Complement receptor 1/CD35 is a receptor for mannan-binding lectin.
Mannan-binding lectin (MBL), a member of the collectin family, is known to have opsonic function, although identification of its cellular receptor has been elusive. Complement C1q, which is homologous to MBL, binds to complement receptor 1 (CR1/CD35), and thus we investigated whether CR1 also functions as the MBL receptor. Radioiodinated MBL bound to recombinant soluble CR1 (sCR1) that had been immobilized on plastic with an apparent equilibrium dissociation constant of 5 nM. N-acetyl-d-glucosamine did not inhibit sCR1-MBL binding, indicating that the carbohydrate binding site of MBL is not involved in binding CR1. C1q inhibited MBL binding to immobilized sCR1, suggesting that MBL and C1q might bind to the same or adjacent sites on CR1. MBL binding to polymorphonuclear leukocytes (PMNs) was associated positively with changes in CR1 expression induced by phorbol myristate acetate. Finally, CR1 mediated the adhesion of human erythrocytes to immobilized MBL and functioned as a phagocytic receptor on PMNs for MBL-immunoglobulin G opsonized bacteria. Thus, MBL binds to both recombinant sCR1 and cellular CR1, which supports the role of CR1 as a cellular receptor for the collectin MBL.
Ghiran
I
I
Harvard-Thorndike Laboratory, Division of Allergy and Inflammation, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
Barbashov
S F
SF
Klickstein
L B
LB
Tas
S W
SW
Jensenius
J C
JC
Nicholson-Weller
A
A
D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D037222:Collectins; D015922:Complement C1q / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects; D005353:Fibronectins / Q000494:pharmacology; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology / Q000494:pharmacology; D007457:Iodine Radioisotopes; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D017463:Receptors, Complement 3b / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism; D012475:Salmonella / Q000276:immunology / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002352:Carrier Proteins; D037222:Collectins; D005353:Fibronectins; D007140:Immunoglobulin Fab Fragments; D007457:Iodine Radioisotopes; D017463:Receptors, Complement 3b; D011994:Recombinant Proteins; D015922:Complement C1q; D013755:Tetradecanoylphorbol Acetate