Nestorone® as a Novel Progestin for Nonoral Contraception:Structure-Activity Relationships and Brain Metabolism Studies

Nestorone® (NES) is a highly potent non-androgenic progestin being developed for contraception. NES is a synthetic progestin that may possess neuroprotective and myelin regenerative potential as an added health benefits. In receptor transactivation experiments, NES displayed greater potency than progesterone to transactivate the human progesterone receptor (hPR). This was confirmed by docking experiments which revealed that NES adopts the same docking position within the PR ligand-binding domain (LBD) as progesterone and forms additional stabilizing contacts between 17α-acetoxy and 16-methylene groups and PR LBD supporting its higher potency than progesterone. The analogue 13-ethyl NES also establishes similar contacts as NES with Met909, leading to comparable potency as NES. In contrast, NES is not stabilized within the human androgen receptor (hAR)-LBD leading to negligible AR transactivation. Since progesterone acts in the brain by both PR-binding and indirectly via the metabolite allopregnanolone binding to GABA_A receptor (GABA_A_R), we investigated if NES is metabolized to 3α, 5α-tetrahydronestorone (3α, 5α-THNES) in the brain and if this metabolite could interact with GABA_A_R. In female mice, low concentrations of reduced NES metabolites were identified by Gas Chromatography-Mass Spectrometry in both plasma and brain. However, electrophysiological studies showed that 3α, 5α-THNES exhibited only limited activity to enhance GABAAR-evoked responses with WSS-1 cells and did not modulate synaptic GABA_A_Rs of mouse cortical neurons. Thus the inability of reduced metabolite of NES (3α, 5α-THNES) to activate GABA_A_R suggests that the neuroprotective and myelin regenerative effects of NES are mediated via PR binding and not via its interaction with the GABA_A_R

Etude des mécanismes d'activation et d'inactivation du récepteur de la progestérone

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

The folded and disordered domains of human ribosomal protein SA have both idiosyncratic and shared functions as membrane receptors

International audienceThe human RPSA [ribosomal protein SA; also known as LamR1(laminin receptor 1)] belongs to the ribosome but is also a membrane receptor for laminin, growth factors, prion, pathogens and the anticarcinogen EGCG (epigallocatechingallate). It contributes to the crossing of the blood-brain barrier by neurotropic viruses and bacteria, and is a biomarker of metastasis. RPSA includes an N-terminal domain, which is folded and homologous to the prokaryotic RPS2, and a C-terminal extension, which is intrinsically disordered and conserved in vertebrates. We used recombinant derivatives of RPSA and its N-and C-domains to quantify its interactions with ligands by in-vitro immunochemical and spectrofluorimetric methods. Both N-and C-domains bound laminin with K D (dissociation constants) of 300 nM. Heparin bound only to the N-domain and competed for binding to laminin with the negatively charged C-domain, which therefore mimicked heparin. EGCG bound only to the N-domain with a K D of 100 nM. Domain 3 of the envelope protein from yellow fever virus and serotypes-1 and-2 of dengue virus bound preferentially to the C-domain whereas that from West Nile virus bound only to the N-domain. Our quantitative in-vitro approach should help clarify the mechanisms of action of RPSA, and ultimately fight against cancer and infectious agents

Met909 plays a key role in the activation of the progesterone receptor and also in the high potency of 13-ethyl progestins

ABSTRACT Many progestins have been developed for use in contraception, menopausal hormone therapy, and treatment of gynecological diseases. They are derived from either progesterone or testosterone, and they act by binding to the progesterone receptor (PR), a hormone-inducible transcription factor belonging to the nuclear receptor superfamily. Unlike mineralocorticoid, glucocorticoid, and androgen receptors, the steroid-receptor contacts that trigger the switch of the ligand-binding domain from an inactive to an active conformation have not yet been identified for the PR. With this aim, we solved the crystal structure of the ligand-binding domain of the human PR complexed with levonorgestrel, a potent testosterone-derived progestin characterized by a 13-ethyl substituent. Via mutagenesis analysis and functional studies, we identified Met909 of the helix 12 as the key residue for PR activation by both testosterone-and progesterone-derived progestins with a 13-methyl or a 13-ethyl substituent. We also showed that Asn719 contributes to PR activation by testosterone-derived progestins only, and that Met759 and Met909 are responsible for the high potency of 19-norprogestins and of 13-ethyl progestins, respectively. Our findings provide a structural guideline for the rational synthesis of potent PR agonist and antagonist ligands that could have therapeutic uses in women's health

Multiple Folding States and Disorder of Ribosomal Protein SA, a Membrane Receptor for Laminin, Anticarcinogens, and Pathogens

The human ribosomal protein SA (RPSA) is a multilocus protein, present in most cellular compartments. It is a multifunctional protein, which belongs to the ribosome but is also a membrane receptor for laminin, growth factors, prion, pathogenic microorganisms, toxins, and the anticarcinogen epigallocatechin gallate. It contributes to the crossing of the blood–brain barrier by neurotropic viruses and bacteria and is used as a biomarker of metastasis. RPSA includes an N-terminal domain, which is homologous to the prokaryotic ribosomal proteins S2, and a C-terminal extension, which is conserved in vertebrates. The structure of its N-domain has been determined from crystals grown at 17 °C. The structure of its C-domain remains unknown. We produced in <i>Escherichia coli</i> and purified the full-length RPSA and its N- and C-domains. We characterized the folding states of these recombinant proteins mainly by methods of fluorescence and circular dichroism spectrometry, in association with quantitative analyses of their unfolding equilibria, induced with heat or urea. The necessary equations were derived from first principles. The results showed that the N-domain unfolded according to a three-state equilibrium. The monomeric intermediate was predominant at the body temperature of 37 °C. It also existed in the full-length RPSA and bound ANS, a small fluorescent molecule. The C-domain was in an intrinsically disordered state. The recombinant N- and C-domains weakly interacted together. These results indicated a high plasticity of RPSA, which could be important for its multiple cellular localizations and functional interactions