Drosophila MUS312 Interacts with the Nucleotide Excision Repair Endonuclease MEI-9 to Generate Meiotic Crossovers

AbstractMEI-9 is the Drosophila homolog of the human structure-specific DNA endonuclease XPF. Like XPF, MEI-9 functions in nucleotide excision repair and interstrand crosslink repair. MEI-9 is also required to generate meiotic crossovers, in a function thought to be associated with resolution of Holliday junction intermediates. We report here the identification of MUS312, a protein that physically interacts with MEI-9. We show that mutations in mus312 elicit a meiotic phenotype identical to that of mei-9 mutants. A missense mutation in mei-9 that disrupts the MEI-9–MUS312 interaction abolishes the meiotic function of mei-9 but does not affect the DNA repair functions of mei-9. We propose that MUS312 facilitates resolution of meiotic Holliday junction intermediates by MEI-9

Design, synthesis, and subtype selectivity of 3,6-disubstituted β-carbolines at Bz/GABA(A)ergic receptors. SAR and studies directed toward agents for treatment of alcohol abuse

A series of 3,6-disubstituted β-carbolines was synthesized and evaluated for their in vitro affinities at αxβ3γ2 GABAA/benzodiazepine receptor subtypes by radioligand binding assays in search of α1 subtype selective ligands to treat alcohol abuse. Analogues of β-carboline-3-carboxylate-t-butyl ester (βCCt, 1) were synthesized via a CDI-mediated process and the related 6-substituted β-carboline-3-carboxylates 6 including WYS8 (7) were synthesized via a Sonogashira or Stille coupling processes from 6-iodo βCCt (5). The bivalent ligands of βCCt (32 and 33) were also designed and prepared via a palladium-catalyzed homocoupling process to expand the structure-activity relationships (SAR) to larger ligands. Based on the pharmacophore/receptor model, a preliminary SAR study on 34 analogues illustrated that large substituents at position -6 of the β-carbolines were well tolerated. As expected, these groups are proposed to project into the extracellular domain (LDi region) of GABAA/Bz receptors (see 32 and 33). Moreover, substituents located at position -3 of the β-carboline nucleus exhibited a conserved stereo interaction in lipophilic pocket L1, while N(2) presumably underwent a hydrogen bonding interaction with H1. Three novel β-carboline ligands (βCCt, 3PBC and WYS8), which preferentially bound to α1 BzR subtypes permitted a comparison of the pharmacological efficacies with a range of classical BzR antagonists (flumazenil, ZK93426) from several different structural groups and indicated these β-carbolines were “near GABA neutral antagonists”. Based on the SAR, the most potent (in vitro) α1 selective ligand was the 6-substituted acetylenyl βCCt (WYS8, 7). Earlier both βCCt and 3PBC had been shown to reduce alcohol self-administration in alcohol preferring (P) and high alcohol drinking (HAD) rats but had little or no effect on sucrose self-administration.1–3 These data prompted the synthesis of the β-carbolines presented here

Novel positive allosteric modulators of GABAA receptors: Do subtle differences in activity at alpha 1 plus alpha 5 versus alpha 2 plus alpha 3 subunits account for dissimilarities in behavioral effects in rats?

Over the last years, genetic studies have greatly improved Our knowledge on the receptor subtypes mediating various pharmacological effects of positive allosteric modulators at GABA(A) receptors. This stimulated the development of new benzodiazepine (BZ)-like ligands, especially those inactive/low-active at GABA(A) receptors containing the alpha(1) subunit, with the aim of generating more selective drugs. Hereby, the affinity and efficacy of four recently synthesized BZ site ligands: SH-053-2'N, SH-053-S-CH3-2'F, SH-053-R-CH3-2'F and JY-XHe-053 were assessed. They were also studied in behavioral tests of spontaneous locomotor activity, elevated plus maze, and water maze in rats, which are considered predictive of. respectively, the sedative, anxiolytic, and amnesic influence of BZs. The novel ligands had moderately low to low affinity and mild to partial agonistic efficacy at GABA(A) receptors containing the a, subunit, with variable, but more pronounced efficacy at other BZ-sensitive binding sites. While presumably alpha(1) receptor-mediated sedative effects of GABA(A) modulation were not fully eliminated with any of the ligands tested, only SH-053-2'N and SH-053-S-CH3-2'F, both dosed at 30 mg/kg, exerted anxiolytic effects. The lack of clear anxiolytic-like activity of JY-XHe-053, despite its efficacy at alpha(2)- and alpha(3)-GABA(A) receptors, may have been partly connected with its preferential affinity at alpha(5)-GABA(A) receptors coupled with weak agonist activity at alpha(1)-containing subtypes. The memory impairment in water-maze experiments, generally reported with BZ site agonists, was completely circumvented with all four ligands. The results suggest that a substantial amount of activity at a I GABA(A) receptors is needed for affecting spatial learning and memory impairments, while much weaker activity at alpha(1) and alpha(5)-GABA(A) receptors is sufficient for eliciting sedation

Novel positive allosteric modulators of GABAA receptors: Do subtle differences in activity at α1 plus α5 versus α2 plus α3 subunits account for dissimilarities in behavioral effects in rats?

Over the last years, genetic studies have greatly improved our knowledge on the receptor subtypes mediating various pharmacological effects of positive allosteric modulators at GABAA receptors. This stimulated the development of new benzodiazepine (BZ)-like ligands, especially those inactive/low-active at GABAA receptors containing the α1 subunit, with the aim of generating more selective drugs. Hereby, the affinity and efficacy of four recently-synthesized BZ site ligands: SH-053-2’N, SH-053-S-CH3-2’F, SH-053-R-CH3-2’F and JY-XHe-053 were assessed. They were also studied in behavioral tests of spontaneous locomotor activity, elevated plus maze, and water maze in rats, which are considered predictive of, respectively, the sedative, anxiolytic, and amnesic influence of BZs. The novel ligands had moderately low to low affinity and mild to partial agonistic efficacy at GABAA receptors containing the α1 subunit, with variable, but more pronounced efficacy at other BZ-sensitive binding sites. While presumably α1 receptor-mediated sedative effects of GABAA modulation were not fully eliminated with any of the ligands tested, only SH-053-2’N and SH-053-S-CH3-2’F, both dosed at 30 mg/kg, exerted anxiolytic effects. The lack of clear anxiolytic-like activity of JY-XHe-053, despite its efficacy at α2- and α3-GABAA receptors, may have been partly connected with its preferential affinity at α5-GABAA receptors coupled with weak agonist activity at α1-containing subtypes. The memory impairment in water-maze experiments, generally reported with BZ site agonists, was completely circumvented with all four ligands. The results suggest that a substantial amount of activity at α1 GABAA receptors is needed for effecting spatial learning and memory impairments, while much weaker activity at α1- and α5-GABAA receptors is sufficient for eliciting sedation

Search for α3β2/3γ2 subtype selective ligands that are stable on human liver microsomes

Selective modulation of specific benzodiazepine receptor (BzR) gamma amino butyric acid-A (GABAA) receptor ion channels has been identified as an important method for separating out the variety of pharmacological effects elicited by BzR-related drugs. Importantly, it has been demonstrated that both α2β(2/3)γ2 (α2BzR) and α3BzR (and/or α2/α3) BzR subtype selective ligands exhibit anxiolytic effects with little or no sedation. Previously we have identified several such ligands; however, three of our parent ligands exhibited significant metabolic liability in rodents in the form of a labile ester group. Here eight analogs are reported which were designed to circumvent this liability by utilizing a rational replacement of the ester moiety based on medicinal chemistry precedents. In a metabolic stability study using human liver microsomes, four compounds were found to undergo slower metabolic transformation, as compared to their corresponding ester analogs. These compounds were also evaluated in in vitro binding as well as efficacy assays. Additionally, bioisostere 11 was evaluated in a rodent model of anxiety. It exhibited anxiolytic activity at doses of 10 and 100 mg/kg and was devoid of sedative properties

Antiseizure Activity of Novel γ-Aminobutyric Acid (A) Receptor Subtype-Selective Benzodiazepine Analogues in Mice and Rat Models

The antiseizure activity of benzodiazepines (BDZs) 1-5 in mice and rats as animal models is described. These BDZs have selective efficacy for α2β3γ2 and α3β3γ2 GABAA-receptors. Significant anticonvulsant activity with little or no motor impairment and therapeutic indexes (TI) of 2.8-44 (mice, ip) were observed for compounds 2-4 in the subcutaneous metrazole seizure (scMET) test. In rats orally (po) the TI was >5 to 105. These compounds represent novel leads in the search for anticonvulsants devoid of sedative, ataxic and amnestic side effects

Anxiolytic-like effects of 8-acetylene imidazobenzodiazepines in a rhesus monkey conflict procedure

Conflict procedures can be used to study the receptor mechanisms underlying the anxiolytic effects of benzodiazepines and other GABAA receptor modulators. In the present study, we first determined the efficacy and binding affinity of the benzodiazepine diazepam and recently synthesized GABAA receptor modulators JY-XHe-053, XHe-II-053, HZ-166, SH-053-2'F-S-CH3 and SH-053-2'F-R-CH3 at GABAA receptors containing α1, α2, α3 and α5 subunits. Results from these studies suggest that each compound displayed lower efficacy at GABAA receptors containing α1 subunits and varying degrees of efficacy and affinity at GABAA receptors containing α2, α3 and α5 subunits. Next, we assessed their anxiolytic effects using a rhesus monkey conflict procedure in which behavior was maintained under a fixed-ratio schedule of food delivery in the absence (non-suppressed responding) and presence (suppressed responding) of response-contingent electric shock. Relatively non-selective compounds, such as diazepam and JY-XHe-053 produced characteristic increases in rates of suppressed responding at low to intermediate doses and decreased the average rates of non-suppressed responding at higher doses. XHe-II-053 and HZ-166 also produced increases in suppressed responding at low to intermediate doses, but were ineffective at decreasing rates of non-suppressed responding, consistent with their relatively low efficacy at GABAA receptors containing α1 and α5 subunits. In contrast, SH-053-2’F-S-CH3 and SH-053-2’F-R-CH3 produced only partial increases in suppressed responding and were ineffective on non-suppressed responding, consistent with their profiles as partial agonists at GABAA receptors containing α2, α3 and α5 subunits. These behavioral effects suggest that the anxiolytic and rate-reducing effects of GABAA receptor positive modulators are dependent on their relative efficacy and affinity at different GABAA receptor subtypes

A study of the structure–activity relationship of GABAA–benzodiazepine receptor bivalent ligands by conformational analysis with low temperature NMR and X-ray analysis

The stable conformations of GABAA-benzodiazepine receptor bivalent ligands were determined by low temperature NMR spectroscopy and confirmed by single crystal X-ray analysis. The stable conformations in solution correlated well with those in the solid state. The linear conformation was important for these dimers to access the binding site and exhibit potent in vitro affinity and was illustrated for α5 subtype selective ligands. Bivalent ligands with an oxygen-containing linker folded back upon themselves both in solution and the solid state. Dimers which are folded do not bind to Bz receptors

Evaluating the anti-fouling performance of electrochemically active nickel based membrane

Fouling is inevitable for membrane-based processes. To increase longevity of membranes, anti-fouling mechanisms are crucial. Current anti-fouling mechanisms are often chemical-intensive, expensive and are known to hinder the membrane matrix. This study examined the potential of electrified membranes to induce electro-repulsion and trigger specific electrochemical reactions to remove fouling. A series of experiments were conducted. In general, in all the experiments, electrochemical self-cleaning performance of the membrane was tested by applying different voltages across the membrane. 100 mM NaCl, 1g/L diatomaceous earth and Lake Water were used as foulant mediums for different experiments. As water flux recovery is a characteristic of anti-fouling, it was observed that with an increase in voltage, the water flux increased simultaneously. This observation can be related to the presence of reactive hydroxyl species and free chlorine present inside the membrane module responsible for the degradation of foulants from the membrane surface. For example, with diatomaceous earth as model foulant, the water increased from 9.2 ± 4.12 Kg/m2/h to 30.82 ± 3.92 Kg/m2/h when the voltage was stepped up from 0V to 2.5V. Severe membrane fouling was observed without any voltage. As continuous application of voltage increases energy consumption, intermittent self-cleaning was therefore performed when lake water was introduced as the feed solution. Experiments reveal higher water flux recovery with 10 minute intermittent self-cleaning at the end of 3 hours of membrane operation over a 12 hour period. State-of-the-art backwashing process was also investigated and compared with electrochemical cleaning and results suggest a 7% increase in water flux retention when the latter was used, around 93.25%. In all the cases, flux decline was observed as a consistent effect of fouling. To counteract this effect, Electrocoagulation was tested with the current setup. Compared to previous experiments, water flux increased by almost 25-30% and never declined to an absolute 0 kg/m2/h suggesting superior anti-fouling performance

Notch Signaling in Myeloid Cells as a Regulator of Tumor Immune Responses

Cancer immunotherapy, which stimulates or augments host immune responses to treat malignancies, is the latest development in the rapidly advancing field of cancer immunology. The basic principles of immunotherapies are either to enhance the functions of specific components of the immune system or to neutralize immune-suppressive signals produced by cancer cells or tumor microenvironment cells. When successful, these approaches translate into long-term survival for patients. However, durable responses are only seen in a subset of patients and so far, only in some cancer types. As for other cancer treatments, resistance to immunotherapy can also develop. Numerous research groups are trying to understand why immunotherapy is effective in some patients but not others and to develop strategies to enhance the effectiveness of immunotherapy. The Notch signaling pathway is involved in many aspects of tumor biology, from angiogenesis to cancer stem cell maintenance to tumor immunity. The role of Notch in the development and modulation of the immune response is complex, involving an intricate crosstalk between antigen-presenting cells, T-cell subpopulations, cancer cells, and other components of the tumor microenvironment. Elegant studies have shown that Notch is a central mediator of tumor-induced T-cell anergy and that activation of Notch1 in CD8 T-cells enhances cancer immunotherapy. Tumor-infiltrating myeloid cells, including myeloid-derived suppressor cells, altered dendritic cells, and tumor-associated macrophages along with regulatory T cells, are major obstacles to the development of successful cancer immunotherapies. In this article, we focus on the roles of Notch signaling in modulating tumor-infiltrating myeloid cells and discuss implications for therapeutic strategies that modulate Notch signaling to enhance cancer immunotherapy