title: The adhesion protein TAG-1 has a ganglioside environment in the sphingolipid-enriched membrane domains of neuronal cells in culture.
abstract: We studied the interactions between gangliosides and proteins at the exoplasmic surface of the sphingolipid-enriched membrane domains by ganglioside photolabeling combined with cell surface biotin labeling. After cell photolabeling with radioactive photoactivable derivatives of GM3, GM1 and GD1b gangliosides, followed by cell surface biotin labeling, sphingolipid-enriched domains were prepared and immunoprecipitated with streptavidin-coupled beads, under experimental conditions preserving the integrity of the lipid domain. About 50% of the total radioactivity linked to proteins was associated with acylated tubulin, about 10% with a 135-kDa protein present as a series of species with pI ranging from 6.5 to 8.0, about 5% with a protein of about 70 kDa and with pI near to 6.5. By immunoprecipitation with streptavidin-coupled beads under conditions disrupting the integrity of the lipid domain, the 135 kDa protein was recovered in the immunoprecipitate, that did not contain tubulin. Thus, the 135 kDa protein has an exoplasmic domain, and it was then identified as the GPI-anchored neural cell adhesion molecule TAG-1. Remarkably, TAG-1 was cross-linked in a similar extent by the photoactivated ganglioside GM3, GM1 and GD1b. The three gangliosides bear different oligosaccharide chains, suggesting that the ganglioside/TAG-1 interaction is not specifically associated with the ganglioside oligosaccharide structure.
authors.affiliation: Center of Excellence on Neurodegenerative Diseases, Study Center for the Biochemistry and Biotechnology of Glycolipids, Department of Medical Chemistry, Biochemistry and Biotechnology, University of Milan, Segrate, Italy.
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Loberto
authors.forename: Simona
authors.initials: S
authors.lastname: Prioni
authors.forename: Alessandro
authors.initials: A
authors.lastname: Prinetti
authors.forename: Elena
authors.initials: E
authors.lastname: Ottico
authors.forename: Vanna
authors.initials: V
authors.lastname: Chigorno
authors.forename: Domna
authors.initials: D
authors.lastname: Karagogeos
authors.forename: Sandro
authors.initials: S
authors.lastname: Sonnino
mesh_terms: D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D002531:Cerebellum / Q000166:cytology; D058969:Contactin 2; D004591:Electrophoresis, Polyacrylamide Gel; D005677:G(M1) Ganglioside / Q000737:chemistry / Q000378:metabolism; D005679:G(M3) Ganglioside / Q000737:chemistry / Q000378:metabolism; D005732:Gangliosides / Q000737:chemistry / Q000378:metabolism*; D009474:Neurons / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D010777:Photochemistry; D011233:Precipitin Tests; D051381:Rats; D017207:Rats, Sprague-Dawley; D013107:Sphingolipids / Q000737:chemistry / Q000378:metabolism*; D013347:Subcellular Fractions / Q000737:chemistry
chemical_list: D015816:Cell Adhesion Molecules, Neuronal; D058969:Contactin 2; D005679:G(M3) Ganglioside; D005732:Gangliosides; D013107:Sphingolipids; C033851:ganglioside, GD1b; D005677:G(M1) Ganglioside