NALOXONE-SENSITIVE, HALOPERIDOL-SENSITIVE [H-3] (-10047-BINDING PROTEIN PARTIALLY PURIFIED FROM RAT-LIVER AND RAT-BRAIN MEMBRANES - AN OPIOID()SKF)SIGMA RECEPTOR/

A naloxone-sensitive, haloperidol-sensitive, [H-3](+)SKF-10047-binding protein was partially purified from rat liver and rat brain membranes in an affinity chromatography originally designed to purify sigma rec eptors. Detergent-solubilized extracts from membranes were adsorbed to Sephadex G-25 resin containing an affinity ligand for sigma receptors : l)-N-(6-aminohexyl)-(2-[1-pyrrolidinyl])ethylamine (DAPE). After elu ting the resin with haloperidol, a protein that bound [H-3](+)SKF-1004 7 was detected in the eluates. However, the protein was not the sigma receptor [H-3](+)SKF-10047 binding to the protein was inhibited by the following compounds in the order of decreasing potency: (+)pentazocin e > (-) pentazocine > (+/-)cyclazocine > (-)morphine > (-)naloxone > h aloperidol > (+)SKF-10047 > DADLE > (-)SKF-10047. Further, the prototy pic sigma receptor ligands, such as 1,3-di-o-tolylguanidine (DTG), (+) 3-PPP, and progesterone, bound poorly to the protein. Tryptic digestio n and heat treatment of the affinity-purified protein abolished radiol igand binding. Sodium dodecyl sulfate/polyacrylamide gel electrophores is (SDS/PAGE) of the partially-purified protein from the liver reveale d a major diffuse band with a molecular mass of 31 kDa, a polypeptide of 65 kDa, and another polypeptide of > 97 kDa. This study demonstrate s the existence of a novel protein in the rat liver and rat brain whic h binds opioids, benzomorphans, and haloperidol with namomolar affinit y. The protein resembles the opioid/sigma receptor originally proposed by Martin et al. [(1976): J. Pharmacol. Exp. Ther., 197:5 17-532.]. A high degree of purification of this protein has been achieved in the present study. (C) 1997 Wiley-Liss, Inc.