title: Direct interaction between the Lu/B-CAM adhesion glycoproteins and erythroid spectrin.
abstract: Lutheran (Lu) and Lu(v13), two glycoprotein (gp) isoforms belonging to the immunoglobulin superfamily, represent adhesion molecules that act as erythrocyte receptors for laminin 10/11. These two gps, which differ only by the length of their cytoplasmic tail, carry both Lu blood group and Basal Cell Adhesion Molecule (B-CAM) antigens. Here, analysis of the Triton extractability of recombinant Lu and Lu(v13) gps in K562 transfected cells showed that both gps were mainly associated with the detergent-insoluble material. Patching experiments using Cholera Toxin subunit B indicated that Lu gps were not localized in lipid rafts. Glutathione-S-transferase capture assays showed that the cytoplasmic domain of Lu and Lu(v13) bound to erythroid spectrin, present in a low ionic strength extract from red cell ghosts. Direct interaction with spectrin was confirmed by plasmon resonance assays. Site-directed mutagenesis mapped a major interaction site with spectrin to the RK573-574 motif, located on the cytoplasmic tail of Lu gp, in close vicinity to the inner leaflet of the membrane lipid bilayer. The two Lu adhesion gps represent the first example of a direct link between transmembrane proteins and spectrin in red blood cells. Since Lu gps are low abundant proteins, we speculate that their interaction with spectrin might be critical for signalling and receptor function rather than for participating in the linkage of the lipid bilayer to the red cell skeleton.
authors.affiliation: INSERM U76, Institut National de la Transfusion Sanguine, Paris, France. levankim@idf.inserm.fr
authors.forename: Yolande
authors.initials: Y
authors.lastname: Kroviarski
authors.forename: Wassim
authors.initials: W
authors.lastname: El Nemer
authors.forename: Pierre
authors.initials: P
authors.lastname: Gane
authors.forename: Cécile
authors.initials: C
authors.lastname: Rahuel
authors.forename: Emilie
authors.initials: E
authors.lastname: Gauthier
authors.forename: Marie Christine
authors.initials: MC
authors.lastname: Lecomte
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Cartron
authors.forename: Yves
authors.initials: Y
authors.lastname: Colin
authors.forename: Caroline
authors.initials: C
authors.lastname: Le Van Kim
mesh_terms: D015153:Blotting, Western; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000737:chemistry*; D004913:Erythrocytes, Abnormal / Q000378:metabolism; D006801:Humans; D007797:Laminin / Q000378:metabolism*; D008051:Lipid Bilayers; D008188:Lutheran Blood-Group System; D008856:Microscopy, Fluorescence; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins / Q000378:metabolism*; D013049:Spectrin / Q000378:metabolism*
chemical_list: C090228:BCAM protein, human; D015815:Cell Adhesion Molecules; D007797:Laminin; D008051:Lipid Bilayers; D008188:Lutheran Blood-Group System; D009363:Neoplasm Proteins; C119013:laminin 10; D013049:Spectrin