Conformational flexibility of apolipoprotein A-I amino- and carboxy-termini is necessary for lipid binding but not cholesterol efflux.

Because of its critical role in HDL formation, significant efforts have been devoted to studying apolipoprotein A-I (APOA1) structural transitions in response to lipid binding. To assess the requirements for the conformational freedom of its termini during HDL particle formation, we generated three dimeric APOA1 molecules with their termini covalently joined in different combinations. The dimeric (d)-APOA1C-N mutant coupled the C-terminus of one APOA1 molecule to the N-terminus of a second with a short alanine linker, whereas the d-APOA1C-C and d-APOA1N-N mutants coupled the C-termini and the N-termini of two APOA1 molecules, respectively, using introduced cysteine residues to form disulfide linkages.

Apolipoprotein A-I modulates HDL particle size in the absence of apolipoprotein A-II.

Human high-density lipoproteins (HDLs) are a complex mixture of structurally related nanoparticles that perform distinct physiological functions. We previously showed that human HDL containing apolipoprotein A-I (APOA1) but not apolipoprotein A-II (APOA2), designated LpA-I, is composed primarily of two discretely sized populations. Here, we isolated these particles directly from human plasma by antibody affinity chromatography, separated them by high-resolution size-exclusion chromatography and performed a deep molecular characterization of each species.

MUTATIONS IN LIVER X RECEPTOR ALPHA THAT IMPAIR DIMERIZATION AND LIGAND DEPENDENT TRANSACTIVATION.

Liver X receptor alpha (LXRα) is crucial for the maintenance of lipid and cholesterol homeostasis. Ligand binding and dimerization with retinoid X receptor (RXR) or peroxisome proliferator-activated receptor (PPAR) is required for forming active DNA binding complexes leading to gene regulation. Structure based prediction and solvent accessibility of LXRα LBD shows that residues H383, E387, H390, L414, and R415 which are located in helices 9 and 10 may be critical for mediating protein-protein interactions.

Cullin-4 regulates Wingless and JNK signaling-mediated cell death in the Drosophila eye.

In all multicellular organisms, the fundamental processes of cell proliferation and cell death are crucial for growth regulation during organogenesis. Strict regulation of cell death is important to maintain tissue homeostasis by affecting processes like regulation of cell number, and elimination of unwanted/unfit cells. The developing Drosophila eye is a versatile model to study patterning and growth, where complex signaling pathways regulate growth and cell survival.

Fatty acid binding profile of the liver X receptor α.

Liver X receptor (LXR)α is a nuclear receptor that responds to oxysterols and cholesterol overload by stimulating cholesterol efflux, transport, conversion to bile acids, and excretion. LXRα binds to and is regulated by synthetic (T-0901317, GW3695) and endogenous (oxysterols) ligands. LXRα activity is also modulated by FAs, but the ligand binding specificity of FA and acyl-CoA derivatives for LXRα remains unknown.

Phosphatidic Acid (PA) can Displace PPARα/LXRα Binding to The EGFR Promoter Causing its Transrepression in Luminal Cancer Cells.

The expression of the epidermal growth factor receptor (EGFR) is highly regulated in normal cells, whereas some cancer cells have high constitutive levels. Understanding naturally-occurring ways of downregulating EGFR in cancer cells was investigated. Phosphatidic acid (PA) or Nuclear Receptors (NR) PPARα/RXRα/LXRα, enhance EGFR expression, mediated by the promoter region -856(A) to -226(T).

Divergence between human and murine peroxisome proliferator-activated receptor alpha ligand specificities.

Peroxisome proliferator-activated receptor α (PPARα) belongs to the family of ligand-dependent nuclear transcription factors that regulate energy metabolism. Although there exists remarkable overlap in the activities of PPARα across species, studies utilizing exogenous PPARα ligands suggest species differences in binding, activation, and physiological effects. While unsaturated long-chain fatty acids (LCFA) and their thioesters (long-chain fatty acyl-CoA; LCFA-CoA) function as ligands for recombinant mouse PPARα (mPPARα), no such studies have been conducted with full-length human PPARα (hPPARα).

Activation of JNK signaling mediates amyloid-ß-dependent cell death.

Background: Alzheimer's disease (AD) is an age related progressive neurodegenerative disorder. One of the reasons for Alzheimer's neuropathology is the generation of large aggregates of Aß42 that are toxic in nature and induce oxidative stress, aberrant signaling and many other cellular alterations that trigger neuronal cell death. However, the exact mechanisms leading to cell death are not clearly understood.