Chemical genetics screen for enhancers of rapamycin identifies a specific inhibitor of an SCF family E3 ubiquitin ligase

The target of rapamycin (TOR) plays a central role in eukaryotic cell growth control. With prevalent hyperactivation of the mammalian TOR (mTOR) pathway in human cancers, strategies to enhance TOR pathway inhibition are needed. We used a yeast-based screen to identify small-molecule enhancers of rapamycin (SMERs) and discovered an inhibitor (SMER3) of the Skp1-Cullin-F-box (SCF)^(Met30) ubiquitin ligase, a member of the SCF E3-ligase family, which regulates diverse cellular processes including transcription, cell-cycle control and immune response. We show here that SMER3 inhibits SCF^(Met30) in vivo and in vitro, but not the closely related SCF^(Cdc4). Furthermore, we demonstrate that SMER3 diminishes binding of the F-box subunit Met30 to the SCF core complex in vivo and show evidence for SMER3 directly binding to Met30. Our results show that there is no fundamental barrier to obtaining specific inhibitors to modulate function of individual SCF complexes

Combination of Tmprss6-ASO and the iron chelator deferiprone improves erythropoiesis and reduces iron overload in a mouse model of beta-thalassemia intermedia Combination of Tmprss6-ASO and the iron chelator deferiprone improves erythropoiesis and reduces

Haematologica 2015 [Epub ahead of print] Citation: Casu C, Aghajan M, Rea Oikonomidou P, Guo S, Monia BP, and Rivella S. Combination of Tmprss6-ASO and the iron chelator deferiprone improves erythropoiesis and reduces iron overload in a mouse model of beta-thalassemia intermedia. Haematologica. 2015; 100:xxx doi:10.3324/haematol.2015.133348 Publisher's Disclaimer. Beta-thalassemia is one of the most frequently inherited disorders caused by mutations in the beta globin gene or its promoter leading to reduced or absent beta globin synthesis. Ineffective erythropoiesis (IE) and consequent extramedullary hematopoiesis, splenomegaly and systemic iron overload are major features of this disease. The disease course can be associated with severe anemia and need for lifelong transfusion therapy (thalassemia major, TM) or relatively less severe anemia (non-transfusion dependent thalassemia-NTDT or thalassemia intermedia-TI). Patients affected by beta thalassemia intermedia do not require chronic blood transfusions for survival. However, transfusion-independence is still associated with a variety of serious clinical morbidities. E-publishing ahead of print is increasingly important for the rapid dissemination of science. Haematologica is, therefore, E-publishing PDF files of an early version of manuscripts that have completed a regular peer review and have been accepted for publication. E-publishing of this PDF file has been approved by the authors. After having E-published Ahead of Print 8, 9 Suppression of Tmprss6 led to an increase in hepcidin synthesis and hemoglobin levels. These observations were also associated with a net reduction in splenomegaly, iron overload, transferrin saturation (Tfsat), formation of insoluble membrane-bound globins (hemichrome) and reactive oxygen species (ROS). 9 Thus, we hypothesized that the simultaneous use of the iron chelator deferiprone (DFP) with Tmprss6-ASO (Tmprss6-ASO+DFP) could combine the positive effects of Tmprss6-ASO on erythropoiesis and iron absorption with the chelation benefit on organ iron content. In this study, 3-to 4-month-old Hbb th3/+ females were treated with 50 mg/kg of Tmprss6 antisense 2 oligonucleotide (Tmprss6-ASO, twice a week for 6 weeks) or Tmprss6-ASO in combination with the oral iron chelator DFP dissolved in the drinking water at 1.25 mg/ml using either a commercial diet (normally used in the facility where animals were housed) containing 200 ppm of iron or a physiological diet containing 35ppm of iron. The majority of the animals available were treated using the commercial diet and just a few animals per group received the physiological one. With both diets we obtained the same trend in behavior but considering that the numbers were not comparable, we decided to show the data obtained from the 200ppm diet only. As expected, Tmprss6-ASO treatment, alone or in combination with DFP, suppressed Tmprss6 expression in the liver reaching an 82% decrease (P<1.8E-08) ( 11 Amelioration of erythropoiesis in this model of NTDT requires decreased erythroid iron intake and hemichrome formation. 9 Since DFP did not decrease Tfsat, we postulated that hemichrome formation was not decreased in this setting. In fact, hemichrome levels were unchanged in DFP-treated animals compared to Hbb th3/+ controls, while they were reduced in animals that received Tmprss6-ASO alone or Tmprss6-ASO+DFP 12 In 3 this study only upon hemichrome reduction there was a correlation with improvement of IE, observed as reduced proportions of immature erythroid cells. Using Ter119 and CD44 antibodies on BM and spleen cells we were able to perform FACS analysis which allowed us to discriminate different stages of erythroid differentiatio

A multi-enzyme model for pyrosequencing

Pyrosequencing is a DNA sequencing technique based on sequencing-by-synthesis enabling rapid real-time sequence determination. This technique employs four enzymatic reactions in a single tube to monitor DNA synthesis. Nucleotides are added iteratively to the reaction and in case of incorporation, pyrophosphate (PPi) is released. PPi triggers a series of reactions resulting in production of light, which is proportional to the amount of DNA and number of incorporated nucleotides. Generated light is detected and recorded by a detector system in the form of a peak signal, which reflects the activity of all four enzymes in the reaction. We have developed simulations to model the kinetics of the enzymes. These simulations provide a full model for the Pyrosequencing four-enzyme system, based on which the peak height and shape can be predicted depending on the concentrations of enzymes and substrates. Simulation results are shown to be compatible with experimental data. Based on these simulations, the rate-limiting steps in the chain can be determined, and K(M) and k(cat) of all four enzymes in Pyrosequencing can be calculated

Silencing of STE20-type kinase MST3 in mice with antisense oligonucleotide treatment ameliorates diet-induced nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is emerging as a leading cause of chronic liver disease worldwide. Despite intensive nonclinical and clinical research in this field, no specific pharmacological therapy is currently approved to treat NAFLD, which has been recognized as one of the major unmet medical needs of the 21st century. Our recent studies have identified STE20-type kinase MST3, which localizes to intracellular lipid droplets, as a critical regulator of ectopic fat accumulation in human hepatocytes. Here, we explored whether treatment with Mst3-targeting antisense oligonucleotides (ASOs) can promote hepatic lipid clearance and mitigate NAFLD progression in mice in the context of obesity. We found that administration of Mst3-targeting ASOs in mice effectively ameliorated the full spectrum of high-fat diet-induced NAFLD including liver steatosis, inflammation, fibrosis, and hepatocellular damage. Mechanistically, Mst3 ASOs suppressed lipogenic gene expression, as well as acetyl-CoA carboxylase (ACC) protein abundance, and substantially reduced lipotoxicity-mediated oxidative and endoplasmic reticulum stress in the livers of obese mice. Furthermore, we found that MST3 protein levels correlated positively with the severity of NAFLD in human liver biopsies. In summary, this study provides the first in vivo evidence that antagonizing MST3 signaling is sufficient to mitigate NAFLD progression in conditions of excess dietary fuels and warrants future investigations to assess whether MST3 inhibitors may provide a new strategy for the treatment of patients with NAFLD

Targeted Delivery of Stk25 Antisense Oligonucleotides to Hepatocytes Protects Mice Against Nonalcoholic Fatty Liver DiseaseSummary

Background & Aims: Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are emerging as leading causes of liver disease worldwide. Currently, no specific pharmacologic therapy is available for NAFLD/NASH, which has been recognized as one of the major unmet medical needs of the 21st century. Our recent studies in genetic mouse models, human cell lines, and well-characterized patient cohorts have identified serine/threonine protein kinase (STK)25 as a critical regulator of hepatic lipid partitioning and NAFLD/NASH. Here, we studied the metabolic benefit of liver-specific STK25 inhibitors on NAFLD development and progression in a mouse model of diet-induced obesity. Methods: We developed a hepatocyte-specific triantennary N-acetylgalactosamine (GalNAc)-conjugated antisense oligonucleotide (ASO) targeting Stk25 and evaluated its effect on NAFLD features in mice after chronic exposure to dietary lipids. Results: We found that systemic administration of hepatocyte-targeting GalNAc-Stk25 ASO in obese mice effectively ameliorated steatosis, inflammatory infiltration, hepatic stellate cell activation, nutritional fibrosis, and hepatocellular damage in the liver compared with mice treated with GalNAc-conjugated nontargeting ASO, without any systemic toxicity or local tolerability concerns. We also observed protection against high-fat-diet–induced hepatic oxidative stress and improved mitochondrial function with Stk25 ASO treatment in mice. Moreover, GalNAc-Stk25 ASO suppressed lipogenic gene expression and acetyl-CoA carboxylase protein abundance in the liver, providing insight into the molecular mechanisms underlying repression of hepatic steatosis. Conclusions: This study provides in vivo nonclinical proof-of-principle for the metabolic benefit of liver-specific inhibition of STK25 in the context of obesity and warrants future investigations to address the therapeutic potential of GalNAc-Stk25 ASO in the prevention and treatment of NAFLD. Keywords: NAFLD, NASH, Hepatic Steatosis, Liver Fibrosis, Antisense Oligonucleotide Therap

Expression of mitochondrial membrane-linked SAB determines severity of sex-dependent acute liver injury

SAB is an outer membrane docking protein for JNK mediated impaired mitochondrial function. Deletion of Sab in hepatocytes inhibits sustained JNK activation and cell death. Current work demonstrated that increasing SAB enhanced the severity of APAP liver injury. Female mice were resistant to liver injury and exhibited markedly decreased hepatic SAB protein expression versus males. The mechanism of SAB repression involved a pathway from ERalpha to p53 expression which induced miR34a-5p. miR34a-5p targeted the Sab mRNA coding region, repressing SAB expression. Fulvestrant or p53 knockdown decreased miR34a-5p and increased SAB in females leading to increased injury from APAP and TNF/galactosamine. In contrast, ERalpha agonist increased p53 and miR34a-5p which decreased SAB expression and hepatotoxicity in males. Hepatocyte-specific deletion of miR34a also increased severity of liver injury in females, which was prevented by GalNAc-ASO knockdown of Sab. Similar to mice, premenopausal human females also expressed high hepatic p53 and low SAB levels while age-matched males expressed low p53 and high SAB levels, but there was no sex difference of SAB expression in postmenopause. In conclusion, the level of SAB expression determined the severity of JNK dependent liver injury. Females expressed low hepatic SAB protein levels due to an ERalpha-p53-miR34a pathway which repressed SAB expression, accounting for resistance to liver injury

Ligand conjugated antisense oligonucleotide for the treatment of transthyretin amyloidosis: preclinical and phase 1 data

AimsAmyloidogenic transthyretin (ATTR) amyloidosis is a fatal disease characterized by progressive cardiomyopathy and/or polyneuropathy. AKCEA-TTR-LRx (ION-682884) is a ligand-conjugated antisense drug designed for receptor-mediated uptake by hepatocytes, the primary source of circulating transthyretin (TTR). Enhanced delivery of the antisense pharmacophore is expected to increase drug potency and support lower, less frequent dosing in treatment.Methods and resultsAKCEA-TTR-LRx demonstrated an approximate 50-fold and 30-fold increase in potency compared with the unconjugated antisense drug, inotersen, in human hepatocyte cell culture and mice expressing a mutated human genomic TTR sequence, respectively. This increase in potency was supported by a preferential distribution of AKCEA-TTR-LRx to liver hepatocytes in the transgenic hTTR mouse model. A randomized, placebo-controlled, phase 1 study was conducted to evaluate AKCEA-TTR-LRx in healthy volunteers (ClinicalTrials.gov: NCT03728634). Eligible participants were assigned to one of three multiple-dose cohorts (45, 60, and 90 mg) or a single-dose cohort (120 mg), and then randomized 10:2 (active : placebo) to receive a total of 4 SC doses (Day 1, 29, 57, and 85) in the multiple-dose cohorts or 1 SC dose in the single-dose cohort. The primary endpoint was safety and tolerability; pharmacokinetics and pharmacodynamics were secondary endpoints. All randomized participants completed treatment. No serious adverse events were reported. In the multiple-dose cohorts, AKCEA-TTR-LRx reduced TTR levels from baseline to 2 weeks after the last dose of 45, 60, or 90 mg by a mean (SD) of -85.7% (8.0), -90.5% (7.4), and -93.8% (3.4), compared with -5.9% (14.0) for pooled placebo (P < 0.001). A maximum mean (SD) reduction in TTR levels of -86.3% (6.5) from baseline was achieved after a single dose of 120 mg AKCEA-TTR-LRx .ConclusionsThese findings suggest an improved safety and tolerability profile with the increase in potency achieved by productive receptor-mediated uptake of AKCEA-TTR-LRx by hepatocytes and supports further development of AKCEA-TTR-LRx for the treatment of ATTR polyneuropathy and cardiomyopathy