Our research group studies the mechanisms that regulate normal and malignant leukocyte interactions with endothelial cells. We demonstrated that the three selectins interact with their major ligand P-selectin glycoprotein ligand-1 (PSGL-1) to support leukocyte rolling along inflamed vessels and showed that E-selectin interact with several distinct ligands to mediate normal leukocytes and leukemia cell adhesion. During leukocyte rolling on endothelial selectins and ICAM-1 we observed that selectin interactions with their ligands induces aLß2-dependent leukocyte slow rolling mediated through the activation of Src family kinases wich play a critical role in regulating leukocyte adhesion.
Study of PSGL-1 structure/function relationship
To analyze the relationship between PSGL-1structure and function, we constructed several PSGL-1 mutants by swapping CD44 and PSGL-1 mutants by swapping CD44 and PGSGL-1 extracellular or cytoplasmic domains and generalted deletion mutantsdevoid of highly evolutionary conserved sequences of the cytoplasmic domain. We have identified a new motif involved in PSGL-1 export from the endoplasmic reticulum. Other studies assessing the involvement of various cytoplsmic sequences in the regulation of endoplasmic reticulum. Other studies assessing the involvement of various cytoplasmic sequences in the regulation of PSGL-1 dependent adhesion and activation of MAPK and Src family kinase pathways are currently under investigation.
Identification ofselectin ligands on acute leukemia and multiple myeloma cells
Selectins interact through their amino-terminal lectin domain with fucosylated carbohydrate determinants like sialyl-Lewis* and related fucosylated carbohydrates (Lewis* and the cutaneous lymphocyte antigen, CLA) carried on N- or O-glycan chains attached to glycoprotein lignads. By immunoprecipitating E-selectin ligands using E-selectin/IgM chimeric molecule as probe and by performing blot rolling assays we identified PSGL-1, CD44 and CD43 and other ligands as E-selectin ligands on acute leukemia and multiple myeloma cells. we are currently studying their respective involvement in generating intracellular signals promoting cell survival, proliferation and drug resistance.
Identification of fucosyltransferase involved in the biosynthesis of selectin ligands
Selectins interact with glycoconjugated ligands carrying fucosylated carbohydrate determinants. Among these ligands, several glycoproteins play a major role in supporting leukocyte rolling. However several observations indicate that glycolipids may also be involved. We compared the contribution of several fucosyltransferases in the biosynthsis of selectin ligands and identified one of them mainly involved in synthetizing glycolipid ligands of E-selectin. We are curretly studying the involvement of this enzyme in generating ligands supporting shear-resistant leukocyte rolling.