Oligomycins as inhibitors of K-Ras plasma membrane localisation

Abstract

Frequently present in pancreatic, colorectal and non-small cell lung carcinomas, oncogenic mutant K-Ras must be localised to the plasma membrane (PM) to be functional. Inhibitors of K-Ras PM localisation are therefore putative cancer chemotherapeutics. By screening a microbial extract library in a high content cell-based assay we detected the rare oligomycin class of Streptomyces polyketides as inhibitors of K-Ras PM localisation. Cultivation and fractionation of three unique oligomycin producing Streptomyces strains yielded oligomycins A–E (1–5) and 21-hydroxy-oligomycin A (6), together with the new 21-hydroxy-oligomycin C (7) and 40-hydroxy-oligomycin B (8). Structures for 1–8 were assigned by detailed spectroscopic analysis. Cancer cell viability screening confirmed 1–8 were cytotoxic to human colorectal carcinoma cells (IC50 >3 μM), and were inhibitors of the ABC transporter efflux pump P-glycoprotein (P-gp), with 5 being comparable in potency to the positive control verapamil. Significantly, oligomycins 1–8 proved to be exceptionally potent inhibitors of K-Ras PM localisation (Emax 0.67–0.75 with an IC50 ~1.5–14 nM).

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

“…Among a set of compounds that displace K-RasG12V but not H-RasG12V from the PM in an HCS (18), we found an oligomycin family and a rare neoantimycin family of Streptomyces-derived molecules and the antidiabetic drug metformin (22)(23)(24)35) (Fig. 1A and B).…”

“…1A and B). All of these compounds have been reported to inhibit various aspects of mitochondrial function (22)(23)(24)35). Since inhibition of mitochondrial activity depletes cellular ATP levels and activates AMPK (36, 37), we tested whether direct AMPK activation would also mislocalize K-RasG12V.…”

“…Since PtdSer is an anionic phospholipid that provides much of the electrostatic surface potential to the inner PM, a reduced PtdSer PM content leads to K-Ras dissociation. A second group of compounds includes a diverse set of mitochondrial inhibitors (22)(23)(24) that all triggered activation of the master metabolic kinase, AMPactivated protein kinase (AMPK). In dissecting the molecular mechanism, we identified cyclic GMP (cGMP)-dependent protein kinases (PKGs) regulated by nitric oxide (NO) signaling to be novel K-Ras kinases.…”

Synthesis and Biological Activity of 7(7,11)-Hydroderivatives of Oligomycin A

“…Недавние исследования показали, что олигомицин А ингибирует активацию онкогенных RAS-белков, блокируя их связывание с плазматической мембраной. [4] Недостатками этого природного антибиотика, препятствующими его применению в качестве лекарственного препарата, являются сравнительно низкий терапевтический индекс и низкая растворимость в воде. Кроме того, к настоящему времени полная картина механизма биологического действия олигомицина А в клетках про-и эукариот остается невыясненной.…”

“…According to recent investigations, the development of anti-cancer drugs based on oligomycin A is quite perspective due to its high cytotoxic activity toward tumor cells, ability to inhibit a multidrug resistance protein p-gp and to prevent an activation of oncogenic K-Ras by inhibition of its localization at the plasma membrane. [2][3][4] However, high toxicity for mammalian cells and low water solubility are significant limitations of oligomycin A, making it unacceptable for clinical application. Chemical modification is a promising way to improve pharmacological properties of natural compounds.…”