Receptor binding and biological activity of IL-1 alpha, IL-1 beta, IL-1 beta analogues and an IL-1 antagonist in A375 human melanoma cells

Construction of A375·S2 Melanoma Cell Line with High Sensibility to IL-1 by Overexpressing IL-1 Receptor

We described an operation that co-overexpress interleukin receptor 1 (IL-1R1) and its co-receptor (IL-1R1AcP) genes in wild-type A375·S2 cells in order to increase their sensibility to IL-1. Firstly, laser scanning confocal microscope observed that IL-1R1 could be expressed on the surface of A375·S2 cells. qPCR was performed to estimate the ratio of two genes and result showed the ratio was almost 4.57:1. Then two genes were linked to vectors and co-transfected into A375·S2 cells. qPCR and Western blotting showed the protein content improved markedly. Finally, MTS assay was executed and the sensitivity of A375·S2 cells that co-transfected receptors to IL-1β increased significantly. Another MTS assay showed the cell activity variation changed significantly (P < 0.05) and the reliability of the experiment was high, indicating that cell line established in this study could be further used for the activity test of IL-1Ra.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-022-01027-8.

Allosteric switching of agonist/antagonist activity by a single point mutation in the interluekin-1 receptor antagonist, IL-1Ra

The pleiotropic pro-inflammatory cytokine interleukin (IL)-1β has co-evolved with a competitive inhibitor, IL-1 receptor antagonist (IL-1Ra). IL-1β initiates cell signaling by binding the IL-1 receptor (IL-1R) whereas IL-1Ra acts as an antagonist, blocking receptor signaling. The current paradigm for agonist/antagonist functions for these two proteins is based on the receptor-ligand interaction observed in the crystal structures of the receptor-ligand complexes. While IL-1Ra and IL-1β are structurally homologous, IL-1Ra engages only two of the three extracellular domains of the receptor, whereas IL-1β engages all three. We find that an allosteric functional switch exists within a highly conserved pocket of residues, residues 111-120. This region is maintained across all IL-1 family members and serves as a hydrophobic mini-core for IL-1β folding. A key difference across species is a conserved aromatic residue at position 117 in IL-1β, versus a conserved cysteine in IL-1Ra at the analogous position, 116. We find that the replacement of C116 with a phenylalanine switches the protein from an antagonist to an agonist despite the distant location of C116 relative to receptor interaction sites. These results suggest new ways to develop designer cytokine activity into the β-trefoil fold and may be of general use in regulation of this large family of signaling proteins.

Interleukin-1 and interleukin-1 fragments as vaccine adjuvants

The human interleukin-1beta (IL-1beta) domain in position 163-171, comprising the amino acids VQGEESNDK, has been synthesized as a nine-amino-acid-long peptide and used in vivo as a nontoxic HCl salt. The IL-1beta nonapeptide reproduces the immunostimulatory and adjuvant effects of the whole mature IL-1beta, but does not possess any of the IL-1beta inflammatory, vasoactive, tumor-promoting, and systemically toxic effects, nor it can synergize with tumor necrosis factor alpha or other molecules in inducing toxicity and shock. The IL-1beta fragment is active as adjuvant either when administered together with the antigen or if inoculated separately; it can be physically linked to the antigen or used as a discrete peptide. Moreover, the DNA sequence encoding the IL-1beta domain has been included in an experimental DNA vaccine with positive results. Thus, immunostimulatory sequences can be identified within a pleiotropic cytokine like IL-1 and used in the rational design of novel vaccination strategies.

MSH receptors and the response of human A375 melanoma cells to interleukin-1 beta

alpha-Melanocyte-stimulating hormone (alpha-MSH, alpha-melanotropin) has been shown to be an inhibitory factor in many immunologic and inflammatory processes involving the cytokine interleukin-1 (IL-1). As the mechanism of the interaction between IL-1 and alpha-MSH at the receptor level is unknown, we have studied the role of MC1 melanocortin receptors in two variants of the human melanoma cell line A375 differing in their sensitivity to the cytostatic effects of IL-1 beta. Both IL-1 sensitive (A375r-) and resistant cells (A375r+) carry specific high affinity receptors for IL-1, albeit their concentration is 10-fold higher in A375r+ cells. In A375r- cells, MC1 receptors are absent or below the level for reliable detection in the binding assay. Conversion of A375r- to A375r+ cells by prolonged culture in medium not depleted of endotoxin led to the appearance of MC1 receptors (KD 0.4 +/- 0.123 nmol/l; 608 +/- 134 receptors/cell). Stable transfection of A375r- cells with the human MC1 receptor did not, however, render them resistant to the cytostatic effect of IL-1 beta on concomitant treatment with alpha-MSH or result in the production of IL-6 on treatment with IL-1 beta. Therefore, the presence of MC1 receptors on the surface of A375 cells or their binding to alpha-MSH does not seem to be a factor in cytokine resistance or IL-6 secretion. No interaction between IL-1 beta and alpha-MSH could be demonstrated at the cellular level in this melanoma cell line.