CD45 Modulates Galectin-1-Induced T Cell Death: Regulation by Expression of Core 2 O -Glycans

Abstract

Galectin-1 induces death of immature thymocytes and activated T cells. Galectin-1 binds to T cell-surface glycoproteins CD45, CD43, and CD7, although the precise roles of each receptor in cell death are unknown. We have determined that CD45 can positively and negatively regulate galectin-1-induced T cell death, depending on the glycosylation status of the cells. CD45+ BW5147 T cells lacking the core 2 β-1,6-N-acetylglucosaminyltransferase (C2GnT) were resistant to galectin-1 death. The inhibitory effect of CD45 in C2GnT− cells appeared to require the CD45 cytoplasmic domain, because Rev1.1 cells expressing only CD45 transmembrane and extracellular domains were susceptible to galectin-1 death. Moreover, treatment with the phosphotyrosine-phosphatase inhibitor potassium bisperoxo(1,10-phenanthroline)oxovanadate(V) enhanced galectin-1 susceptibility of CD45+ T cell lines, but had no effect on the death of CD45− T cells, indicating that the CD45 inhibitory effect involved the phosphatase domain. Expression of the C2GnT in CD45+ T cell lines rendered the cells susceptible to galectin-1, while expression of the C2GnT in CD45− cells had no effect on galectin-1 susceptibility. When CD45+ T cells bound to galectin-1 on murine thymic stromal cells, only C2GnT+ T cells underwent death. On C2GnT+ cells, CD45 and galectin-1 co-localized in patches on membrane blebs while no segregation of CD45 was seen on C2GnT− T cells, suggesting that oligosaccharide-mediated clustering of CD45 facilitated galectin-1-induced cell death.