Identification of small molecule regulators of the nuclear receptor HNF4alpha based on naphthofuran scaffolds.

Nuclear receptors are ligand-activated transcription factors involved in all major physiological functions of complex organisms. In this respect, they are often described as drugable targets for a number of pathological states including hypercholesterolemia and atherosclerosis. HNF4alpha (NR2A1) is a recently 'deorphanized' nuclear receptor which is bound in vivo by linoleic acid, although this natural ligand does not seem to promote transcriptional activation. In mouse, HNF4alpha is a major regulator of liver development and hepatic lipid metabolism and mutations in human have been linked to diabetes. Here, we have used a yeast one-hybrid system to identify small molecule activators of HNF4alpha in a library of synthetic compounds and found one hit bearing a methoxy group branched on a nitronaphthofuran backbone. A collection of molecules deriving from the discovered hit was generated and tested for activity toward HNF4alpha in yeast one-hybrid system. It was found that both the nitro group and a complete naphthofuran backbone were required for full activity of the compounds. Furthermore, adding a hydroxy group at position 7 of the minimal backbone led to the most active compound of the collection. Accordingly, a direct interaction of the hydroxylated compound with the ligand binding domain of HNF4alpha was detected by NMR and thermal denaturation assays. When used in mammalian cell culture systems, these compounds proved to be highly toxic, except when methylated on the furan ring. One such compound was able to modulate HNF4alpha-driven transcription in transfected HepG2C3A cells. These data indicate that HNF4alpha activity can be modulated by small molecules and suggest new routes for targeting the receptor in humans.

Aza-beta3-cyclotetrapeptides.

The cyclization of aza-beta(3)-tetrapeptides gives access to new CTP (cyclotetrapeptide) analogues. These stereocontrolled templates are assembled without any asymmetric synthesis. X-ray crystallographic structure and NMR analysis show that the macrocyclic scaffold is characterized by a fully cooperative intramolecular H-bond network, in sharp contrast with the nanotubular assemblies observed for beta(3)-cyclotetrapeptides. This folding property reduces considerably the polarity of aza-beta(3)-tetrapeptides and should be useful in addressing intracellular targets.

Biological and biophysical properties of the histone deacetylase inhibitor suberoylanilide hydroxamic acid are affected by the presence of short alkyl groups on the phenyl ring.

Inhibition of histone deacetylases (HDACs) leads to growth arrest, differentiation, or apoptosis of tumor cell lines, suggesting HDACs as promising targets for cancer therapy. At present, only one HDAC inhibitor (HDACi) is used in therapy: suberoylanilide hydroxamic acid (SAHA). Here, we describe the synthesis and biological evaluation of a new series of compounds derived from SAHA by substituting short alkyl chains at various positions of the phenyl ring. Such modifications induced variable effects ranging from partial loss of activity to increased potency. Through molecular modeling, we describe a possible interaction between HDAC7 proline 809, a residue that is strictly conserved within class 2 enzymes only, and the amide group of HDACi, while nuclear magnetic resonance experiments indicated that dimethyl m-substitution may stabilize the inhibitor in the active site. Our data provide novel information on the structure-activity relationship of HDACi and suggest new ways for developing second generation SAHA-like molecules.