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The immunoregulatory glycan-binding protein galectin-1 triggers human platelet activation

Natalia Pacienza^*,1, Roberto G. Pozner^*,1, Germán A. Bianco, Lina P. D'Atri^*, Diego O. Croci, Soledad Negrotto^*, Elisa Malaver^*, Ricardo M. Gómez, Gabriel A. Rabinovich^,,2,3 and Mirta Schattner^*,2,3

^* Hematological Research Institute, National Academy of Medicine, and

Laboratory of Immunopathology, Institute of Biology and Experimental Medicine (IBYME), National Research Council (CONICET), Buenos Aires, Argentina;

Biochemistry and Molecular Biology Institute, Department of Biological Sciences, National University of La Plata, La Plata, Argentina; and

Department of Biological Chemistry, Faculty of Exact and Natural Sciences, University of Buenos Aires, Buenos Aires, Argentina

³Correspondence: M.S., Instituto de Investigaciones Hematológicas, Academia Nacional de Medicina, Pacheco de Melo 3081, Buenos Aires (1425), Argentina. E-mail: mschattner{at}hematologia.anm.edu.ar; G.A.R., Instituto de Biologia y Medicina Experimental, CONICET, Vuelta de Obligado 2490, Buenos Aires (1428), Argentina. E-mail: gabyrabi{at}ciudad.com.ar

Platelet activation is a critical process during inflammation, thrombosis, and cancer. Here, we show that galectin-1, an endogenous lectin with immunoregulatory properties, plays a key role in human platelet activation and function. Galectin-1 binds to human platelets in a carbohydrate-dependent manner and synergizes with ADP or thrombin to induce platelet aggregation and ATP release. Furthermore, galectin-1 induces F-actin polymerization, up-regulation of P-selectin, and GPIIIa expression; promotes shedding of microvesicles; and triggers conformational changes in GPIIb/IIIa. In addition, exposure to this lectin favors the generation of leukocyte-platelet aggregates. A further mechanistic analysis revealed the involvement of Ca²⁺ and cyclic nucleotide-dependent pathways in galectin-1-mediated control of platelet activation. Finally, expression of endogenous galectin-1 in human platelets contributes to ADP-induced aggregation. Our study reveals a novel unrecognized role for galectin-1 in the control of platelet physiology with potential implications in thrombosis, inflammation, and metastasis.—Pacienza, N., Pozner, R. G., Bianco, G. A., D’Atri, L. P., Croci, D. O., Negrotto, S., Malaver, E., Gómez, R. M., Rabinovich, G. A., Schattner, M. The immunoregulatory glycan-binding protein galectin-1 triggers human platelet activation.

Key Words: lectin • P-selectin • inflammation • hemostasis