PRESENCE OF VARIOUS CARBOHYDRATE MOIETIES INCLUDING BETA-GALACTOSE AND N-ACETYLGLUCOSAMINE RESIDUES ON SOLUBILIZED PORCINE BRAIN NEUROKININ-1/SUBSTANCE P-RECEPTORS

Neurokinin-1 (NK-1)/substance P (SP) receptors were solubilized using 10 mM 3-[(cholamidopropyl)-dimethylammonio]-1-propanesulfate from porcine striatal membranes (solubilization yield, 80%). In solubilized preparations, [H-3]SP apparently bound to a single class of high-affinity sites (K(D) = 0.82 +/- 0.13 nM) as in membrane homogenates. The ligand selectivity pattern observed in both membrane and solubilized receptor preparations indicated that [Sar9,Met(O2)11]SP = SP >> senktide = [Nle10]neurokinin A4-10. This suggests the selective labeling of the NK-1 receptor class in both assays. Solubilized receptors were retained on agarose-coupled lectins that bind N-acetylglucosamine-galactose and beta-galactose (Ricinus communis I and Ricinus communis II), mannose (concanavalin A and lentil), and N-acetylglucosamine (wheat germ agglutinin) but not on lectins binding fucose (Lotus A) and N-acetylgalactosamine (Dolichos biflorus A). Thus, it appears that porcine brain NK-1/SP receptors are enriched with various carbohydrate moieties, beta-galactose and N-acetylglucosamine-galactose residues being especially abundant. This situation is rather different from that in various other members of the rhodopsin seven-transmembrane receptor superfamily.