Antti Poso

A rhodopsin-based model for melatonin recognition at its G protein-coupled receptor

The recent elucidation of the primary structures of different melatonin receptors as well as the deduction of the secondary structure of rhodopsin has allowed us to construct a model for melatonin recognition at its G protein-coupled receptor. To achieve this, we have used the quantum mechanics method Austin model 1 to fully optimize the structures of melatonin and several analogs. We also synthesized three compounds and used the three-dimensional analysis comparative molecular field analysis (CoMFA) to generate a model for the structure-activity relationships of melatonin and 27 melatonin-like compounds. This model predicted with good accuracy the affinities of the synthesized compounds for the melatonin receptor. We propose that recognition of the functional moieties of melatonin occurs through specific interaction of these moieties with fully conserved amino acid residues present in transmembrane helices V, VI and VII of the melatonin receptor. These residues are not found in other members of the G protein-coupled receptor family. The rhodopsin-based model can explain the importance of some structural features of melatonin and related active compounds.

Discovery of Boronic Acids as Novel and Potent Inhibitors of Fatty Acid Amide Hydrolase

A series of commercial phenyl-, heteroaryl-, alkyl-, and alkenylboronic acids were evaluated for their FAAH and MGL inhibitory activities. The compounds were generally selective for FAAH, with IC50 in the nanomolar or low-micromolar range. Eight of these compounds inhibited MGL with IC50 in the micromolar range. The most potent compound, phenylboronic acid with para-nonyl substituent (13), inhibited FAAH and MGL with IC50 of 0.0091 and 7.9 microM, respectively.

Oxadiazole-carbonylaminothioureas as SIRT1 and SIRT2 Inhibitors

A new inhibitor for human sirtuin type proteins 1 and 2 (SIRT1 and SIRT2) was discovered through virtual database screening in search of new scaffolds. A series of compounds was synthesized based on the hit compound (3-[[3-(4-tert-butylphenyl)1,2,4-oxadiazole-5-carbonyl]amino]-1-[3-(trifluoromethyl)phenyl]thiourea). The most potent compound in the series was nearly as potent as the reference compound (6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide).

N(epsilon)-thioacetyl-lysine-containing tri-, tetra-, and pentapeptides as SIRT1 and SIRT2 inhibitors.

N()-Thioacetyl-lysine-containing tri-, tetra-, and pentapeptides, based on the alpha-tubulin and p53 protein sequences, were studied as SIRT1 and SIRT2 inhibitors. The potency of the pentapeptides depended on the selection of the side chains. The removal of N- and C-terminal residues of the pentapeptides yielded tripeptides with retained SIRT1 inhibitory activity but decreased SIRT2 inhibitory activity. The most potent SIRT1 inhibitors were equipotent with the reference compound (6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide) with the IC(50) values of 180-330 nM.

Dehydration of theophylline monohydrate : a two step process

The physicochemical properties of theophylline monohydrate and anhydrous polymorphic form II were evaluated using crystallographic, calorimetric and computational methods. The heats of solution of theophylline monohydrate and its anhydrous form were 28.6 and 19.4 kJ/mol, respectively, and the heat of hydration of theophylline anhydrous was 12.2 kJ/mol, as determined by solution calorimetry. Dehydration of theophylline monohydrate was studied by DSC. Under closed, hermetic conditions, the heat of dehydration, 10.7 kJ/mol, was almost equal to the heat of hydration. Under open conditions, the measured heat of dehydration was 47.3 kJ/mol. The dehydration phenomenon was examined also by molecular modelling and the computed heat changes were equal to those determined experimentally. The obtained experimental and theoretical results indicated that the monohydrate-anhydrate transition of theophylline is energetically reversible. Under closed conditions and in the aqueous media, the reversible monohydrate-anhydrate transition comprised only the dehydration or hydration step and the heat of transitions were considerably lower than under open conditions. Under open conditions, the dehydration of theophylline monohydrate proceeds in two steps even though the steps are overlapping. The first step is dehydration and the second is evaporation of the loosened crystal water.

Predicting Plasticization Efficiency from Three-Dimensional Molecular Structure of a Polymer Plasticizer

AbstractPurpose. In polymeric coatings, plasticizers are used to improve the film-forming characteristic of the polymers. In this study, a computerized method (VolSurf with GRID) was used as a novel tool for the prediction plasticization efficiency (β) of test compounds, and for determining the critical molecular properties needed for polymer plasticization. Methods. The film-former, starch acetate DS 2.8 (SA), was plasticized with each of 24 tested compounds. A decrease in glass transition temperature of the plasticized free films (determined by differential scanning calorimeter (DSC)) was used as an indicator for β. Partial least squares discriminant analysis was used to correlate the experimental data with the theoretical molecular properties of the plasticizers. Results. A good correlation (r2 = 0.77, q2 = 0.58) between the molecular modeling results and the experimental data demonstrated that β can be predicted from the three-dimensional molecular structure of a compound. Favorable structural properties identified for the potent SA plasticizer were strong hydrogen bonding capacity and a definitive hydrophobic region on the molecule. Conclusions. The VolSurf method is a valuable tool for predicting the plasticization efficiency of a compound. The correlation between experimental and calculated glass transition temperature values verifies that physicochemical properties are primary factors influencing plasticization efficiency of a compound.

A MYC-aurora kinase A protein complex represents an actionable drug target in p53-altered liver cancer

MYC oncoproteins are involved in the genesis and maintenance of the majority of human tumors but are considered undruggable. By using a direct in vivo shRNA screen, we show that liver cancer cells that have mutations in the gene encoding the tumor suppressor protein p53 (Trp53 in mice and TP53 in humans) and that are driven by the oncoprotein NRAS become addicted to MYC stabilization via a mechanism mediated by aurora kinase A (AURKA). This MYC stabilization enables the tumor cells to overcome a latent G2/M cell cycle arrest that is mediated by AURKA and the tumor suppressor protein p19ARF. MYC directly binds to AURKA, and inhibition of this protein–protein interaction by conformation-changing AURKA inhibitors results in subsequent MYC degradation and cell death. These conformation-changing AURKA inhibitors, with one of them currently being tested in early clinical trials, suppressed tumor growth and prolonged survival in mice bearing Trp53-deficient, NRAS-driven MYC-expressing hepatocellular carcinomas (HCCs). TP53-mutated human HCCs revealed increased AURKA expression and a positive correlation between AURKA and MYC expression. In xenograft models, mice bearing TP53-mutated or TP53-deleted human HCCs were hypersensitive to treatment with conformation-changing AURKA inhibitors, thus suggesting a therapeutic strategy for this subgroup of human HCCs.

Discovery of Salermide-Related Sirtuin Inhibitors: Binding Mode Studies and Antiproliferative Effects in Cancer Cells Including Cancer Stem Cells

Chemical changes performed on 1a (sirtinol) led to a series of SIRT1/2 inhibitors, in some cases more potent than 1a mainly against SIRT1. Tested in human leukemia U937 cells, the benzamide and anilide derivatives 1b, 1c, 2b, and 2c as well as the 4-(2-phenylpropyl)thioanalogue 4c showed huge apoptosis induction, while some sulfinyl and sulfonyl derivatives (5b, 5c, and 6a-c) were highly efficient in granulocytic differentiation. When assayed in human leukemia MOLT4 as well as in human breast MDA-MB-231 and colon RKO cancer cell lines, the anilide 2b (salermide) and the phenylpropylthio analogue 4b emerged as the most potent antiproliferative agents. Tested on colorectal carcinoma and glioblastoma multiforme cancer stem cells (CSCs) from patients, 2b was particularly potent against colorectal carcinoma CSCs, while 4b, 6a, and the SIRT2-selective inhibitor AGK-2 showed the highest effect against glioblastoma multiforme CSCs. Such compounds will be further explored for their broad-spectrum anticancer properties.

A comparative molecular field analysis of cytochrome P450 2A5 and 2A6 inhibitors.

Structure-activity relationships of 23 P450 2A5 and 2A6 inhibitors were analysed using the CoMFA [1] and GOLPE/GRID with smart region definition (SRD) [2]. The predictive power of the resulting models was validated using five compounds not belonging to the model set. All models have high internal and external predictive power and resulting 3D-QSAR models are supporting each other. Both Sybyl and GOLPE highlight properties near lactone moiety to be important for 2A5 and 2A6 inhibition. Another important feature for pIC50 was the size of the substituent in the 7-positon of coumarin. The models suggest that the 2A5 binding site is larger that that of 2A6 due to larger steric regions in the CoMFA coefficient maps and corresponding GOLPE maps. In addition, the maps reveal that 2A6 disfavours negative charge near the lactone moiety of coumarin.

Identification of WIN55212-3 as a competitive neutral antagonist of the human cannabinoid CB2 receptor

1 Several G protein‐coupled receptors (GPCRs), including cannabinoid CB1 and CB2 receptors, show constitutive activity under heterologous expression. Such a tonic response is generated in the absence of an activating ligand, and can be inhibited by inverse agonists. Neutral antagonists, however, are silent at such receptors, but can reverse both agonist and inverse agonist responses. To date, no neutral antagonist for the CB2 receptor has been reported. 2 Here, by monitoring receptor‐dependent G protein activation, we demonstrate that WIN55212‐3 acts as a neutral antagonist at the human CB2 (hCB2) receptor. WIN55212‐3 alone, at concentrations 10−4 M, behaved as a silent ligand exhibiting no agonist or inverse agonist activity. However, WIN55212‐3 competitively antagonized cannabinoid agonist CP‐55,940‐stimulated responses (pA2 6.1). Importantly, the inverse agonism evoked by SR144528 in hCB2 was dose‐dependently reversed by WIN55212‐3 (pEC50 5.3±0.2), indicating true neutral antagonist behavior. 3 Furthermore, WIN55212‐3 also antagonized CB1 receptor signaling in a competitive manner (pA2 5.6), but behaved as a partial inverse agonist (pIC50 5.5±0.1) at the constitutively active human CB1. 4 Additionally, WIN55212‐3 antagonized signaling of the human melatonin MT1 receptor, with modest activity at the human muscarinic M4 receptor, but it was inactive towards several other GPCRs. 5 These data identify WIN55212‐3 as a true neutral hCB2 receptor antagonist. WIN55212‐3 offers a valuable tool for further characterization of ligand activities at the CB2 receptor and may serve as a lead compound in further efforts to develop more potent and selective neutral CB2 receptor antagonists.