Synthesis and biological evaluation of methylene-bridged analogs of the potent cannabinoid receptor antagonist rimonabant

Methylene-bridged analogs of rimonabant were synthesized and evaluated for their activity on CB1 receptors. The pyrazine derivative showed some activity as a CB1 antagonist

KV7.1 channels in the vasculature

Chadha PS, Zunke F, Davis AJ, et al. Pharmacological dissection of Kv7.1 channels in systemic and pulmonary arteries. British Journal of Pharmacology. 2012;166(4):1377-1387.BACKGROUND AND PURPOSE: The aim of this study was to characterize the functional impact of KCNQ1-encoded voltage-dependent potassium channels (Kv7.1) in the vasculature. EXPERIMENTAL APPROACH: Mesenteric arteries, intrapulmonary arteries and thoracic aortae were isolated from adult rats. Kv7.1 channel expression was established by fluorescence immunocytochemistry. Wire myography determined functionality of these channels in response to selective blockers and activators. Xenopus oocytes expressing Kv7.1 channels were used to assess the effectiveness of selective Kv7.1 channel blockers. KEY RESULTS: Kv7.1 channels were identified in arterial myocytes by immunocytochemistry. Kv7.1 blockers HMR1556, L-768,673 (10 µM) and JNJ39490282 (JNJ282; 1 µM) had no contractile effects in arteries, whereas the pan-Kv7 channel blocker linopirdine (10 µM) evoked robust contractions. Application of two compounds purported to activate Kv7.1 channels, L-364 373 (R-L3) and mefenamic acid, relaxed mesenteric arteries preconstricted by methoxamine. These responses were reversed by HMR1556 or L-768,673 but not JNJ282. Similar effects were observed in the thoracic aorta and intrapulmonary arteries. CONCLUSIONS AND IMPLICATIONS: In contrast to previous assumptions, Kv7.1 channels expressed in arterial myocytes are functional ion channels. Although these channels do not appear to contribute to resting vascular tone, Kv7.1 activators were effective vasorelaxants

Quantitative Phosphoproteomics Analysis of ERBB3/ERBB4 Signaling.

The four members of the epidermal growth factor receptor (EGFR/ERBB) family form homo- and heterodimers which mediate ligand-specific regulation of many key cellular processes in normal and cancer tissues. While signaling through the EGFR has been extensively studied on the molecular level, signal transduction through ERBB3/ERBB4 heterodimers is less well understood. Here, we generated isogenic mouse Ba/F3 cells that express full-length and functional membrane-integrated ERBB3 and ERBB4 or ERBB4 alone, to serve as a defined cellular model for biological and phosphoproteomics analysis of ERBB3/ERBB4 signaling. ERBB3 co-expression significantly enhanced Ba/F3 cell proliferation upon neuregulin-1 (NRG1) treatment. For comprehensive signaling studies we performed quantitative mass spectrometry (MS) experiments to compare the basal ERBB3/ERBB4 cell phosphoproteome to NRG1 treatment of ERBB3/ERBB4 and ERBB4 cells. We employed a workflow comprising differential isotope labeling with mTRAQ reagents followed by chromatographic peptide separation and final phosphopeptide enrichment prior to MS analysis. Overall, we identified 9686 phosphorylation sites which could be confidently localized to specific residues. Statistical analysis of three replicate experiments revealed 492 phosphorylation sites which were significantly changed in NRG1-treated ERBB3/ERBB4 cells. Bioinformatics data analysis recapitulated regulation of mitogen-activated protein kinase and Akt pathways, but also indicated signaling links to cytoskeletal functions and nuclear biology. Comparative assessment of NRG1-stimulated ERBB4 Ba/F3 cells revealed that ERBB3 did not trigger defined signaling pathways but more broadly enhanced phosphoproteome regulation in cells expressing both receptors. In conclusion, our data provide the first global picture of ERBB3/ERBB4 signaling and provide numerous potential starting points for further mechanistic studies

Contribution of ERBB3 to phosphosite regulation.

<p>Scatter plot of the mean ERBB3/ERBB4 ± NRG1 ratios with mean ERBB3/ERBB4 <i>versus</i> ERBB4 ratios from NRG1-treated cells. Reproducibly quantified ERBB3 phosphosites are encircled.</p

Identification of significantly different phosphorylation sites.

<p>(A) Volcano plot of NRG1-regulated phosphorylation in Ba/F3 cells expressing ERBB3 and ERBB4. (B) Volcano plot comparison of phosphorylation sites in NRG1-treated ERBB3/ERBB4 <i>versus</i> NRG1-treated ERBB4 expressing Ba/F3 cells. In both comparisons, log₁₀-transformed, average phosphosite ratios are plotted against their standard deviations determined from mTRAQ replicate quantifications. Significantly regulated class I sites according to the Global Mean Rank test are depicted in red, all other sites in blue. The dashed grey lines indicate two-fold regulation.</p

MELK-T1, a small-molecule inhibitor of protein kinase MELK, decreases DNA-damage tolerance in proliferating cancer cells

Maternal embryonic leucine zipper kinase (MELK), a serine/threonine protein kinase, has oncogenic properties and is overexpressed in many cancer cells. The oncogenic function of MELK is attributed to its capacity to disable critical cell-cycle checkpoints and reduce replication stress. Most functional studies have relied on the use of siRNA/shRNAmediated gene silencing. In the present study, we have explored the biological function of MELK using MELK-T1, a novel and selective small-molecule inhibitor. Strikingly, MELK-T1 triggered a rapid and proteasome-dependent degradation of the MELK protein. Treatment of MCF-7 (Michigan Cancer Foundation-7) breast adenocarcinoma cells with MELKT1 induced the accumulation of stalled replication forks and double-strand breaks that culminated in a replicative senescence phenotype. This phenotype correlated with a rapid and long-lasting ataxia telangiectasia-mutated (ATM) activation and phosphorylation of checkpoint kinase 2 (CHK2). Furthermore, MELK-T1 induced a strong phosphorylation of p53 (cellular tumour antigen p53), a prolonged up-regulation of p21 (cyclin-dependent kinase inhibitor 1) and a down-regulation of FOXM1 (Forkhead Box M1) target genes. Our data indicate that MELK is a key stimulator of proliferation by its ability to increase the threshold for DNA-damage tolerance (DDT). Thus, targeting MELK by the inhibition of both its catalytic activity and its protein stability might sensitize tumours to DNA-damaging agents or radiation therapy by lowering the DNA-damage threshold

NRG1-induced proliferation and signaling of Ba/F3 cells expressing ERBB3 and/or ERBB4.

<p>(A) Cells expressing either ERBB4 (upper panel), ERBB4 and ERBB3 (middle panel) or ERBB3 receptors (lower panel) were cultured in medium without ligand, in the presence of 10 ng/ml IL3, or in the presence of 10 or 100 ng/ml NRG1. Cell numbers were counted at the indicated time points. (B) Parental Ba/F3 or Ba/F3 cells expressing ERBB3, ERBB4 or both receptors were incubated in the absence of IL3 and treated with 100 ng/mL NRG1 where indicated. Total cell lysate were then prepared and immunoblotted with phosphoepitope- and protein-specific antibodies for ERBB3, ERBB4, Akt and MEK.</p

Quantitative phosphoproteomics workflow and experimental design.

<p>Ba/F3 ERBB3/ERBB4 or ERBB4 cells were treated in the three replicate experiments as indicated. Upon lysis and proteolytic digestion, peptides were differentially labeled with the three isotopic variant of mTRAQ and then pooled prior to peptide separation by high pH reversed phase chromatography and IMAC phosphopeptide enrichment. Phosphopeptide fractions were then analyzed by quantitative LC-MS on a LTQ Orbitrap Velos instrument. Lower panel: Characteristic mTRAQ patterns shown for a peptide harboring a NRG1-induced phosphosite in ERBB3/ERBB4 cells, which less strongly up-regulated in the absence of ERBB3 in ERBB4-expressing Ba/F3 cells. </p