241 human active and 13 inactive phosphatases in total;
194 phosphatases have substrate data;
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336 protein substrates;
83 non-protein substrates;
1215 dephosphorylation interactions;
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299 KEGG pathways;
876 Reactome pathways;
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last scientific update: 11 Mar, 2019
last maintenance update: 01 Sep, 2023
Cytoplasm Nucleus Note=Phosphorylation andsubsequent activation releases the autoinhibitory helix, resultingin the export from the nucleus into the cytoplasm
Function (UniProt annotation)
Stress-activated serine/threonine-protein kinaseinvolved in cytokine production, endocytosis, reorganization ofthe cytoskeleton, cell migration, cell cycle control, chromatinremodeling, DNA damage response and transcriptional regulationFollowing stress, it is phosphorylated and activated by MAP kinasep38-alpha/MAPK14, leading to phosphorylation of substratesPhosphorylates serine in the peptide sequence, Hyd-X-R-X(2)-S,where Hyd is a large hydrophobic residue Phosphorylates ALOX5,CDC25B, CDC25C, CEP131, ELAVL1, HNRNPA0, HSP27/HSPB1, KRT18,KRT20, LIMK1, LSP1, PABPC1, PARN, PDE4A, RCSD1, RPS6KA3, TAB3 andTTP/ZFP36 Phosphorylates HSF1; leading to the interaction withHSP90 proteins and inhibiting HSF1 homotrimerization, DNA-bindingand transactivation activities (PubMed:16278218) Mediatesphosphorylation of HSP27/HSPB1 in response to stress, leading tothe dissociation of HSP27/HSPB1 from large small heat-shockprotein (sHsps) oligomers and impairment of their chaperoneactivities and ability to protect against oxidative stresseffectively Involved in inflammatory response by regulating tumornecrosis factor (TNF) and IL6 production post-transcriptionally:acts by phosphorylating AU-rich elements (AREs)-binding proteinsELAVL1, HNRNPA0, PABPC1 and TTP/ZFP36, leading to the regulationof the stability and translation of TNF and IL6 mRNAsPhosphorylation of TTP/ZFP36, a major post-transcriptionalregulator of TNF, promotes its binding to 14-3-3 proteins andreduces its ARE mRNA affinity, leading to inhibition of dependentdegradation of ARE-containing transcripts Phosphorylates CEP131in response to cellular stress induced by ultraviolet irradiationwhich promotes binding of CEP131 to 14-3-3 proteins and inhibitsformation of novel centriolar satellites (PubMed:26616734) Alsoinvolved in late G2/M checkpoint following DNA damage through aprocess of post-transcriptional mRNA stabilization: following DNAdamage, relocalizes from nucleus to cytoplasm and phosphorylatesHNRNPA0 and PARN, leading to stabilization of GADD45A mRNAInvolved in toll-like receptor signaling pathway (TLR) indendritic cells: required for acute TLR-induced macropinocytosisby phosphorylating and activating RPS6KA3
The mitogen-activated protein kinase (MAPK) cascade is a highly conserved module that is involved in various cellular functions, including cell proliferation, differentiation and migration. Mammals express at least four distinctly regulated groups of MAPKs, extracellular signal-related kinases (ERK)-1/2, Jun amino-terminal kinases (JNK1/2/3), p38 proteins (p38alpha/beta/gamma/delta) and ERK5, that are activated by specific MAPKKs: MEK1/2 for ERK1/2, MKK3/6 for the p38, MKK4/7 (JNKK1/2) for the JNKs, and MEK5 for ERK5. Each MAPKK, however, can be activated by more than one MAPKKK, increasing the complexity and diversity of MAPK signalling. Presumably each MAPKKK confers responsiveness to distinct stimuli. For example, activation of ERK1/2 by growth factors depends on the MAPKKK c-Raf, but other MAPKKKs may activate ERK1/2 in response to pro-inflammatory stimuli.
Cellular senescence is a state of irreversible cellular arrest and can be triggered by a number of factors, such as telomere shortening, oncogene activation, irradiation, DNA damage and oxidative stress. It is characterized by enlarged flattened morphology, senescence-associated beta-galactosidase (SA-b-gal) activity, secretion of inflammatory cytokines, growth factors and matrix metalloproteinases, as part of the senescence-associated secretory phenotype (SASP). Cellular senescence is functionally associated with many biological processes including aging, tumor suppression, placental biology, embryonic development, and wound healing.
There is now much evidence that VEGFR-2 is the major mediator of VEGF-driven responses in endothelial cells and it is considered to be a crucial signal transducer in both physiologic and pathologic angiogenesis. The binding of VEGF to VEGFR-2 leads to a cascade of different signaling pathways, resulting in the up-regulation of genes involved in mediating the proliferation and migration of endothelial cells and promoting their survival and vascular permeability. For example, the binding of VEGF to VEGFR-2 leads to dimerization of the receptor, followed by intracellular activation of the PLCgamma;PKC-Raf kinase-MEK-mitogen-activated protein kinase (MAPK) pathway and subsequent initiation of DNA synthesis and cell growth, whereas activation of the phosphatidylinositol 3' -kinase (PI3K)-Akt pathway leads to increased endothelial-cell survival. Activation of PI3K, FAK, and p38 MAPK is implicated in cell migration signaling.
C-type lectin receptors (CLRs) are a large superfamily of proteins characterized by the presence of one or more C-type lectin-like domains (CTLDs). CLRs function as pattern-recognition receptors (PRRs) for pathogen-derived ligands in dendric cells, macrophages, neutrophils, etc., such as Dectin-1 and Dectin-2 for recognition of fungi-derived B-glucan and high mannose-type carbohydrates. Upon ligand binding, CLRs stimulate intracellular signaling cascades that induce the production of inflammatory cytokines and chemokines, consequently triggering innate and adaptive immunity to pathogens.
Neurotrophins are a family of trophic factors involved in differentiation and survival of neural cells. The neurotrophin family consists of nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and neurotrophin 4 (NT-4). Neurotrophins exert their functions through engagement of Trk tyrosine kinase receptors or p75 neurotrophin receptor (p75NTR). Neurotrophin/Trk signaling is regulated by connecting a variety of intracellular signaling cascades, which include MAPK pathway, PI-3 kinase pathway, and PLC pathway, transmitting positive signals like enhanced survival and growth. On the other hand, p75NTR transmits both positive and nagative signals. These signals play an important role for neural development and additional higher-order activities such as learning and memory.
Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8), is the most recently identified human tumor virus, and is associated with the pathogenesis of Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and Multicentric Castleman's disease (MCD). Like all other herpesviruses, KSHV displays two modes of life cycle, latency and lytic replication, which are characterized by the patterns of viral gene expression. Genes expressed in latency (LANA, v-cyclin, v-FLIP, Kaposins A, B and C and viral miRNAs) are mainly thought to facilitate the establishment of life long latency in its host and survival against the host innate, and adaptive immune surveillance mechanisms. Among the viral proteins shown to be expressed during lytic replication are potent signaling molecules such as vGPCR, vIL6, vIRFs, vCCLs, K1 and K15, which have been implicated experimentally in the angiogenic and inflammatory phenotype observed in KS lesions. Several of these latent viral and lytic proteins are known to transform host cells, linking KSHV with the development of severe human malignancies.
There is a strong association between viruses and the development of human malignancies. We now know that at least six human viruses, Epstein-Barr virus (EBV), hepatitis B virus (HBV), hepatitis C virus (HCV), human papilloma virus (HPV), human T-cell lymphotropic virus (HTLV-1) and Kaposi's associated sarcoma virus (KSHV) contribute to 10-15% of the cancers worldwide. Via expression of many potent oncoproteins, these tumor viruses promote an aberrant cell-proliferation via modulating cellular cell-signaling pathways and escape from cellular defense system such as blocking apoptosis. Human tumor virus oncoproteins can also disrupt pathways that are necessary for the maintenance of the integrity of host cellular genome. Viruses that encode such activities can contribute to initiation as well as progression of human cancers.
NGF induces sustained activation of p38, a member of the MAPK family (Morooka T, Nishida E, 1998). Both p38 and the ERKs appear to be involved in neurite outgrowth and differentiation caused by NGF in PC12 cells. As a matter of fact, PC12 cell differentiation appears to involve activation of both ERK/MAPK and p38. Both ERK/MAPK and p38 pathways contribute to the phosphorylation of the transcription factor CREB and the activation of immediate-early genes (Xing J, 1998). p38 activation by NGF may occur by at least two mechanisms, involving SRC or MEK kinases
Nerve growth factor (NGF) activates multiple signalling pathways that mediate the phosphorylation of CREB at the critical regulatory site, serine 133. CREB phosphorylation at serine 133 is a crucial event in neurotrophin signalling, being mediated by ERK/RSK, ERK/MSK1 and p38/MAPKAPK2 pathways. Several kinases, such as MSK1, RSK1/2/3 (MAPKAPK1A/B/C), and MAPKAPK2, are able to directly phosphorylate CREB at S133. MSK1 is also able to activate ATF (Cyclic-AMP-dependent transcription factor). However, the NGF-induced CREB phosphorylation appears to correlate better with activation of MSK1 rather than RSK1/2/3, or MAPKAPK2. In retrograde signalling, activation of CREB occurs within 20 minutes after neurotrophin stimulation of distal axons
Leukotrienes (LTs) are biologically active molecules formed in response to inflammatory stimuli. They cause contraction of bronchial smooth muscles, stimulation of vascular permeability, and attraction and activation of leukocytes. LTs were discovered in 1938 and were termed the \slow release substance\(SRS) until their structures were determined in 1979 and they were then renamed to leukotrienes. LTs are derived from arachidonic acid through action by arachidonate 5-lipoxygenase (ALOX5). Cysteinyl leukotrienes (LTC4, LTD4, and LTE4) are generated as products derived from leukotriene A4 (LTA4). Eoxins are generated from leukotrienes (LTs) and resemble cysteinyl leukotrienes but have a different three-dimensional structure (Murphy & Gijon 2007, Hammarstrom 1983, MA.Claesson 2009, Vance & Vance 2008, Buczynski et al. 2009)
Oxidative stress, caused by increased concentration of reactive oxygen species (ROS) in the cell, can happen as a consequence of mitochondrial dysfunction induced by the oncogenic RAS (Moiseeva et al. 2009) or independent of oncogenic signaling. Prolonged exposure to interferon-beta (IFNB, IFN-beta) also results in ROS increase (Moiseeva et al. 2006). ROS oxidize thioredoxin (TXN), which causes TXN to dissociate from the N-terminus of MAP3K5 (ASK1), enabling MAP3K5 to become catalytically active (Saitoh et al. 1998). ROS also stimulate expression of Ste20 family kinases MINK1 (MINK) and TNIK through an unknown mechanism, and MINK1 and TNIK positively regulate MAP3K5 activation (Nicke et al. 2005).
MAP3K5 phosphorylates and activates MAP2K3 (MKK3) and MAP2K6 (MKK6) (Ichijo et al. 1997, Takekawa et al. 2005), which act as p38 MAPK kinases, as well as MAP2K4 (SEK1) (Ichijo et al. 1997, Matsuura et al. 2002), which, together with MAP2K7 (MKK7), acts as a JNK kinase.
MKK3 and MKK6 phosphorylate and activate p38 MAPK alpha (MAPK14) and beta (MAPK11) (Raingeaud et al. 1996), enabling p38 MAPKs to phosphorylate and activate MAPKAPK2 (MK2) and MAPKAPK3 (MK3) (Ben-Levy et al. 1995, Clifton et al. 1996, McLaughlin et al. 1996, Sithanandam et al. 1996, Meng et al. 2002, Lukas et al. 2004, White et al. 2007), as well as MAPKAPK5 (PRAK) (New et al. 1998 and 2003, Sun et al. 2007).
Phosphorylation of JNKs (MAPK8, MAPK9 and MAPK10) by MAP3K5-activated MAP2K4 (Deacon and Blank 1997, Fleming et al. 2000) allows JNKs to migrate to the nucleus (Mizukami et al. 1997) where they phosphorylate JUN. Phosphorylated JUN binds FOS phosphorylated by ERK1 or ERK2, downstream of activated RAS (Okazaki and Sagata 1995, Murphy et al. 2002), forming the activated protein 1 (AP-1) complex (FOS:JUN heterodimer) (Glover and Harrison 1995, Ainbinder et al. 1997).
Activation of p38 MAPKs and JNKs downstream of MAP3K5 (ASK1) ultimately converges on transcriptional regulation of CDKN2A locus. In dividing cells, nucleosomes bound to the CDKN2A locus are trimethylated on lysine residue 28 of histone H3 (HIST1H3A) by the Polycomb repressor complex 2 (PRC2), creating the H3K27Me3 (Me3K-28-HIST1H3A) mark (Bracken et al. 2007, Kotake et al. 2007). The expression of Polycomb constituents of PRC2 (Kuzmichev et al. 2002) - EZH2, EED and SUZ12 - and thereby formation of the PRC2, is positively regulated in growing cells by E2F1, E2F2 and E2F3 (Weinmann et al. 2001, Bracken et al. 2003). H3K27Me3 mark serves as a docking site for the Polycomb repressor complex 1 (PRC1) that contains BMI1 (PCGF4) and is therefore named PRC1.4, leading to the repression of transcription of p16-INK4A and p14-ARF from the CDKN2A locus, where PCR1.4 mediated repression of p14-ARF transcription in humans may be context dependent (Voncken et al. 2005, Dietrich et al. 2007, Agherbi et al. 2009, Gao et al. 2012). MAPKAPK2 and MAPKAPK3, activated downstream of the MAP3K5-p38 MAPK cascade, phosphorylate BMI1 of the PRC1.4 complex, leading to dissociation of PRC1.4 complex from the CDKN2A locus and upregulation of p14-ARF transcription (Voncken et al. 2005). AP-1 transcription factor, formed as a result of MAP3K5-JNK signaling, as well as RAS signaling, binds the promoter of KDM6B (JMJD3) gene and stimulates KDM6B expression. KDM6B is a histone demethylase that removes H3K27Me3 mark i.e. demethylates lysine K28 of HIST1H3A, thereby preventing PRC1.4 binding to the CDKN2A locus and allowing transcription of p16-INK4A (Agger et al. 2009, Barradas et al. 2009, Lin et al. 2012).
p16-INK4A inhibits phosphorylation-mediated inactivation of RB family members by CDK4 and CDK6, leading to cell cycle arrest (Serrano et al. 1993). p14-ARF inhibits MDM2-mediated degradation of TP53 (p53) (Zhang et al. 1998), which also contributes to cell cycle arrest in cells undergoing oxidative stress. In addition, phosphorylation of TP53 by MAPKAPK5 (PRAK) activated downstream of MAP3K5-p38 MAPK signaling, activates TP53 and contributes to cellular senescence (Sun et al. 2007)
The ability of HSF1 to respond to cellular stresses is under negative regulation by chaperones, modulation of nucleocytoplasmic shuttling, post-translational modifications and transition from monomeric to trimeric state
Angiogenesis is the formation of new blood vessels from preexisting vasculature. One of the most important proangiogenic factors is vascular endothelial growth factor (VEGF). VEGF exerts its biologic effect through interaction with transmembrane tyrosine kinase receptors VEGFR, selectively expressed on vascular endothelial cells. VEGFA signaling through VEGFR2 is the major pathway that activates angiogenesis by inducing the proliferation, survival, sprouting and migration of endothelial cells (ECs), and also by increasing endothelial permeability (Lohela et al. 2009, Shibuya & Claesson-Welsh 2006, Claesson-Welsh & Welsh, 2013). The critical role of VEGFR2 in vascular development is highlighted by the fact that VEGFR2-/- mice die at E8.5-9.5 due to defective development of blood islands, endothelial cells and haematopoietic cells (Shalaby et al. 1995)
p38 mitogen-activated protein kinase (MAPK) belongs to a highly conserved family of serine/threonine protein kinases.
The p38 MAPK-dependent signaling cascade is activated by pro-inflammatory or stressful stimuli such as ultraviolet radiation, oxidative injury, heat shock, cytokines, and other pro-inflammatory stimuli. p38 MAPK exists as four isoforms (alpha, beta, gamma, and delta). Of these, p38alpha and p38beta are ubiquitously expressed while p38gamma and p38delta are differentially expressed depending on tissue type. Each isoform is activated by upstream kinases including MAP kinase kinases (MKK) 3, 4, and 6, which in turn are phosphorylated by activated TAK1 at the typical Ser-Xaa-Ala-Xaa-Thr motif in their activation loops.
Once p38 MAPK is phosphorylated it activates numerous downstream substrates, including MAPK-activated protein kinase-2 and 3 (MAPKAPK-2 or 3) and mitogen and stress-activated kinase-1/2 (MSK1/2). MAPKAPK-2/3 and MSK1/2 function to phosphorylate heat shock protein 27 (HSP27) and cAMP-response element binding protein transcriptional factor, respectively. Other transcription factors, including activating transcription factor 2, Elk, CHOP/GADD153, and myocyte enhancer factor 2, are known to be regulated by these kinases
Butyrate Response Factor 1 (BRF1, ZFP36L1, not to be confused with transcription factor IIIB) binds AU-rich elements in the 3' region of mRNAs. After binding, BRF1 recruits exonucleases (XRN1 and the exosome) and decapping enzymes (DCP1a and DCP2) to hydrolyze the RNA. The ability of BRF1 to direct RNA degradation is controlled by phosphorylation of BRF1. Protein kinase B/AKT1 phosphorylates BRF1 at serines 92 and 203. Phosphorylated BRF1 can still bind RNA but is sequestered by binding 14-3-3 protein, preventing BRF1 from destabilizing RNA. BRF1 is also phosphorylated by MK2 at serines 54, 92, 203, and at an unknown site in the C-terminus. It is unknown if this particular phosphorylated form of BRF1 binds 14-3-3
Tristetraproline (TTP) binds RNAs that contain AU-rich elements and recruits enzymes that degrade RNA. TTP interacts with the exosome (3' to 5' exonuclease), XRN1 (5' to 3' exonuclease), and the decapping enzymes DCP1 and DCP2a.The activity of TTP is regulated by phosphorylation. MK2 phosphorylates TTP, which then binds 14-3-3.The interaction with 14-3-3 prevents phosphorylated TTP from entering stress granules and stabilizes mRNA bound by phosphorylated TTP. Tristetraproline is known to bind AU-rich elements in the following mRNAs: Tumor necrosis factor alpha (TNFA), Granulocyte-macrophage colony stimulating factor (CSF2, GM-CSF), Interleukin-2 (IL-2), and Proto-oncogene C-FOS (FOS, c-fos). Mice deficient in TTP exhibit arthritis, weight loss, skin lesions, autoimmunity, and myeloid hyperplasia
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