simulations on CEACAM1-S in an asymmetric phospholipid bilayer show migration of Ca(2+) ions to the lipid leaflet containing POPS and reveal two conformations for Phe-454 explaining the reversible availability of this residue for G-actin binding. NMR transverse relaxation optimized spectroscopic analysis of (13)C-labeled Phe-454 CEACAM1-S peptide in liposomes plus actin further confirmed the existence of two peptide conformers and the Ca(2+) dependence of actin binding. These findings explain how a receptor with a short cytoplasmic domain can recruit a cytosolic protein in a phospholipid and Ca(2+)-specific manner. In addition, this model system provides a powerful approach that can be applied to study other membrane protein interactions with their cytosolic targets.
authors.affiliation: Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, Duarte, California 91010, USA.
authors.forename: Rongze
authors.initials: R
authors.lastname: Lu
authors.forename: Michiel J M
authors.initials: MJ
authors.lastname: Niesen
authors.forename: Weidong
authors.initials: W
authors.lastname: Hu
authors.forename: Nagarajan
authors.initials: N
authors.lastname: Vaidehi
authors.forename: John E
authors.initials: JE
authors.lastname: Shively
mesh_terms: D000199:Actins / Q000378:metabolism*; D015703:Antigens, CD / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D016000:Cluster Analysis; D008081:Liposomes; D009682:Magnetic Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding; D020349:Surface Plasmon Resonance
chemical_list: D000199:Actins; D015703:Antigens, CD; C069847:CD66 antigens; D015815:Cell Adhesion Molecules; D008081:Liposomes; D010743:Phospholipids