Développement de modulateurs allostériques peptidiques inhibiteurs de l’activité des récepteurs de l’interleukine 1 et de la vasopressine

The Module X approach was conceived to generate small allosteric peptides that do not (by definition) compete with the natural ligand to inhibit or modulate signalling.  Orthosteric inhibition blocks the entire signalling pathways while allosteric modulators will bind to another site on the target and show functional selectivity.  By reproducing  parts of the flexible regions (loops) of two receptors, the IL-1 and vasopressin receptors, we generated small peptides that showed allosteric properties.  To prove our concept we started with a pro-inflammatory target:  IL-1 receptor.  Interleukin (IL)-1 is a major pro-inflammatory cytokine which interacts with the IL-1 receptor I (IL-1RI) complex, composed of IL-1RI and IL-1R accessory protein (IL-1RacP) subunits. Presently, there are no small antagonists of the IL-1RI complex. Given this void, we derived 15 peptides from loops of IL-1RacP, which are putative interactive sites with the IL-1RI subunit. Here we substantiate the merits of one of these peptides, rytvela (we termed, 101.10), as an inhibitor of IL-1R and describe its properties consistent with those of an allosteric negative modulator. 101.10 (IC50  1 nM) blocked human thymocyte proliferation in vitro, and demonstrated robust in vivo effects in models of hyperthermia and inflammatory bowel disease as well as topically in contact dermatitis, superior to corticosteroids and IL-1ra; 101.10 did not bind to IL-1RI deficient cells and was ineffective in vivo in IL-1RI knockout mice. Importantly, characterization of 101.10, revealed non-competitive antagonist actions and functional selectivity by blocking certain IL-1R pathways while not affecting others.   The second study involved a representative of the biggest family of membrane proteins:  G-protein coupled receptors.  Vasopressin type 2 receptor (V2R) exhibits mostly important properties for hydro-osmotic equilibrium and to a lesser extent on vasomotricity. Drugs currently acting on this receptor are analogs of the natural neuropeptide, vasopressin (AVP), and hence are competitive ligands. Six peptides reproducing juxtamembranous regions of V2R were designed and screened; the most effective peptide, CRAVKY (labelled VRQ397), was characterized. VRQ397 was potent (IC50 = 0.69 ± 0.25 nM) and fully effective in inhibiting V2R-dependent physiological function (specifically DDAVP-induced cremasteric vasorelaxation; this physiological functional assay was utilized to avoid overlooking interference of specific signaling events). Dose-response profile revealed non-competitive property of VRQ397; correspondingly, VRQ397 bound specifically to V2R-expressing cells, could not displace its natural ligand, AVP, but modulated AVP binding kinetics (dissociation rate). VRQ397 exhibited pharmacological permissiveness on V2R-induced signals as it inhibited DDAVP-induced PGI2 generation, but not that of cAMP or recruitment of — arrestin2. Consistent with in vitro and ex vivo effects as a V2R antagonist, VRQ397 displayed anticipated in vivo aquaretic efficacy. Findings describe the discovery of potent and specific small (peptide) antagonists of IL-1RI and V2R with properties in line with an allosteric negative modulator.

Keyphrases: Peptides, Allosteric, Interleukin-1, Allosterism, Receptor, Interleukine-1