CHARACTERIZATION OF A NOVEL MEMBER OF THE MACROPHAGE MANNOSE RECEPTOR-TYPE-C LECTIN FAMILY

The recognition of a diversity of carbohydrates by the various calcium dependent (type C) lectin family members has been shown to be critica l for a variety of processes ranging from cell adhesion to antigen pre sentation, Examination of the expressed sequence tag (EST) data base f or novel type C lectins using E-selectin as a probe resulted in the id entification of a distantly related short polypeptide sequence contain ing many of the conserved residues found in these carbohydrate-binding proteins. Cloning of the full-length murine cDNA containing this regi on revealed that this protein is a novel member of the family that inc ludes the macrophage mannose, the phospholipase A(2), and the DEC 205 receptors, with a cysteine-rich domain, a fibronectin type 2 domain, e ight type C lectin domains, a transmembrane domain, and a short cytopl asmic carboxyl terminus, Genomic Southern analysis suggests that this is a conserved protein, and examination of a human homologue revealed a high degree of sequence homology with the murine form. Northern blot analysis revealed expression of a large transcript in a number of dif ferent human and murine tissues and tumor cells and an alternatively s pliced smaller transcript with a divergent 5' sequence was expressed s pecifically in the human fetal liver. Analysis of the genomic structur e revealed that the gene encoding this lectin was interrupted by a lar ge number of introns, and the intron structure was similar to the macr ophage mannose receptor gene, Finally, in situ hybridization analysis demonstrated that the transcript encoding this lectin was found in a n umber of highly endothelialized sites as well as in chondrocytes in ca rtilaginous regions of the embryo.