Ipomoeassin F Binds Sec61α to Inhibit Protein Translocation

Funding Information: We thank the Arkansas Nano & Bio Materials Characterization Facility at the Institute for Nano Sciences & Engineering for our imaging studies, and Prof Yoshito Kishi (Harvard University) for the kind gift of synthetic mycolactone A/B used by S.H. and R.S. W.S. is supported by Grant No. R15GM116032 from the National Institute of General Medical Sciences of the National Institutes of Health (NIH) and startup funds from the University of Arkansas. This work was also supported in part by Grant No. P30 GM103450 from the National Institute of General Medical Sciences of the NIH and by seed money from the Arkansas Biosciences Institute (ABI). S.O’K. is the recipient of a Biotechnology and Biological Sciences Research Council (BBSRC) Doctoral Training Programme Award (BB/J014478/ 1), and S.H. holds a Welcome Trust Investigator Award in Science (204957/Z/16/Z). The alpha-1 antitrypsin work was supported by the Alpha-1 Foundation (J.I. and M.J.I.). J.I. and M.J.H. were supported by the intramural program of NCATS, National Institutes of Health, projects 1ZIATR000048-03 (J.I.) and ZIATR000063-04 (M.J.H.). R.S. holds a Welcome Trust Investigator Award in Science (202843/Z/16/Z). C.D. received funding from the Institut Pasteur, the Institut National de la Santé et de la Recherche Med́ icale, and the Fondation Raoul Follereau. N.B.’s synthesis and chemical biology studies of mycolactone were supported by CNRS, Université de Strasbourg, Fondations Potier et Follereau, and the Investisse-ment d’Avenir (Idex Unistra). V.O.P. is supported by the Academy of Finland (Grants 289737 and 314672) and the Sigrid Juselius Foundation. Funding Information: We thank the Arkansas Nano & Bio Materials Characterization Facility at the Institute for Nano Sciences & Engineering for our imaging studies, and Prof Yoshito Kishi (Harvard University) for the kind gift of synthetic mycolactone A/B used by S.H. and R.S. W.S. is supported by Grant No. R15GM116032 from the National Institute of General Medical Sciences of the National Institutes of Health (NIH) and startup funds from the University of Arkansas. This work was also supported in part by Grant No. P30 GM103450 from the National Institute of General Medical Sciences of the NIH and by seed money from the Arkansas Biosciences Institute (ABI). S.O'K. is the recipient of a Biotechnology and Biological Sciences Research Council (BBSRC) Doctoral Training Programme Award (BB/J014478/1), and S.H. holds a Welcome Trust Investigator Award in Science (204957/Z/16/Z). The alpha-1 antitrypsin work was supported by the Alpha-1 Foundation (J.I. and M.J.I.). J.I. and M.J.H. were supported by the intramural program of NCATS, National Institutes of Health, projects 1ZIATR000048-03 (J.I.) and ZIATR000063-04 (M.J.H.). R.S. holds a Welcome Trust Investigator Award in Science (202843/Z/16/Z). C.D. received funding from the Institut Pasteur, the Institut National de la Sante et de la Recherche Medicale, and the Fondation Raoul Follereau. N.B.'s synthesis and chemical biology studies of mycolactone were supported by CNRS, Universite de Strasbourg, Fondations Potier et Follereau and the Investissement d'Avenir (Idex Unistra). V.O.P. is supported by the Academy of Finland (Grants 289737 and 314672) and the Sigrid Juselius Foundation. Publisher Copyright: © 2019 American Chemical Society.Ipomoeassin F is a potent natural cytotoxin that inhibits growth of many tumor cell lines with single-digit nanomolar potency. However, its biological and pharmacological properties have remained largely unexplored. Building upon our earlier achievements in total synthesis and medicinal chemistry, we used chemical proteomics to identify Sec61 alpha (protein transport protein Sec61 subunit alpha isoform 1), the pore-forming subunit of the Sec61 protein translocon, as a direct binding partner of ipomoeassin F in living cells. The interaction is specific and strong enough to survive lysis conditions, enabling a biotin analogue of ipomoeassin F to pull down Sec61 alpha from live cells, yet it is also reversible, as judged by several experiments including fluorescent streptavidin staining, delayed competition in affinity pulldown, and inhibition of TNF biogenesis after washout. Sec61 alpha forms the central subunit of the ER protein translocation complex, and the binding of ipomoeassin F results in a substantial, yet selective, inhibition of protein translocation in vitro and a broad ranging inhibition of protein secretion in live cells. Lastly, the unique resistance profile demonstrated by specific amino acid single-point mutations in Sec61 alpha provides compelling evidence that Sec61 alpha is the primary molecular target of ipomoeassin F and strongly suggests that the binding of this natural product to Sec61 alpha is distinctive. Therefore, ipomoeassin F represents the first plant-derived, carbohydrate-based member of a novel structural class that offers new opportunities to explore Sec61 alpha function and to further investigate its potential as a therapeutic target for drug discovery.Peer reviewe

Mycolactone subverts immunity by selectively blocking the Sec61 translocon

Mycolactone, an immunosuppressive macrolide released by the human pathogen Mycobacterium ulcerans, was previously shown to impair Sec61-dependent protein translocation, but the underlying molecular mechanism was not identified. In this study, we show that mycolactone directly targets the alpha subunit of the Sec61 translocon to block the production of secreted and integral membrane proteins with high potency. We identify a single-amino acid mutation conferring resistance to mycolactone, which localizes its interaction site near the lumenal plug of Sec61 alpha. Quantitative proteomics reveals that during T cell activation, mycolactone-mediated Sec61 blockade affects a selective subset of secretory proteins including key signal-transmitting receptors and adhesion molecules. Expression of mutant Sec61 alpha in mycolactone-treated T cells rescued their homing potential and effector functions. Furthermore, when expressed in macrophages, the mycolactone-resistant mutant restored IFN-gamma receptor-mediated antimicrobial responses. Thus, our data provide definitive genetic evidence that Sec61 is the host receptor mediating the diverse immunomodulatory effects of mycolactone and identify Sec61 as a novel regulator of immune cell functions.Peer reviewe

Creation and preclinical evaluation of genetically attenuated malaria parasites arresting growth late in the liver.

Whole-sporozoite (WSp) malaria vaccines induce protective immune responses in animal malaria models and in humans. A recent clinical trial with a WSp vaccine comprising genetically attenuated parasites (GAP) which arrest growth early in the liver (PfSPZ-GA1), showed that GAPs can be safely administered to humans and immunogenicity is comparable to radiation-attenuated PfSPZ Vaccine. GAPs that arrest late in the liver stage (LA-GAP) have potential for increased potency as shown in rodent malaria models. Here we describe the generation of four putative P. falciparum LA-GAPs, generated by CRISPR/Cas9-mediated gene deletion. One out of four gene-deletion mutants produced sporozoites in sufficient numbers for further preclinical evaluation. This mutant, PfΔmei2, lacking the mei2-like RNA gene, showed late liver growth arrest in human liver-chimeric mice with human erythrocytes, absence of unwanted genetic alterations and sensitivity to antimalarial drugs. These features of PfΔmei2 make it a promising vaccine candidate, supporting further clinical evaluation. PfΔmei2 (GA2) has passed regulatory approval for safety and efficacy testing in humans based on the findings reported in this study

Search for heavy resonances decaying to two Higgs bosons in final states containing four b quarks

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Results of the Model Unspecific Search in CMS (MUSiC), using proton-proton collision data recorded at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.Peer reviewe

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