Surface expression and rapid internalization of macrosialin (mouse CD68) on elicited mouse peritoneal macrophages.
Macrosialin, the mouse homolog of human CD68, is a heavily glycosylated transmembrane protein found almost exclusively in macrophages. Its function remains uncertain. It has a high affinity for oxidized low-density lipoprotein (LDL) in ligand blots and antibodies against the human homolog, CD68, inhibit the binding of oxidized LDL to a human monocyte-derived cell line (THP-1). However, there is still controversy as to whether macrosialin, found predominantly in late endosomes, is expressed at all on the plasma membrane. The present studies, done in thioglycollate-elicited peritoneal macrophages, confirm that macrosialin is predominantly intracellular but show clearly that 10-15% of it is expressed on the cell surface. Exchange with intracellular pools occurs at an extremely high rate. The results are compatible with a surface function, including internalization of bound ligands or adhesion to surfaces.
Kurushima
H
H
Department of Medicine, University of California, San Diego, La Jolla 92093-0682, USA.
Ramprasad
M
M
Kondratenko
N
N
Foster
D M
DM
Quehenberger
O
O
Steinberg
D
D
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000378:metabolism*; D051379:Mice; D000097382:CD68 Molecule
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D008077:Lipoproteins, LDL; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C081026:CD68 protein, mouse; C099252:oxidized low density lipoprotein