Tachykinin peptides affect differently the second messenger pathways after binding to CHO-expressed human NK-1 receptors.
The human NK-1 receptor transfected in Chinese hamster ovary (CHO) cells was studied with use of different tachykinin analogs: Substance P, [Pro9]SP, [Sar9, Met(O2)11]SP, [Gly9 psi (CH2CH2) Leu10]SP, Ac-Arg-septide, septide, [Gly9 psi (CH2CH2) Gly10]SP, NKA, [pGlu6]SP(6-11) and [Lys5]NKA(4-10). Binding experiments with [3H][Pro9]SP discriminated two classes of peptides with either high affinity (K iota in the nanomolar range) for the human NK-1 receptor or with low affinity (K iota in the micromolar range); this second group of peptides included NKA and [pGlu6]SP(6-11). In spite of these differences, both peptide families evoked potent stimulation of phosphatidylinositol hydrolysis (EC50 in the nanomolar range). In contrast, only NK-1 agonists, with high affinity, stimulated with great potency cyclic AMP formation (EC50 from 8 to 50 nM), whereas the second family of peptides were only weak agonists (EC50 in the micromolar range). RP 67580, CP 96345 and GR 94800, a NK-2 antagonist, were either competitive or uncompetitive inhibitors of inositol phosphates or cyclic AMP formations induced by [Pro9]SP, septide or NKA, independently of the agonist or the response studied. Thus, NKA, the presumed NK-2 endogenous peptide that may be co-released with SP, and the enzymatically produced C-terminal fragment of SP, [pGlu6]SP(6-11), may trigger specific pharmacological responses via the NK-1 receptor, at nanomolar concentrations, and thus regulate the action of SP at the NK-1 receptor.
Sagan
S
S
Laboratoire de Chimie Organique Biologique, Université P. & M. Curie, Paris, France.
Chassaing
G
G
Pradier
L
L
Lavielle
S
S
D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells / Q000187:drug effects*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D018040:Receptors, Neurokinin-1 / Q000187:drug effects*; D015290:Second Messenger Systems / Q000187:drug effects*; D013373:Substance P / Q000494:pharmacology; D015320:Tachykinins / Q000494:pharmacology*
D018040:Receptors, Neurokinin-1; D015320:Tachykinins; D005576:Colforsin; D013373:Substance P