Author: David Harold Giles
Publisher:
ISBN:
Category :
Languages : en
Pages : 202
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Book Description
Translation of mRNA to protein is essential to all life, and is carried out by the ribosome with the assistance of various initiation and elongation factors. The rate and location at which translation occurs is subject to regulation by an intricate network of positive and negative signaling mechanisms. Such regulation allows the cell to respond to changes in external conditions, such as a sudden drop in nutrient availability. In higher eukaryotes, a key component of this regulation is the phosphorylation of elongation factor 2 (eEF-2) - the enzyme which catalyzes ribosome translocation along the mRNA - by eEF-2 kinase (eEF-2K) on Thr56. This event impedes the affinity of eEF-2 for the ribosome and therefore lowers the rate of protein synthesis. The activity of eEF-2K is tightly regulated by upstream signals, including Ca2+-calmodulin and post-translational modification. Aberrant regulation of the eEF-2K axis is known in various disease states, including cancer and depression, yet the molecular mechanisms by which eEF-2K processes the multiple signals that communicate with it are poorly defined. This gap in knowledge precludes the rational design of eEF-2Ktargeting treatments which may be effective at treating such diseases. Here, three broad topics are discussed. First, an overview of what is currently known about the structure, function, and regulation of eEF-2K is presented. Second, we elucidate the mechanisms by which eEF-2K integrates signals at the nutrient-sensitive signaling node. Finally, we characterize a highly active form of eEF-2K which provides insight into the potential structure-function relationship of key portions of the enzyme. Taken together, this work is an important step towards a complete description of the biochemical mechanisms by which eEF-2K is regulated by diverse inputs
Author: Clint Damian Jaxon Tavares
Publisher:
ISBN:
Category :
Languages : en
Pages : 528
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Book Description
Eukaryotic elongation factor 2 kinase (eEF-2K) is an atypical calcium/calmodulin-dependent protein kinase (CaMK-III). The kinase provides a mechanism by which cells can globally control the rate of the elongation phase of protein synthesis, through inhibition of its only known substrate, elongation factor 2 (eEF-2). eEF-2K has been reported to promote proliferation, migration and survival of cancer cells, and has also been implicated in depression. Understanding the regulation of kinase activity is important for development of inhibitors to treat these disease states. However, the mechanisms through which upstream kinases regulate eEF-2K activity via multisite phosphorylation, and how calcium and calmodulin contribute to this, are still unclear. This deficiency may result from the difficulty of obtaining the recombinant kinase in a form suitable for biochemical analysis. This work reports the purification (a three-step protocol using a calmodulin-affinity column) and characterization of recombinant human eEF-2K expressed in E. coli. Mass spectrometry identified Thr-348 and Ser-500 as major calcium/calmodulin-stimulated autophosphorylation sites. Rapid quench analysis indicates that the rate of Thr-348 autophosphorylation is extremely fast (k = 2.6 s−1, t [subscript 1⁄2] ~ 279 ms), and requires calmodulin. Mutagenesis studies suggest that phosphorylation at Thr-348 is required for eEF-2 phosphorylation both in vitro and in cells. However, while T348A has an overall lower activity than the WT kinase, the extent of stimulation of eEF-2K activity by 2-deoxy-D-glucose, hydrogen peroxide, ionomycin or cellular starvation is the same for both forms of the kinase. Thus, to control the amplitude of eEF-2K activity in cells following a stimulus that promotes calmodulin binding, phosphorylation at Thr-348 could act as an additional allosteric switch. This could potentially occur though interaction with a putative phosphate-binding pocket comprised of Lys-205, Arg-252 and Thr-254. Additionally, we observed that Ser-500 phosphorylation promotes an increase in affinity for calmodulin, and we provide evidence that Ser-500 phosphorylation on the eEF-2K•calmodulin complex significantly enhances the already rapid rate of Thr-348 autophosphorylation. Here we propose a two-step model involving calcium/calmodulin binding and Thr-348 autophosphorylation to modulate eEF-2K activity. Phosphorylation at Ser-500 is able to alter the kinetics at both these levels of regulation.
Author: Catrina Ann Chitjian
Publisher:
ISBN:
Category :
Languages : en
Pages : 332
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Book Description
Eukaryotic elongation factor 2 kinase (eEF-2K) is a calmodulin (CaM)/calcium regulated kinase whose activity disrupts translation elongation resulting in the global decrease of protein synthesis1. Translation is one of the most energy intensive processes in a cell; eEF-2K is critical in maintaining cellular homeostasis. The dysregulation of eEF-2K is associated with an assortment of diseases including several types of cancer2, depression [superscript 3,4], and Alzheimer’s disease5, which has prompted closer examination across multiple studies of the enzyme in recent decades. Notably, the kinetic mechanism of eEF-2K has been detailed as a two-step process: 1) The binding of Ca2+-CaM enables the autophosphorylation of Thr-348 and 2) The resulting conformational change enables eEF-2K to bind and phosphorylate its substrate. We have uncovered many surprising layers of eEF-2K regulation in past years, from kinetic mechanism to upstream affecters to models of CaM binding. This study focuses on the role of pH in regulating eEF-2K. pH homeostasis is also vital for cellular function. Even a slight disruption between the intra- and extracellular pH ratio can affect an array of processes such as ATP synthesis, enzyme function, as well as the proliferation, migration, and invasion of tumor cells6. Acidosis is a common effect of high intensity exercise, diabetic ketoacidosis, ischemia, and solid tumors [superscript 7–9]. It has been demonstrated that eEF-2K activity is increased and protein translation decreased in cells under acidic conditions, suggesting the enzyme’s potential cytoprotective effects [superscript 10–12]. This work reports the following: 1) A novel mechanism where H+ instead of Ca2+ activates eEF-2K; 2) A novel mechanism where H+ can replace Ca2+ in promoting eEF-2K substrate phosphorylation; 3) H+ promotes the binding of CaM to eEF-2K in a Ca2+-independent manner; 4) There are five histidine residues on eEF-2K that may contribute to the stabilized activity of eEF-2K under acidic conditions.
Author: Linda J. Van Eldik
Publisher: Academic Press
ISBN: 0080926363
Category : Science
Languages : en
Pages : 497
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Book Description
Calmodulin and Signal Transduction focuses on emerging themes in the molecular mechanisms of calcium signal transduction through calmodulin-regulated pathways. It provides the reader with selected examples and experimental precedents that underlie current models of cell regulation through calmodulin-regulated pathways and their linkage with other regulatory pathways. - Molecular mechanisms of calcium signal transduction through calmodulin-regulated enzymes - Selected case studies and precedents related to molecular mechanisms - Protein-protein recognition between calmodulin and the enzymes it regulates - Cross-talk and interdigitation with other signal transduction pathways
Author: Kelly Hooper
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Author: Friedrich Marks
Publisher: Garland Science
ISBN: 1136977244
Category : Science
Languages : en
Pages : 649
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Book Description
Cellular Signal Processing is intended for use in signal transduction courses for undergraduate and graduate students. It offers a unifying view of cell signaling that is based on the concept of protein interactions acting as sophisticated data processing networks that govern intracellular and extracellular communication. The content is guided by three major principles that are central to signal transduction: the protein network, its energy supply, and its evolution. It includes coverage of all important aspects of cell signaling, ranging from prokaryotic signal transduction to neuronal signaling. It also highlights the clinical aspects of cell signaling in health and disease.
Author: Ralph A. Bradshaw
Publisher: Academic Press
ISBN: 0080920918
Category : Science
Languages : en
Pages : 3188
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Book Description
Handbook of Cell Signaling, Three-Volume Set, 2e, is a comprehensive work covering all aspects of intracellular signal processing, including extra/intracellular membrane receptors, signal transduction, gene expression/translation, and cellular/organotypic signal responses. The second edition is an up-to-date, expanded reference with each section edited by a recognized expert in the field. Tabular and well illustrated, the Handbook will serve as an in-depth reference for this complex and evolving field. Handbook of Cell Signaling, 2/e will appeal to a broad, cross-disciplinary audience interested in the structure, biochemistry, molecular biology and pathology of cellular effectors. - Contains over 350 chapters of comprehensive coverage on cell signaling - Includes discussion on topics from ligand/receptor interactions to organ/organism responses - Provides user-friendly, well-illustrated, reputable content by experts in the field
Author: Antonius M. VanDongen
Publisher: CRC Press
ISBN: 142004415X
Category : Medical
Languages : en
Pages : 368
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Book Description
The NMDA receptor plays a critical role in the development of the central nervous system and in adult neuroplasticity, learning, and memory. Therefore, it is not surprising that this receptor has been widely studied. However, despite the importance of rhythms for the sustenance of life, this aspect of NMDAR function remains poorly studied. Written
Author: Sam Thiagalingam
Publisher: Cambridge University Press
ISBN: 0521493390
Category : Mathematics
Languages : en
Pages : 597
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Book Description
An overview of the current systems biology-based knowledge and the experimental approaches for deciphering the biological basis of cancer.
Author: Kenneth Maiese
Publisher: Academic Press
ISBN: 012802755X
Category : Science
Languages : en
Pages : 474
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Book Description
Molecules to Medicine with mTOR: Translating Critical Pathways into Novel Therapeutic Strategies is a one-stop reference that thoroughly covers the mechanistic target of rapamycin (mTOR). mTOR, also known as the mammalian target of rapamycin, is a 289-kDa serine/threonine protein kinase that is ubiquitous throughout the body and has a critical role in gene transcription and protein formation, stem cell development, cell survival and senescence, aging, immunity, tissue regeneration and repair, metabolism, tumorigenesis, oxidative stress, and pathways of programmed cell death that include apoptosis and autophagy. Incorporating a translational medicine approach, this important reference highlights the basic cellular biology of mTOR pathways, presents the role of mTOR during normal physiologic function and disease, and illustrates how the mechanisms of mTOR can be targeted for current and future therapeutic treatment strategies. Coverage of mTOR signaling includes the entire life cycle of cells that impacts multiple systems of the body including those of nervous, cardiovascular, immune, musculoskeletal, endocrine, reproductive, renal, and respiratory origin. - Covers the role of mTOR by internationally recognized expert contributors in the field. - Provides a clear picture of the complexity of mTOR signaling as well as of the different approaches that could target this pathway at various levels. - Includes analysis of the role of mTOR and in both health and disease. - Serves as an important resource for a broad audience of healthcare providers, scientists, drug developers, and students in both clinical and research settings.
