Unique Interactome Network Signatures for Peroxisome Proliferator-activated Receptor Gamma (PPARγ) Modulation by Functional Selective Ligands

Peroxisome proliferator-activated receptors (PPARs) as a mediator of dietary fatty acids affects reproductive performance in broiler breeder roosters

This study analyzed the effects of dietary sources of omega-3 and omega-6 fatty acids on semen parameters and fertility potential in broiler breeder roosters. The mRNA and protein profiles of peroxisome proliferator-activated receptors-γ (PPAR-γ) expression in sperm as potential mediator of FAs were considered. Roosters were categorized into three groups and received their diets for 24 weeks as follows: 1) control diet received a basal diet (CTRL); 2) Fish oil based diet (FO) received the basal diet supplemented with 15 g/kg of diet fish oil; and 3) sunflower oil based diet (SO) received the basal diet supplemented with 15 g/kg of diet sunflower oil. While the different diets had significant effects on semen parameters, the effect of sampling time was not significant. The effect of the diets on sperm parameters were significantly higher in the SO and FO groups in total motility, progressive motility, amplitude of lateral head displacement, linearity, straightness, wobble and viability (P ≤ 0.05). Fertility rate was significantly improved in the FO and SO groups (P = 0001). The highest value for PPAR-γ mRNA was observed in the SO group compared to other groups (P ≤ 0.05). Moreover, supplementation of the roosters' diets with FO and SO increased PPAR-γ protein expression compared to the control. It seems that PPAR-γ could be a strong potential mediator of the underlying mechanism of improvement in semen parameters and reproductive performance of roosters under the effects of both dietary omega-3 and omega-6 polyunsaturated fatty acids.

Definition of functionally and structurally distinct repressive states in the nuclear receptor PPARγ

The repressive states of nuclear receptors (i.e., apo or bound to antagonists or inverse agonists) are poorly defined, despite the fact that nuclear receptors are a major drug target. Most ligand bound structures of nuclear receptors, including peroxisome proliferator-activated receptor γ (PPARγ), are similar to the apo structure. Here we use NMR, accelerated molecular dynamics and hydrogen-deuterium exchange mass spectrometry to define the PPARγ structural ensemble. We find that the helix 3 charge clamp positioning varies widely in apo and is stabilized by efficacious ligand binding. We also reveal a previously undescribed mechanism for inverse agonism involving an omega loop to helix switch which induces disruption of a tripartite salt-bridge network. We demonstrate that ligand binding can induce multiple structurally distinct repressive states. One state recruits peptides from two different corepressors, while another recruits just one, providing structural evidence of ligand bias in a nuclear receptor.

The repressive states of peroxisome proliferator-activated receptor γ (PPARγ) are ill-defined, despite nuclear receptors being a major drug target. Here authors demonstrate multiple structurally distinct repressive states, providing a structural rationale for ligand bias in a nuclear receptor.

Elucidating the Beneficial Role of PPAR Agonists in Cardiac Diseases

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that bind to DNA and regulate transcription of genes involved in lipid and glucose metabolism. A growing number of studies provide strong evidence that PPARs are the promising pharmacological targets for therapeutic intervention in various diseases including cardiovascular disorders caused by compromised energy metabolism. PPAR agonists have been widely used for decades as lipid-lowering and anti-inflammatory drugs. Existing studies are mainly focused on the anti-atherosclerotic effects of PPAR agonists; however, their role in the maintenance of cellular bioenergetics remains unclear. Recent studies on animal models and patients suggest that PPAR agonists can normalize lipid metabolism by stimulating fatty acid oxidation. These studies indicate the importance of elucidation of PPAR agonists as potential pharmacological agents for protection of the heart from energy deprivation. Here, we summarize and provide a comprehensive analysis of previous studies on the role of PPARs in the heart under normal and pathological conditions. In addition, the review discusses the PPARs as a therapeutic target and the beneficial effects of PPAR agonists, particularly bezafibrate, to attenuate cardiomyopathy and heart failure in patients and animal models.

Profiling of 3696 Nuclear Receptor-Coregulator Interactions: A Resource for Biological and Clinical Discovery

Nuclear receptors (NRs) are ligand-inducible transcription factors that play critical roles in metazoan development, reproduction, and physiology and therefore are implicated in a broad range of pathologies. The transcriptional activity of NRs critically depends on their interaction(s) with transcriptional coregulator proteins, including coactivators and corepressors. Short leucine-rich peptide motifs in these proteins (LxxLL in coactivators and LxxxIxxxL in corepressors) are essential and sufficient for NR binding. With 350 different coregulator proteins identified to date and with many coregulators containing multiple interaction motifs, an enormous combinatorial potential is present for selective NR-mediated gene regulation. However, NR-coregulator interactions have often been determined experimentally on a one-to-one basis across diverse experimental conditions. In addition, NR-coregulator interactions are difficult to predict because the molecular determinants that govern specificity are not well established. Therefore, many biologically and clinically relevant NR-coregulator interactions may remain to be discovered. Here, we present a comprehensive overview of 3696 NR-coregulator interactions by systematically characterizing the binding of 24 nuclear receptors with 154 coregulator peptides. We identified unique ligand-dependent NR-coregulator interaction profiles for each NR, confirming many well-established NR-coregulator interactions. Hierarchical clustering based on the NR-coregulator interaction profiles largely recapitulates the classification of NR subfamilies based on the primary amino acid sequences of the ligand-binding domains, indicating that amino acid sequence is an important, although not the only, molecular determinant in directing and fine-tuning NR-coregulator interactions. This NR-coregulator peptide interactome provides an open data resource for future biological and clinical discovery as well as NR-based drug design.