Search

Alternative splicing is a potent modifier of protein function. Stromal interaction molecule 1 (Stim1) is the essential activator of store-operated Ca

Medical research has identified over 500 brain disorders. Among these, there are still only very few neuropathologies whose causes are fully understood and, consequently, very few drugs whose mechanism of action is known. No FDA drug has been identified for major neurodegenerative diseases, such as Alzheimer's and Parkinson's. We still lack effective treatments and strategies for modulating progression or even early neurodegenerative disease onset diagnostic tools. A great support toward the highly needed identification of neuroactive drugs comes from computer simulation methods and, in particular, from molecular dynamics (MD). This provides insight into structure–function relationship of a target and predicts structure, dynamics and energetics of ligand/target complexes under biologically relevant conditions like temperature and physiological saline concentration. Here, we present examples of the predictive power of MD for neuroactive ligands/target complexes. This brief survey from our own research shows the usefulness of partnerships between academia and industry, and from joint efforts between experimental and theoretical groups.

P2X receptors constitute a seven-member family (P2X1-7) of extracellular ATP-gated cation channels of widespread expression. Because P2X receptors have been implicated in neurological, inflammatory and cardiovascular diseases, they constitute promising drug targets. Since the first P2X cDNA sequences became available in 1994, numerous site-directed mutagenesis studies have been conducted to disclose key sites of P2X receptor function and oligomerization. The publication of the 3-A crystal structures of the zebrafish P2X4 (zfP2X4) receptor in the homotrimeric apo-closed and ATP-bound open states in 2009 and 2012, respectively, has ushered a new era by allowing for the interpretation of the wealth of molecular data in terms of specific three-dimensional models and by paving the way for designing more-decisive experiments. Thanks to these structures, the last five years have provided invaluable insight into our understanding of the structure and function of the P2X receptor class of ligandgated ion channels. In this review, we provide an overview of mutagenesis studies of the pre- and post-crystal structure eras that identified amino acid residues of key importance for ligand binding, channel gating, ion flow, formation of the pore and the channel gate, and desensitization. In addition, the sites that are involved in the trimerization of P2X receptors are reviewed based on mutagenesis studies and interface contacts that were predicted by the zfP2X4 crystal structures.

Drug induced phospholipidosis (PLD) may be observed in the preclinical phase of drug development and pose strategic questions. As lysosomes have a central role in pathogenesis of PLD, assessment of lysosomal concentrations is important for understanding the pharmacokinetic basis of PLD manifestation and forecast of potential clinical appearance. Herein we present a systematic approach to provide insight into tissue-specific PLD by evaluation of unbound intracellular and lysosomal (reflecting acidic organelles) concentrations of two structurally related diprotic amines, GRT1 and GRT2. Their intratissue distribution was assessed using brain and lung slice assays. GRT1 induced PLD both in vitro and in vivo. GRT1 showed a high intracellular accumulation that was more pronounced in the lung, but did not cause cerebral PLD due to its effective efflux at the blood-brain barrier. Compared to GRT1, GRT2 revealed higher interstitial fluid concentrations in lung and brain, but more than 30-fold lower lysosomal trapping capacity. No signs of PLD were seen with GRT2. The different profile of GRT2 relative to GRT1 is due to a structural change resulting in a reduced basicity of one amino group. Hence, by distinct chemical modifications, undesired lysosomal trapping can be separated from desired drug delivery into different organs. In summary, assessment of intracellular unbound concentrations was instrumental in delineating the intercompound and intertissue differences in PLD induction in vivo and could be applied for identification of potential lysosomotropic compounds in drug development.

In a previous communication, our efforts leading from 1 to the identification of spiro[cyclohexane-dihydropyrano[3,4-b]indole]-amine 2a as analgesic NOP and opioid receptor agonist were disclosed and their favorable in vitro and in vivo pharmacological properties revealed. We herein report our efforts to further optimize lead 2a, toward trans-6'-fluoro-4',9'-dihydro-N,N-dimethyl-4-phenyl-spiro[cyclohexane-1,1'(3'H)-pyrano[3,4-b]indol]-4-amine (cebranopadol, 3a), which is currently in clinical development for the treatment of severe chronic nociceptive and neuropathic pain.

We report the discovery of spiro[cyclohexane-pyrano[3,4-b]indole]-amines, as functional nociceptin/orphanin FQ peptide (NOP) and opioid receptor agonists with strong efficacy in preclinical models of acute and neuropathic pain. Utilizing 4-(dimethylamino)-4-phenylcyclo-hexanone 1 and tryptophol in an oxa-Pictet-Spengler reaction led to the formation of spiroether 2, representing a novel NOP and opioid peptide receptor agonistic chemotype. This finding initially stems from the systematic derivatization of 1, which resulted in alcohols 3-5, ethers 6 and 7, amines 8-10, 22-24, and 26-28, amides 11 and 25, and urea 12, many with low nanomolar binding affinities at the NOP and mu opioid peptide (MOP) receptors.

Store-operated Ca2+ entry mediated by STIM1-gated Orai1 channels is essential to activate immune cells and its inhibition or gain-of-function can lead to immune dysfunction and other pathologies. Reactive oxygen species interacting with cysteine residues can alter protein function. Pretreatment of the Ca2+ selective Orai1 with the oxidant H2O2 reduces ICRAC with C195, distant to the pore, being its major redox sensor. However, the mechanism of inhibition remained elusive. Here we combine experimental and theoretical approaches and show that oxidation of Orai1 leads to reduced subunit interaction, slows diffusion and that either oxidized C195 or its oxidomimetic mutation C195D located at the exit of transmembrane helix 3 virtually eliminates channel activation by intramolecular interaction with S239 of transmembrane helix 4, thereby locking the channel in a closed conformation. Our results demonstrate a novel mechanistic model for ROS-mediated inhibition of Orai1 and identify a candidate residue for pharmaceutical intervention.

Blockade of voltage-gated sodium channels (VGSCs) has been used successfully in the clinic to enable control of pathological firing patterns that occur in conditions as diverse as chronic pain, epilepsy, and arrhythmias. Herein we review the state of the art in marketed sodium channel inhibitors, including a brief compendium of their binding sites and of the cellular and molecular biology of sodium channels. Despite the preferential action of this drug class toward over-excited cells, which significantly limits potential undesired side effects on other cells, the need to develop a second generation of sodium channel inhibitors to overcome their critical clinical shortcomings is apparent. Current approaches in drug discovery to deliver novel and truly innovative sodium channel inhibitors is next presented by surveying the most recent medicinal chemistry breakthroughs in the field of small molecules and developments in automated patch-clamp platforms. Various strategies aimed at identifying small molecules that target either particular isoforms of sodium channels involved in specific diseases or anomalous sodium channel currents, irrespective of the isoform by which they have been generated, are critically discussed and revised.

The human P2X7 receptor (hP2X7R) is an ATP-gated nonspecific cation channel. It is expressed in cells of the immune system. Via this receptor, ATP, released during cell damage or hypoxia, serves as danger associated molecular pattern to induce inflammatory reactions. In comparison to other P2X receptors, P2X7R-dependent ionic currents differ in their activation kinetics by an absence of desensitization and induction of large membrane pores by long lasting agonist applications, i.e. the gating and permeation mechanisms of P2X7 receptors are not fully understood.G338 within the second transmembrane domain (TM2) is part of the narrow ion channel pore domain. Substitution of G338 to cysteine reversed the gating behaviour of the hP2X7R channel, i.e. hP2X7G338C expressing Xenopus oocytes displayed a leak conductance which is decreased by application of ATP or by the P2X7R agonist, BzATP. Substitution of extracellular Na+ by the larger organic Tris+ significantly decreased the ion conductance and shifted the reversal potential of the ATP-induced current to more negative potentials indicating that the leak current was carried by cations.Modeling the structural changes of hP2X7G338C during ATP application with the recently published truncated zebrafish P2X4 receptor model as template we found that G338 is located at the narrowest part of the closed ion channel pore and substitution by cysteine pushes the TM2 of the three subunits apart leading to an incomplete channel closure. ATP application leads to a conformation switch of hP2X7G338C which allows an interaction of C338 with Y40 and Y343 decreasing the ion channel pore diameter and leading to a reduced ion current.These findings point to a critical role of G338 in gating the P2X7 receptor.This work was supported by the German research foundation (DFG, Ma 1581/15-1, Schm 536/9-1

A comparative study on the reaction of (CO)3Mo(CH3CN)3 with a series of homologous chiral and prochiral trisphosphines is presented. Only one of the tripodal ligands formed the desired unique complex (CO)3Mo(η3-triphos) (3b) being the first example of a Mo(0)-complex containing a seven- as well as an eight-membered chelate ring. Spectroscopic properties of this complex and two different η2-coordinated species are discussed. The molecular structure of the η3-coordinated complex 3b has been determined by X-ray crystallography.

The synthesis of the chiral polyfunctional diphosphine salenophos 1 is described. The new ligand bearing hard and soft coordination sites chelates titanium(IV) as well as palladium(II) in a defined manner provided a certain order during the introduction of the two metals was kept. In this way the first chiral early-late heterobimetallic complex could be synthesized. It was fully characterized by NMR spectroscopy and X-ray structural analysis. Remarkable features of the heterobimetallic complex are the trans coordination of the phosphine groups on palladium and the distance between Ti and Pd which is more than 4.13 A.

The complexation behaviour of cis- und trans-3-diphenylphosphino-4-hydroxyl-tetrahydrofurans with [Rh(COD)2]BF4 is studied with the help of NMR and IR spectroscopy. In dependence of the spatial arrangement of hydroxyl and phosphino group the formation of different intra- and intermolecular bridged O-P complexes has been observed.

The synthesis of (4R,5R)-4,5-bis(diphenylphosphinomethyl)-2-hydroxymethyl-2-phenyl-1,3-dioxolane 1 which is related to DIOP is described. The application of this new ligand in asymmetric catalysis is illustrated in the stereodifferentiating hydrogenation.

The synthesis of enantiomerically pure ( R,R )-N,N′-bis(3-diphenylphosphino-2-hydroxybenzylidene)-1,2-diphenyl-1,2-ethanediamine ( 1 ) is described. This multidentate salentype ligand offers several possibilities for the construction of chiral mono-nuclear or bi-nuclear metal complexes, which may be useful in bifunctional asymmetric catalysis.