Fiorella Meneghetti

Proprotein convertase subtilisin/kexin type 9 (PCSK9): From structure–function relation to therapeutic inhibition

AIMS This short review aims at summarizing the current information on Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) structure and function focusing also on the therapeutic possibilities based on the inhibition of this protein. DATA SYNTHESIS PCSK9 has been recently discovered as the third gene involved in autosomal dominant hypercholesterolemia. PCSK9 binds and favors degradation of the low-density lipoprotein receptor (LDLR) and thereby modulates the plasma levels of LDL-cholesterol (LDL-C). Some of the natural occurring PCSK9 mutations increase the protein function (gain of function) and cause hypercholesterolemia, whereas loss of function mutations associate with hypocholesterolemia. Since the loss of a functional PCSK9 in humans is not associated with apparent deleterious effects, this protease is an attractive target for the development of lowering plasma LDL-C agents, either alone or in combination with statins. CONCLUSION Inhibition of PCSK9 is emerging as a novel strategy for the treatment of hypercholesterolemia and data obtained from pre-clinical studies show that use of monoclonal antibodies, antisense oligonucleotides and short interfering RNA are effective in reducing LDL-C, clinical studies, accompanied by a better understanding of PCSK9 biology, are now necessary to address whether these new compounds will have a future in clinical practice.

Signal transducer and activator of transcription 3 (STAT3): a promising target for anticancer therapy

Signal transducer and activator of transcription 3 (STAT3) is an oncogenic protein whose inhibition is sought for the prevention and treatment of cancer. In this review, the validated therapeutic strategy to block aberrant activity of STAT3 in many tumor cell lines is evaluated by presenting the most promising inhibitors to date. The compounds are discussed in classes based on their different mechanisms of action, which are critically explained. In addition, their future clinical development as anticancer agents is considered. Furthermore, the efforts devoted to the comprehension of the structure-activity relationships and to the identification of the biological effects are brought to attention. The synthetic and technological approaches recently developed to overcome the difficulties in the obtainment of clinically suitable drugs are also presented.

Synthesis, binding, and modeling studies of new cytisine derivatives, as ligands for neuronal nicotinic acetylcholine receptor subtypes.

The availability of drug affecting neuronal nicotinic acetylcholine receptors (nAChRs) may have important therapeutic potential for the treatment of several CNS pathologies. Pursuing our efforts on the systematic structural modification of cytisine and N-arylalkyl and N-aroylalkyl cytisines were synthesized and tested for the displacement of [(3)H]-epibatidine and [(125)I]-alpha-bungarotoxin from the most widespread brain nAChRs subtypes alpha(4)beta(2) and alpha(7), respectively. While the affinity for alpha(7) subtype was rather poor (K(i) from 0.4 to >50 microM), the affinity for alpha(4)beta(2) subtype was very interesting, with nanomolar K(i) values for the best compounds. The N-substituted cytisines were docked into the rat and human alpha(4)beta(2) nAChR models based on the extracellular domain of a molluscan acetylcholine binding protein. The docking results agreed with the binding data, allowing the detection of discrete amino acid residues of the alpha and beta subunits essential for the ligand binding on rat and human nAChRs, providing a novel structural framework for the development of new alpha(4)beta(2) selective ligands.

Green tea catechins in chemoprevention of cancer: A molecular docking investigation into their interaction with glutathione S-transferase (GST P1-1)

The anti- and pro-oxidant effects of green tea catechins have been implicated in the alterations of cellular functions determining their chemoprotective and therapeutic potentials in toxiCIT000y and diseases. The glutathione S-transferases (GSTs; EC 2.5.1.18) family is a widely distributed phase-II detoxifying enzymes and the GST P1-1 isoenzyme has been shown to catalyze the conjugation of GSH with some alkylating anti-cancer agents, suggesting that over-expression of GST P1-1 would result in tumor cell resistance. Here we report the docking study of four green tea catechins and four alkylating anticancer drugs into the GST P1-1 model, as GSTs were found to be affected by tea catechins. The EGCG ligands exhibit higher docking potential with respect to the anticancer agents, with a ligand-receptor interaction pattern indicating an high conformational stability. Consequently, the competition mechanisms favourable for the green tea catechins could lead to enzyme(s) desensitisation with a reduction of the alkylating drugs metabolism. The results provide a useful theoretical contribution in understanding the biochemical mechanisms implicated in the chemotherapeutic use of green tea catechins in oxidative stress-related diseases.

Evidence for platinum(II)–vinylidene complexes and their reactions with water to give hydrocarbons and olefins ☆

Abstract Treatment of the alkynyl complexes trans -[Pt(Me)(CCR)(PPh 3 ) 2 ] (R= p -tolyl ( 1a ), Ph ( 1b )) at low temperature in a CD 2 Cl 2 solution with stoichiometric amounts of the acids HBF 4 ·Et 2 O or CF 3 SO 3 H affords the corresponding vinylidene derivatives trans -[Pt(Me){CC(H)R}(PPh 3 ) 2 ]X (R= p -tolyl, X=BF 4 ( 2aBF 4 ); R= p -tolyl, X=CF 3 SO 3 ( 2aCF 3 SO 3 ); R=Ph, X=BF 4 ( 2bBF 4 )) on the basis of 1 H- and 31 P{ 1 H}-NMR data. The reactions of the in situ generated complexes 2 with water, which were followed by 1 H- and 31 P{ 1 H}-NMR, lead to the formation of a mixture of the carbonyl complex [Pt(Me)(CO)(PPh 3 ) 2 ]X ( 3 ) and the hydroxo-bridged dinuclear compound [Pt(μ-OH)(PPh 3 ) 2 ] 2 X 2 ( 4 ) in a ca. 1:2 ratio. The formation of 3 and 4 is accompanied with the liberation of hydrocarbons R–CH 3 and olefins CH 3 CHCHR (R= p -tolyl, Ph), respectively, which arise from the vinylidene ligand likely via an hydroxycarbene intermediate.

Asymmetric Ugi 3CR on isatin-derived ketimine: synthesis of chiral 3,3-disubstituted 3-aminooxindole derivatives.

Summary An efficient Ugi three-component reaction of a preformed chiral ketimine derived from isatin with various isonitrile and acid components has been developed. The reactions proceeded smoothly and in a stereocontrolled manner with regard to the new center of the Ugi products due to the stereoinduction of the amine chiral residue. A wide variety of novel chiral 3,3-disubstituted 3-aminooxindoles were obtained, a selection of which were subjected to post-Ugi transformations, paving the way to application as peptidomimetics.

Organocatalytic Asymmetric Biginelli-like Reaction Involving Isatin

The first asymmetric, Brønsted acid catalyzed Biginelli-like reaction of a ketone has been developed, employing N-substituted isatins as carbonyl substrates, and urea and alkyl acetoacetates as further components. BINOL-derived phosphoric acid catalysts have been used to achieve the synthesis of a small library of chiral, enantioenriched spiro(indoline-pyrimidine)-diones derivatives. The absolute configuration of the new spiro stereocenter was assessed on diastereoisomeric derivatives through computer-assisted NMR spectroscopy. X-ray diffractometry allowed the disclosure of the overall molecular conformation in the solid state and the characterization of the crystal packing of a Br-substituted Biginelli-like derivative, while computational studies on the reaction transition state allowed us to rationalize the stereochemical outcome.

Dipeptide Nanotubes Containing Unnatural Fluorine-Substituted β2,3-Diarylamino Acid and l-Alanine as Candidates for Biomedical Applications

The synthesis and the structural characterization of dipeptides composed of unnatural fluorine-substituted β(2,3)-diarylamino acid and L-alanine are reported. Depending on the stereochemistry of the β amino acid, these dipeptides are able to self-assemble into proteolytic stable nanotubes. These architectures were able to enter the cell and locate in the cytoplasmic/perinuclear region and represent interesting candidates for biomedical applications.

Comparison of the refined crystal structures of wild-type (1.34 Å) flavodoxin from Desulfovibrio vulgaris and the S35C mutant (1.44 Å) at 100 K

Engineered flavodoxins in which a surface residue has been replaced by an exposed cysteine are useful modules to link multi-domain redox proteins obtained by gene fusion to electrode surfaces. In the present work, the crystal structure of the S35C mutant of Desulfovibrio vulgaris flavodoxin in the oxidized state has been determined and compared with a refined structure of the wild type (wt). The structure of wt flavodoxin (space group P4(3)2(1)2, unit-cell parameters a = 50.52, b = 50.52, c = 138.59 A) at 1.34 A resolution has been refined to R = 0.16 and R(free) = 0.18. The structure of the S35C mutant (space group P4(3)2(1)2, unit-cell parameters a = 50.55, b = 50.55, c = 138.39 A) at 1.44 A resolution has been refined to R = 0.13 and R(free) = 0.16. Data sets were collected with synchrotron radiation at 100 K. In the S35C mutant, the Cys35 thiol group points towards a hydrophobic region, whilst in the wt the Ser35 hydroxyl group points towards a more polar region. The solvent exposure of Cys35 is 43 A(2), of which 8 A(2) is for the sulfur. This is comparable to the exposure of 48 A(2) found for the wt Ser35, where that of the hydroxyl oxygen is also 8 A(2).

Synthesis of Aminocarbonyl N-Acylhydrazones by a Three-Component Reaction of Isocyanides, Hydrazonoyl Chlorides, and Carboxylic Acids

A novel one-pot multicomponent synthesis of α-aminocarbonyl N-acylhydrazones starting from readily available hydrazonoyl chlorides, isocyanides, and carboxylic acids is reported. The strategy exploits the ability of the carboxylic acid as a third component to suppress all competing reactions between nitrile imines and isocyanides, channeling the course of the reaction toward the formation of this novel class of compounds.