A membrane-associated form of C-reactive protein is the galactose-specific particle receptor on rat liver macrophages.
Rat liver macrophages express a galactose-specific receptor which mediates endocytosis of particles or neuraminidase-treated blood cells. From rat serum we now have isolated and purified a galactose-specific lectin by affinity chromatography. Comparative analysis of this serum galactose-binding protein with the galactose-particle receptor protein purified from rat liver macrophages and with C-reactive protein (CRP) reveals close relation or identity of these proteins. An apparent m.w. of 30,000 was determined for all three proteins by SDS-PAGE under reducing conditions and m.w. of about 130,000 by native PAGE. All three proteins exhibit the same pentameric, ring-shaped structure in electron microscopy after negative staining. Antibodies raised against the serum galactose-binding protein or against the macrophage receptor cross-react. A mAb specific for rat neo-CRP labels liver macrophages but not hepatocytes and reacts with the isolated protein in a Western blot assay. Furthermore, the galactose-particle receptor can be functionally replaced by purified CRP: the binding capacity for neuraminidase-treated E of receptor-depleted liver macrophages can be restored by preincubation with purified rat CRP. We therefore conclude that CRP occurs as a membrane-associated protein constitutively expressed on liver macrophages functioning as a receptor mediating galactose-specific binding of particulate ligands.
Kempka
G
G
Abteilung für Immunbiologie, Medizinische Einrichtungen der Universität Düsseldorf, FRG.
Roos
P H
PH
Kolb-Bachofen
V
V
D000818:Animals; D015153:Blotting, Western; D002097:C-Reactive Protein / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002846:Chromatography, Affinity; D004492:Edetic Acid / Q000494:pharmacology; D004705:Endocytosis; D005690:Galactose / Q000378:metabolism*; D037161:Galectins; D006388:Hemagglutinins / Q000302:isolation & purification / Q000378:metabolism*; D008099:Liver / Q000166:cytology; D008264:Macrophages / Q000378:metabolism*; D008854:Microscopy, Electron; D008970:Molecular Weight; D051381:Rats; D011919:Rats, Inbred Strains
D037161:Galectins; D006388:Hemagglutinins; D002097:C-Reactive Protein; D004492:Edetic Acid; D005690:Galactose