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Chandrasekhar A, Komirishetty P, Areti A, Krishnan A, Zochodne DW. Dual Specificity Phosphatases Support Axon Plasticity and Viability. Mol Neurobiol 2021; 58:391-407. [PMID: 32959171 DOI: 10.1007/s12035-020-02119-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Accepted: 09/05/2020] [Indexed: 02/07/2023]
Abstract
In peripheral neuropathies, axonal degeneration (AxD) impairs the prognosis for recovery. Here, we describe a role for dual specificity phosphatases (DUSPs; MAP kinase phosphatases, MKPs), in supporting autonomous axon plasticity and viability. Both DUSPs 1 and 4 were identified within intact or axotomized sensory neurons. Knockdown of DUSP 1 or 4 independently or combined impaired neurite outgrowth in adult dissociated sensory neurons. Furthermore, adult sensory neurons with DUSP knockdown were rendered sensitive to axonopathy in vitro following exposure to low, subtoxic TrpV1 (transient receptor potential cation channel subfamily V member 1) activation by capsaicin, an intervention normally supportive of growth. This was not prevented by concurrent DLK (dual leucine zipper kinase) knockdown. Ex vivo neurofilament dissolution was heightened by DUSP inhibition within explanted nerves. In vivo DUSP knockdown or inhibition was associated with more rapid loss of motor axon excitability. The addition of SARM1 (sterile alpha and TIR motif containing 1) siRNA abrogated DUSP1 and 4 mediated loss of excitability. DUSP knockdown accelerated neurofilament breakdown and there was earlier morphological evidence of myelinated axon degeneration distal to axotomy. Taken together, the findings identify a key role for DUSPs in supporting axon plasticity and survival.
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Affiliation(s)
- Ambika Chandrasekhar
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Prashanth Komirishetty
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Aparna Areti
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
| | - Anand Krishnan
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, Canada
| | - Douglas W Zochodne
- Neuroscience and Mental Health Institute and Division of Neurology, Department of Medicine, University of Alberta, 7-132A Clinical Sciences Building, 11350-83 Ave, Edmonton, AB, T6G 2G3, Canada.
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Schmitz L, Schwier MA, Heimel K. The Unfolded Protein Response Regulates Pathogenic Development of Ustilago maydis by Rok1-Dependent Inhibition of Mating-Type Signaling. mBio 2019; 10:e02756-19. [PMID: 31848283 DOI: 10.1128/mBio.02756-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The unfolded protein response (UPR) is crucial for endoplasmic reticulum (ER) homeostasis and disease development in fungal pathogens. In the plant-pathogenic fungus Ustilago maydis, the UPR supports fungal proliferation in planta and effector secretion for plant defense suppression. In this study, we uncovered that UPR activity, which is normally restricted to the biotrophic stage in planta, inhibits mating and the formation of infectious filaments by Rok1-dependent dephosphorylation of the pheromone responsive mitogen-activated protein kinase (MAPK) Kpp2. This observation is relevant for understanding how the fungal virulence program is regulated by cellular physiology. UPR-mediated control of mating-type signaling pathways predicts that effector gene expression and the virulence potential are controlled by ER stress levels. Fungal pathogens require the unfolded protein response (UPR) to maintain protein homeostasis of the endoplasmic reticulum (ER) during pathogenic development. In the corn smut fungus Ustilago maydis, pathogenic development is controlled by the a and b mating-type loci. The UPR is specifically activated after plant penetration and required for efficient secretion of effectors and suppression of the plant defense response. The interaction between the UPR regulator Cib1 and the central developmental regulator Clp1 modulates the pathogenic program and triggers fungal colonization of the host plant. By contrast, when activated before plant penetration, the UPR interferes with fungal virulence by reducing expression of bE and bW, the central regulators of pathogenic development encoded by the b mating-type locus. Here, we show that this inhibitory effect results from UPR-mediated suppression of the pheromone response pathway upstream of the b regulatory network. UPR activity prompts dephosphorylation of the pheromone-responsive mitogen-activated protein kinase (MAPK) Kpp2, reducing activity of the pheromone response factor Prf1 that regulates expression of bE and bW. Deletion of the dual specificity phosphatase rok1 fully suppressed UPR-dependent inhibition of Kpp2 phosphorylation, formation of infectious filaments, and fungal virulence. Rok1 determines the activity of mating-type signaling pathways and thus the degree of fungal virulence. We propose that UPR-dependent regulation of Rok1 aligns ER physiology with fungal aggressiveness and effector gene expression during biotrophic growth of U. maydis in the host plant.
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Nunes-Xavier CE, Zaldumbide L, Aurtenetxe O, López-Almaraz R, López JI, Pulido R. Dual-Specificity Phosphatases in Neuroblastoma Cell Growth and Differentiation. Int J Mol Sci 2019; 20:ijms20051170. [PMID: 30866462 PMCID: PMC6429076 DOI: 10.3390/ijms20051170] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 03/01/2019] [Accepted: 03/01/2019] [Indexed: 12/19/2022] Open
Abstract
Dual-specificity phosphatases (DUSPs) are important regulators of neuronal cell growth and differentiation by targeting proteins essential to neuronal survival in signaling pathways, among which the MAP kinases (MAPKs) stand out. DUSPs include the MAPK phosphatases (MKPs), a family of enzymes that directly dephosphorylate MAPKs, as well as the small-size atypical DUSPs, a group of low molecular-weight enzymes which display more heterogeneous substrate specificity. Neuroblastoma (NB) is a malignancy intimately associated with the course of neuronal and neuroendocrine cell differentiation, and constitutes the source of more common extracranial solid pediatric tumors. Here, we review the current knowledge on the involvement of MKPs and small-size atypical DUSPs in NB cell growth and differentiation, and discuss the potential of DUSPs as predictive biomarkers and therapeutic targets in human NB.
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Affiliation(s)
- Caroline E Nunes-Xavier
- Biomarkers in Cancer Unit, Biocruces-Bizkaia Health Research Institute, Barakaldo, Bizkaia 48903, Spain.
- Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital HF Radiumhospitalet, Oslo 0424, Norway.
| | - Laura Zaldumbide
- Department of Pathology, Cruces University Hospital, University of the Basque Country (UPV/EHU), Barakaldo, Bizkaia 48903, Spain.
| | - Olaia Aurtenetxe
- Biomarkers in Cancer Unit, Biocruces-Bizkaia Health Research Institute, Barakaldo, Bizkaia 48903, Spain.
| | - Ricardo López-Almaraz
- Pediatric Oncology and Hematology, Cruces University Hospital, Barakaldo, Bizkaia 48903, Spain.
| | - José I López
- Biomarkers in Cancer Unit, Biocruces-Bizkaia Health Research Institute, Barakaldo, Bizkaia 48903, Spain.
- Department of Pathology, Cruces University Hospital, University of the Basque Country (UPV/EHU), Barakaldo, Bizkaia 48903, Spain.
| | - Rafael Pulido
- Biomarkers in Cancer Unit, Biocruces-Bizkaia Health Research Institute, Barakaldo, Bizkaia 48903, Spain.
- IKERBASQUE, Basque Foundation for Science, Bilbao 48011, Spain.
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Abstract
MAP kinases and their regulators are critical components of eukaryotic signaling pathways implicated in normal cell behavior as well as abnormal behaviors linked to diseases such as cancer. The mating pathway of the yeast Saccharomyces cerevisiae was central in establishing the MAP kinase paradigm. Here we investigate the mating pathway in a different ascomycete, the fungal pathogen C. albicans. In this dimorphic fungus MAP kinases are also implicated in the mating response, with two MAP kinases apparently playing redundant roles in the mating process. This work establishes that while some level of mating can occur in the presence of a single kinase, the Cek1 kinase is most important for mating, while the Cek2 kinase is involved in adaptation to signaling. While both kinases appear to be themselves regulated by dephosphorylation through the action of the Cpp1 phosphatase, this process appears important for mating only in the case of Cek1. We investigated the relationships of the Cek1 and Cek2 mitogen-activated protein (MAP) kinases and the putative MAP kinase phosphatase Cpp1 in the mating process of Candida albicans. Mutants of the CPP1 gene are hyperresponsive to pheromone, generating large halos, high levels of projections, and an increase in pheromone-responsive gene expression. Mating-type-homozygous opaque cells that lack both kinases are sterile, consistent with previous observations, although several lines of evidence show that the two kinases do not simply provide redundant functions in the mating process. Loss of CEK1 reduces mating significantly, to about 0.3% of wild-type strains, and also reduces projection formation and pheromone-mediated gene expression. In contrast, loss of CEK2 has less of an effect, reducing mating to approximately one-third that of the wild-type strain and moderately reducing projection formation but having little influence on the induction of gene expression. However, loss of Cek2 function reduces adaptation to pheromone-mediated arrest. The mutation enhances pheromone response halos to a level similar to that of cpp1 mutants, although the cpp1 mutants are considerably more mating defective than the cek2 mutant. The double cek2 cpp1 mutant shows enhanced responsiveness relative to either single mutant in terms of gene expression and halo formation, suggesting the kinase and phosphatase roles in the adaptation process are independent. Analysis of protein phosphorylation shows that Cek1 undergoes pheromone-mediated phosphorylation of the activation loop, and this phosphorylation is enhanced in cells lacking either the Cpp1 phosphatase or the Cek2 kinase. In addition, Cek1-GFP shows enhanced nuclear localization in response to pheromone treatment. In contrast, Cek2 shows no evidence for pheromone-mediated phosphorylation or pheromone-mediated nuclear localization. Intriguingly, however, deletion of CPP1 enhances both the phosphorylation state and the nuclear localization of Cek2-GFP. Overall, these results identify a complex interaction among the MAP kinases and MAP kinase phosphatase that function in the C. albicans mating pathway. IMPORTANCE MAP kinases and their regulators are critical components of eukaryotic signaling pathways implicated in normal cell behavior as well as abnormal behaviors linked to diseases such as cancer. The mating pathway of the yeast Saccharomyces cerevisiae was central in establishing the MAP kinase paradigm. Here we investigate the mating pathway in a different ascomycete, the fungal pathogen C. albicans. In this dimorphic fungus MAP kinases are also implicated in the mating response, with two MAP kinases apparently playing redundant roles in the mating process. This work establishes that while some level of mating can occur in the presence of a single kinase, the Cek1 kinase is most important for mating, while the Cek2 kinase is involved in adaptation to signaling. While both kinases appear to be themselves regulated by dephosphorylation through the action of the Cpp1 phosphatase, this process appears important for mating only in the case of Cek1.
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Shi H, Gatzke F, Molle JM, Lee HB, Helm ET, Oldham JJ, Zhang L, Gerrard DE, Bennett AM. Mice lacking MKP-1 and MKP-5 Reveal Hierarchical Regulation of Regenerative Myogenesis. ACTA ACUST UNITED AC 2015; 1:1-7. [PMID: 27064463 DOI: 10.15436/2741-0598.15.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The relative contribution of the MAP kinase phosphatases (MKPs) in the integration of MAP kinase-dependent signaling during regenerative myogenesis has yet to be fully investigated. MKP-1 and MKP-5 maintain skeletal muscle homeostasis by providing positive and negative effects on regenerative myogenesis, respectively. In order to define the hierarchical contributions of MKP-1 and MKP-5 in the regulation of regenerative myogenesis we genetically ablated both MKPs in mice. MKP-1/MKP 5-deficient double-knockout (MKP1/5- DKO) mice were viable, and upon skeletal muscle injury, were severely impaired in their capacity to regenerate skeletal muscle. Satellite cells were fewer in number in MKP1/5-DKO mice and displayed a reduced proliferative capacity as compared with those derived from wild-type mice. MKP1/5-DKO mice exhibited increased inflammation and the macrophage M1 to M2 transition during the resolution of inflammation was impaired following injury. These results demonstrate that the actions of MKP-1 to positively regulate myogenesis predominate over those of MKP-5, which negatively regulates myogenesis. Hence, MKP-1 and MKP-5 function to maintain skeletal muscle homeostasis through non-overlapping and opposing signaling pathways.
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Affiliation(s)
- Hao Shi
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | | | - Julia M Molle
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | - Han Bin Lee
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | - Emma T Helm
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | - Jessie J Oldham
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | | | - David E Gerrard
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | - Anton M Bennett
- Department of Pharmacology; Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, Connecticut, USA
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Abstract
There are three well-defined subgroups of mitogen-activated protein kinases (MAPKs): the extracellular signal-regulated kinases (ERKs), the c-Jun N-terminal kinases (JNKs), and the p38 MAPKs. Three subgroups of MAPKs are involved in both cell growth and cell death, and the tight regulation of these pathways, therefore, is paramount in determining cell fate. MAPK pathways have been shown to be activated not only by receptor ligand interactions but also by different stressors placed on the cell. MAPK phosphatases (MKPs) dephosphorylate and deactivate MAPKs. Reactive oxygen species (ROS), such as hydrogen peroxide, have been reported to activate ERKs, JNKs, and p38 MAPKs, but the mechanisms by which ROS can activate these kinases are unclear. Oxidative modifications of MAPK signaling proteins and inactivation and/or degradation of MKPs may provide the plausible mechanisms for activation of MAPK pathways by ROS, which will be reviewed in this chapter.
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Affiliation(s)
- Yong Son
- Department of Anesthesiology and Pain Medicine, Wonkwang University School of Medicine, Iksan, Republic of Korea
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Abstract
Continuous free radical assault upsets cellular homeostasis and dysregulates associated signaling pathways to promote stress-induced cell death. In spite of the continuous development and implementation of effective therapeutic strategies, limitations in treatments for stress-induced toxicities remain. The purpose of the present study was to determine the potential therapeutic efficacy of bacterial fucose polysaccharides against hydrogen peroxide (H2O2)-induced stress in human lung fibroblast (WI38) cells and to understand the associated molecular mechanisms. In two different fermentation processes, Bacillus megaterium RB-05 biosynthesized two non-identical fucose polysaccharides; of these, the polysaccharide having a high-fucose content (∼42%) conferred the maximum free radical scavenging efficiency in vitro. Structural characterizations of the purified polysaccharides were performed using HPLC, GC-MS, and 1H/13C/2D-COSY NMR. H2O2 (300 µM) insult to WI38 cells showed anti-proliferative effects by inducing intracellular reactive oxygen species (ROS) and by disrupting mitochondrial membrane permeability, followed by apoptosis. The polysaccharide (250 µg/mL) attenuated the cell death process by directly scavenging intracellular ROS rather than activating endogenous antioxidant enzymes. This process encompasses inhibition of caspase-9/3/7, a decrease in the ratio of Bax/Bcl2, relocalization of translocated Bax and cytochrome c, upregulation of anti-apoptotic members of the Bcl2 family and a decrease in the phosphorylation of MAPKs (mitogen activated protein kinases). Furthermore, cellular homeostasis was re-established via stabilization of MAPK-mediated Nrf2/Keap1 signaling and transcription of downstream cytoprotective genes. This molecular study uniquely introduces a fucose-rich bacterial polysaccharide as a potential inhibitor of H2O2-induced stress and toxicities.
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