Galectin-1 Purified from Human Platelets.

Galectins are a family of lectins which exhibit β-galactoside-binding activity. They are Ca⁺⁺-independent and have a common consensus sequence in the carbohydrate binding domain. Fourteen mammalian members of this family have been sequenced and well-characterised in different species, although galectins-1 and -3 have been the most thoroughly studied. They have biological functions in the regulation of the immune system such as allergic inflammation and host defence (activation of mast cells, neutrophils and eosinophils, stimulation of interleukins production and in the generation of oxidizing radicals), but scarse information is avalaible on biological functions in platelet function and hemostasia. The objective of this work was to detect and purified galectins from human platelets. Platelet-rich plasma obtained from blood bank, with negative serology for HIV, HBsAg and HVC, was filtered by a Pall Purecell PL filter (USA) to produce leucoreduction. Later, platelets were centrifuged and the pellet was homogenized in MEPBS (mercaptoethanol-EDTA-phosphate buffer saline)-200 mM lactose. The supernatant was treated by anion-exchange and affinity chromatography (lactose-agarose) followed by size exclusion in FPLC. We determined that an amount of 6-10 fg was present in a single platelet. The molecule was a dimer with a subunit of 14 kDa. Purified protein was isolated by PAGE-SDS and electroblotted onto nitrocellulose sheets. Identity was revealed employing polyclonal and monoclonal anti-galectin antibodies. Positive and negative controls were running simultaneously. Amino acid sequencing of galectin peptides performed indicated that it was a galectin-1. We conclude that galectin-1 is present in human platelets. Potential roles of galectin-1 in platelet function and hemostasia are under study.