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Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) is a key regulator of protein synthesis in mammalian cells. It phosphorylates and inhibits eEF2, the translation factor necessary for peptide translocation during the elongation phase of protein synthesis. When cellular energy demand outweighs energy supply, AMP-activated protein kinase (AMPK) and eEF2K become activated, leading to eEF2 phosphorylation, which reduces the rate of protein synthesis, a process that consumes a large proportion of cellular energy under optimal conditions. The goal of the present study was to elucidate the mechanisms by which AMPK activation leads to increased eEF2 phosphorylation to decrease protein synthesis. Using genetically modified mouse embryo fibroblasts (MEFs), effects of treatments with commonly used AMPK activators to increase eEF2 phosphorylation were compared with that of the novel compound 991. Bacterially expressed recombinant eEF2K was phosphorylated in vitro by recombinant activated AMPK for phosphorylation site-identification by mass spectrometry followed by site-directed mutagenesis of the identified sites to alanine residues to study effects on the kinetic properties of eEF2K. Wild-type eEF2K and a Ser491/Ser492 mutant were retrovirally re-introduced in eEF2K-deficient MEFs and effects of 991 treatment on eEF2 phosphorylation and protein synthesis rates were studied in these cells. AMPK activation leads to increased eEF2 phosphorylation in MEFs mainly by direct activation of eEF2K and partly by inhibition of mammalian target of rapamycin complex 1 (mTORC1) signaling. Treatment of MEFs with AMPK activators can also lead to eEF2K activation independently of AMPK probably via a rise in intracellular Ca. AMPK activates eEF2K by multi-site phosphorylation and the newly identified Ser491/Ser492 is important for activation, leading to mTOR-independent inhibition of protein synthesis. Our study provides new insights into the control of eEF2K by AMPK, with implications for li

Biguanides such as metformin have previously been shown to antagonize hepatic glucagon-stimulated cyclic AMP (cAMP) signalling independently of AMP-activated protein kinase (AMPK) via direct inhibition of adenylate cyclase by AMP. Here we show that incubation of hepatocytes with the small-molecule AMPK activator 991 decreases glucagon-stimulated cAMP accumulation, cAMP-dependent protein kinase (PKA) activity and downstream PKA target phosphorylation. Moreover, incubation of hepatocytes with 991 increases the Vmax of cyclic nucleotide phosphodiesterase 4B (PDE4B) without affecting intracellular adenine nucleotide concentrations. The effects of 991 to decrease glucagon-stimulated cAMP concentrations and activate PDE4B are lost in hepatocytes deleted for both catalytic subunits of AMPK. PDE4B is phosphorylated by AMPK at three sites, and by site-directed mutagenesis, Ser304 phosphorylation is important for activation. In conclusion, we provide a new mechanism by which AMPK antagonizes hepatic glucagon signalling via phosphorylation-induced PDE4B activation.

We re-investigate the scalar potential and the Higgs sector of the supersymmetric economical 3-3-1 model (SUSYE331) in the presence of the B/\mu type terms which has many important consequences. First, the model contains no massless Higgs fields. Second, we prove that the soft mass parameters of Higgses must be at the SU(3)_L scale. As a result, the masses of the Higgses drift toward this scale except one light real neutral Higgs with the mass of m_Z|cos(2\gamma)| at the tree level. We also show that there are some Higgses containing many properties of the Higgses in the minimal supersymmetric standard model (MSSM), especially in the neutral Higgs sector. One exact relation in the MSSM, m^2_H^{+/-}=m^2_A+m^2_W, is still true in the SUSYE331. Based on this result we make some comments on the lepton flavor violating decays of these Higgses as one of signatures of new physics in the SUSYE331 model which may be detected by present colliders., Comment: Matches version accepted for publication in EPJC. Typos are corrected. We add a new section, a new appendix, a new figure and new references to explain more clearly the properties of the lightest neutral Higgs. Results unchanged

In this work, we study the charged lepton flavor violating (cLFV) decays $\tau-> \mu\gamma$, $\tau-> 3\mu$ and $Z->\mu\tau$ in the framework of the Supersymmetric economical 3-3-1 model. Analytic formulas for branching ratios (BR) of these decays are presented. We assume that there exist lepton flavor violation (LFV) sources in both right- and left-handed slepton sectors. This leads to the strong enhancement of cLFV decay rates. We also show that the effects of the LFV source to the cLFV decay rates in the left-handed slepton sector are greater than those in the right- handed slepton sector. By numerical investigation, we show that the model under consideration contains the relative light mass spectrum of sleptons which satisfies the current experimental bounds on LFV processes in the limit of small $\tan \gamma$. The interplay between monopole and dipole operators also was studied., Comment: $B/\mu$-type parameters are included to guarantee the vacuum stability condition as well as satisfy current electroweak precision test. Mass parameter of gaugino in numerical investigation is shifted to be larger than 300 GeV. Few conclusions are changed. New references are added. This version was accepted by Nuclear Physics B

We build an supersymmetric version of the minimal 3-3-1 model with just two Higgs triplets using the superfield formalism. We study the mass spectrum of all particles in concordance with the experimental bounds. At the tree level, the masses of charged gauge bosons are the same as those of charged Higgs bosons. We also show that the electron, muon and their neutrinos as well as down and strange quarks gain mass through the loop correction. The narrow constraint on the ratio t_w = \frac{w}{w^\prime} is given by studying the new invisible decay mode of the Z boson., Comment: Journal version, 4 pictures are added for more details in explanation the generating masses of leptons

The glucose-lowering drug metformin has been shown to activate hepatic AMP-activated protein kinase (AMPK), a master kinase regulating cellular energy homeostasis. However, the underlying mechanisms remain controversial and have never been investigated in primary human hepatocytes.

Contraction-induced glucose uptake is only partly mediated by AMPK activation. We examined whether the diacylglycerol-sensitive protein kinase D (PKD; also known as novel PKC isoform mu) is also involved in the regulation of glucose uptake in the contracting heart. As an experimental model, we used suspensions of cardiac myocytes, which were electrically stimulated to contract or treated with the contraction-mimicking agent oligomycin. Induction of contraction at 4 Hz in cardiac myocytes or treatment with 1 mu M oligomycin enhanced (i) autophosphorylation of PKD at Ser916 by 5.1- and 3.8-fold, respectively, (ii) phosphorylation of PKD's downstream target cardiac-troponin-I (cTnI) by 2.9- and 2.1-fold, respectively, and (iii) enzymatic activity of immunoprecipitated PKD towards the substrate peptide syntide-2 each by 1.5-fold. Although AMPK was also activated under these same conditions, in vitro phosphorylation assays and studies with cardiac myocytes from AMPK alpha 2(-/-) mice indicated that activation of PKD occurs independent of AMPK activation. CaMKK beta, and the cardiac-specific PKC isoforms alpha, beta, and epsilon were excluded as upstream kinases for PKD in contraction signaling because none of these kinases were activated by oligomycin. Stimulation of glucose uptake and induction of GLUT4 translocation in cardiac myocytes by contraction and oligomycin each were sensitive to inhibition by the PKC/PKD inhibitors staurosporin and calphostin-C. Together, these data elude to a role of PKD in contraction-induced GLUT4 translocation. Finally, the combined actions of PKD on cTnI phosphorylation and on GLUT4 translocation would efficiently link accelerated contraction mechanics to increased energy production when the heart is forced to increase its contractile activity.