Regulated expression of a 16-kd Galectin-like protein in activated rat macrophages.

RABINOVICH GA; CASTAGNA L; LANDA C; RIERA CM; SOTOMAYOR CE

JOURNAL OF LEUKOCYTES BIOLOGY

Society for Leukocyte Biology

Año: 1996 vol. 59 p. 363 - 370

We investigated the presence of a galectin-like protein in rat mononuclear cells using a polyclonal antibody raised against a soluble lactose-binding lectin purified from adult chicken liver that immunoreacted strongly with a broad protein band of about 16 kd in Western blot assays. Immunochemical studies revealed a constitutive expression of this protein in mononuclear cells mainly in the macrophage (M4) population. Subcellular localization was assessed by Western blot assays of the cytosolic and membrane fractions of different cell populations studied: ( 1 ) spleen mononuclear cells, (2) T cell-enriched, (3) B cell- and M
-enriched populations, and (4) peritoneal cells, processed in the presence of lactose. In broad agreement with immunocytochemical studies of nonpermeabilized and permeabilized cells, Western blot assays suggest that this protein is localized mainly in the cytoplasmic compartment but also associated with the cell surface. By flow cytometric analyses we detected about a 14% of ED! double-positive cells corresponding to M4s that constitutively express this galectin-like protein associated with their cell surface. The cytosolic fraction obtained from the M4-enriched cell population showed hemagglutinating activity specilhcally inhibited by
-galactoside-related sugars. Moreover, this galectin-like protein was retained in a lactosyl-Sepharose matrix and specifically eluted with lactose. In this work, evidence is also provided to show that different stimuli are able to modulate the expression of the galectin-like protein. Expression was upregulated in inflammatory and activated M4s, revealing a significant increase in phorbol ester- and formylmethionine oligopeptide-treated cells. Both stimuli involving protein kinase C activation pathway have been able not only to up-regulate the total expression of this protein but also to modulate its subcellular localization. J. Leukoc. Biol. 59: 363-370; 1996.