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Molecular Plant May 2023Pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) are required for host defense against pathogens. Although PTI and ETI are intimately connected,...
Pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) are required for host defense against pathogens. Although PTI and ETI are intimately connected, the underlying molecular mechanisms remain elusive. In this study, we demonstrate that flg22 priming attenuates Pseudomonas syringae pv. tomato DC3000 (Pst) AvrRpt2-induced hypersensitive cell death, resistance, and biomass reduction in Arabidopsis. Mitogen-activated protein kinases (MAPKs) are key signaling regulators of PTI and ETI. The absence of MPK3 and MPK6 significantly reduces pre-PTI-mediated ETI suppression (PES). We found that MPK3/MPK6 interact with and phosphorylate the downstream transcription factor WRKY18, which regulates the expression of AP2C1 and PP2C5, two genes encoding protein phosphatases. Furthermore, we observed that the PTI-suppressed ETI-triggered cell death, MAPK activation, and growth retardation are significantly attenuated in wrky18/40/60 and ap2c1 pp2c5 mutants. Taken together, our results suggest that the MPK3/MPK6-WRKYs-PP2Cs module underlies PES and is essential for the maintenance of plant fitness during ETI.
Topics: Arabidopsis Proteins; Mitogen-Activated Protein Kinases; Arabidopsis; Signal Transduction; Plant Development; Plant Immunity; Gene Expression Regulation, Plant; Pseudomonas syringae; Phosphoprotein Phosphatases
PubMed: 37041748
DOI: 10.1016/j.molp.2023.04.004 -
Hepatology (Baltimore, Md.) Jul 2021Following mild liver injury, pre-existing hepatocytes replicate. However, if hepatocyte proliferation is compromised, such as in chronic liver diseases, biliary...
BACKGROUND AND AIMS
Following mild liver injury, pre-existing hepatocytes replicate. However, if hepatocyte proliferation is compromised, such as in chronic liver diseases, biliary epithelial cells (BECs) contribute to hepatocytes through liver progenitor cells (LPCs), thereby restoring hepatic mass and function. Recently, augmenting innate BEC-driven liver regeneration has garnered attention as an alternative to liver transplantation, the only reliable treatment for patients with end-stage liver diseases. Despite this attention, the molecular basis of BEC-driven liver regeneration remains poorly understood.
APPROACH AND RESULTS
By performing a chemical screen with the zebrafish hepatocyte ablation model, in which BECs robustly contribute to hepatocytes, we identified farnesoid X receptor (FXR) agonists as inhibitors of BEC-driven liver regeneration. Here we show that FXR activation blocks the process through the FXR-PTEN (phosphatase and tensin homolog)-PI3K (phosphoinositide 3-kinase)-AKT-mTOR (mammalian target of rapamycin) axis. We found that FXR activation blocked LPC-to-hepatocyte differentiation, but not BEC-to-LPC dedifferentiation. FXR activation also suppressed LPC proliferation and increased its death. These defects were rescued by suppressing PTEN activity with its chemical inhibitor and ptena/b mutants, indicating PTEN as a critical downstream mediator of FXR signaling in BEC-driven liver regeneration. Consistent with the role of PTEN in inhibiting the PI3K-AKT-mTOR pathway, FXR activation reduced the expression of pS6, a marker of mTORC1 activation, in LPCs of regenerating livers. Importantly, suppressing PI3K and mTORC1 activities with their chemical inhibitors blocked BEC-driven liver regeneration, as did FXR activation.
CONCLUSIONS
FXR activation impairs BEC-driven liver regeneration by enhancing PTEN activity; the PI3K-AKT-mTOR pathway controls the regeneration process. Given the clinical trials and use of FXR agonists for multiple liver diseases due to their beneficial effects on steatosis and fibrosis, the detrimental effects of FXR activation on LPCs suggest a rather personalized use of the agonists in the clinic.
Topics: Animals; Animals, Genetically Modified; Biliary Tract; Cell Differentiation; Cell Proliferation; Drug Evaluation, Preclinical; Epithelial Cells; Hepatocytes; Liver; Liver Regeneration; Mutation; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphoprotein Phosphatases; Proto-Oncogene Proteins c-akt; Receptors, Cytoplasmic and Nuclear; Stem Cells; TOR Serine-Threonine Kinases; Zebrafish; Zebrafish Proteins
PubMed: 33314176
DOI: 10.1002/hep.31679 -
Critical Reviews in Biochemistry and... Aug 2020The Eyes Absent (EYA) proteins are the only known instance of a single polypeptide housing the following three separable biochemical activities: tyrosine phosphatase,... (Review)
Review
The Eyes Absent (EYA) proteins are the only known instance of a single polypeptide housing the following three separable biochemical activities: tyrosine phosphatase, threonine phosphatase, and transactivation. This uniquely positions the EYAs to participate in both transcriptional regulation and signal transduction pathways. But it also complicates the assignment of biological roles to individual biochemical activities through standard loss-of-function experiments. Nevertheless, there is an emerging literature linking developmental and pathological functions with the various EYA activities, and a growing list of disease states that might benefit from EYA-targeted therapeutics. There also remain multiple unresolved issues with significant implications for our understanding of how the EYAs might impact such ubiquitous signaling cascades as the MYC and Notch pathways. This review will describe the unique juxtaposition of biochemical activities in the EYAs, their interaction with signaling pathways and cellular processes, emerging evidence of roles in disease states, and the feasibility of therapeutic targeting of individual EYA activities. We will focus on the phosphatase activities of the vertebrate EYA proteins and will examine the current state of knowledge regarding: • substrates and signaling pathways affected by the EYA tyrosine phosphatase activity; • modes of regulation of the EYA tyrosine phosphatase activity; • signaling pathways that implicate the threonine phosphatase activity of the EYAs including a potential interaction with PP2A-B55α; • the interplay between the two phosphatase activities and the transactivation function of the EYAs; • disease states associated with the EYAs and the current state of development of EYA-targeted therapeutics.
Topics: Animals; Humans; Phosphoprotein Phosphatases; Protein Tyrosine Phosphatases; Signal Transduction; Trans-Activators
PubMed: 32727223
DOI: 10.1080/10409238.2020.1796922 -
Molecular Cell Feb 2023Integrator is a metazoan-specific protein complex capable of inducing termination at all RNAPII-transcribed loci. Integrator recognizes paused, promoter-proximal RNAPII... (Review)
Review
Integrator is a metazoan-specific protein complex capable of inducing termination at all RNAPII-transcribed loci. Integrator recognizes paused, promoter-proximal RNAPII and drives premature termination using dual enzymatic activities: an endonuclease that cleaves nascent RNA and a protein phosphatase that removes stimulatory phosphorylation associated with RNAPII pause release and productive elongation. Recent breakthroughs in structural biology have revealed the overall architecture of Integrator and provided insights into how multiple Integrator modules are coordinated to elicit termination effectively. Furthermore, functional genomics and biochemical studies have unraveled how Integrator-mediated termination impacts protein-coding and noncoding loci. Here, we review the current knowledge about the assembly and activity of Integrator and describe the role of Integrator in gene regulation, highlighting the importance of this complex for human health.
Topics: Animals; Humans; Gene Expression Regulation; Phosphoprotein Phosphatases; Phosphorylation; RNA Polymerase II; Transcription, Genetic; Proteins
PubMed: 36634676
DOI: 10.1016/j.molcel.2022.11.012 -
Drug Discovery Today Oct 2022That reversible protein phosphorylation by kinases and phosphatases occurs in metabolic disorders is well known. Various studies have revealed that a multi-faceted and... (Review)
Review
That reversible protein phosphorylation by kinases and phosphatases occurs in metabolic disorders is well known. Various studies have revealed that a multi-faceted and tightly regulated phosphatase, pleckstrin homology domain leucine-rich repeat protein phosphatase (PHLPP)-1/2 displays robust effects in cardioprotection, ischaemia/reperfusion (I/R), and vascular remodelling. PHLPP1 promotes foamy macrophage development through ChREBP/AMPK-dependent pathways. Adipocyte-specific loss of PHLPP2 reduces adiposity, improves glucose tolerance,and attenuates fatty liver via the PHLPP2-HSL-PPARα axis. Discoveries of PHLPP1-mediated insulin resistance and pancreatic β cell death via the PHLPP1/2-Mst1-mTORC1 triangular loop have shed light on its significance in diabetology. PHLPP1 downregulation attenuates diabetic cardiomyopathy (DCM) by restoring PI3K-Akt-mTOR signalling. In this review, we summarise the functional role of, and cellular signalling mediated by, PHLPPs in metabolic tissues and discuss their potential as therapeutic targets.
Topics: AMP-Activated Protein Kinases; Glucose; Humans; Insulin Resistance; Mechanistic Target of Rapamycin Complex 1; Nuclear Proteins; PPAR alpha; Phosphatidylinositol 3-Kinases; Phosphoprotein Phosphatases; Proto-Oncogene Proteins c-akt; TOR Serine-Threonine Kinases
PubMed: 35835313
DOI: 10.1016/j.drudis.2022.07.002 -
Biomolecules Nov 2020Protein phosphorylation is a post-translational modification essential for the control of the activity of most enzymes in the cell. This protein modification results... (Review)
Review
Protein phosphorylation is a post-translational modification essential for the control of the activity of most enzymes in the cell. This protein modification results from a fine-tuned balance between kinases and phosphatases. PP2A is one of the major serine/threonine phosphatases that is involved in the control of a myriad of different signaling cascades. This enzyme, often misregulated in cancer, is considered a tumor suppressor. In this review, we will focus on PP2A-B55, a particular holoenzyme of the family of the PP2A phosphatases whose specific role in cancer development and progression has only recently been highlighted. The discovery of the Greatwall (Gwl)/Arpp19-ENSA cascade, a new pathway specifically controlling PP2A-B55 activity, has been shown to be frequently altered in cancer. Herein, we will review the current knowledge about the mechanisms controlling the formation and the regulation of the activity of this phosphatase and its misregulation in cancer.
Topics: Animals; Holoenzymes; Humans; Intercellular Signaling Peptides and Proteins; Microtubule-Associated Proteins; Neoplasms; Phosphoproteins; Protein Phosphatase 2; Protein Serine-Threonine Kinases; Signal Transduction
PubMed: 33266510
DOI: 10.3390/biom10111586 -
Nature Reviews. Drug Discovery Apr 2023Protein phosphatases act as key regulators of multiple important cellular processes and are attractive therapeutic targets for various diseases. Although extensive... (Review)
Review
Protein phosphatases act as key regulators of multiple important cellular processes and are attractive therapeutic targets for various diseases. Although extensive effort has been dedicated to phosphatase-targeted drug discovery, early expeditions for competitive phosphatase inhibitors were plagued by druggability issues, leading to the stigmatization of phosphatases as difficult targets. Despite challenges, persistent efforts have led to the identification of several drug-like, non-competitive modulators of some of these enzymes - including SH2 domain-containing protein tyrosine phosphatase 2, protein tyrosine phosphatase 1B, vascular endothelial protein tyrosine phosphatase and protein phosphatase 1 - reigniting interest in therapeutic targeting of phosphatases. Here, we discuss recent progress in phosphatase drug discovery, with emphasis on the development of selective modulators that exhibit biological activity. The roles and regulation of protein phosphatases in immune cells and their potential as powerful targets for immuno-oncology and autoimmunity indications are assessed.
Topics: Humans; Protein Tyrosine Phosphatases; Phosphoprotein Phosphatases; Autoimmune Diseases; Neoplasms; Immunotherapy
PubMed: 36693907
DOI: 10.1038/s41573-022-00618-w -
Cell Communication and Signaling : CCS Apr 2021Toll-like receptors (TLRs) are critical sensors for the detection of potentially harmful microbes. They are instrumental in initiating innate and adaptive immune... (Review)
Review
Toll-like receptors (TLRs) are critical sensors for the detection of potentially harmful microbes. They are instrumental in initiating innate and adaptive immune responses against pathogenic organisms. However, exaggerated activation of TLR receptor signaling can also be responsible for the onset of autoimmune and inflammatory diseases. While positive regulators of TLR signaling, such as protein serine/threonine kinases, have been studied intensively, only little is known about phosphatases, which counterbalance and limit TLR signaling. In this review, we summarize protein phosphorylation events and their roles in the TLR pathway and highlight the involvement of protein phosphatases as negative regulators at specific steps along the TLR-initiated signaling cascade. Then, we focus on individual phosphatase families, specify the function of individual enzymes in TLR signaling in more detail and give perspectives for future research. A better understanding of phosphatase-mediated regulation of TLR signaling could provide novel access points to mitigate excessive immune activation and to modulate innate immune signaling. Video Abstract.
Topics: Animals; Humans; Models, Biological; Phosphoprotein Phosphatases; Phosphorylation; Signal Transduction; Toll-Like Receptors
PubMed: 33882943
DOI: 10.1186/s12964-021-00722-1 -
Current Topics in Microbiology and... 2022Pleckstrin homology domain leucine-rich repeat protein phosphatases (PHLPP) belong to the protein phosphatase magnesium/manganese-dependent family of Ser/Thr... (Review)
Review
Pleckstrin homology domain leucine-rich repeat protein phosphatases (PHLPP) belong to the protein phosphatase magnesium/manganese-dependent family of Ser/Thr phosphatases. Their general role as tumor suppressors has been documented for over a decade. In recent years, accumulating evidence suggests that PHLPP isozymes have key regulatory roles in both innate and adaptive immunity. In macrophages, PHLPP1 dampens signaling through TLR4 and the IFN-γ receptor by altering cytosolic signaling pathways. Additionally, nuclear-localized PHLPP1 inhibits STAT1-mediated inflammatory gene expression by direct dephosphorylation at Ser 727. PHLPP1 also regulates the migratory and inflammatory capacity of neutrophils in vivo. Furthermore, PHLPP1-mediated dephosphorylation of AKT on Ser 473 is required for both the suppressive function of regulatory T cells and for the pro-apoptotic effects of PHLPP1 in B cell chronic lymphocytic leukemia. In the context of immune homeostasis, PHLPP1 expression is modulated in multiple cell types by inflammatory signals, and the dynamics of its expression have varying effects on the pathogenesis of inflammatory bowel disease and septic shock. In this review, we summarize recent findings on the functions of PHLPP in inflammatory and regulatory signaling in the context of both innate and adaptive immunity.
Topics: Isoenzymes; Magnesium; Manganese; Nuclear Proteins; Phosphoprotein Phosphatases; Proto-Oncogene Proteins c-akt; Toll-Like Receptor 4
PubMed: 36243842
DOI: 10.1007/978-3-031-06566-8_5 -
Molecular Cancer Sep 2023The Eyes Absent (EYA) family of proteins is an atypical group of four dual-functioning protein phosphatases (PP), which have been linked to many vital cellular processes...
The Eyes Absent (EYA) family of proteins is an atypical group of four dual-functioning protein phosphatases (PP), which have been linked to many vital cellular processes and organogenesis pathways. The four family members of this PP family possess transcriptional activation and phosphatase functions, with serine/threonine and tyrosine phosphatase domains. EYA4 has been associated with several human cancers, with tumor-suppressing and tumor-promoting roles. However, EYA4 is the least well-characterized member of this unique family of PP, with its biological functions and molecular mechanisms in cancer progression, particularly in breast cancer, still largely unknown. In the present study, we found that the over-expression of EYA4 in breast tissue leads to an aggressive and invasive breast cancer phenotype, while the inhibition of EYA4 reduced tumorigenic properties of breast cancer cells in vitro and in vivo. Cellular changes downstream of EYA4, including cell proliferation and migration, may explain the increased metastatic power of breast cancer cells over-expressing EYA4. Mechanistically, EYA4 prevents genome instability by inhibiting the accumulation of replication-associated DNA damage. Its depletion results in polyploidy as a consequence of endoreplication, a phenomenon that can occur in response to stress. The absence of EYA4 leads to spontaneous replication stress characterized by the activation of the ATR pathway, sensitivity to hydroxyurea, and accumulation of endogenous DNA damage as indicated by increased γH2AX levels. In addition, we show that EYA4, specifically its serine/threonine phosphatase domain, plays an important and so far, unexpected role in replication fork progression. This phosphatase activity is essential for breast cancer progression and metastasis. Taken together, our data indicate that EYA4 is a novel potential breast cancer oncogene that supports primary tumor growth and metastasis. Developing therapeutics aimed at the serine/threonine phosphatase activity of EYA4 represents a robust strategy for killing breast cancer cells, to limit metastasis and overcome chemotherapy resistance caused by endoreplication and genomic rearrangements.
Topics: Humans; Female; Breast Neoplasms; Trans-Activators; Cell Line, Tumor; Protein Tyrosine Phosphatases; Phosphoprotein Phosphatases; Serine
PubMed: 37777742
DOI: 10.1186/s12943-023-01861-4