![[feed]](/style/images/feed-icon-14x14.png){kind=icon}
Tools
Tools
| Item Type: | Article |
|---|---|
| Title: | From agonist to antagonist: Fab fragments of an agonist-like monoclonal anti-beta2-adrenoceptor antibody behave as antagonists |
| Creators Name: | Mijares, A., Lebesgue, D., Wallukat, G. and Hoebeke, J. |
| Abstract: | We previously demonstrated that the monoclonal antibody Mab6H8 raised against the second extracellular loop of the {beta}2-adrenoceptor ({beta}2-AR) had an agonist-like activity, mediated by the activation of L-type Ca2+ channels by protein kinase A through the adenylyl cyclase pathway. We suggested that this Mab acts by stabilizing an active dimeric conformation of the {beta}2-AR. To substantiate this hypothesis, we prepared monomeric Fab fragments of Mab6H8. Comparison of the physico-chemical parameters of antigen interaction with both the Mab and its Fab fragments were determined by surface plasmon resonance, showing a 5- to 10-fold lower affinity of the fragments compared with the bivalent antibody. We determined the biological activity of antibody and Fab fragments in two systems: spontaneous beating neonatal rat cardiomyocytes to study the chronotropic effects and isolated guinea pig cardiomyocytes to study L-type Ca2+ channel activation. Fab fragments as such had no 'agonist-like' effects in both systems but inhibited receptor activation with the {beta}2-specific agonist clenbuterol. Addition of a cross-linking rabbit anti-mouse IgG restored the agonist-like effect of the Fab fragments. These results suggest that Fab fragments induce a conformational change in the receptor, inhibiting the accessibility of the pharmacophore pocket to clenbuterol. Dimerization of this receptor conformation induces an agonist-like effect. Antireceptor antibodies can thus act both as agonist in the dimeric state and as antagonist in the monomeric state. |
| Keywords: | Adrenergic Beta-Antagonists, Beta-2 Adrenergic Receptors, Calcium, Cytosol, Heart, Immunoglobulin Fab Fragments, L-Type Calcium Channels, Monoclonal Antibodies, Myocardium, Wistar Rats, Animals, Guinea Pigs, Rats |
| Source: | Molecular Pharmacology |
| ISSN: | 0026-895X |
| Publisher: | Amer Soc Pharmacology Experiamental Therapeutics |
| Volume: | 58 |
| Number: | 2 |
| Page Range: | 373-379 |
| Date: | 1 August 2000 |
| Official Publication: | http://molpharm.aspetjournals.org/cgi/content/abstract/58/2/373 |
| PubMed: | View item in PubMed |
Repository Staff Only: item control page
