Galectin-1 induced activation of the apoptotic death-receptor pathway in human Jurkat T lymphocytes

Abstract

Galectin-1 (gal-1), a member of the family of beta-galactoside binding proteins, participates in several biological processes such as immunomodulation, cell adhesion, regulation of cell growth and apoptosis. The aim of this study was to investigate whether gal-1 interferes with the Fas (Apo-1/CD95)-associated apoptosis cascade in the T-cell lines Jurkat and MOLT-4. Gal-1 and an Apo-1 monoclonal antibody (mAb) induced DNA-fragmentation in Jurkat T-cells whereas MOLT-4 cells were resistant. Gal-1 stimulated DNA-fragmentation could be efficiently inhibited by caspase-8 inhibitor II (Z-IETD-FMK) and a neutralizing Fas mAb. Fas could be identified as a target for gal-1 recognition as demonstrated by immunofluorescence staining, binding of the receptor glycoprotein to immobilized gal-1 and analyses by immunoblotting as well as by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Gal-1 stimulates the activation and proteolytic processing of procaspase-8 and downstream procaspase-3 in Jurkat-T cells. Inhibition of gal-1 induced procaspase-8 activation by a neutralizing Fas mAb strongly suggests that gal-1 recognition of Fas is associated with caspase-8 activation. Our data provide the first experimental evidence for targeting of gal-1 to glycotopes on Fas and the subsequent activation of the apoptotic death-receptor pathway.

Novel role for galectin-1 in T-cells under physiological and pathological conditions

“…The apoptotic effect of extracellular Gal-1 on activated T-cells has been described in a number of papers [3,4,6,24,30]. It has also been shown that T-cells express Gal-1 upon activation.…”

“…The result of these authors indicated that even if secreted, Gal-1 amount in unconcentrated supernatant could not be enough to exert cytotoxicity, since the concentration of soluble Gal-1 inducing T-cell death was shown to be between 25-400 g/ml in all published experiments [4,7,30,31]. Moreover, Gal-1 is normally present in serum only in very low quantity (several ng/ml), which is far below the apoptosis inducing concentration of the soluble protein [32].…”

How does it act when soluble? Critical evaluation of mechanism of galectin-1 induced T-cell apoptosis

“…accordingly we have recently described the crucial function of p56 lck and Zap70 in gal-1 induced t cell apoptosis [8,9]. our previous data [7][8][9] and those provided by other laboratories [1,10,21] support that it is a mitochondrial type of caspase-mediated cell death, however other researchers have shown that gal-1 triggers a mitochondrial route independent of the caspase cascade [5]. moreover, stowell et al [20] have published results indicating that gal-1 prepares leukocytes for phagocytic elimination by inducing phosphatidylserine exposure on the outer surface of the plasma membrane without stimulating apoptosis.…”

“…data describing the mechanism of gal-1 induced t-cell apoptosis have been obtained using soluble, recombinant gal-1 and remained highly controversial [1,5,7,9,10,19]. the receptor tyrosine phosphatase cd45, initially described as apoptotic receptor for gal-1 [14,15,23] has recently been shown to be dispensable [4,11,12].…”

Synergistic Induction of Galectin-1 by CCAAT/Enhancer Binding Protein α and Hypoxia-inducible Factor 1α and Its Role in Differentiation of Acute Myeloid Leukemic Cells

“…The recombinant protein was active because it was capable of inducing apoptosis of Jurkat T cells (supplemental Fig. S3, B and C) (5,33,34). Using the solvent of galectin-1 protein as a control buffer, the recombinant galectin-1 was added into the culture medium of U937T…”