Galectins, a family of soluble β-galactoside-binding proteins, are involved in the regulation of various cellular functions, which are essential for adaptive cellular stress responses (CSRs). Although expression patterns of galectins and galectin-binding glycans change during tissue development and cancer, the requirement and role of galectin networks in the CSRs are not completely understood. In this study, we report that the treatment of human promyelocytic HL-60 cells with stimuli mimicking hypoxia (CoCl2), inducing the endoplasmic reticulum stress (tunicamycin), and stimulating cell differentiation, result in stress-specific differential expression of galectin transcripts. In addition, we show that CoCl2 increases the expression of cell surface glycans recognized by both β-galactoside- and GlcNAc-binding lectins. Thus, microenvironmental stress changes the glycobiological status of cells representing expression profiles of endogenous lectins and corresponding glycans. These findings introduce a novel classification of galectins in HL-60 cells, which suggests diverse functions of galectin members in CSRs.

Galectin-1 is an endogenous lectin expressed by thymic and lymph node stromal cells at sites of Ag presentation and T cell death during normal development. It is known to have immunomodulatory activity in vivo and can induce apoptosis in thymocytes and activated T cells (1–3). Here we demonstrate that galectin-1 stimulation cooperates with TCR engagement to induce apoptosis, but antagonizes TCR-induced IL-2 production and proliferation in a murine T cell hybridoma and freshly isolated mouse thymocytes, respectively. Although CD4+CD8+ double positive cells are the primary thymic subpopulation susceptible to galectin-1 treatment alone, concomitant CD3 engagement and galectin-1 stimulation broaden susceptible thymocyte subpopulations to include a subset of each CD4−CD8−, CD4+CD8+, CD4−CD8+, and CD4+CD8− subpopulations. Furthermore, CD3 engagement cooperates with suboptimal galectin-1 stimulation to enhance cell death in the CD4+CD8+ subpopulation. Galectin-1 stimulation is shown to synergize with TCR engagement to dramatically and specifically enhance extracellular signal-regulated kinase-2 (ERK-2) activation, though it does not uniformly enhance TCR-induced tyrosine phosphorylation. Unlike TCR-induced IL-2 production, TCR/galectin-1-induced apoptosis is not modulated by the expression of kinase inactive or constitutively activated Lck. These data support a role for galectin-1 as a potent modulator of TCR signals and functions and indicate that individual TCR-induced signals can be independently modulated to specifically affect distinct TCR functions.