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Biomolecules Aug 2020The family of mitogen-activated protein kinases (MAPKs) consists of fourteen members and has been implicated in regulation of virtually all cellular processes. MAPKs are... (Review)
Review
The family of mitogen-activated protein kinases (MAPKs) consists of fourteen members and has been implicated in regulation of virtually all cellular processes. MAPKs are divided into two groups, conventional and atypical MAPKs. Conventional MAPKs are further classified into four sub-families: extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK1, 2 and 3), p38 (α, β, γ, δ), and extracellular signal-regulated kinase 5 (ERK5). Four kinases, extracellular signal-regulated kinase 3, 4, and 7 (ERK3, 4 and 7) as well as Nemo-like kinase (NLK) build a group of atypical MAPKs, which are activated by different upstream mechanisms than conventional MAPKs. Early studies identified JNK1/2 and ERK1/2 as well as p38α as a central mediators of inflammation-evoked insulin resistance. These kinases have been also implicated in the development of obesity and diabetes. Recently, other members of conventional MAPKs emerged as important mediators of liver, skeletal muscle, adipose tissue, and pancreatic β-cell metabolism. Moreover, latest studies indicate that atypical members of MAPK family play a central role in the regulation of adipose tissue function. In this review, we summarize early studies on conventional MAPKs as well as recent findings implicating previously ignored members of the MAPK family. Finally, we discuss the therapeutic potential of drugs targeting specific members of the MAPK family.
Topics: Animals; Humans; MAP Kinase Kinase 4; MAP Kinase Signaling System; Metabolic Diseases; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinase 7; p38 Mitogen-Activated Protein Kinases
PubMed: 32872540
DOI: 10.3390/biom10091256 -
The Journal of Biological Chemistry Apr 2023The integrated stress response (ISR) is an important mechanism by which cells confer protection against environmental stresses. Central to the ISR is a collection of...
The integrated stress response (ISR) is an important mechanism by which cells confer protection against environmental stresses. Central to the ISR is a collection of related protein kinases that monitor stress conditions, such as Gcn2 (EIF2AK4) that recognizes nutrient limitations, inducing phosphorylation of eukaryotic translation initiation factor 2 (eIF2). Gcn2 phosphorylation of eIF2 lowers bulk protein synthesis, conserving energy and nutrients, coincident with preferential translation of stress-adaptive gene transcripts, such as that encoding the Atf4 transcriptional regulator. While Gcn2 is central for cell protection to nutrient stress and its depletion in humans leads to pulmonary disorders, Gcn2 can also contribute to the progression of cancers and facilitate neurological disorders during chronic stress. Consequently, specific ATP-competitive inhibitors of Gcn2 protein kinase have been developed. In this study, we report that one such Gcn2 inhibitor, Gcn2iB, can activate Gcn2, and we probe the mechanism by which this activation occurs. Low concentrations of Gcn2iB increase Gcn2 phosphorylation of eIF2 and enhance Atf4 expression and activity. Of importance, Gcn2iB can activate Gcn2 mutants devoid of functional regulatory domains or with certain kinase domain substitutions derived from Gcn2-deficient human patients. Other ATP-competitive inhibitors can also activate Gcn2, although there are differences in their mechanisms of activation. These results provide a cautionary note about the pharmacodynamics of eIF2 kinase inhibitors in therapeutic applications. Compounds designed to be kinase inhibitors that instead directly activate Gcn2, even loss of function variants, may provide tools to alleviate deficiencies in Gcn2 and other regulators of the ISR.
Topics: Humans; Adenosine Triphosphate; Enzyme Activation; Eukaryotic Initiation Factor-2; Phosphorylation; Protein Kinase Inhibitors; Protein Kinases; Protein Serine-Threonine Kinases
PubMed: 36898579
DOI: 10.1016/j.jbc.2023.104595 -
International Journal of Molecular... Sep 2016Pancreatic β-cell failure and death is considered to be one of the main factors responsible for type 2 diabetes. It is caused by, in addition to hyperglycemia, chronic... (Review)
Review
Pancreatic β-cell failure and death is considered to be one of the main factors responsible for type 2 diabetes. It is caused by, in addition to hyperglycemia, chronic exposure to increased concentrations of fatty acids, mainly saturated fatty acids. Molecular mechanisms of apoptosis induction by saturated fatty acids in β-cells are not completely clear. It has been proposed that kinase signaling could be involved, particularly, c-Jun N-terminal kinase (JNK), protein kinase C (PKC), p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), and Akt kinases and their pathways. In this review, we discuss these kinases and their signaling pathways with respect to their possible role in apoptosis induction by saturated fatty acids in pancreatic β-cells.
Topics: Animals; Apoptosis; Endoplasmic Reticulum Stress; Fatty Acids; Humans; Insulin-Secreting Cells; JNK Mitogen-Activated Protein Kinases; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 1; Protein Kinase C; Proto-Oncogene Proteins c-akt; p38 Mitogen-Activated Protein Kinases
PubMed: 27626409
DOI: 10.3390/ijms17091400 -
Cancer Science Apr 2018Double-stranded (ds) RNA-dependent protein kinase (PKR) is a ubiquitously expressed serine/threonine protein kinase. It was initially identified as an innate immune... (Review)
Review
Double-stranded (ds) RNA-dependent protein kinase (PKR) is a ubiquitously expressed serine/threonine protein kinase. It was initially identified as an innate immune antiviral protein induced by interferon (IFN) and activated by dsRNA. PKR is recognized as a key executor of antiviral host defense. Moreover, it contributes to inflammation and immune regulation through several signaling pathways. In addition to IFN and dsRNA, PKR is activated by multiple stimuli and regulates various signaling pathways including the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B cells pathways. PKR was initially thought to be a tumor suppressor as a result of its ability to suppress cell growth and interact with major tumor suppressor genes. However, in several types of malignant disease, such as colon and breast cancers, its role remains controversial. In hepatocellular carcinoma, hepatitis C virus (HCV) is the main cause of liver cancer, and PKR inhibits HCV replication, indicating its role as a tumor suppressor. However, PKR is overexpressed in cirrhotic patients, and acts as a tumor promoter through enhancement of cancer cell growth by mediating MAPK or signal transducer and activator of transcription pathways. Moreover, PKR is reportedly required for the activation of inflammasomes and influences metabolic disorders. In the present review, we introduce the multifaceted roles of PKR such as antiviral function, tumor cell growth, regulation of inflammatory immune responses, and maintaining metabolic homeostasis; and discuss future perspectives on PKR biology including its potential as a therapeutic target for liver cancer.
Topics: Animals; Humans; Inflammation; Liver Neoplasms; Mitogen-Activated Protein Kinases; Protein Serine-Threonine Kinases; eIF-2 Kinase
PubMed: 29478262
DOI: 10.1111/cas.13551 -
Methods in Enzymology 2022Pseudoenzymes resemble active enzymes, but lack key catalytic residues believed to be required for activity. Many pseudoenzymes appear to be inactive in conventional...
Pseudoenzymes resemble active enzymes, but lack key catalytic residues believed to be required for activity. Many pseudoenzymes appear to be inactive in conventional enzyme assays. However, an alternative explanation for their apparent lack of activity is that pseudoenzymes are being assayed for the wrong reaction. We have discovered several new protein kinase-like families which have revealed how different binding orientations of adenosine triphosphate (ATP) and active site residue migration can generate a novel reaction from a common kinase scaffold. These results have exposed the catalytic versatility of the protein kinase fold and suggest that atypical kinases and pseudokinases should be analyzed for alternative transferase activities. In this chapter, we discuss a general approach for bioinformatically identifying divergent or atypical members of an enzyme superfamily, then present an experimental approach to characterize their catalytic activity.
Topics: Adenosine Triphosphate; Catalysis; Catalytic Domain; Humans; Protein Kinases
PubMed: 35525554
DOI: 10.1016/bs.mie.2022.03.047 -
Analytical Sciences : the International... Oct 2021We have developed a novel FRET-based assay to monitor protein kinase activity using quantum dots (QDs) and fluorophore-labeled substrate peptides. To develop a...
We have developed a novel FRET-based assay to monitor protein kinase activity using quantum dots (QDs) and fluorophore-labeled substrate peptides. To develop a FRET-based protein kinase assay, it is important to consider the phosphate group recognition strategy and to ensure that the FRET pairs are close enough because the FRET efficiency is highly dependent on the distance between the FRET pairs. Here, we incorporated a phos-tag, which captures phosphate groups strongly and selectively, into a protein kinase assay to recognize phosphorylation. Our detection system was composed of phos-tag-modified QDs and Cy5-labeled substrate peptides. Because the phos-tags capture phosphate groups by forming dinuclear complexes, the Cy5-labeled substrate peptides are captured by the phos-tags on the QD surface upon protein kinase-mediated phosphorylation, which induces FRET from the QDs to Cy5 because of the approximation of Cy5 to the QDs. On the basis of the difference of this FRET efficiency, we successfully measured protein kinase A activity, which demonstrated the feasibility of our assay.
Topics: Fluorescence Resonance Energy Transfer; Peptides; Protein Kinases; Pyridines; Quantum Dots
PubMed: 33716259
DOI: 10.2116/analsci.20P443 -
International Journal of Molecular... Mar 2019Protein phosphorylation regulated by protein kinases, as well as their dephosphorylation, is one of the most common post-translational modifications, and plays important... (Review)
Review
Protein phosphorylation regulated by protein kinases, as well as their dephosphorylation, is one of the most common post-translational modifications, and plays important roles in physiological activities, such as intracellular signal communications, gene transcription, cell proliferation and apoptosis. Over-expression of protein kinases is closely associated with various diseases. Consequently, accurate detection of protein kinases activities and their relevant inhibitors screening is critically important, not only to the biochemical research, but also to the clinical diagnosis and therapy. Nanomaterials, taking advantage of large surface areas, as well as excellent electrical, catalytic, magnetic and optical properties, have been utilized as target concentrators, recognition components, signal transducer or amplification elements in protein kinase related assays. This review summarizes the recent representative works to highlight the applications of nanomaterials in different biosensor technologies for protein kinases activities detection and their inhibitors screening. First, different nanomaterials developed for phosphoprotein/phosphopeptide enrichment and phosphate recognition are introduced. Next, representative works are selected that mainly focus on the utilization of nanomaterials as signal transducer or amplification elements in various protein kinases sensing platforms, such as electrochemical, colorimetric, fluorescent, and mass spectroscopy-based approaches. Finally, the major challenges and perspectives of nanomaterials being applied in protein kinases related assays are discussed.
Topics: Animals; Biosensing Techniques; Colorimetry; Electrochemical Techniques; Enzyme Activation; Humans; Nanostructures; Nanotechnology; Phosphates; Phosphoproteins; Phosphorylation; Photochemistry; Protein Binding; Protein Kinases; Signal Transduction
PubMed: 30901923
DOI: 10.3390/ijms20061440 -
ImmunoHorizons Jul 2022Caspase-8 (Casp8) suppresses receptor-interacting protein kinase-3 (RIPK3)/mixed lineage kinase domain-like protein (MLKL)-dependent necroptosis, demonstrated by the...
Caspase-8 (Casp8) suppresses receptor-interacting protein kinase-3 (RIPK3)/mixed lineage kinase domain-like protein (MLKL)-dependent necroptosis, demonstrated by the genetic evidence that deletion of or prevented embryonic lethality of -deficient mice. However, the detailed mechanisms by which deficiency triggers necroptosis during embryonic development remain unclear. In this article, we show that deletion caused formation of the RIPK1-RIPK3 necrosome in the yolk sac, leading to vascularization defects, prevented by MLKL and RIPK3 deficiency, or RIPK3 RHIM mutant (RIPK3 V448P), but not by the RIPK1 kinase-dead mutant (RIPK1 K45A). In addition, mice died on embryonic day 14.5, which was delayed to embryonic day 17.5 by ablation of one allele in and was completely rescued by ablation of Our results revealed an in vivo role of RIPK3 RHIM and RIPK1 scaffold-mediated necroptosis in deficiency embryonic development and suggested that the Casp8-deficient yolk sac might be implicated in identifying novel regulators as an in vivo necroptotic model.
Topics: Animals; Caspase 8; Embryonic Development; Mice; Necroptosis; Protein Kinases; Receptor-Interacting Protein Serine-Threonine Kinases
PubMed: 35858757
DOI: 10.4049/immunohorizons.2200021 -
Essays in Biochemistry Sep 2022Plant immunity is crucial to plant health but comes at an expense. For optimal plant growth, tight immune regulation is required to prevent unnecessary rechannelling of... (Review)
Review
Plant immunity is crucial to plant health but comes at an expense. For optimal plant growth, tight immune regulation is required to prevent unnecessary rechannelling of valuable resources. Pattern- and effector-triggered immunity (PTI/ETI) represent the two tiers of immunity initiated after sensing microbial patterns at the cell surface or pathogen effectors secreted into plant cells, respectively. Recent evidence of PTI-ETI cross-potentiation suggests a close interplay of signalling pathways and defense responses downstream of perception that is still poorly understood. This review will focus on controls on plant immunity through phosphorylation, a universal and key cellular regulatory mechanism. Rather than a complete overview, we highlight "what's new in protein kinase/phosphatase signalling" in the immunity field. In addition to phosphoregulation of components in the pattern recognition receptor (PRR) complex, we will cover the actions of the major immunity-relevant intracellular protein kinases/phosphatases in the 'signal relay', namely calcium-regulated kinases (e.g. calcium-dependent protein kinases, CDPKs), mitogen-activated protein kinases (MAPKs), and various protein phosphatases. We discuss how these factors define a phosphocode that generates cellular decision-making 'logic gates', which contribute to signalling fidelity, amplitude, and duration. To underscore the importance of phosphorylation, we summarize strategies employed by pathogens to subvert plant immune phosphopathways. In view of recent game-changing discoveries of ETI-derived resistosomes organizing into calcium-permeable pores, we speculate on a possible calcium-regulated phosphocode as the mechanistic control of the PTI-ETI continuum.
Topics: Calcium; Mitogen-Activated Protein Kinases; Phosphoprotein Phosphatases; Plant Immunity; Protein Kinases; Receptors, Pattern Recognition
PubMed: 35723080
DOI: 10.1042/EBC20210088 -
Seminars in Cell & Developmental Biology Jan 2021Receptor Interacting Protein Kinases (RIPKs) are a family of Ser/Thr/Tyr kinases whose functions, regulation and pathophysiologic roles have remained an enigma for a... (Review)
Review
Receptor Interacting Protein Kinases (RIPKs) are a family of Ser/Thr/Tyr kinases whose functions, regulation and pathophysiologic roles have remained an enigma for a long time. In recent years, these proteins garnered significant interest due to their roles in regulating a variety of host defense functions including control of inflammatory gene expression, different forms of cell death, and cutaneous and intestinal barrier functions. In addition, there is accumulating evidence that while these kinases seemingly follow typical kinase blueprints, their functioning in cells can take forms that are atypical for protein kinases. Lastly, while these kinases generally belong to distinct areas of innate immune regulation, there are emerging overarching themes that may unify the functions of this kinase family. Our review seeks to discuss the biology of RIPKs, and how typical and atypical features of this family informs the activity of a rapidly growing repertoire of RIPK inhibitors.
Topics: Humans; Protein Kinases; Receptor-Interacting Protein Serine-Threonine Kinases
PubMed: 32732131
DOI: 10.1016/j.semcdb.2020.06.014