p70S6 Kinase Phosphorylates AMPK on Serine 491 to Mediate Leptin's Effect on Food Intake

SummaryThe PI3K-AKT, mTOR-p70S6 kinase and AMPK pathways play distinct and critical roles in metabolic regulation. Each pathway is necessary for leptin's anorexigenic effects in the hypothalamus. Here we show that these pathways converge in an integrated phosphorylation cascade to mediate leptin action in the hypothalamus. We identify serine491 on α2AMPK as the site of convergence and show that p70S6 kinase forms a complex with α2AMPK, resulting in phosphorylation on serine491. Blocking α2AMPK-serine491 phosphorylation increases hypothalamic AMPK activity, food intake, and body weight. Serine491 phosphorylation is necessary for leptin's effects on hypothalamic α2AMPK activity, neuropeptide expression, food intake, and body weight. These results identify an inhibitory AMPK kinase, p70S6 kinase, and demonstrate that AMPK is a substrate for mTOR-p70S6 kinase. This discovery has broad biologic implications since mTOR-p70S6 kinase and AMPK have multiple, fundamental and generally opposing cellular effects that regulate metabolism, cell growth, and development

DNA Dynamics Is Likely to Be a Factor in the Genomic Nucleotide Repeats Expansions Related to Diseases

Trinucleotide repeats sequences (TRS) represent a common type of genomic DNA motif whose expansion is associated with a large number of human diseases. The driving molecular mechanisms of the TRS ongoing dynamic expansion across generations and within tissues and its influence on genomic DNA functions are not well understood. Here we report results for a novel and notable collective breathing behavior of genomic DNA of tandem TRS, leading to propensity for large local DNA transient openings at physiological temperature. Our Langevin molecular dynamics (LMD) and Markov Chain Monte Carlo (MCMC) simulations demonstrate that the patterns of openings of various TRSs depend specifically on their length. The collective propensity for DNA strand separation of repeated sequences serves as a precursor for outsized intermediate bubble states independently of the G/C-content. We report that repeats have the potential to interfere with the binding of transcription factors to their consensus sequence by altered DNA breathing dynamics in proximity of the binding sites. These observations might influence ongoing attempts to use LMD and MCMC simulations for TRS–related modeling of genomic DNA functionality in elucidating the common denominators of the dynamic TRS expansion mutation with potential therapeutic applications

Complement factors are secreted in human follicular fluid by granulosa cells and are possible oocyte maturation factors

Aims: In this study, we identify components of the complement system present in human follicular fluid that affect oocyte development and maturation. Material and Methods: Using bottom-up liquid chromatography/mass spectrometry/mass spectrometry, we identified complement factors as consistently present in human follicular fluid from 15 different subjects. Results: According to our gene-chip data, these complement factors are actively produced by granulosa cells. Conclusions: By applying the computational Ingenuity Pathway Analysis software and database we have identified complement pathways that play a role in oocyte maturation and follicular development. © 2012 Japan Society of Obstetrics and Gynecology

PKD1 Inhibits AMPK2 through Phosphorylation of Serine 491 and Impairs Insulin Signaling in Skeletal Muscle Cells

Background: Diminished activity of the enzyme AMP-activated protein kinase (AMPK) is associated with impaired insulin signaling. Results: Protein Kinase (PK)C/D1 activation inhibits AMPK2 via Ser491 phosphorylation; PKD1 inhibition prevents this in skeletal muscle cells. Conclusion: PKD1 is a novel upstream AMPK-kinase that phosphorylates AMPK on Ser491 and regulates insulin signaling. Significance: PKD1 inhibition may be a novel strategy for improving insulin sensitivity.This article is published as Coughlan KA, Valentine RJ, Sudit BS, Allen K, Dagon Y, Kahn BB, Ruderman NB, Saha AK. PKD1 inhibits AMPKα2 through phosphorylation of Ser491 and impairs insulin signaling in skeletal muscle cells. Journal Biological Chemistry. 2016; 291(11):5664-75. DOI: 10.1074/jbc.M115.696849. Posted with permission.</p

The TRS expansion has an effect on the DNA bubble spectrum.

<p>EPBD based LMD simulations have been conducted on the: a) (CAG.CTG)₄₅ repeats and healthy (CAG.CTG)₁₀ repeats with 30 bp flanking huntington gene sequence; b) (GAA.TTC)₁₂₀ and (GAA.TTC)₆ MRS that are embedded in 50 bp frataxin gene sequence; c) (CGG.GCC)₂₄₀ and (CGG.GCC)₂₀ repeats together with 50 bp FMR1 gene flanking sequence. The y-axis represents the length of the bubbles in bp; the x-axis represents the number of the base pairs; the color axis gives the bubble duration in psec. The brackets above the panels denote the repeated sequence; red arrows- the largest and long-lived base-pairs openings.</p

Accumulation of (GAA.TTC) repeats leads to changes in local DNA breathing.

<p>BAD criteria are used to describe and compare the local base pair breathing of DNA sequences with different numbers of (GAA.TTC) repeats embedded within the frataxin gene [B7] promoter sequence. a) BAD coordinates [Å] are calculated with EPBD based MCMC simulations for sequence inserts with different numbers of repeats: (GAA.TTC)₆-black line, (GAA.TTC)₄₅-red line, and (GAA.TTC)₁₂₀-blue line. The position of the flanking sequence (fl) is shown above the panel. b) BAD coordinates for a randomized sequence with the same number of base pairs and G+C content as the (GAA.TTC)₄₁ sequence. The random sequence (red line) is missing the synchronized average base pair openings behavior of the symmetric (GAA.TTC)₄₁ (blue line). The nucleotide position is shown on the horizontal. The BAD coordinates are shown on the vertical in [Å].</p

Rho-kinase/AMPK axis regulates hepatic lipogenesis during overnutrition

This work was supported by grants from the NIH (R01DK083567 to YBK), the American Diabetes Association (1-09-RA-87 to YBK), the American Heart Association (12GRANT12040170 to YBK), the East Carolina University Start-up fund (to HH), the National Research Foundation (NRF-2014M3A9D8034464 to M Shong, NRF-2016R1A2B3010373 to KSP, NRF-2015R1C1A1A02037164 to SHL), the National Research Foundation of Korea (2013M3C7A1056024 to MSK), and the Korean Diabetes Association (to JAS, 2017). In addition, structural funding for the Center for Neuroscience and Cell Biology, University of Coimbra, NMR facility is supported by FEDER-PT2020 (UID/BIA/04004/2013 and CENTRO-07-CT62-FEDER-002012) and by the Portuguese Foundation for Science and Technology (FCT) through grants PTDC/CVT-NUT/2851/2014, PTDC/BIM-MET/4265/2014, and RECI/QEQ-QFI/0168/2012. ISL is a recipient of an FCT fellowship from Portugal (SFRH/BD/71021/2010), and MCK is a recipient of a postdoctoral fellowship award from the American Diabetes Association (1-17-PDF-146). GDB is supported by the European Union's Horizon 2020 Research and Innovation programme under Marie Sklodowska-Curie Grant Agreement 722619. We thank Farhad Danesh for CA-ROCK1-knockin mice; Huseyin Ozkan, Ivan Viegas, Cristina Barosa, Hyun Cheol Rho, Xuemei Ma, Yao Yang, and Alexander Banks for technical help; and Barbara Kahn, Tony Hollenberg, Sonia Najjar, and Terry Flier for helpful discussion.Obesity is a major risk factor for developing nonalcoholic fatty liver disease (NAFLD). NAFLD is the most common form of chronic liver disease and is closely associated with insulin resistance, ultimately leading to cirrhosis and hepatocellular carcinoma. However, knowledge of the intracellular regulators of obesity-linked fatty liver disease remains incomplete. Here we showed that hepatic Rho-kinase 1 (ROCK1) drives obesity-induced steatosis in mice through stimulation of de novo lipogenesis. Mice lacking ROCK1 in the liver were resistant to diet-induced obesity owing to increased energy expenditure and thermogenic gene expression. Constitutive expression of hepatic ROCK1 was sufficient to promote adiposity, insulin resistance, and hepatic lipid accumulation in mice fed a high-fat diet. Correspondingly, liver-specific ROCK1 deletion prevented the development of severe hepatic steatosis and reduced hyperglycemia in obese diabetic (ob/ob) mice. Of pathophysiological significance, hepatic ROCK1 was markedly upregulated in humans with fatty liver disease and correlated with risk factors clustering around NAFLD and insulin resistance. Mechanistically, we found that hepatic ROCK1 suppresses AMPK activity and a ROCK1/AMPK pathway is necessary to mediate cannabinoid-induced lipogenesis in the liver. Furthermore, treatment with metformin, the most widely used antidiabetes drug, reduced hepatic lipid accumulation by inactivating ROCK1, resulting in activation of AMPK downstream signaling. Taken together, our findings establish a ROCK1/AMPK signaling axis that regulates de novo lipogenesis, providing a unique target for treating obesity-related metabolic disorders such as NAFLD.publishersversionpublishe