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Biological & Pharmaceutical Bulletin Jul 2018AMP-activated protein kinase (AMPK) is a metabolic sensor in mammals that is activated when ATP levels in the cell decrease. AMPK is a heterotrimeric protein that... (Review)
Review
AMP-activated protein kinase (AMPK) is a metabolic sensor in mammals that is activated when ATP levels in the cell decrease. AMPK is a heterotrimeric protein that comprises 3 subunits, each of which has multiple phosphorylation sites that play critical roles in the regulation of either anabolism or catabolism by directly phosphorylating proteins or modulating gene transcription in multiple pathways, such as synthesis, oxidation and lipolysis of lipid. Research focused on the phosphorylation sites that are involved in lipid metabolism will lead to a better recognition of the role of AMPK in therapeutics for several common diseases. In this review, close attention is paid to the recent research on the structure, and multisite phosphorylation of AMPK subunits, as well as AMPK regulation of lipid metabolism via phosphorylation of related molecules.
Topics: AMP-Activated Protein Kinases; Adipose Tissue; Animals; Energy Metabolism; Humans; Lipid Metabolism; Liver; Phosphorylation; Protein Multimerization; Protein Subunits
PubMed: 29709897
DOI: 10.1248/bpb.b17-00724 -
Cell Reports Jul 2023Protein phosphorylation modification is crucial for signaling transduction in plant development and environmental adaptation. By precisely phosphorylating crucial... (Review)
Review
Protein phosphorylation modification is crucial for signaling transduction in plant development and environmental adaptation. By precisely phosphorylating crucial components in signaling cascades, plants can switch on and off the specific signaling pathways needed for growth or defense. Here, we have summarized recent findings of key phosphorylation events in typical hormone signaling and stress responses. More interestingly, distinct phosphorylation patterns on proteins result in diverse biological functions of these proteins. Thus, we have also highlighted latest findings that show how the different phosphosites of a protein, also named phosphocodes, determine the specificity of downstream signaling in both plant development and stress responses.
Topics: Phosphorylation; Signal Transduction; Plants; Plant Development; Plant Proteins
PubMed: 37405922
DOI: 10.1016/j.celrep.2023.112729 -
Molecular Plant Feb 2023Aluminum (Al) toxicity can seriously restrict crop production on acidic soils, which comprise 40% of the world's potentially arable land. The zinc finger transcription...
Aluminum (Al) toxicity can seriously restrict crop production on acidic soils, which comprise 40% of the world's potentially arable land. The zinc finger transcription factor STOP1 has a conserved and essential function in mediating plant Al resistance. Al stress induces STOP1 accumulation via post-transcriptional regulatory mechanisms. However, the upstream signaling pathway involved in Al-triggered STOP1 accumulation remains unclear. Here, we report that the MEKK1-MKK1/2-MPK4 cascade positively regulates STOP1 phosphorylation and stability. Mutations of MEKK1, MKK1/2, or MPK4 lead to decreased STOP1 stability and Al resistance. Al stress induces the kinase activity of MPK4, which interacts with and phosphorylates STOP1. The phosphorylation of STOP1 reduces its interaction with the F-box protein RAE1 that mediates STOP1 degradation, thereby leading to enhanced STOP1 stability and Al resistance. Taken together, our results suggest that the MEKK1-MKK1/2-MPK4 cascade is important for Al signaling and confers Al resistance through phosphorylation-mediated enhancement of STOP1 accumulation in Arabidopsis.
Topics: Arabidopsis; Phosphorylation; Aluminum; Arabidopsis Proteins; MAP Kinase Signaling System; Gene Expression Regulation, Plant; Transcription Factors
PubMed: 36419357
DOI: 10.1016/j.molp.2022.11.010 -
Autophagy 2016Lipids stored in lipid droplets are hydrolyzed via either cytosolic lipases or a selective form of macroautophagy known as lipophagy. We recently demonstrated that...
Lipids stored in lipid droplets are hydrolyzed via either cytosolic lipases or a selective form of macroautophagy known as lipophagy. We recently demonstrated that chaperone-mediated autophagy (CMA) is required for the initiation of lipolysis by either of these independent lipolytic pathways. CMA selectively degrades the lipid droplet proteins perilipins (PLIN) 2 and 3 from the lipid droplet surface, thus, facilitating the recruitment of cytosolic lipases and autophagy effector proteins to the lipid droplets. PLIN2 phosphorylation was observed upon induction of lipolysis, but the phosphorylating kinase and the relation of this phosphorylation with CMA of PLIN2 remained unknown. Here, we report that phosphorylation of PLIN2 is dependent on AMPK and occurs after the interaction of PLIN2 with the CMA chaperone HSPA8/Hsc70. Our results highlight a role for posttranslational modifications in priming proteins to be amenable for degradation by CMA.
Topics: AMP-Activated Protein Kinases; Animals; Autophagy; Lipid Droplets; Lipolysis; Mice; Models, Biological; Molecular Chaperones; NIH 3T3 Cells; Perilipin-2; Phosphorylation; Protein Kinase Inhibitors; Proteolysis
PubMed: 26902588
DOI: 10.1080/15548627.2015.1124226 -
Nature Communications Aug 2023PPARα corepressor NCoR1 is a key regulator of fatty acid β-oxidation and ketogenesis. However, its regulatory mechanism is largely unknown. Here, we report that...
PPARα corepressor NCoR1 is a key regulator of fatty acid β-oxidation and ketogenesis. However, its regulatory mechanism is largely unknown. Here, we report that oncoprotein p21-activated kinase 4 (PAK4) is an NCoR1 kinase. Specifically, PAK4 phosphorylates NCoR1 at T1619/T2124, resulting in an increase in its nuclear localization and interaction with PPARα, thereby repressing the transcriptional activity of PPARα. We observe impaired ketogenesis and increases in PAK4 protein and NCoR1 phosphorylation levels in liver tissues of high fat diet-fed mice, NAFLD patients, and hepatocellular carcinoma patients. Forced overexpression of PAK4 in mice represses ketogenesis and thereby increases hepatic fat accumulation, whereas genetic ablation or pharmacological inhibition of PAK4 exhibites an opposite phenotype. Interestingly, PAK4 protein levels are significantly suppressed by fasting, largely through either cAMP/PKA- or Sirt1-mediated ubiquitination and proteasome degradation. In this way, our findings provide evidence for a PAK4-NCoR1/PPARα signaling pathway that regulates fatty acid β-oxidation and ketogenesis.
Topics: Animals; Mice; Co-Repressor Proteins; Fatty Acids; p21-Activated Kinases; PPAR alpha; Nuclear Receptor Co-Repressor 1; Humans; Phosphorylation; Signal Transduction
PubMed: 37591884
DOI: 10.1038/s41467-023-40597-z -
Molecular Cell Jun 2022Protein phosphorylation is a reversible post-translational modification. Nine of the 20 natural amino acids in proteins can be phosphorylated, but most of what we know... (Review)
Review
Protein phosphorylation is a reversible post-translational modification. Nine of the 20 natural amino acids in proteins can be phosphorylated, but most of what we know about the roles of protein phosphorylation has come from studies of serine, threonine, and tyrosine phosphorylation. Much less is understood about the phosphorylation of histidine, lysine, arginine, cysteine, aspartate, and glutamate, so-called non-canonical phosphorylations. Phosphohistidine (pHis) was discovered 60 years ago as a mitochondrial enzyme intermediate; since then, evidence for the existence of histidine kinases and phosphohistidine phosphatases has emerged, together with examples where protein function is regulated by reversible histidine phosphorylation. pHis is chemically unstable and has thus been challenging to study. However, the recent development of tools for studying pHis has accelerated our understanding of the multifaceted functions of histidine phosphorylation, revealing a large number of proteins that are phosphorylated on histidine and implicating pHis in a wide range of cellular processes.
Topics: Histidine; Phosphorylation; Phosphotyrosine; Proteins
PubMed: 35654043
DOI: 10.1016/j.molcel.2022.05.007 -
Proceedings of the National Academy of... Aug 2023To ensure optimal growth, plants actively regulate their growth and development based on environmental changes. Among these, salt stress significantly influences growth...
To ensure optimal growth, plants actively regulate their growth and development based on environmental changes. Among these, salt stress significantly influences growth and yield. In this study, we demonstrate that the growth of root hairs of salt-stressed seedlings is regulated by the SALT OVERLY SENSITIVE 2 (SOS2)-GUANOSINE NUCLEOTIDE DIPHOSPHATE DISSOCIATION INHIBITOR 1 (RhoGDI1)-Rho GTPASE OF PLANTS 2 (ROP2) module. We show here that the kinase SOS2 is activated by salt stress and subsequently phosphorylates RhoGDI1, a root hair regulator, thereby decreasing its stability. This change in RhoGDI1 abundance resulted in a fine-tuning of polar localization of ROP2 and root hair initiation followed by polar growth, demonstrating how SOS2-regulated root hair development is critical for plant growth under salt stress. Our results reveal how a tissue-specific response to salt stress balances the relationship of salt resistance and basic growth.
Topics: rho Guanine Nucleotide Dissociation Inhibitor alpha; Arabidopsis; Phosphorylation; Guanosine Diphosphate; Salt Stress
PubMed: 37590409
DOI: 10.1073/pnas.2217957120 -
Science Advances Apr 2022Replication-coupled DNA repair and damage tolerance mechanisms overcome replication stress challenges and complete DNA synthesis. These pathways include fork reversal,...
Replication-coupled DNA repair and damage tolerance mechanisms overcome replication stress challenges and complete DNA synthesis. These pathways include fork reversal, translesion synthesis, and repriming by specialized polymerases such as PRIMPOL. Here, we investigated how these pathways are used and regulated in response to varying replication stresses. Blocking lagging-strand priming using a POLα inhibitor slows both leading- and lagging-strand synthesis due in part to RAD51-, HLTF-, and ZRANB3-mediated, but SMARCAL1-independent, fork reversal. ATR is activated, but CHK1 signaling is dampened compared to stalling both the leading and lagging strands with hydroxyurea. Increasing CHK1 activation by overexpressing CLASPIN in POLα-inhibited cells promotes replication elongation through PRIMPOL-dependent repriming. CHK1 phosphorylates PRIMPOL to promote repriming irrespective of the type of replication stress, and this phosphorylation is important for cellular resistance to DNA damage. However, PRIMPOL activation comes at the expense of single-strand gap formation, and constitutive PRIMPOL activity results in reduced cell fitness.
Topics: DNA Damage; DNA Repair; DNA Replication; DNA-Directed DNA Polymerase; Phosphorylation
PubMed: 35353580
DOI: 10.1126/sciadv.abm0314 -
International Journal of Molecular... Nov 2021Mitogen-activated protein kinase (MAPK) signaling pathways are highly conserved regulators of eukaryotic cell function. These enzymes regulate many biological processes,... (Review)
Review
Mitogen-activated protein kinase (MAPK) signaling pathways are highly conserved regulators of eukaryotic cell function. These enzymes regulate many biological processes, including the cell cycle, apoptosis, differentiation, protein biosynthesis, and oncogenesis; therefore, tight control of the activity of MAPK is critical. Kinases and phosphatases are well established as MAPK activators and inhibitors, respectively. Kinases phosphorylate MAPKs, initiating and controlling the amplitude of the activation. In contrast, MAPK phosphatases (MKPs) dephosphorylate MAPKs, downregulating and controlling the duration of the signal. In addition, within the past decade, pseudoenzymes of these two families, pseudokinases and pseudophosphatases, have emerged as bona fide signaling regulators. This review discusses the role of pseudophosphatases in MAPK signaling, highlighting the function of phosphoserine/threonine/tyrosine-interacting protein (STYX) and TAK1-binding protein (TAB 1) in regulating MAPKs. Finally, a new paradigm is considered for this well-studied cellular pathway, and signal transduction pathways in general.
Topics: Humans; Intracellular Signaling Peptides and Proteins; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase Phosphatases; Phosphorylation
PubMed: 34830476
DOI: 10.3390/ijms222212595 -
Journal of Proteome Research Jun 2023Post-translational modifications (PTMs) alter the function and fate of proteins and cells in almost every conceivable way. Protein modifications can occur as a result of...
Post-translational modifications (PTMs) alter the function and fate of proteins and cells in almost every conceivable way. Protein modifications can occur as a result of specific regulating actions of enzymes, such as tyrosine kinases phosphorylating tyrosine residues or by nonenzymatic reactions, such as oxidation related to oxidative stress and diseases. While many studies have addressed the multisite, dynamic, and network-like properties of PTMs, only little is known of the interplay of the same site modifications. In this work, we studied the enzymatic phosphorylation of oxidized tyrosine (l-DOPA) residues using synthetic insulin receptor peptides, in which tyrosine residues were replaced with l-DOPA. The phosphorylated peptides were identified by liquid chromatography-high-resolution mass spectrometry and the site of phosphorylation by tandem mass spectrometry. The results clearly show that the oxidized tyrosine residues are phosphorylated, displaying a specific immonium ion peak in the MS spectra. Furthermore, we detected this modification in our reanalysis (MassIVE ID: MSV000090106) of published bottom-up phosphoproteomics data. The modification, where both oxidation and phosphorylation take place at the same amino acid, has not yet been published in PTM databases. Our data indicate that there can be multiple PTMs that do not exclude each other at the same modification site.
Topics: Phosphorylation; Tyrosine; Levodopa; Peptides; Tandem Mass Spectrometry; Protein Processing, Post-Translational
PubMed: 37146082
DOI: 10.1021/acs.jproteome.3c00061