Characteristics of Non-opioid beta-Endorphin Receptor

E. V. Navolotskaya^1*, Yu. A. Kovalitskaya¹, Yu. A. Zolotarev², A. A. Kolobov³, E. A. Kampe-Nemm³, N. V. Malkova¹, V. V. Yurovsky⁴, and V. M. Lipkin¹

¹Branch of Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, pr. Nauki 6, Pushchino 142290, Moscow Region, Russia; fax: (0967) 33-0527; E-mail: navolots@fibkh.serpukhov.su

²Institute of Molecular Genetics, Russian Academy of Sciences, pl. Kurchatova 2, Moscow 123182, Russia; fax: (7-095) 196-0221

³State Research Center, Institute of Highly Pure Biopreparations, Ministry of Health of the Russian Federation, ul. Pudozhskaya 7, St. Petersburg 197110, Russia; fax: (7-812) 235-5504

⁴Department of Medicine, University of Maryland, Baltimore, MD 21201, USA; fax: (410) 706-0231

^* To whom correspondence should be addressed.

Received May 13, 2003; Revision received June 2, 2003

---

Tritium-labeled selective agonist of non-opioid beta-endorphin receptor, the decapeptide immunorphine ([³H]SLTCLVKGFY) with specific activity of 24 Ci/mmol has been prepared. By its use, non-opioid beta-endorphin receptors were revealed and characterized on mouse peritoneal macrophages and rat myocardium, spleen, adrenal, and brain membranes. The non-opioid beta-endorphin receptor of macrophages has in addition to immunorphine (K_d of the [³H]immunorphine-receptor complex was 2.4 ± 0.1 nM) and beta-endorphin (K_i of the [³H]immunorphine specific binding was 2.9 ± 0.2 nM) a high affinity for Fc-fragment of human IgG1, pentarphine (VKGFY), cyclopentarphine [cyclo(VKGFY)], and [Pro³]pentarphine (VKPFY) (K_i values were 0.0060 ± 0.0004, 2.7 ± 0.2, 2.6 ± 0.2, and 2.8 ± 0.2 nM, respectively) and is insensitive to naloxone and [Met⁵]enkephalin (K_i > 100 µM). Treatment of macrophages with trypsin resulted in the loss of their ability for the specific binding of [³H]immunorphine. Values of the specific binding of 8.4 nM [³H]immunorphine to rat adrenal, spleen, myocardium, and brain membranes were determined to be 1146.0 ± 44.7, 698.6 ± 28.1, 279.1 ± 15.4, and 172.2 ± 1.8 fmol/mg protein, respectively. Unlabeled beta-endorphin, pentarphine, [Pro³]pentarphine, cyclopentarphine, cyclodipentarphine [cyclo(VKGFYVKGFY)], and Fc-fragment of IgG1 inhibited the binding of [³H]immunorphine to membranes from these organs. No specific binding of [³H]immunorphine to rat liver, lung, kidney, and intestine membranes was found.

---

KEY WORDS: beta-endorphin, naloxone, immunoglobulin G, peptides, receptors

---