Oligomycins as inhibitors of K-Ras plasma membrane localisation

Structures, Biosynthesis, and Bioactivity of Oligomycins from the Marine-Derived Streptomyces sp. FXY-T5

Oligomycins are potent antifungal and antitumor agents. Mass spectrometry (MS)- and nuclear magnetic resonance (NMR)-based metabolomic fingerprinting analysis of marine-derived actinomycetes in our in-house library provided an oligomycin-producing strain, Streptomyces sp. FXY-T5. Chemical investigation led to the discovery of five new oligomycins, 24-lumooligomycin B (1), 4-lumooligomycin B (2), 6-lumooligomycin B (3), 40-homooligomycin B (4), and 15-hydroxy-oligomycin B (5), together with seven biosynthetically related known derivatives. Their structures were assigned by MS, NMR, electronic circular dichroism (ECD), and single-crystal X-ray diffraction analyses. The biosynthesis pathway of oligomycins was first proposed based on the analysis of a type I modular polyketide synthase (PKS) system and targeted gene disruption. As expected, the isolated oligomycins showed significant antiagricultural fungal pathogen activity and antiproliferative properties from which the possible structure-activity relationships were first suggested. More importantly, oligomycins induced significant G1-phase cell cycle arrest on cancer cells and significantly attenuated their Cyclin D1 and PCNA expression through a β-catenin signaling pathway.

Comprehensive pan‑cancer analysis of potassium voltage-gated channel Q4 (KCNQ4) gene across multiple human malignant tumors

A large number of studies indicate that Potassium Voltage-Gated Channel Q4 (KCNQ4) gene is the cause of non-syndromic hearing loss, but there are few studies investigating the role of KCNQ4 in cancers and scarcity of comprehensive analysis of its involvement in the diagnosis, methylation, mutation, prognosis of various cancer types. Therefore, the aim of this study is to examine the anticancerous and immune effects of KCNQ4 in various cancers and its potential value in breast cancer. In this study, we explored the potential role of KCNQ4 in cancers using public databases and the R software for bioinformatics analysis. The results showed that the low expression of KCNQ4 across specific cancer types was positively associated with low mutation frequency and methylation, and the improved survival. Eight small molecule compounds were identified that could potentially target KCNQ4. In addition, immunohistochemistry confirmed that the KCNQ4 expression was low in breast cancer. In vitro experiments confirmed that overexpression of KCNQ4 inhibited cell migration and invasion and promoted apoptosis. In summary, our comprehensive pan-cancer analysis highlights the potential of KCNQ4 as a cancer marker, and can be used as an auxiliary prognostic indicator and an indicator for immunotherapy in certain tumor types.

Mitochondrial and glycolytic extracellular flux analysis optimization for isolated pig intestinal epithelial cells

Intestinal epithelial cells (IECs) are crucial to maintain intestinal function and the barrier against the outside world. To support their function they rely on energy production, and failure to produce enough energy can lead to IEC malfunction and thus decrease intestinal barrier function. However, IEC metabolic function is not often used as an outcome parameter in intervention studies, perhaps because of the lack of available methods. We therefore developed a method to isolate viable IECs, suitable to faithfully measure their metabolic function by determining extracellular glycolytic and mitochondrial flux. First, various methods were assessed to obtain viable IECs. We then adapted a previously in-house generated image-analysis algorithm to quantify the amount of seeded IECs. Correcting basal respiration data of a group of piglets using this algorithm reduced the variation, showing that this algorithm allows for more accurate analysis of metabolic function. We found that delay in metabolic analysis after IEC isolation decreases their metabolic function and should therefore be prevented. The presence of antibiotics during isolation and metabolic assessment also decreased the metabolic function of IECs. Finally, we found that primary pig IECs did not respond to Oligomycin, a drug that inhibits complex V of the electron transport chain, which may be because of the presence of drug exporters. A method was established to faithfully measure extracellular glycolytic and mitochondrial flux of pig primary IECs. This tool is suitable to gain a better understanding of how interventions affect IEC metabolic function.

Screening study of cancer-related cellular signals from microbial natural products

To identify bioactive natural products from various natural resources, such as plants and microorganisms, we investigated programs to screen for compounds that affect several cancer-related cellular signaling pathways, such as BMI1, TRAIL, and Wnt. This review summarizes the results of our recent studies, particularly those involving natural products isolated from microbial resources, such as actinomycetes, obtained from soil samples collected primarily around Chiba, Japan.

Ras Variant Biology and Contributions to Human Disease

Analysis of cancer and RASopathy genetic databases reveals that ~19% of all cancer cases and ~4% of developmental disorders contain Ras mutations. Ras isoform and mutation variants differentially contribute to these diseases and provide an opportunity for deeper understanding of Ras function. The putative mechanisms underpinning these differences, new approaches that are being applied, and some of the key questions and challenges that remain are discussed.

Marine-Derived Macrolides 1990-2020: An Overview of Chemical and Biological Diversity

Macrolides are a significant family of natural products with diverse structures and bioactivities. Considerable effort has been made in recent decades to isolate additional macrolides and characterize their chemical and bioactive properties. The majority of macrolides are obtained from marine organisms, including sponges, marine microorganisms and zooplankton, cnidarians, mollusks, red algae, bryozoans, and tunicates. Sponges, fungi and dinoflagellates are the main producers of macrolides. Marine macrolides possess a wide range of bioactive properties including cytotoxic, antibacterial, antifungal, antimitotic, antiviral, and other activities. Cytotoxicity is their most significant property, highlighting that marine macrolides still encompass many potential antitumor drug leads. This extensive review details the chemical and biological diversity of 505 macrolides derived from marine organisms which have been reported from 1990 to 2020.

Androgen Receptor Stimulates Hexokinase 2 and Induces Glycolysis by PKA/CREB Signaling in Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) escapes growth inhibition by upregulating hexokinase 2 (HK2); however, the mechanism by which tumor cells upregulate HK2 remains unclear.

AIM

We aimed to investigate the role of androgen receptor (AR) signalling in promoting HK2 expression in HCC.

METHODS

The expressions of AR and HK2 in HCC tissues were analyzed by immunohistochemistry. Cell proliferation was determined using the CCK-8 assay, and the molecular mechanism of AR in the regulation of HK2 was evaluated by immunoblotting and luciferase assays.

RESULTS

AR expression is positively correlated with HK2 staining by an immunohistochemical analysis. The manipulation of AR expression changed HK2 expression and glycolysis. AR signaling promoted the growth of HCC by enhancing HK2-mediated glycolysis. Moreover, AR stimulated HK2 levels and glycolysis by potentiating protein kinase A/cyclic adenosine monophosphate response element-binding (CREB) protein signaling. CREB silencing decreased HK2 expression and inhibited AR-mediated HCC glycolysis. AR affected the sensitivity of HCC cells to glycolysis inhibitors by regulating downstream phosphorylated (p)-CREB.

CONCLUSIONS

These results indicate that AR at least partially induced glycolysis via p-CREB regulation of HK2 in HCC cells. Thus, this pathway should be considered for the design of novel therapeutic methods to target AR-overexpressing HCC.

Biodiversity, Bioactivity, and Metabolites of High Desert Derived Oregonian Soil Bacteria

From arid, high desert soil samples collected near Bend, Oregon, 19 unique bacteria were isolated. Each strain was identified by 16S rRNA gene sequencing, and their organic extracts were tested for antibacterial and antiproliferative activities. Noteworthy, six extracts (30 %) exhibited strong inhibition resulting in less than 50 % cell proliferation in more than one cancer cell model, tested at 10 μg/mL. Principal component analysis (PCA) of LC/MS data revealed drastic differences in the metabolic profiles found in the organic extracts of these soil bacteria. In total, fourteen potent antibacterial and/or cytotoxic metabolites were isolated via bioactivity-guided fractionation, including two new natural products: a pyrazinone containing tetrapeptide and 7-methoxy-2,3-dimethyl-4H-chromen-4-one, as well as twelve known compounds: furanonaphthoquinone I, bafilomycin C1 and D, FD-594, oligomycin A, chloramphenicol, MY12-62A, rac-sclerone, isosclerone, tunicamycin VII, tunicamycin VIII, and (6S,16S)-anthrabenzoxocinone 1.264-C.

Natural products and other inhibitors of F1FO ATP synthase

F₁F_O ATP synthase is responsible for the production of >95% of all ATP synthesis within the cell. Dysregulation of its expression, activity or localization is linked to various human diseases including cancer, diabetes, and Alzheimer's and Parkinson's disease. In addition, ATP synthase is a novel and viable drug target for the development of antimicrobials as evidenced by bedaquiline, which was approved in 2012 for the treatment of tuberculosis. Historically, natural products have been a rich source of ATP synthase inhibitors that help unravel the role of F₁F_O ATP synthase in cellular bioenergetics. During the last decade, new modulators of ATP synthase have been discovered through the isolation of novel natural products as well as through a ligand-based drug design process. In addition, new data has been obtained with regards to the structure and function of ATP synthase under physiological and pathological conditions. Crystal structure studies have provided a significant insight into the rotary function of the enzyme and may provide additional opportunities to design a new generation of inhibitors. This review provides an update on recently discovered ATP synthase modulators as well as an update on existing scaffolds.

Recent Advances in Developing K-Ras Plasma Membrane Localization Inhibitors

The Ras proteins play an important role in cell growth, differentiation, proliferation and survival by regulating diverse signaling pathways. Oncogenic mutant K-Ras is the most frequently mutated class of Ras superfamily that is highly prevalent in many human cancers. Despite intensive efforts to combat various K-Ras-mutant-driven cancers, no effective K-Ras-specific inhibitors have yet been approved for clinical use to date. Since K-Ras proteins must be associated to the plasma membrane for their function, targeting K-Ras plasma membrane localization represents a logical and potentially tractable therapeutic approach. Here, we summarize the recent advances in the development of K-Ras plasma membrane localization inhibitors including natural product-based inhibitors achieved from high throughput screening, fragment-based drug design, virtual screening, and drug repurposing as well as hit-to-lead optimizations.

Depletion of phosphatidylinositol 4-phosphate at the Golgi translocates K-Ras to mitochondria

Ras proteins are small GTPases localized to the plasma membrane (PM), which regulate cellular proliferation, apoptosis and differentiation. After a series of post-translational modifications, H-Ras and N-Ras traffic to the PM from the Golgi via the classical exocytic pathway, but the exact mechanism of K-Ras trafficking to the PM from the ER is not fully characterized. ATP5G1 (also known as ATP5MC1) is one of the three proteins that comprise subunit c of the F ₀ complex of the mitochondrial ATP synthase. In this study, we show that overexpression of the mitochondrial targeting sequence of ATP5G1 perturbs glucose metabolism, inhibits oncogenic K-Ras signaling, and redistributes phosphatidylserine (PtdSer) to mitochondria and other endomembranes, resulting in K-Ras translocation to mitochondria. Also, it depletes phosphatidylinositol 4-phosphate (PI4P) at the Golgi. Glucose supplementation restores PtdSer and K-Ras PM localization and PI4P at the Golgi. We further show that inhibition of the Golgi-localized PI4-kinases (PI4Ks) translocates K-Ras, and PtdSer to mitochondria and endomembranes, respectively. We conclude that PI4P at the Golgi regulates the PM localization of PtdSer and K-Ras.This article has an associated First Person interview with the first author of the paper.

Recent progress in the isolation, bioactivity, biosynthesis, and total synthesis of natural spiroketals

The isolation, bioactivity, biosynthesis, and total synthesis of natural spiroketals from 2011 to July 2017 have been summarized in this review.

Targeting RAS signaling pathway as a potential therapeutic target in the treatment of colorectal cancer

The V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) is frequently dysregulated in colorectal cancer (CRC). It is involved in the modulation of several downstream effectors, that include: Raf/Mek/Erk, PI3K/Akt, RalGDS/p38MAPK, and Rac/Rho, and thereby influences tumorigenesis, the invasive behaviors of tumor cell, and resistance to therapy. There is growing evidence exploring the use of drugs that target these pathways in the treatment of CRC. Cetuximab has been approved for CRC patients without a KRAS mutation, or for EGFR-expressing metastatic CRC, although some of the patients have a mutation of KRAS and NRAS. This review summarizes the recent knowledge about the therapeutic potential of targeting RAS with particular emphasis on recent preclinical and clinical studies in treatment of CRC.

AMPK and Endothelial Nitric Oxide Synthase Signaling Regulates K-Ras Plasma Membrane Interactions via Cyclic GMP-Dependent Protein Kinase 2

K-Ras must localize to the plasma membrane and be arrayed in nanoclusters for biological activity. We show here that K-Ras is a substrate for cyclic GMP-dependent protein kinases (PKGs). In intact cells, activated PKG2 selectively colocalizes with K-Ras on the plasma membrane and phosphorylates K-Ras at Ser181 in the C-terminal polybasic domain. K-Ras phosphorylation by PKG2 is triggered by activation of AMP-activated protein kinase (AMPK) and requires endothelial nitric oxide synthase and soluble guanylyl cyclase. Phosphorylated K-Ras reorganizes into distinct nanoclusters that retune the signal output. Phosphorylation acutely enhances K-Ras plasma membrane affinity, but phosphorylated K-Ras is progressively lost from the plasma membrane via endocytic recycling. Concordantly, chronic pharmacological activation of AMPK → PKG2 signaling with mitochondrial inhibitors, nitric oxide, or sildenafil inhibits proliferation of K-Ras-positive non-small cell lung cancer cells. The study shows that K-Ras is a target of a metabolic stress-signaling pathway that can be leveraged to inhibit oncogenic K-Ras function.