Steroid-binding G-protein-coupled receptors: new drug discovery targets for old ligands

How to Prepare a Compound Collection Prior to Virtual Screening

Virtual screening is a well-established technique that has proven to be successful in the identification of novel biologically active molecules, including drug repurposing. Whether for ligand-based or for structure-based virtual screening, a chemical collection needs to be properly processed prior to in silico evaluation. Here we describe our step-by-step procedure for handling very large collections (up to billions) of compounds prior to virtual screening.

Non-classical testosterone signaling in spermatogenic GC-2 cells is mediated through ZIP9 interacting with Gnα11

Although classical and non-classical signaling of testosterone has been documented in several investigations, the nature of the receptor involved in the non-classical pathway remains a source of controversy. While some investigators favor the exclusive participation of the cytosolic/nuclear androgen receptor (AR) in both pathways, others propose a membrane-bound receptor as the mediator of the non-classical testosterone signaling. Evidence is provided here that in the spermatogenic cell line GC-2 the non-classical signaling pathway of testosterone, characterized through the activation of Erk1/2 and transcription factors like CREB or ATF-1, is not mediated through the classical nuclear androgen receptor (AR) but rather by a membrane-associated receptor. This receptor is ZIP9, a Zn(2+) transporter from the family of the ZRT, IRT-like proteins (ZRT=zinc-regulated transporter; IRT=iron-regulated transporter), which directly interacts with the G-protein Gnα11. siRNA-induced abrogation of the expression of either of these two proteins, whose close contacts are demonstrated by an in situ proximity assay, completely prevents all non-classical signaling effects of testosterone addressed. In contrast, silencing of AR expression does not influence the same signaling events. The identification of ZIP9/Gnα11 interactions as the mediators of the non-classical testosterone signaling cascade in spermatogenic GC-2 cells might help to supplement our knowledge concerning the role of testosterone in male fertility and reproduction.

Compound collection preparation for virtual screening

Virtual screening is an established technique that has successfully been deployed in the identification of novel biologically active molecules. Whether for ligand-based or for structure-based virtual screening, a chemical collection needs to be properly processed prior to in silico evaluation. Here we describe our step-by-step procedure for handling large collections of compounds prior to virtual screening.

Linkage effects on binding affinity and activation of GPR30 and estrogen receptors ERalpha/beta with tridentate pyridin-2-yl hydrazine tricarbonyl-Re/(99m)Tc(I) chelates

We describe a new structural class of neutral tridentate pyridin-2-yl hydrazine chelates for labeling with tricarbonyl Re/99mTc(I) under aqueous conditions and investigate the receptor binding of synthetic estradiol derivatives with the novel G-protein-coupled receptor GPR30 and estrogen receptors ERalpha/beta. The steroid linkage affected the affinity and selectivity of estrogen binding with these receptors. Fluorescence assays based on calcium signaling demonstrate that membrane-permeable chelates 2 and 3 interact with the receptors in whole cells. These results suggest that in vitro assays will facilitate the development of targeted imaging agents for intracellular receptors and the feasibility of targeting GPR30 and ERalpha/beta for diagnostic tumor imaging.