Further Delineation of the Two Binding Sites (R*n) Associated with Tachykinin Neurokinin-1 Receptors Using [3-Prolinomethionine11]SP Analogues

Abstract

Two binding sites are associated with neurokinin-1 substance P receptors in both transfected cells and mammalian tissues. To further delineate the interactions between the crucial C-terminal methionine of substance P and these two binding sites, we have incorporated newly designed constrained methionines, i.e.

The Neurokinin A Receptor Activates Calcium and cAMP Responses through Distinct Conformational States

“…Although tachykinin receptors do not mediate cAMP accumulation when expressed at low density in heterologous systems (33), phosphorylation by PKA may nevertheless contribute to the regulation of their state of activity. Indeed, different cell types may express receptors activating cAMP/PKA signaling pathways, together with tachykinin receptors.…”

Functional consequences of alteration of N-linked glycosylation sites on the neurokinin 1 receptor

“…Although SP is the preferred ligand for NK1R, several groups have shown that NKA binds NK1R with high enough affinity to elicit a biologic response (22)(23)(24). More recently, it has been found that benzoylphenylalanine 3 -SP, a photoactivatable ligand for the NK1R, covalently labeled the N-terminal region of the NK1R between residues 11 and 21 (25).…”

Involvement of the Second Extracellular Loop (E2) of the Neurokinin-1 Receptor in the Binding of Substance P

“…Altogether these results suggest that the differences in B max values for the two types of ligands cannot be explained by effects secondary to G-protein interactions. With a plethora of SP analogs in CHO cells expressing high levels of the human NK-1 receptor, the binding affinity for the more abundant binding site could be correlated to the potency to accumulate cAMP, whereas the binding affinity for the less abundant site could be correlated to the potency to activate inositol phosphate production (8). In the CHO clone used herein, the more and less abundant binding sites represent 85 and 15% of the total population of receptors (6 pmol/mg of proteins), respectively (7).…”

“…In the CHO clone used herein, the more and less abundant binding sites represent 85 and 15% of the total population of receptors (6 pmol/mg of proteins), respectively (7). Substance P binds the two binding sites with high affinity, whereas some C-terminal fragment analogs of substance P and some substance P-(1-11) analogs, as well as the endogenous tachykinin NK-2 ligand neurokinin A, bind only the less abundant one (7)(8)(9)(10)(11)(12). Although several structure-activity relationship studies have been carried out, little is known about the differences in the molecular recognition of these two binding sites (8 -12).…”

“…4 for a review). Binding experiments with SP analogs in tissues and in cells transfected with the NK-1 receptor have shown that two types of non-stoichiometric binding sites with distinct pharmacological profiles are associated with the NK-1 receptor (5)(6)(7)(8)(9)(10)(11)(12). In CHO cells, B max values for the two binding sites were found to be 6000 fmol/mg proteins and 800 fmol/mg proteins for the major binding site ( 11 ]SP-(7-11), respectively (7).…”