Naloxone-sensitive, haloperidol-sensitive, [3H] (+) SKF-10047-binding protein partially purified from rat liver and rat brain membranes: An opioid/sigma receptor?
✍ Scribed by Li-i Tsao; Tsung-Ping Su
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 111 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0887-4476
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✦ Synopsis
A naloxone-sensitive, haloperidol-sensitive, 3 HSKF-10047-binding protein was partially purified from rat liver and rat brain membranes in an affinity chromatography originally designed to purify sigma receptors. Detergent-solubilized extracts from membranes were adsorbed to Sephadex G-25 resin containing an affinity ligand for sigma receptors:
)ethylamine (DAPE). After eluting the resin with haloperidol, a protein that bound 3 HSKF-10047 was detected in the eluates. However, the protein was not the sigma receptor. 3 HSKF-10047 binding to the protein was inhibited by the following compounds in the order of decreasing potency: (1)pentazocine . (2)pentazocine . (6)cyclazocine . (2)morphine . (2)naloxone . haloperidol . (1)SKF-10047 . DADLE .
(2)SKF-10047. Further, the prototypic sigma receptor ligands, such as 1,3-di-o-tolylguanidine (DTG), (1)3-PPP, and progesterone, bound poorly to the protein. Tryptic digestion and heat treatment of the affinity-purified protein abolished radioligand binding. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE) of the partially-purified protein from the liver revealed a major diffuse band with a molecular mass of 31 kDa, a polypeptide of 65 kDa, and another polypeptide of . 97 kDa. This study demonstrates the existence of a novel protein in the rat liver and rat brain which binds opioids, benzomorphans, and haloperidol with namomolar affinity. The protein resembles the opioid/sigma receptor originally proposed by Martin et al. [(1976):