title: Galectin-8 tandem-repeat structure is essential for T-cell proliferation but not for co-stimulation.
abstract: Gal (galectin)-8 is a tandem-repeat Gal containing N-CRDs (Nterminal carbohydrate-recognition domains) and C-CRDs (C-terminal carbohydrate-recognition domains) with differential glycan-binding specificity fused by a linker peptide. Gal-8 has two distinct effects on CD4 T-cells: at high concentrations it induces antigen-independent proliferation, whereas at low concentrations it co-stimulates antigen-specific responses. Associated Gal-8 structural requirements were dissected in the present study. Recombinant homodimers N-N (two N-terminal CRD chimaera) and C-C (two C-terminal CRD chimaera), but not single C-CRDs or N-CRDs, induced proliferation; however, single domains induced co-stimulation. These results indicate that the tandem-repeat structure was essential only for the proliferative effect, suggesting the involvement of lattice formation, whereas co-stimulation could be mediated by agonistic interactions. In both cases, C-C chimaeras displayed higher activity than Gal-8, indicating that the C-CRD was mainly involved, as was further supported by the strong inhibition of proliferation and co-stimulation in the presence of blood group B antigen, specifically recognized by this domain. Classic Gal inhibitors (lactose and thiodigalactoside) prevented proliferation but not co-stimulatory activity, which was inhibited by 3-O-β-D-galactopyranosyl-D-arabinose. Interestingly, Gal-8 induced proliferation of naïve human CD4 T-cells, varying from non- to high-responder individuals, whereas it promoted cell death of phytohaemagglutinin or CD3/CD28 pre-activated cells. The findings of the present study delineate the differential molecular requirements for Gal-8 activities on T-cells, and suggest a dual activity relying on activation state.
authors.affiliation: Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín, San Martin, Argentina.
authors.forename: Valentina
authors.initials: V
authors.lastname: Cattaneo
authors.forename: María V
authors.initials: MV
authors.lastname: Tribulatti
authors.forename: Oscar
authors.initials: O
authors.lastname: Campetella
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D037161:Galectins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins; D013601:T-Lymphocytes / Q000166:cytology* / Q000502:physiology*
chemical_list: D037161:Galectins; D011994:Recombinant Proteins; C526554:galectin-8, mouse