Beta-galactoside-binding lectins or galectins are a family of closely related carbohydrate-binding proteins which functions still remain to be elucidated. Several evidence suggest they could play a role in different biological processes, such as cell grow

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

JOURNAL OF BIOCHEMISTRY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 1997 vol. 122 p. 365 - 373

0021-924X

?À-Galactoside-binding lectins or galectins are a family of closely related carbohydratebinding proteins which functions still remain to be elucidated. Several evidence suggest they could play a role in different biological processes, such as cell growth regulation and immunomodulation. In the present study we report that affinity-purified CLL-I (chicken lactose lectin-I), an acidic 16-kDa galectin exhibits specific growth regulatory properties. Con A-stimulated rat spleen mononuclear cells showed a marked dose-dependent growth inhibition upon incubation with the galectin protein. Cell growth arrest was highly prevented by galectin-specific sugars. In addition, biochemical, cytofluorometrical, and morphological evidence are also provided to show that these inhibitory properties are related to a positive control in the apoptotic threshold of spleen mononuclear cells. Flow cytometric analysis showed a dose- and time-dependent increase of cells with hypodiploid DNA content upon exposure to CLL-I. Moreover, cells treated with CLL-I displayed the typical ultrastructural changes compatible with apoptosis, mainly chromatin condensation and margination along the inner surface of the nuclear envelope. Finally, the highly characteristic "ladder" pattern of DNA fragmentation into oligonucleosome-length frag ments of -180-200 by could be found within 6 h of cell culture with CLL-I, mainly in the T cell-enriched population. Induction of apoptosis by a ?À-galactosidebinding protein highlights a potentially novel mechanism for regulating the immune response and points to a rational basis for the postulated immunomodulatory properties of this protein family: