Characterization of Galectin-9-Induced Death of Jurkat T Cells

Abstract

Galectin-9, a mammalian lectin with affinity for beta-galactosides, is known as an apoptosis inducer of activated T lymphocytes. In the present study, we examined the properties of galectin-9-mediated cell death of Jurkat T cells. Galectin-9NC (wild-type), consisting of two CRDs (N-terminal and C-terminal carbohydrate recognition domains), and derivatives of it, galectins-9-NN and -9-CC, induced Jurkat T-cell apoptosis. However, a single CRD (galectin-9NT or -CT) had no effect, suggesting the stable dimeric structure of two CRDs is required for the activity. The apoptosis was inhibited by pretreatment with an N-glycan synthesis inhibitor, indicating that the expression of N-glycans in the cells is essential for galectin-9-induced apoptosis. We previously showed that the apoptosis of MOLT-4 cell is mediated by galectin-9 via a Ca(2+)-calpain-caspase-1-dependent pathway. In Jurkat cells, the cell death by galectin-9, was insufficiently suppressed by caspase inhibitors, Ca(2+)-chelator or calpain inhibitor. Furthermore, we observed the loss of mitochondrial membrane potential and significant AIF release in galectin-9-treated cells. These findings suggest that caspase-dependent and-independent death pathways exist in Jurkat cells, and the main pathway might vary with the T-cell type.

Structural Features of Galectin-9 and Galectin-1 That Determine Distinct T Cell Death Pathways

“…First, galectin-9 is much more potent than galectin-1 in inducing T cell death; even when galectin-1 is made as a leucine zipper dimer or a bivalent single chain molecule, minimal cell death is observed in vitro at concentrations Ͻ1 M (31, 32). In contrast, 0.1 M galectin-9 is sufficient to induce significant apoptosis of MOLT-4 and Jurkat T cells, thymocytes, and peripheral blood T cells (19,20,28). Second, galectin-9 and galectin-1 appear to recognize different T cell surface glycoprotein receptors; Tim-3 and CD44 have been identified as glycoprotein receptors for galectin-9 (33, 34), whereas galectin-1 binds to several T cell surface glycoproteins including CD2, CD3, CD7, CD43, and CD45 (8,10,13,35).…”

“…However, the mechanism of galectin-9 cell death is not yet elucidated in detail, nor is it understood how galectins trigger these different death pathways (16,19,28). We thus examined the requirement for specific glycan ligands and cell surface glycoprotein receptors in galectin-9 death.…”

“…Specific glycoprotein receptors involved in galectin-1 death and specific types of O-and N-glycan ligands required for galectin-1 death have been identified, and galectin-1 has been shown to trigger a novel intracellular death pathway (6 -14). Other galectins have also been reported to trigger death of T cell lines and various T cell subsets, including galectin-2, galectin-3, galectin-8, and galectin-9 (15)(16)(17)(18)(19). Relatively little is known about the glycoprotein receptors, glycan ligands, and intracellular death pathways used by these galectins.…”

Functions of cell surface galectin-glycoprotein lattices

“…Galectin-1, -2, -3 and -9 bind distinct cell surface glycoprotein receptors and trigger distinct intracellular signaling pathways to promote T-cell death [17,19,[35][36][37]. Remarkably, a number of factors determine the responsiveness of cells to galectin-mediated signals which include the repertoire of glycosylated molecules expressed on the cell surface and the activities of specific glycosyltransferases, which are responsible for creating or masking galectin ligands [5,6,18].…”

Galectin-9 exhibits anti-myeloma activity through JNK and p38 MAP kinase pathways

“…[4][5][6][7][8][9][10] Moreover, recent studies have indentified anti-cancer properties of galectin-9 against several cancers. [11][12][13][14][15] In this study, we show the anti-multiple myeloma (MM) activity of a recombinant mutant form of human galectin-9 (hGal9) through the activation of c-Jun NH 2 -terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) signaling pathways, those share crucial roles in the survival and death of myeloma cells. 16 …”