Study of the N-Terminus Domain of the Androgen Receptor, related to the prostate cancer. – ARIA

Prostate cancer is a leading cause of death of men in the industrialized world. The prostate gland is under a strict hormonal androgen control, and prostate cancer develops initially as an androgen-dependent disease that relies on the androgen receptor (AR) for growth and progression. Relapsed prostate cancer, known as castration-resistant prostate cancer (CRPC), is associated with high mortality due to the lack of effective long-term treatment strategies, and is very often associated to important mutations in AR, such as loss of the Ligand Binding Domain (Delta-LBD) mutation.

AR has the peculiarity of presenting a very large NTerminal Domain of about 560 residues. This domain is flexible with a high degree of intrinsic disorder characteristics of an Intrinsically Disordered domain (IDP). Several homoresidues tracts are present. It also presents numerous hydrophobic and aromatic residues usually absent in disordered regions.

The limited structure of the NTerminal Domain of AR (NTD-AR ) is thought to require interactions with other proteins to assume correct folding for further protein-protein interactions including interactions with bridging factors such as CBP and the basal transcriptional machinery for active transcription. It was shown recently that some partial structure is present in the NTD-AR and is enhanced by the presence of osmolyte such as TFE or TMAO. The same work showed by fluorescence that the environment of the tryptophane residues located in the 400-530 region are affected by the length of the polyQ located more than 300 residues away. NTD-AR is also known to be the site of many cancer related mutation, either as genetic predisposition for prostate cancer or as somatic mutations, usually specific to the CRPC. Finally, small organic molecules and peptides have recently be found to interact with NTD-AR and modulate its activity, and thus could show the way to new therapeutic routes.

The ARIA project consists in bringing together different expertise (in oncology, in biology, biophysics, and in modeling) in order to improve significantly the understanding of the role of the NTD-AR domain, in particular in the context of the Prostate cancer. The aim is to establish a correspondence between biophysical properties of the NTD-AR and the cellular response of AR. To attain this goal, a multi- level approach, organized around 3 groups : PMT / IGBMC / CRCM, is necessary.

The study will be performed at several levels :
• clinicallevel/analysisofvariousphenotypefrommutationanalysisobtainedfromgeneticautopsy of prostate tumors available in the PTM group
• cellular level /activity test developed by the PTM group and molecular partner determination per- formed in collaboration between PTM and IGBMC.
• biophysical level / molecular systems analyzed using the various biophysical and modeling tech- niques available in IGBMC and CRCM, to structurally characterize dynamic of NTD-AR alone and in interactions with partners.

And using several experimental approaches
• in-cell tests of transcription activity
• biophysics of the NTD-AR: NMR, SAXS, MD, fluorescence, ITC, etc. . . alone and in interaction with protein partners and DNA Response Elements.
• proteomic search for partners, using Tap-Tag and Co-ImunoPrecipitation,

Finally, the main result sought by this study is finer understanding the NTD-AR function and organiza- tion, from which a definition of potential targets for novel therapeutic agents for prostate cancer could be made.