Protean agonism at the muscarinic M2 receptor De Min A. (1), Matera C. (2), Messerer R. (3), Dallanoce C. (2), Holzgrabe U. (3), Mohr K. (1) (1) University of Bonn Pharmacology and Toxicology - Bonn, Deutschland (2) University of Milan Pharmaceutical Sciences - Milan, Italien (3) University of Würzburg Pharmaceutical and Medicinal Chemistry - Würzburg, Deutschland Muscarinic acetylcholine receptors, with their five different subtypes, belong to the class A of GPCRs and have been extensively studied with the purpose of finding selective ligands for their modulation. In this respect, in the last years a new strategy was developed, i.e. the synthesis of so-called dualsteric ligands that bind simultaneously to both the highly conserved orthosteric site and the less conserved allosteric site of the M2 receptor subtype . Recently, we found out that one dualsteric ligand, a hybrid derived from the orthosteric superagonist iperoxo and the negative allosteric modulator naphmethonium, showed a peculiar behavior known as “protean agonism”. Given that protean agonism has not been described so far for muscarinic receptors, additional studies were performed, in order to gain better insight into structure/activity-relationships. Therefore, a series of compounds of different middle chain length and iperoxo-related orthosteric agonist moieties were chosen for testing. [35S]GTPγS binding assays were carried out in order to study the effect of the hybrids in the Gi signaling pathway. Experiments were performed in Tris buffer either with low sodium concentration, that assured a stable spontaneously active M2 receptor system, or in Tris buffer supplemented with 200 mM NaCl, that abolished M2 constitutive activity. The results revealed a great variety of activities of the structurally related hybrids, including inverse agonism, partial agonism and protean agonism. The tested compounds had similar potencies (pEC50) in this assay, ranging between 7.5-8.5, except for two protean agonists and one inverse agonist. The former two revealed significantly lower potencies and efficacies in Tris buffer with “low sodium” concentration. These results might suggest that in this buffer the ligands adopt a purely allosteric pose rather than a dualsteric pose. Concerning the inverse agonist, it had a low pEC50 in both buffers. This result might indicate that the hybrid adopts a purely allosteric binding pose in both conditions, thus inactivating the receptor through the negative allosteric fragment. Taken together, linker length and nature of orthosteric moiety are both relevant in determining the intensity and the direction of the effect. Two protean agonists were identified for the muscarinic M2 receptor. Antony, J. et al.: FASEB J. 2009, 23: 442-50.
Protean agonism at the muscarinic M2 receptor / A. De Min, C. Matera, R. Messerer, C.M.L. Dallanoce, U. Holzgrabe, K. Mohr. - In: NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY. - ISSN 0028-1298. - 388:Suppl. 1(2015 Feb), pp. S4-S4. ((Intervento presentato al 81. convegno Deutsche Gesellschaft für Experimentelle und Klinische Pharmakologie und Toxikologie e.V. - Annual Meeting tenutosi a Kiel nel 2015.
|Titolo:||Protean agonism at the muscarinic M2 receptor|
MATERA, CARLO (Secondo)
|Parole Chiave:||protean agonism; muscarinic receptors; GPCRs; mAChRs; buffer; M2|
|Settore Scientifico Disciplinare:||Settore BIO/11 - Biologia Molecolare|
Settore BIO/12 - Biochimica Clinica e Biologia Molecolare Clinica
Settore BIO/14 - Farmacologia
Settore CHIM/08 - Chimica Farmaceutica
|Data di pubblicazione:||feb-2015|
|Appare nelle tipologie:||01 - Articolo su periodico|