[Interaction of synthetic decapeptide SLTCLVKGFY with human T lymphocytes]. / Vzaimodeistvie sinteticheskogo dekapeptida SLTCLVKGFY s T-limfotsitami cheloveka.

The synthetic peptide SLTCLVKGFY, corresponding to the 364-373 amino acid sequence of the human IgG heavy chain (Immunorphin), was found to compete with [125I] beta-endorphin for binding by high-affinity receptors on T lymphocytes isolated from the blood of healthy donors (Ki 0.6 nM). The fragments 3-10, 4-10, 5-10, and 6-10 of Immunorphin also inhibited the binding (Ki 2.2, 3.4, 8.0, and 15 nM, respectively). Specificity of these receptors was studied: they turned out to be insensitive to naloxone and, therefore, are not opioid. The Kd values of the specific binding of 125I-labeled Immunorphin and its 6-10 fragment to the receptor were found to be 7.4 and 36.3 nM, respectively.

Effect of synthetic beta-endorphin-like peptide immunorphin on human T lymphocytes.

Beta-endorphin and the synthetic beta-endorphin-like decapeptide Ser-Leu-Thr-Cys-Leu-Val-Lys-Gly-Phe-Tyr (referred to as immunorphin), corresponding to the sequence 364-373 of the CH3 domain of human immunoglobulin G heavy chain, were shown to stimulate concanavalin A-induced proliferation of T lymphocytes from the blood of healthy donors. [Met(5)]Enkephalin and the antagonist of opioid receptors naloxone examined in parallel were inactive. The stimulating effect of beta-endorphin and immunorphin on T lymphocyte proliferation is not inhibited by naloxone. Studies on receptor binding of (125)I-labeled immunorphin to T lymphocytes revealed that it binds with high affinity to naloxone-insensitive receptors (K(d) = 7.0 +/- 0.3 nM). Unlabeled immunorphin completely inhibits (125)I-labeled beta-endorphin specific binding to naloxone-insensitive receptors on T lymphocytes (K(i) = 0.6 +/- 0.1 nM). Thus, beta-endorphin and immunorphin interact with common naloxone-insensitive receptors on T lymphocytes.

beta-Endorphin-like peptide SLTCLVKGFY is a selective agonist of nonopioid beta-endorphin receptor.

It has been found that beta-endorphin (beta-END) and a synthetic beta-END-like decapeptide Ser-Leu-Thr-Cys-Leu-Val-Lys-Gly-Phe-Tyr (termed immunorphin, IMN) corresponding to the sequence 364-373 of human IgG heavy chain stimulate Con A-induced proliferation of T lymphocytes from the blood of healthy donors. [Met(5)]enkephalin ([Met(5)]ENK) and an antagonist of opioid receptors naloxone (NAL) tested in parallel were not active. The stimulating effect of beta-END and IMN on T lymphocyte proliferation was not inhibited by NAL. Studies on receptor binding of (125)I-labeled IMN to T lymphocytes revealed that it binds with high affinity to NAL-insensitive binding sites (K(d) = 7.0 +/- 0.3 nM). Unlabeled beta-END completely inhibited the specific binding of (125)I-labeled IMN to NAL-insensitive binding sites on T lymphocytes (K(i) = 1.1 +/- 0.2 nM). Thus, beta-END and IMN bind to common NAL-insensitive binding sites on T lymphocytes and enhance Con A-induced proliferation of these cells.

Synthetic peptide VKGFY and its cyclic analog stimulate macrophage bactericidal activity through non-opioid beta-endorphin receptors.

We synthesized linear and cyclic pentapeptides corresponding to the sequence 369-373 of human immunoglobulin G heavy chain--VKGFY (referred to as pentarphin and cyclopentarphin, respectively). The effect of pentarphin and cyclopentarphin on phagocytosis of Salmonella typhimurium virulent 415 strainbacteria by mouse peritoneal macrophages in vitro was studied. Control experiments showed that macrophages actively captured these bacteria, but did not digest them: the captured microbes were viable and continued to proliferate inside the phagocytes; within 12 h all macrophage monolayer was destroyed (incomplete phagocytosis). If 1 nM pentarphin or cyclopentarphin was added to the cultivation medium, macrophage bactericidal activity was significantly increased and they digested all captured microorganisms within 6 h (complete phagocytosis). To study the receptor binding properties of pentarphin and cyclopentarphin we prepared (125)I-labeled pentarphin (179 Ci/mmol specific activity). The binding of (125)I-labeled pentarphin to mouse peritoneal macrophages was high-affinity (K(d) = 3.6 +/- 0.3 nM) and saturable. Studies on binding specificity revealed that this binding was insensitive to naloxone and [Met(5)]enkephalin, but completely inhibited by unlabeled cyclopentarphin (K(i) = 2.6 +/- 0.3 nM), immunorphin (K(i) = 3.2 +/- 0.3 nM), and beta-endorphin (K(i) = 2.8 +/- 0.2 nM). Thus, the effects of pentarphin and cyclopentarphin on macrophages are mediated by naloxone-insensitive receptors common for pentarphin, cyclopentarphin, immunorphin, and beta-endorphin.