Ikarugamycin: A Natural Product Inhibitor of Clathrin-Mediated Endocytosis.

Ikarugamycin (IKA) is a previously discovered antibiotic, which has been shown to inhibit the uptake of oxidized low-density lipoproteins in macrophages. Furthermore, several groups have previously used IKA to inhibit clathrin-mediated endocytosis (CME) in plant cell lines. However, detailed characterization of IKA has yet to be performed. Consequently, we performed biochemistry and microscopy experiments to further characterize the effects of IKA on CME. We show that IKA has an IC50 of 2.7 µm in H1299 cells and acutely inhibits CME, but not other endocytic pathways, in a panel of cell lines. Although long-term incubation with IKA has cytotoxic effects, the short-term inhibitory effects on CME are reversible. Thus, IKA can be a useful tool for probing routes of endocytic trafficking.

FUSION-Guided Hypothesis Development Leads to the Identification of N6,N6-Dimethyladenosine, a Marine-Derived AKT Pathway Inhibitor.

Chemicals found in nature have evolved over geological time scales to productively interact with biological molecules, and thus represent an effective resource for pharmaceutical development. Marine-derived bacteria are rich sources of chemically diverse, bioactive secondary metabolites, but harnessing this diversity for biomedical benefit is limited by challenges associated with natural product purification and determination of biochemical mechanism. Using Functional Signature Ontology (FUSION), we report the parallel isolation and characterization of a marine-derived natural product, N6,N6-dimethyladenosine, that robustly inhibits AKT signaling in a variety of non-small cell lung cancer cell lines. Upon validation of the elucidated structure by comparison with a commercially available sample, experiments were initiated to understand the small molecule's breadth of effect in a biological setting. One such experiment, a reverse phase protein array (RPPA) analysis of >50 kinases, indicated a specific cellular response to treatment. In all, leveraging the FUSION platform allowed for the rapid generation and validation of a biological mechanism of action hypothesis for an unknown natural product and permitted accelerated purification of the bioactive component from a chemically complex fraction.

Author Correction: Small-molecule TFEB pathway agonists that ameliorate metabolic syndrome in mice and extend C. elegans lifespan.

The originally published version of this Article contained an error in the spelling of the author Nathaniel W. Oswald, which was incorrectly given as Nathaniel W. Olswald. This has now been corrected in both the PDF and HTML versions of the Article.

HORMAD1 Is a Negative Prognostic Indicator in Lung Adenocarcinoma and Specifies Resistance to Oxidative and Genotoxic Stress.

Cancer testis antigens (CTA) are expressed in testis and placenta and anomalously activated in a variety of tumors. The mechanistic contribution of CTAs to neoplastic phenotypes remains largely unknown. Using a chemigenomics approach, we find that the CTA HORMAD1 correlates with resistance to the mitochondrial complex I inhibitor piericidin A in non-small cell lung cancer (NSCLC). Resistance was due to a reductive intracellular environment that attenuated the accumulation of free radicals. In human lung adenocarcinoma (LUAD) tumors, patients expressing high HORMAD1 exhibited elevated mutational burden and reduced survival. HORMAD1 tumors were enriched for genes essential for homologous recombination (HR), and HORMAD1 promoted RAD51-filament formation, but not DNA resection, during HR. Accordingly, HORMAD1 loss enhanced sensitivity to γ-irradiation and PARP inhibition, and HORMAD1 depletion significantly reduced tumor growth in vivo These results suggest that HORMAD1 expression specifies a novel subtype of LUAD, which has adapted to mitigate DNA damage. In this setting, HORMAD1 could represent a direct target for intervention to enhance sensitivity to DNA-damaging agents or as an immunotherapeutic target in patients.Significance: This study uses a chemigenomics approach to demonstrate that anomalous expression of the CTA HORMAD1 specifies resistance to oxidative stress and promotes HR to support tumor cell survival in NSCLC. Cancer Res; 78(21); 6196-208. ©2018 AACR.

Small-molecule TFEB pathway agonists that ameliorate metabolic syndrome in mice and extend C. elegans lifespan.

Drugs that mirror the cellular effects of starvation mimics are considered promising therapeutics for common metabolic disorders, such as obesity, liver steatosis, and for ageing. Starvation, or caloric restriction, is known to activate the transcription factor EB (TFEB), a master regulator of lipid metabolism and lysosomal biogenesis and function. Here, we report a nanotechnology-enabled high-throughput screen to identify small-molecule agonists of TFEB and discover three novel compounds that promote autophagolysosomal activity. The three lead compounds include the clinically approved drug, digoxin; the marine-derived natural product, ikarugamycin; and the synthetic compound, alexidine dihydrochloride, which is known to act on a mitochondrial target. Mode of action studies reveal that these compounds activate TFEB via three distinct Ca2+-dependent mechanisms. Formulation of these compounds in liver-tropic biodegradable, biocompatible nanoparticles confers hepatoprotection against diet-induced steatosis in murine models and extends lifespan of Caenorhabditis elegans. These results support the therapeutic potential of small-molecule TFEB activators for the treatment of metabolic and age-related disorders.

Precursor-Directed Generation of Amidine Containing Ammosamide Analogs: Ammosamides E-P.

Ammosamides E-F (1-2), are amidine analogs of the ammosamide family of alkaloids isolated from a marine-derived Streptomyces variabilis. Further studies with S. variabilis revealed a variety of aryl and alkyl amines added into the fermentation media could be efficiently incorporated into the ammosamide framework to generate a library of precursor-directed amidine analogs, ammosamides G-P (9 - 18). We demonstrate that the amines are introduced via non-enzymatic addition to the iminium ion of ammosamide C. Biological evaluation of the amidine analogs against quinone reductase 2 (QR2) showed low nM potency for a number of analogs. When tested for in vivo activity against a panel of non-small cell lung cancer (NSCLC) cell-lines there was a clear increase in potency by incorporation of lipophilic alkylamines, with the most potent compounds having sub µM IC(50) values (0.4 to 0.8 µM).