作者:Sandrine Sagan、Hubert Josien、Philippe Karoyan、Alié Brunissen、Gérard Chassaing、Solange Lavielle
DOI:10.1016/s0968-0896(96)00230-1
日期:1996.12
The action of rotameric probes introduced either in position 7 or 8 in the sequence of substance P (SP) was investigated, i.e. L-tetrahydroisoquinoleic acid (Tie), L-fluorenylglycine (Flg), L-diphenylalanine (Dip), the diastereoisomers of L-1-indanylglycine (Ing) and L-benz[f]indanylglycine (Bfi), the Z- and E-isomers of dehydrophenylalanine and dehydronaphthylalanine (Delta(Z)Phe, Delta(E)Phe, Delta(Z)Nal, Delta(E)Nal) and L-o,o'-dimethylphenylalanine (Dmp). The aim of this study was the topographical characterization of the binding subsites of human NK-1 receptor expressed in CHO cells, especially the S-7 and S-8 subsites, corresponding to residues Phe(7) and Phe(8) of substance P. According to the binding potencies of these substituted-SP analogues, the S-7 binding subsite is smaller than the S-8 subsite: the S-7 subsite accepts only one aromatic nucleus, while the S-8 can accommodate three coplanar nuclei altogether. These findings are compatible with the idea that the S, binding subsite may reside in the extracellular loops of the hNK-1 receptor. NK-1 agonists bind to human NK-1 receptor and activate the production of both inositol phosphates and cyclic AMP. As already quoted for septide, [pGlu(6), Pro(9)]SP(6-11), discrepancies are observed between affinity (K-i) and activity (EC(50)) values for IPs production. While a weak correlation between K-i and EC(50) values for IPs production could be found (r=0.70), an excellent correlation could be demonstrated between their affinities (K-i) and their potencies (EC(50)) for cAMP production (r=0.97). The high potency (EC(50)) observed for 'septide-like' molecules on PI hydrolysis, compared to their affinity is not an artefact related to the high level of NK-1 receptors expressed on CHO cells since a good correlation was found between EC(50) values obtained for PI hydrolysis and those measured for spasmogenic activity in guinea pig ileum bioassay (r=0.94). Copyright (C) 1996 Elsevier Science Ltd