Specificity of interactions of galectin-3 with Chrp, a cysteine- and histidine-rich cytoplasmic protein

Earlier work described the cloning of a gene from murine 3T3 cells encoding a cytoplasmic protein Chrp containing a cysteine- and histidine-rich motif characteristic of Zn-finger proteins. The interaction of Chrp with murine galectin-3 first became evident in a yeast two-hybrid screen, but it was also observed in co-precipitation experiments from 3T3 cell lysates. Here, the formation of equimolar complexes by murine Chip and hamster galectin-3 is shown. Moreover, we found that Chip binds to the carbohydrate-recognition domain (CRD) of hamster galectin-3 and not to the N-terminal domain carrying the proline- and glycine-rich repeats characteristic of galectin-3 and absent in other galectins. However, galectin-1 does not bind to Chip, although its CRD is homologous to the galectin-3 CRD. Finally, we report that galectin-3, in a complex with Chrp, binds to laminin in surface plasmon resonance experiments with similar kinetics and affinity as it does in the free state. The formation of higher-order complexes containing these proteins and additional binding partners may be relevant to cytoplasmic functions involving galectin-3. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Societe francaise de biochimie et biologie moleculaire. All rights reserved.