Mechanisms underlying the relaxation by A484954, a eukaryotic elongation factor 2 kinase inhibitor, in rat isolated mesenteric artery

Eukaryotic elongation factor 2 kinase inhibitor, A484954 induced diuresis via nitric oxide production in spontaneously hypertensive rats

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) is a protein kinase that inactivates eEF2, a protein that mediates a peptidyl-tRNA translocation during an elongation step of protein synthesis. We have previously shown that eEF2K was involved in pathogenesis of essential and pulmonary hypertension. A484954 (7-amino-1-cyclopropyl-3-ethyl-2,4-dioxo-1,2,3,4-tetrahydropyrido[2,3-d] pyrimidine-6-carboxamide), a selective eEF2K inhibitor, is a membrane permeable small molecule. We have previously shown that A484954 lowered blood pressure and induced diuretic effects in spontaneously hypertensive rats (SHR) due to an increase in renal blood flow. Here we aimed to reveal mechanisms underlying the diuretic effects of A484954 in SHR. A484954-induced diuresis and increase in urinary Na+ excretion were inhibited by N (G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor. A484954 increased mRNA expression of angiotensin type 2 receptor (AT2R) and nuclear factor-erythroid 2-related factor 2 (Nrf2). In summary, we for the first time revealed that A484954 induces diuresis in SHR at least partly via the activation of NO/Nrf2/AT2R pathway.

Translational control of Ybx1 expression regulates cardiac function in response to pressure overload in vivo

RNA-protein interactions are central to cardiac function, but how activity of individual RNA-binding protein is regulated through signaling cascades in cardiomyocytes during heart failure development is largely unknown. The mechanistic target of rapamycin kinase is a central signaling hub that controls mRNA translation in cardiomyocytes; however, a direct link between mTOR signaling and RNA-binding proteins in the heart has not been established. Integrative transcriptome and translatome analysis revealed mTOR dependent translational upregulation of the RNA binding protein Ybx1 during early pathological remodeling independent of mRNA levels. Ybx1 is necessary for pathological cardiomyocyte growth by regulating protein synthesis. To identify the molecular mechanisms how Ybx1 regulates cellular growth and protein synthesis, we identified mRNAs bound to Ybx1. We discovered that eucaryotic elongation factor 2 (Eef2) mRNA is bound to Ybx1, and its translation is upregulated during cardiac hypertrophy dependent on Ybx1 expression. Eef2 itself is sufficient to drive pathological growth by increasing global protein translation. Finally, Ybx1 depletion in vivo preserved heart function during pathological cardiac hypertrophy. Thus, activation of mTORC1 links pathological signaling cascades to altered gene expression regulation by activation of Ybx1 which in turn promotes translation through increased expression of Eef2.

eEF2K Inhibitor Design: The Progression of Exemplary Structure-Based Drug Design

The α-kinase, eEF2K, phosphorylates the threonine 56 residue of eEF2 to inhibit global peptide elongation (protein translation). As a master regulator of protein synthesis, in combination with its unique atypical kinase active site, investigations into the targeting of eEF2K represents a case of intense structure-based drug design that includes the use of modern computational techniques. The role of eEF2K is incredibly diverse and has been scrutinized in several different diseases including cancer and neurological disorders-with numerous studies inhibiting eEF2K as a potential treatment option, as described in this paper. Using available crystal structures of related α-kinases, particularly MHCKA, we report how homology modeling has been used to improve inhibitor design and efficacy. This review presents an overview of eEF2K related drug discovery efforts predating from the 1990's, to more recent in vivo studies in rat models. We also provide the reader with a basic introduction to several approaches and software programs used to undertake such drug discovery campaigns. With the recent exciting publication of an eEF2K crystal structure, we present our view regarding the future of eEF2K drug discovery.

Eukaryotic elongation factor 2 kinase inhibitor, A484954 induces diuretic effect via renal vasorelaxation in spontaneously hypertensive rats

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K), alternatively known as calmodulin-dependent protein kinase III, inhibits protein translation via phosphorylating its sole substrate, eEF2. We previously demonstrated that expression and activity of eEF2K change in mesenteric artery from spontaneously hypertensive rats (SHR) with aging and that eEF2K is involved in pathogenesis of essential hypertension. In addition, we have recently revealed that acute intravenous injection with A484954, a selective eEF2K inhibitor, lowers blood pressure specifically in SHR partly via inducing vasorelaxation. In this study, we examined whether A484954 induces diuretic effect. After male SHR and normotensive Wistar Kyoto rats (WKY) were given a single intraperitoneal injection of A484954 (2.5 mg/kg, 0.5-9 h), urine was collected using metabolic cage. Contraction of isolated renal arteries form SHR was isometrically measured. While A484954 did not induce diuretic effect in WKY, it increased urine output, water intake, and urinary sodium excretion in SHR. A484954 (10 μM) induced vasorelaxation in isolated renal arteries, which was inhibited by a β-adrenergic receptor antagonist, propranolol. It was confirmed that A484954 increased renal blood flow in SHR as measured by renal ultrasonography. In summary, it was for the first time revealed that A484954 induces diuretic effect in SHR at least partly via renal vasorelaxation through β-adrenergic receptor.

Insights Into the Pathologic Roles and Regulation of Eukaryotic Elongation Factor-2 Kinase

Eukaryotic Elongation Factor-2 Kinase (eEF2K) acts as a negative regulator of protein synthesis, translation, and cell growth. As a structurally unique member of the alpha-kinase family, eEF2K is essential to cell survival under stressful conditions, as it contributes to both cell viability and proliferation. Known as the modulator of the global rate of protein translation, eEF2K inhibits eEF2 (eukaryotic Elongation Factor 2) and decreases translation elongation when active. eEF2K is regulated by various mechanisms, including phosphorylation through residues and autophosphorylation. Specifically, this protein kinase is downregulated through the phosphorylation of multiple sites via mTOR signaling and upregulated via the AMPK pathway. eEF2K plays important roles in numerous biological systems, including neurology, cardiology, myology, and immunology. This review provides further insights into the current roles of eEF2K and its potential to be explored as a therapeutic target for drug development.

Progress in the Development of Eukaryotic Elongation Factor 2 Kinase (eEF2K) Natural Product and Synthetic Small Molecule Inhibitors for Cancer Chemotherapy

Eukaryotic elongation factor 2 kinase (eEF2K or Ca2+/calmodulin-dependent protein kinase, CAMKIII) is a new member of an atypical α-kinase family different from conventional protein kinases that is now considered as a potential target for the treatment of cancer. This protein regulates the phosphorylation of eukaryotic elongation factor 2 (eEF2) to restrain activity and inhibit the elongation stage of protein synthesis. Mounting evidence shows that eEF2K regulates the cell cycle, autophagy, apoptosis, angiogenesis, invasion, and metastasis in several types of cancers. The expression of eEF2K promotes survival of cancer cells, and the level of this protein is increased in many cancer cells to adapt them to the microenvironment conditions including hypoxia, nutrient depletion, and acidosis. The physiological function of eEF2K and its role in the development and progression of cancer are here reviewed in detail. In addition, a summary of progress for in vitro eEF2K inhibitors from anti-cancer drug discovery research in recent years, along with their structure-activity relationships (SARs) and synthetic routes or natural sources, is also described. Special attention is given to those inhibitors that have been already validated in vivo, with the overall aim to provide reference context for the further development of new first-in-class anti-cancer drugs that target eEF2K.

Age-dependent increase in activity of eukaryotic elongation factor 2 kinase in mesenteric arteries from spontaneously hypertensive rats

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) negatively regulates protein translation through the phosphorylation of its specific substrate, eEF2. We previously found that expression of eEF2K was increased in arteries from 13-15-week-old spontaneously hypertensive rats (SHR) as well as in left ventricles of cardiac hypertrophy models. Furthermore, we demonstrated that eEF2K mediates the development of essential hypertension and pulmonary arterial hypertension in animal models. Protein expression changes with age during development of hypertension in SHR. In the present study, we examined whether activity and expression of eEF2K change in isolated mesenteric arteries dependent on the age. After superior mesenteric arteries were isolated from 4-10-week-old Wistar Kyoto rats (WKY) and SHR, Western blotting was performed. The phosphorylation of eEF2K at Ser500, an activating phosphorylation site, was increased in the arteries from 10-week-old SHR, whereas the phosphorylation of eEF2K at Ser366, an inactivating phosphorylation site, was increased in the arteries from 4-5-week-old SHR compared with WKY. The expression of eEF2K was increased in the arteries from 10-week-old SHR compared with WKY. The phosphorylation of eEF2 at Thr56 was decreased in the arteries from 4-5-week-old SHR, whereas it was increased in the arteries from 10-week-old SHR compared with WKY. We for the first time revealed that eEF2K activity is lower in prehypertensive stage but higher in hypertensive stage in SHR, suggesting that an inhibition of eEF2K activity may be a potential therapeutic strategy for the treatment of essential hypertension.

Designing an eEF2K-Targeting PROTAC small molecule that induces apoptosis in MDA-MB-231 cells

Eukaryotic elongation factor 2 kinase (eEF2K) is a key α-kinase that negatively regulates the extension step of protein synthesis, which consumes most of the energy and amino acids required for protein synthesis. Studies have found that eEF2K protein is related to the breast cancer. However, existing inhibitor effect has not achieved the desired effect in cancer therapy. Proteolysis target chimeric (PROTAC) technology is uses proteasome to degrade target protein to achieve the purpose of inhibiting tumour cell growth. Here, we reported that the use of PROTAC strategy in combining with star eEF2K inhibitor A484954 and its potential derivatives. Consequently, candidate compound 11l was found to degrade eEF2K and induce apoptosis in human breast carcinoma MDA-MB-231 cells. Together, these findings demonstrate that our eEF2K-targeting PROTAC small molecule would be a potential new strategy for future breast cancer therapy.

Eukaryotic elongation factor 2 kinase inhibitor, A484954 lowered blood pressure in spontaneously hypertensive rats via inducing vasorelaxation

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) suppresses protein translation. We previously reported eEF2K expression was upregulated in mesenteric arteries (MA) from spontaneously hypertensive rats (SHR). We have recently revealed A484954, an eEF2K inhibitor, acutely suppressed vasopressor agonists-induced increase of blood pressure (BP) in normal Wistar rats. In this study, we examined the acute effects of A484954 on BP in SHR and explored underlying mechanisms. BP was measured by a carotid cannulation method in SHR. Isometric contraction in MA from SHR was measured. Endothelial nitric oxide synthase (eNOS) dimerization was measured by low-temperature sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. A484954 lowered BP in 15-week-old SHR. A484954 induced relaxation in MA from both 4- and 7-9-week-old SHR. In MA from 4-week-old SHR, A484954-induced relaxation was inhibited almost completely by a NOS inhibitor, N^G-nitro-l-arginine methyl ester (l-NAME) and significantly by a β blocker, propranolol. In MA from 7-9-week-old SHR, on the other hand, A484954-induced relaxation was inhibited partly either by l-NAME, indomethacin, a cyclooxygenase inhibitor, or l-NAME + indomethacin. A484954 promoted the dimerization of eNOS in human endothelial cells. In summary, we have revealed A484954 lowers BP in SHR perhaps through the vasorelaxation via the production of endothelium-derived relaxing factors.

Eukaryotic elongation factor 2 kinase inhibitor, A484954 potentiates β-adrenergic receptor agonist-induced acute decrease in diastolic blood pressure in rats

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) acts to inhibit protein translation through phosphorylating a specific substrate, eEF2. We previously found that the increased eEF2K expression in mesenteric artery mediates hypertension development in spontaneously hypertensive rats. More recently, we have revealed that a selective eEF2K inhibitor, A484954 induced vasorelaxation via opening inward rectifier K⁺ channel and activating β₂-adrenergic receptor in smooth muscle of rat isolated mesenteric artery, which contributes to prevent noradrenaline-induced acute increase in blood pressure (BP). In this study, we further explored acute effects of A484954 on BP in rats, especially focusing the action on β-adrenergic receptor. We also examined whether A484954 affects contraction and heart rate (HR) of isolated heart. BP and HR were measured by a carotid cannulation method in rats. Isometric contraction and HR in rat isolated atria were also measured pharmacologically. A484954 potentiated adrenaline-induced decrease in diastolic BP (DBP) but not increase in systolic BP (SBP). A484954 potentiated isoproterenol-induced decrease in DBP but not SBP. Contrastingly, A484954 prevented a non-β-adrenergic receptor agonist, angiotensin II-induced increase in both SBP and DBP. In isolated left atria, A484954 caused contraction, which was prevented by a β-adrenergic receptor antagonist, propranolol. In isolated right atria, A484954 increased HR. In conclusion, we for the first time demonstrated that A484954 potentiates β-adrenergic receptor agonist-induced decrease in DBP possibly through vasorelaxation mediated via activating β₂-adrenergic receptor. It was also demonstrated that A484954 causes contraction of rat isolated heart via activating β₁-adrenergic receptor.

Eukaryotic elongation factor 2 kinase promotes angiogenesis in hepatocellular carcinoma via PI3K/Akt and STAT3

Hepatocellular carcinoma (HCC) is an aggressive malignancy with increasing mortality in China. Angiogenesis is crucial for tumor formation, development and metastasis in HCC. Previous studies indicated that high expression levels of elongation factor 2 kinase (eEF2K), a protein kinase that negatively regulates the elongation stage of translation, were associated with poor prognosis of HCC. Here, we show that pharmacological inhibition or knockdown of eEF2K in highly metastatic liver cancer cells inhibits their colony forming and migratory capacities, as well as reducing their invasiveness. Importantly, knocking down eEF2K by lentiviral directed shRNA prevented tumor growth and angiogenesis of HCC in mice. Silencing of eEF2K in endothelial cells (HUVECs) led to a reduction in vascularization, evidenced by a decrease in capillary-like structures in the matrigel. Notably, knocking down eEF2K reduced the expression of angiogenesis-related growth factors in liver cancer cells and the expression of growth factor receptors on HUVECs, and thus restricted signaling crosstalk that promotes angiogenesis between HCC cells and endothelial cells. We also showed that silencing of eEF2K effectively reduced protein levels of SP1/KLF5 transcription factors and hence decreased the levels of bound SP1/KLF5 to the VEGF promoter, resulted in a decrease in VEGF mRNA expression. Knocking down eEF2K also led to a striking decrease in the phosphorylation of PI3K/Akt and STAT3, indicating inactivation of these tumorigenic pathways. Taken together, our data suggest that eEF2K contributes to angiogenesis and tumor progression in HCC via SP1/KLF5-mediated VEGF expression, as well as the subsequent stimulation of PI3K/Akt and STAT3 signaling.

Eukaryotic elongation factor 2 kinase inhibitor, A484954 inhibits noradrenaline-induced acute increase of blood pressure in rats

Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) inhibits protein translation through the phosphorylation of its specific substrate, eEF2. We previously demonstrated that eEF2K expression increases in superior mesenteric artery from spontaneously hypertensive rats (SHR) and that eEF2K mediates development of hypertension in SHR. In addition, we recently revealed that A484954, a selective eEF2K inhibitor induced relaxation via opening smooth muscle inward rectifier K⁺ (K_ir) channel in rat isolated superior mesenteric artery. Here, we further examined the effects of A484954 on contractility and blood pressure (BP) in rats. Isometric contraction of rat isolated superior mesenteric artery was measured. BP was measured by a carotid cannulation method. A484954 (10 µM) inhibited noradrenaline (NA)-induced contraction in a biphasic manner (magnitude of inhibition higher at high dose NA). A484954 also inhibited an α₁-receptor agonist, phenylephrine-induced contraction, while it was not biphasic. Specifically, a β-receptor antagonist, propranolol (1 µM) prevented the A484954-mediated inhibition of NA (high-dose)-induced contraction. A484954 (10 µM) potentiated a β-receptor agonist, isoproterenol-induced relaxation, which was completely prevented by BaCl₂ (1 mM), a K_ir channel blocker. In vivo, A484954 (122 µg/kg) inhibited NA-induced increase of BP in rats. Another eEF2K inhibitor, NH125 (22 µg/kg) also inhibited the NA-induced BP increase in rats. In summary, it was concluded that A484954 lowers NA-induced BP rise perhaps through activation of β₂-receptor-K_ir channel and subsequent vasorelaxation via inhibiting eEF2K activity.