Differential activity of the CRDs from Galectin-8 on T cells function.

VALENTINA CATTANEO, MARÍA VIRGINIA TRIBULATTI, OSCAR CAMPETELLA

San Diego, California, Estados Unidos

Conferencia; Annual Conference of the Society for Glycobiology; 2009

Society for Glycobiology

Galectin-8 (Gal-8) belongs to the tandem-repeat group of this protein family, containing two distinct carbohydrate recognition domains (CRDs) joined by a linker peptide. We have recently shown that Gal-8 induces two separate biological activities on T lymphocytes: a robust naïve CD4+T cell proliferation in the absence of antigen and a costimulatory signal that synergized the cognate OVA peptide in DO11.10 mice transgenic for TCRova. To unravel the molecular mechanism by which Gal-8 interacts with T cells, naïve mouse splenocytes were incubated in the presence of each separate CRDs (N or C), and two chimeras (N-N or C-C). Whereas N-N induced proliferation similarly to Gal-8, C-C resulted in a 4-fold increased rate. No apparent proliferation was observed with each CRD alone. However, both CRDs and chimeras presented costimulatory effect on antigen-specific T cell activation, also being C-C the strongest activator. These results showed that C terminal is the principal CRD implicated in Gal-8 functions on T cells and, moreover, that the dimeric structure seems essential for antigen-independent T cell proliferations but not for the costimulatory actitvity. In agreement with these findings, the proliferative effect was inhibited in the presence of lactose, meanwhile costimulative properties was unaffected by lactose or thiodigalactoside but inhibited by other beta-galactoside derivatives which are currently being tested as alternative inhibitors of Gal-8. Affinity-chromatography assays followed by MALDI-MS analysis were also conducted to identify specific binders on mouse CD4+T cells for each CRD.