Mac-2-binding glycoproteins. Putative ligands for a cytosolic beta-galactoside lectin.
Mac-2, a galactose-binding lectin secretion by activated macrophages, is the major non-integrin laminin-binding protein in these cells. Mac-2 is also expressed by epithelial cells in the intestine and kidney. We wished to identify intestinal glycoproteins other than laminin that have a high affinity for Mac-2 and that could be considered as candidate ligands or partners for this lectin in intestinal epithelium. Certain lines of human colon adenocarcinoma cells produce two Mac-2-binding glycoproteins (M2BP-1 and M2BP-2) that were identified by their avid association with Mac-2 following detergent lysis and immunoprecipitation. These glycoproteins do not share a common epitope with Mac-2, and the interaction between Mac-2 and these proteins is mediated through the carbohydrate-binding domain of Mac-2 and sugar moieties on M2BP-1 and M2BP-2. M2BP-1 (98 kDa) and M2BP-2 (70 kDa) were purified by immunoaffinity chromatography and were specifically eluted with either galactose or lactose. Peptide maps revealed that M2BP-1 and M2BP-2 are structurally related. M2BP-1 is secreted and could conceivably associate with Mac-2 extracellularly. N-terminal sequence analysis of M2BP-2 suggests that these glycoproteins represent a unique subset of candidate ligands for this mammalian beta-galactoside lectin.
Molecular Immunology Laboratory, Massachusetts General Hospital, Boston.
I
I
Rosenberg
B J
BJ
Cherayil
K J
KJ
Isselbacher
S
S
Pillai
D000230:Adenocarcinoma; D000595:Amino Acid Sequence; D000943:Antigens, Differentiation / Q000378:metabolism*; D015153:Blotting, Western; D003106:Colon / Q000378:metabolism*; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D005697:Galactosides / Q000378:metabolism*; D037502:Galectin 3; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D037102:Lectins / Q000378:metabolism*; D008024:Ligands; D008264:Macrophages / Q000378:metabolism; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D014407:Tumor Cells, Cultured
D000943:Antigens, Differentiation; D005697:Galactosides; D037502:Galectin 3; D006023:Glycoproteins; D037102:Lectins; D008024:Ligands; C007816:beta-galactoside