EWI-2 is a new component of the tetraspanin web in hepatocytes and lymphoid cells

• Published in: Biochemical journal 2003-07, Vol.373 (Pt 2), p.409-421
• Main Authors: Charrin, Stéphanie, Le Naour, François, Labas, Valérie, Billard, Martine, Le Caer, Jean-Pierre, Emile, Jean-François, Petit, Marie-Anne, Boucheix, Claude, Rubinstein, Eric
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Monoclonal; Antigens, CD - metabolism; CHO Cells; Cricetinae; DNA Primers; Fluorescent Antibody Technique; Hepatocytes - metabolism; Hepatocytes - pathology; Humans; Immunoglobulins - immunology; Immunoglobulins - metabolism; Lymphocytes - metabolism; Lymphocytes - pathology; Membrane Glycoproteins - metabolism; Membrane Proteins - metabolism; Mice; Mice, Inbred BALB C; Microscopy, Confocal; Molecular Sequence Data; Plasmids; Polymerase Chain Reaction; Precipitin Tests; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Tetraspanin 28; Tetraspanin-29; Tumor Cells, Cultured
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj20030343

Several tetraspanins bind directly to a few molecular partners to form primary complexes, which might assemble through tetraspanin-tetraspanin interactions to form a network of molecular interactions, the tetraspanin web. We have produced a monoclonal antibody directed to a 63 kDa molecule (determined under non-reducing conditions) associated with CD9. This molecule was first identified by MS as a molecule with four Ig domains, EWI-2. Like the related molecule CD9P-1, EWI-2 was found to be a partner not only for CD9, but also for CD81, a tetraspanin required for hepatic infection by the parasite responsible for malaria, and also a putative hepatitis C virus receptor. Using chimaeric CD9/CD82 molecules, two separate regions of CD9 of 40 and 47 amino acids were demonstrated to confer the ability to interact with EWI-2. Both EWI-2 and CD9P-1 were detected in the human liver at the surface of hepatocytes and were found to associate with CD81 on freshly isolated hepatocytes. EWI-2 also co-localized with CD81 in the liver. CD9P-1 was not detected on most peripheral blood cells, whereas EWI-2 was expressed on the majority of B-, T- and natural killer cells and was not detected on monocytes, polynuclear cells or platelets. This distribution is identical to that of CD81. Finally, EWI-2 associated with all tetraspanins studied after lysis under conditions preserving tetraspanin-tetraspanin interactions, showing that EWI-2 is a new component of the tetraspanin web.