Showing papers on "Protein kinase complex published in 2015"
TL;DR: The crystal structure of an RSK1 construct in complex with its activator kinase captures the kinase–kinase complex in a precatalytic state where the activation loop of the downstream kinase (RSK1) faces the enzyme's (ERK2) catalytic site.
Abstract: Mitogen-activated protein kinases (MAPKs) bind and activate their downstream kinase substrates, MAPK-activated protein kinases (MAPKAPKs). Notably, extracellular signal regulated kinase 2 (ERK2) phosphorylates ribosomal S6 kinase 1 (RSK1), which promotes cellular growth. Here, we determined the crystal structure of an RSK1 construct in complex with its activator kinase. The structure captures the kinase–kinase complex in a precatalytic state where the activation loop of the downstream kinase (RSK1) faces the enzyme9s (ERK2) catalytic site. Molecular dynamics simulation was used to show how this heterodimer could shift into a signaling-competent state. This structural analysis combined with biochemical and cellular studies on MAPK→MAPKAPK signaling showed that the interaction between the MAPK binding linear motif (residing in a disordered kinase domain extension) and the ERK2 “docking” groove plays the major role in making an encounter complex. This interaction holds kinase domains proximal as they “readjust,” whereas generic kinase domain surface contacts bring them into a catalytically competent state.
31 citations
TL;DR: The data demonstrate the importance of searching for new mechanisms associated with TorC1 activation and/or the regulation of Gln3 localization/function in response to changes in the cells’ nitrogen environment, and the idea that TorC 1 activation may not be as central to nitrogen-responsive intracellular Gln 3 localization as envisioned previously.
Abstract: The TorC1 protein kinase complex is a central component in a eukaryotic cell’s response to varying nitrogen availability, with kinase activity being stimulated in nitrogen excess by increased intracellular leucine. This leucine-dependent TorC1 activation requires functional Gtr1/2 and Ego1/3 complexes. Rapamycin inhibition of TorC1 elicits nuclear localization of Gln3, a GATA-family transcription activator responsible for the expression of genes encoding proteins required to transport and degrade poor nitrogen sources, e.g., proline. In nitrogen-replete conditions, Gln3 is cytoplasmic and Gln3-mediated transcription minimal, whereas in nitrogen limiting or starvation conditions, or after rapamycin treatment, Gln3 is nuclear and transcription greatly increased. Increasing evidence supports the idea that TorC1 activation may not be as central to nitrogen-responsive intracellular Gln3 localization as envisioned previously. To test this idea directly, we determined whether Gtr1/2- and Ego1/3-dependent TorC1 activation also was required for cytoplasmic Gln3 sequestration and repressed GATA factor-mediated transcription by abolishing the Gtr-Ego complex proteins. We show that Gln3 is sequestered in the cytoplasm of gtr1Δ, gtr2Δ, ego1Δ, and ego3Δ strains either long term in logarithmically glutamine-grown cells or short term after refeeding glutamine to nitrogen-limited or -starved cells; GATA factor−dependent transcription also was minimal. However, in all but a gtr1Δ, nuclear Gln3 localization in response to nitrogen limitation or starvation was adversely affected. Our data demonstrate: (i) Gtr-Ego-dependent TorC1 activation is not required for cytoplasmic Gln3 sequestration in nitrogen-rich conditions; (ii) a novel Gtr-Ego-TorC1 activation-independent mechanism sequesters Gln3 in the cytoplasm; (iii) Gtr and Ego complex proteins participate in nuclear Gln3-Myc13 localization, heretofore unrecognized functions for these proteins; and (iv) the importance of searching for new mechanisms associated with TorC1 activation and/or the regulation of Gln3 localization/function in response to changes in the cells’ nitrogen environment.
9 citations
TL;DR: It is demonstrated that the speed of a systemic infection with a plant DNA geminivirus in Arabidopsis thaliana is KU80-dependent, and the early emergence of Euphorbia yellow mosaic virus DNA was significantly increased in ku80 knockout mutants compared with wild-type sibling controls.
Abstract: KU80 is well-known as a key component of the non-homologous end-joining pathway used to repair DNA double-strand breaks. In addition, the KU80-containing DNA-dependent protein kinase complex in mammals can act as a cytoplasmic sensor for viral DNA to activate innate immune response. We have now, to our knowledge for the first time, demonstrated that the speed of a systemic infection with a plant DNA geminivirus in Arabidopsis thaliana is KU80-dependent. The early emergence of Euphorbia yellow mosaic virus DNA was significantly increased in ku80 knockout mutants compared with wild-type sibling controls. The possible impact of KU80 on geminivirus multiplication by generating non-productive viral DNAs or its role as a pattern-recognition receptor against DNA virus infection is discussed.
9 citations
TL;DR: It is shown that pan‐neuronal loss or gain of CycD/Cdk4 increases mitochondrial superoxide, oxidative stress markers, and neurodegeneration and decreases lifespan, and that RNAi‐mediated depletion of the mitochondrial transcription factor, Tfam, can abrogate Cycd/C DK4's detrimental effects.
Abstract: Mitochondrial dysfunction has been implicated in human diseases, including cancer, and proposed to accelerate aging. The Drosophila Cyclin-dependent protein kinase complex cyclin D/cyclin-dependent kinase 4 (CycD/Cdk4) promotes cellular growth by stimulating mitochondrial biogenesis. Here, we examine the neurodegenerative and aging consequences of altering CycD/Cdk4 function in Drosophila. We show that pan-neuronal loss or gain of CycD/Cdk4 increases mitochondrial superoxide, oxidative stress markers, and neurodegeneration and decreases lifespan. We find that RNAi-mediated depletion of the mitochondrial transcription factor, Tfam, can abrogate CycD/Cdk4’s detrimental effects on both lifespan and neurodegeneration. This indicates that CycD/Cdk4’s pathological consequences are mediated through altered mitochondrial function and a concomitant increase in reactive oxygen species. In support of this, we demonstrate that CycD/Cdk4 activity levels in the brain affect the expression of a set of ‘oxidative stress’ genes. Our results indicate that the precise regulation of neuronal CycD/Cdk4 activity is important to limit mitochondrial reactive oxygen species production and prevent neurodegeneration.
6 citations
01 Jan 2015
TL;DR: This study utilized EHR-linked biobank data to elucidate the impact of genomic variation on glycemic response to metformin and found significant gene- and SNP-level associations within the beta-2 subunit of the heterotrimeric adenosine monophosphate-activated protein kinase complex.
Abstract: Metformin is a commonly prescribed diabetes medication whose mechanism of action is poorly understood. In this study we utilized EHR-linked biobank data to elucidate the impact of genomic variation on glycemic response to metformin. Our study found significant gene- and SNP-level associations within the beta-2 subunit of the heterotrimeric adenosine monophosphate-activated protein kinase complex. Using EHR phenotypes where were able to add additional clarity to ongoing metformin pharmacogenomic dialogue.
5 citations
Journal Article•
TL;DR: Evidence suggests that aprotein kinase complex consisting of the myristoylated calcium-binding protein SOS3 and the serine / threonine protein kinase SOS2 is activated by a salt-stress elicited calcium signal, which phosphorylates and activates various ion transporters, such as the plasma membrane Na+/ H+antiporter SOS1.
Abstract: Under salt stress,plants maintain a high concentration of K+and a low concentration of Na+in the cytosol. They do this by regulating the expression and activity of K+and Na+transporters and of H+pumps that generate the driving force for transport. Although salt-stress sensors remain elusive,some of the intermediary signaling components have been identified. Evidence suggests that a protein kinase complex consisting of the myristoylated calcium-binding protein SOS3 and the serine / threonine protein kinase SOS2 is activated by a salt-stress elicited calcium signal.The protein kinase complex then phosphorylates and activates various ion transporters,such as the plasma membrane Na+/ H+antiporter SOS1.
5 citations