Description
Galectin-3 binding protein (Galectin-3BP), called CyCAP (cyclophilin C-associated protein) in the mouse, is a secreted glycoprotein of the scavenger receptor cysteine-rich (SRCR) super family. Mouse Galectin-3BP is generally considered the paralog of human Galectin-3BP, which is also called MAC-2 binding protein (MAC-2BP), or 90kD tumor associated antigen (TAA90K or 90K). However, mouse Galectin-3BP binds cyclophilin C but not Galectin-3, while the opposite is true of human Galectin-3BP. The 577 amino acid, 77-95kD mouse Galectin-3BP contains an 18aa signal sequence and four definitive domains. Domain 1 is a group A scavenger receptor domain, domain 2 is a BTB/POZ domain that mediates dimerization, and domain 3 is an IVR domain that is also found following the POZ domain in Drosophila kelch protein. Little is known about domain 4. Mature mouse Galectin-3BP shares 88%, 69%, 67% and 65% aa identity with rat, human, dog and cow Galectin-3BP, respectively. The Galectin-3BP dimer interface residues are generally conserved between mouse and human, so linear dimers that occur in humans are also likely in the mouse. Human Galectin-3BP also forms ring-shaped decamers and dodecamers. Mouse Galectin-3BP is widely expressed and modifies innate immune reactions. It is stimulated in macrophages by adhesion, TNF-a or IFN-g. Mice deficient in Galectin-3BP secrete increased amounts of IL-12, TNF-a and IFN-g and have lower survival in response to endotoxin. Galectin-3BP is induced in rat skin fibroblasts, keratinocytes, macrophages and lymphocytes during wound healing, and wounded Galectin-3BP-deficient mice are slow to heal. Rat Galectin-3BP is upregulated after cerebral ischemia. Ligands for human Galectin-3BP include some other galectins, collagens and integrins, but remain to be tested for mouse Galectin-3BP binding