PRODUCTION AND CHARACTERIZATION OF MONOCLONAL-ANTIBODIES AGAINST HUMAN NATRIURETIC PEPTIDE RECEPTOR-A OR RECEPTOR-B

Monoclonal antibodies (mAbs) against human natriuretic peptide recepto r-A (NPR-A) or NPR-B were produced using NPR-expressing Chinese hamste r ovary (CHO) cells and soluble chimeric NPRs consisting of the extrac ellular domain of each receptor fused to Pc region of human IgG. Three anti-NPR-A mAbs, designated as A144, A397 and A416, bound to human NP R-A but not to NPR-B, while an anti-NPR-B mAb B136 reacted with human NPR-B but not with NPR-A, Competition analysis with the anti-NPR-A mAb s revealed that two mAbs, A144 and A416, recognize an identical or the adjacent site of the receptor and that A397 is directed against anoth er epitope. No anti-NPR-A mAb affected binding of atrial natriuretic p eptide (ANP) to NPR-A, while the anti-NPR-B mAb B136 inhibited binding of C-type natriuretic peptide (CNP) to NPR-B. Inhibition of the ligan d-binding by B136 is specific in that the mAb showed no effect on the binding of ANP to NPR-A, B136 also blocked CNP-mediated intracellular cGMP accumulation in NPR-B-expressing cells. These results suggest tha t the region recognized by B136 may be related to the ligand-binding r egion of NPR-B, NPR-A- and NPR-B-expressing cells were selectively det ected by immunostaining using the mAbs. These findings demonstrate tha t the mAbs will be useful to elucidate the role of the natriuretic pep tides and their receptors in normal and disease states in human.