SOT 2018

PamGene and it's collaborators presented the following posters at the Society of Toxicology's 57th Annual Meeting in San Antonio, Texas (March 11th to 15th 2018). 
You can now download PDF copies of the Posters

 

 

9:15am - 4:30pm Tue, Mar 13. Poster number 2320, Poster board P665

Selective Biological Action of Bisphenol A, AF, and S Involves Differential Coregulator Interactions

Y. Li1, L. Perera1, L. Coons1, K. Burns1, J. Ramsey1, K. Pelch1, R. Houtman2, R. Beuningen2, C. Teng1, C. Teng1, and K. Korach1. 1NIEHS, Research Triangle Park, NC; and 2PamGene International, s-Hertogenbosch, Netherlands. Sponsor: Y. Li

 

Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) found to be harmful to human health. Recently, widespread usage of bisphenol chemicals (BPs) such as BPAF and BPS are used as replacements for BPA. However, the potential biological actions, toxicity, and the molecular mechanism of these compounds are still poorly understood. Our objective was to examine the estrogenic effects of BPA, BPAF, and BPS and the molecular mechanisms of action in the estrogen receptor alpha (ERα)-complex. In this study, in vitro cell models were used to compare the estrogenic effects of BPA, BPAF, and BPS to estrogen. Microarray Assay for Real-Time Coregulator-Nuclear receptor Interaction analysis was used to identify coregulators of BPA, BPAF, and BPS and molecular dynamic (MD) simulations were used to determine the bindings in the ERα-complex. We demonstrated that BPA and BPAF have agonistic activity for both ERα and ERβ but BPS has ERα selective specificity. We concluded that coregulators were differentially recruited in the presence of BPA, BPAF, or BPS. Interestingly, BPS recruited more corepressors when compared to BPA and BPAF. From a series of MD analysis, we concluded that BPA, BPAF, and BPS can bind to the ER-ligand binding domain with differing energetics and conformations. In addition, the binding surface of coregulator on ERα was characterized for the BPA, BPAF, and BPS complexes. These findings provide an important basis for the understanding of the molecular mechanisms of EDCs, such as BPs, in ER-mediated transcriptional activation, biological activity, and their effects on physiological functions in human health.

 

9:15am - 4:30pm  Tue, Mar 13. Poster number 1828, Poster board P157

Nuclear Co-Regulator Interactions with the Constitutive Androstane Receptor

R. Houtman1, R. van Beuningen1, N. Bastiaensen1, J. P. Gajewski2, H. M. Cavalier2, and C. J. Omiecinski2. 1PamGene International, 5211HH Den Bosch, Netherlands; and 2Penn State University, University Park, PA.

 

The constitutive androstane receptor (CAR; NR1I3) is a member of the nuclear receptor (NR) superfamily that regulates important toxicological and physiological processes, included xenobiotic metabolism and energy homeostasis. Subsequent to its nuclear translocation in hepatocytes, triggered by receptor activators, CAR recruits both its heterodimerization partner, RXR, together with nuclear co-regulator (CoReg) proteins to modulate transcriptional activity across CAR target genes. Although several CAR-CoReg interactions have been identified, over 300 CoReg proteins exist. As most NRs are ligand activated, the dynamics of specific ligand-NR-CoReg interactions ultimately integrate downstream transcriptional events and determine resulting biological/toxicological responses arising from the ligand exposures. We hypothesize that CAR’s interaction profile with CoRegs likely differs between rodents and humans, among the human CAR splice variants, and even between hepatocytes across the liver lobule. To begin to test this hypothesis, we used a MARCoNI platform (micro array assay for real-time CoReg-NR interaction). CAR interactions across a solid phase matrix of 154 CoReg peptides were simultaneously quantified. Since wild type CAR is constitutively active, the 5 amino acid insertion present in the ligand-activated human CAR3 splice variant was used to assess CAR interactions, in the presence and absence of both direct and indirect CAR activators. Similarly, the 4 amino acid-substituted human CAR2 splice variant was also tested. A protocol was developed enabling E. coli expression of His-tagged ligand binding domains of various CARs from human and mouse as probes for CoReg interaction across the arrays. The assay successfully identified both previously characterized as well as novel CAR-CoReg interactions. Novel interactions included those with MED1 and BRD8, CoRegs described as modulating transcriptional function of the thyroid hormone receptor, of interest given CAR’s role as an energy regulator. The arrays also identified selective DEHP activation of CAR2 with several CoRegs, including NCOA2/3, PRGC1 and NROB2. These results and use of the MARCoNI platform enabled novel discovery insights for CAR-CoReg interactions that underpin the important biological roles of this nuclear receptor.