Lipophilic molecules including steroid hormones, retinoids, fatty acids, and dietary lipids control reproductive, developmental and metabolic processes by directly binding and modulating the activities of nuclear receptors (NRs). NRs bind to DNA and regulate the expression of gene programs that lead to physiological responses to their small-molecule ligands. Structural studies over the past few decades have focused primarily on just the ligand binding domains (LBDs) or DNA-binding domains (DBDs) of NRs, but were unable to reveal how the multi-domain architectures are integrated in a quaternary structure. To understand the physical and functional coupling of different receptor domains, we have been conducting X-ray diffraction studies involving full-length and multi-domain nuclear receptor complexes in their functionally revealing complexes bound to DNA, ligands, and coregulator peptides. Our previous studies revealed that DBDs and LBDs of the PPAR?-RXR? heterodimer and HNF-4? homodimer are physically linked through a highly interfaced arrangement of domain surfaces, some of which are DNA-dependent. We now propose to considerably broaden our understanding of the domain-domain connections and allosteric communications in the nuclear receptor family. We will obtain the crystal structures of three new NR complexes that include the Retinoic-Acid Receptor (RAR) heterodimer with Retinoid X Receptor (RXR), the progesterone receptor (PR) homodimer, and the monomeric Rev-Erb? receptor. These differing NRs also discern distinct response elements consisting of direct repeats, inverted repeats, and single half-sites, thus, distinctive domain-domain interfaces are anticipated as compared to previously seen in PPAR?-RXR? or HNF-4?. We further propose to conduct a series of complementary biochemical and cell-based functional studies to probe and quantitate the mechanistic underpinning of inter- domain allosteric signal propagation in these receptor complexes.

Public Health Relevance

In humans, steroids, retinoids, dietary lipids and a variety of other signaling small-molecules bind directly to nuclear receptors, a family of ligand-activated transcription factors that can transduce these signals into changes in gene expression programs. Approximately, 15% of all the prescription drugs currently in use bind to nuclear receptors, and this proposal seeks to explore the structural basis and molecular mechanisms of how ligand and DNA binding are mediated. The studies focus on three nuclear receptors that function in human embryonic development, fertility, and lipid metabolism.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM120532-02
Application #
9491848
Study Section
Macromolecular Structure and Function C Study Section (MSFC)
Program Officer
Sledjeski, Darren D
Project Start
2017-06-01
Project End
2021-02-28
Budget Start
2018-03-01
Budget End
2019-02-28
Support Year
2
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Sanford Burnham Prebys Medical Discovery Institute
Department
Type
DUNS #
020520466
City
La Jolla
State
CA
Country
United States
Zip Code
92037
Chandra, Vikas; Wu, Dalei; Li, Sheng et al. (2017) The quaternary architecture of RAR?-RXR? heterodimer facilitates domain-domain signal transmission. Nat Commun 8:868