First QSAR report on FSH receptor antagonistic activity: Quantitative investigations on physico-chemical and structural features among 6-amino-4-phenyltetrahydroquinoline derivatives

Para-Selective Dehydrogenative Phenothiazination of Hydroquinolines and Indolines

Nitrogen-containing heterocyclic systems, such as hydroquinolines, indolines, and phenothiazines, are prevalent in pharmaceuticals, natural products, and organic materials. It is therefore important to develop novel reaction strategies that give access to such biologically relevant scaffolds. This report demonstrates a novel robust, para-selective C-N bond formation between phenothiazines and quinolines or indolines under extremely mild and user-friendly conditions. Furthermore, we bring forward a surprising discovery arising from the homocoupling of indolines through an unprecedented C5-H functionalization.

Enantioselective Organocatalytic Transfer Hydrogenation of 1,2-Dihydroquinoline through Formation of Aza-o-xylylene

A new way of forming the aza-o-xylylene with easily accessible 1,2-dihydroquinolines as precursor has been developed. The presence of an electron-donating group at the proper position of 1,2-dihydroquinoline was crucial for protonation of the alkene through dearomatization with a simple Brønsted acid. The in situ forming reactive intermediate was trapped with Hantzsch ester to afford tetrahydroquinolines in excellent yield and enantioselectivity.

Constitutive activity in gonadotropin receptors

Constitutively active mutants (CAMs) of gonadotropin receptors are, in general, rare conditions. Luteinizing hormone-choriogonadotropin receptor (LHCGR) CAMs provoke the dramatic phenotype of familial gonadotropin-independent isosexual male-limited precocious puberty, whereas in females, there is not yet any identified phenotype. Only one isolated follicle-stimulating hormone receptor (FSHR) CAM (Asp567Gly) has so far been detected in a single male patient, besides other FSHR weak CAMs linked to pregnancy-associated ovarian hyperstimulation syndrome or to impaired desensitization and internalization. Several animal models have been developed for studying enhanced gonadotropin action; in addition to unraveling valuable new information about the possible phenotypes of isolated FSHR and LHCGR CAMs in women, the information obtained from these mouse models has served multiple translational goals, including the development of new diagnostic and therapeutic targets as well as the prediction of phenotypes for mutations not yet identified in humans. Mutagenesis and computational studies have shed important information on the physiopathogenic mechanisms leading to constitutive activity of gonadotropin receptors; a common feature in these receptor CAMs is the release of stabilizing interhelical interactions between transmembrane domains (TMDs) 3 and 6 leading to an increase, with respect to the wild-type receptor, in the solvent accessibility at the cytosolic extension of TMDs 3, 5, and 6, which involves the highly conserved Glu/Asp-Arg-Tyr/Trp sequence. In this chapter, we summarize the structural features, functional consequences, and mechanisms that lead to constitutive activation of gonadotropin receptor CAMs and provide information on pharmacological approaches that might potentially modulate gonadotropin receptor CAM function.

QSAR prediction of D2 receptor antagonistic activity of 6-methoxy benzamides

Quantitative structure-activity relationship (QSAR) method was used to predict the pIC(50) value of 58 derivatives of 6-methoxy benzamides in this work. The artificial neural network (ANN) and multiple linear regressions (MLR) were used to construct the non-linear and linear QSAR models, respectively. The standard errors in the prediction of pIC(50) for training, internal and external test sets, are; 0.280, 0.446 and 0.382 by MLR model and are; 0.175, 0.326 and 0.296 by ANN model, respectively. Also these models were further examined by cross-validation methods which produce the statistics of Q(2)=0.8340 and SPRESS=0.322 for MLR model and Q(2)=0.8055 and SPRESS=0.219 for ANN model.

Molecular determinants of juvenile hormone action as revealed by 3D QSAR analysis in Drosophila

BACKGROUND

Postembryonic development, including metamorphosis, of many animals is under control of hormones. In Drosophila and other insects these developmental transitions are regulated by the coordinate action of two principal hormones, the steroid ecdysone and the sesquiterpenoid juvenile hormone (JH). While the mode of ecdysone action is relatively well understood, the molecular mode of JH action remains elusive.

METHODOLOGY/PRINCIPAL FINDINGS

To gain more insights into the molecular mechanism of JH action, we have tested the biological activity of 86 structurally diverse JH agonists in Drosophila melanogaster. The results were evaluated using 3D QSAR analyses involving CoMFA and CoMSIA procedures. Using this approach we have generated both computer-aided and species-specific pharmacophore fingerprints of JH and its agonists, which revealed that the most active compounds must possess an electronegative atom (oxygen or nitrogen) at both ends of the molecule. When either of these electronegative atoms are replaced by carbon or the distance between them is shorter than 11.5 A or longer than 13.5 A, their biological activity is dramatically decreased. The presence of an electron-deficient moiety in the middle of the JH agonist is also essential for high activity.

CONCLUSIONS/SIGNIFICANCE

The information from 3D QSAR provides guidelines and mechanistic scope for identification of steric and electrostatic properties as well as donor and acceptor hydrogen-bonding that are important features of the ligand-binding cavity of a JH target protein. In order to refine the pharmacophore analysis and evaluate the outcomes of the CoMFA and CoMSIA study we used pseudoreceptor modeling software PrGen to generate a putative binding site surrogate that is composed of eight amino acid residues corresponding to the defined molecular interactions.

Characterization of peptide 20-30 of follicle stimulating hormone receptor as an antagonist of receptor activity: significance of charged residues

We had previously reported the region (20-30) from follicle stimulating hormone receptor as being an immunodominant epitope and the smallest reported peptide capable of inhibiting hormone binding. We now report it to be an effective antagonist of ligand-induced cAMP signalling as well. The region (20-30) of follicle stimulating hormone receptor has three charged residues, namely, E(22), D(26) and R(29) that are specific to follicle stimulating hormone receptor and are conserved in mammals. This study aimed to verify whether the charged residues contribute to the activity of the follicle stimulating hormone receptor peptide (20-30). This was done using analogs of follicle stimulating hormone receptor peptide (20-30), each having an alanine substitution for a corresponding charged residue. The analog peptides displayed a loss of activity and could not inhibit hormone binding or the subsequent signal transduction. The ability of follicle stimulating hormone receptor peptide (20-30) to bind antipeptide antibodies against follicle stimulating hormone receptor peptide (9-30) was either decreased or abolished with the alanine substituted analog peptides of follicle stimulating hormone receptor peptide (20-30). The loss of function led us to verify whether there was a conformational change as well. CD spectral analysis did not reveal a significant change. These observations indicate that the charged aminoacids present in follicle stimulating hormone receptor peptide (20-30) are crucial for the observed follicle stimulating hormone antagonistic activity. This information could form the basis for the design of novel compounds capable of functioning as follicle stimulating hormone antagonists.

Prediction of binding affinities to β1 isoform of human thyroid hormone receptor by genetic algorithm and projection pursuit regression

Quantitative structure-activity relationship (QSAR) has been applied to a set of thyroid hormone receptor beta(1) (TRbeta(1)) antagonists, which are of special interest because of their potential role in safe therapies for nonthyroid disorders while avoiding the cardiac side effects. Using the calculated structural descriptors by CODESSA program, principal component analysis (PCA) was performed on the whole compounds to assist the separation of the data into the training set and the test set in QSAR analysis. Six molecular descriptors selected by genetic algorithm (GA) were used as inputs for a projection pursuit regression (PPR) study to develop a more accurate QSAR model. The PPR model performs well both in the fitting and prediction capacity. For the test set, it gave a predictive correlation coefficient (R) of 0.9450, root mean square error (RMSE) of 0.4498, and absolute average relative deviation (AARD) of 4.19%, respectively, confirming the ability of PPR for the prediction of the binding affinities of compounds to beta(1) isoform of human thyroid hormone receptor (TRbeta(1)).

Pharmacogenomic and Structural Analysis of Constitutive G Protein–Coupled Receptor Activity

G protein-coupled receptors (GPCRs) respond to a chemically diverse plethora of signal transduction molecules. The notion that GPCRs also signal without an external chemical trigger, i.e., in a constitutive or spontaneous manner, resulted in a paradigm shift in the field of GPCR pharmacology. The discovery of constitutive GPCR activity and the fact that GPCR binding and signaling can be strongly affected by a single point mutation drew attention to the evolving area of GPCR pharmacogenomics. For a variety of GPCRs, point mutations have been convincingly linked to human disease. Mutations within conserved motifs, known to be involved in GPCR activation, might explain the properties of some naturally occurring, constitutively active GPCR variants linked to disease. In this review, we provide a brief historical introduction to the concept of constitutive receptor activity and the pharmacogenomic and structural aspects of constitutive receptor activity.

Detailed analysis of the region 9-30 of rat follicle stimulating hormone receptor: identification of peptide 20-30 as a potential hormone binding inhibitor

The extracellular domain (ECD) of the follicle stimulating hormone receptor (FSHR) has been shown to be a major determinant of hormone selectivity. The N-terminal 9-30 region, the sequence of which is unique to FSHR, has been extensively studied earlier and has been proposed to be an FSHR neutralizing epitope. In this study antipeptide antibodies specific to the peptide 9-30 were generated and used for identifying a specific immunodominant region within it. Overlapping peptides corresponding to the regions 9-19, 15-25 and 20-30 were synthesized. The ability of the antipeptide antibodies to 9-30 of FSHR to bind to different peptides was checked. The results indicated that the antibodies mainly recognized the peptide 20-30 and not the other two overlapping peptides. Further, the effect of the peptide 20-30 on the binding of radiolabeled FSH to its receptor was monitored. This peptide showed FSH-binding inhibitory activity with an IC(50) value of 0.598 x 10(-4)M and was more effective than the peptide 9-30 itself. Binding kinetics revealed that the observed effect of the peptide 20-30 is due to mixed type of inhibitory mechanism. This is the smallest peptide from the rat FSHR sequence having ability to inhibit FSH binding to its receptor by more than 90%.