Search results for CDC25B

Showing 12 results out of 12

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Protein (3 results from a total of 3)

Identifier: R-HSA-69734
Species: Homo sapiens
Compartment: nucleoplasm
Primary external reference: UniProt: CDC25B: P30305
Identifier: R-HSA-157412
Species: Homo sapiens
Compartment: cytosol
Primary external reference: UniProt: P30305
Identifier: R-HSA-8863644
Species: Homo sapiens
Compartment: cytosol
Primary external reference: UniProt: CDC25B: P30305

Reaction (6 results from a total of 6)

Identifier: R-HSA-170120
Species: Homo sapiens
Compartment: nuclear envelope
Cdc25B shuttles between the nucleus and the cytoplasm. Translocation out of the nucleus involves a nuclear export sequence in the N-terminus of Cdc25B (Lindqvist et al., 2004).
Identifier: R-HSA-8863007
Species: Homo sapiens
Compartment: cytosol
CDK5, activated by binding to p25 phosphorylates CDC25B protein tyrosine phosphatase on serine and threonine residues S50, T69, S160, S321 and S470. In neurons, CDK25B localizes to both nucleus and cytosol and CDK5-mediated phosphorylation does not change its localization. Once activated by CDK5, CDC25B promotes activation of CDK1, CDK2 and CDK4 (Chang et al. 2012).
Identifier: R-HSA-170161
Species: Homo sapiens
Compartment: cytosol
Activation of the mitotic cyclinB:Cdc2 (CCNB:CDK1) complexes at mitosis requires the removal of the inhibitory phosphate groups on Cdc2 (CDK1). This dephosphorylation is achieved by the activity of the CDC25 family of phosphatases, which act on both CCNB1 and CCNB2-bound CDK1 (Galaktionov and Beach 1991, Goda et al. 2003, Timofeev et al. 2010). The CDC25 members, CDC25A, CDC25B, and CDC25C are kept inactive during interphase and are activated at the G2/M transition. CCNB:CDK1 complexes appear to participate in the full activation of CDC25 in a process that involves an amplification loop (see Wolfe and Gould, 2004). The initial activation of the CCNB:CDK1 (cyclin B1:Cdc2 and cyclin-B2:Cdc2) complexes occurs in the cytoplasm in prophase (Jackman et al., 2003). CDC25B, which is present at highest concentrations in the cytoplasm at this time, is thought to trigger the activation of CCNB1:CDK1 (Lindqvist et al. 2004; Honda et al., 1993). Active CCNB1:CDK1 then phosphorylates CDC25C (contributing to its PLK1-mediated activation) and stabilizes CDC25A (Strausfeld et al., 1994; Hoffman et al.,1993; Mailand et al, 2002). This creates positive feedback loops that allows CDC25A and CDC25C to dephosphorylate and further activate CDK1. As active CDC25C is nuclear, it presumably predominantly contributes to activation of nuclear CDK1 (Strausfeld et al. 1994, Toyoshima-Morimoto et al. 2002, Bonnet, Coopman et al. 2008, Bonnet Mayonove et al. 2008).
Identifier: R-HSA-170159
Species: Homo sapiens
Compartment: nuclear envelope
The localization of the Cdc25A, B and C proteins is dynamic involving the shuttling of these proteins between the nucleus and the cytoplasm. Sequences in these proteins mediate both nuclear export and import (Kallstrom et al., 2005; Lindqvist et al., 2004; Graves et al, 2001; Takizawa and Morgan, 2000).
Identifier: R-HSA-174110
Species: Homo sapiens
Compartment: nucleoplasm
Cdc25A, and probably Cdc25B, regulate the entry into S phase cell cycle by removing inhibitory phosphates from the Cdk2 subunit of Cyclin A:Cdk2.
Identifier: R-HSA-170158
Species: Homo sapiens
Compartment: nucleoplasm
Activation of the cyclin A:Cdc2 complexes at mitosis requires the removal of the inhibitory phosphate groups on Cdc2 (CDK1). This dephosphorylation is achieved by the activity of the CDC25A phosphatase (Timofeev et al. 2009). CDC25A, CDC25B, and CDC25C are kept inactive during interphase and are activated at the G2/M transition (see Wolfe and Gould 2004).

Pathway (3 results from a total of 3)

Identifier: R-HSA-170145
Species: Homo sapiens
Compartment: nucleoplasm
Cyclin A:Cdc2 complexes are detected in the nucleus earlier that cyclin B1:Cdc2 complexes and may play a role in the initial events in prophase. Inactivation of Cdc25B by proteasome-mediated degradation is dependent upon cyclin A:Cdc2-mediated phosphorylation (Cans et al, 1999)
Identifier: R-HSA-8862803
Species: Homo sapiens
Post-mitotic neurons do not have an active cell cycle. However, deregulation of Cyclin Dependent Kinase-5 (CDK5) activity in these neurons can aberrantly activate various components of cell cycle leading to neuronal death (Chang et al. 2012). Random activation of cell cycle proteins has been shown to play a key role in the pathogenesis of several neurodegenerative disorders (Yang et al. 2003, Lopes et al. 2009). CDK5 is not activated by the canonical cyclins, but binds to its own specific partners, CDK5R1 and CDK5R2 (aka p35 and p39, respectively) (Tsai et al. 1994, Tang et al. 1995). Expression of p35 is nearly ubiquitous, whereas p39 is largely expressed in the central nervous system. A variety of neurotoxic insults such as beta-amyloid (A-beta), ischemia, excitotoxicity and oxidative stress disrupt the intracellular calcium homeostasis in neurons, thereby leading to the activation of calpain, which cleaves p35 into p25 and p10 (Lee et al. 2000). p25 has a six-fold longer half-life compared to p35 and lacks the membrane anchoring signal, which results in its constitutive activation and mislocalization of the CDK5:p25 complex to the cytoplasm and the nucleus. There, CDK5:p25 is able to access and phosphorylate a variety of atypical targets, triggering a cascade of neurotoxic pathways that culminate in neuronal death. One such neurotoxic pathway involves CDK5-mediated random activation of cell cycle proteins which culminate in neuronal death. Exposure of primary cortical neurons to oligomeric beta-amyloid (1-42) hyper-activates CDK5 due to p25 formation, which in turn phosphorylates CDC25A, CDC25B and CDC25C. CDK5 phosphorylates CDC25A at S40, S116 and S261; CDC25B at S50, T69, S160, S321 and S470; and CDC25C at T48, T67, S122, T130, S168 and S214. CDK5-mediated phosphorylation of CDC25A, CDC25B and CDC25C not only increases their phosphatase activities but also facilitates their release from 14-3-3 inhibitory binding. CDC25A, CDC25B and CDC25C in turn activate CDK1, CDK2 and CDK4 kinases causing neuronal death. Consistent with this mechanism, higher CDC25A, CDC25B and CDC25C activities were observed in human Alzheimer's disease (AD) clinical samples, as compared to age-matched controls. Inhibition of CDC25 isoforms confers neuroprotection to beta-amyloid toxicity, which underscores the contribution of this pathway to AD pathogenesis
Identifier: R-HSA-176187
Species: Homo sapiens
Compartment: nucleoplasm
Genotoxic stress caused by DNA damage or stalled replication forks can lead to genomic instability. To guard against such instability, genotoxically-stressed cells activate checkpoint factors that halt or slow cell cycle progression. Among the pathways affected are DNA replication by reduction of replication origin firing, and mitosis by inhibiting activation of cyclin-dependent kinases (Cdks). A key factor involved in the response to stalled replication forks is the ATM- and rad3-related (ATR) kinase, a member of the phosphoinositide-3-kinase-related kinase (PIKK) family. Rather than responding to particular lesions in DNA, ATR and its binding partner ATRIP (ATR-interacting protein) sense replication fork stalling indirectly by associating with persistent ssDNA bound by RPA. These structures would be formed, for example, by dissociation of the replicative helicase from the leading or lagging strand DNA polymerase when the polymerase encounters a DNA lesion that blocks DNA synthesis. Along with phosphorylating the downstream transducer kinase Chk1 and the tumor suppressor p53, activated ATR modifies numerous factors that regulate cell cycle progression or the repair of DNA damage. The persistent ssDNA also stimulates recruitment of the RFC-like Rad17-Rfc2-5 alternative clamp-loading complex, which subsequently loads the Rad9-Hus1-Rad1 complex onto the DNA. The latter '9-1-1' complex serves to facilitate Chk1 binding to the stalled replication fork, where Chk1 is phosphorylated by ATR and thereby activated. Upon activation, Chk1 can phosphorylate additional substrates including the Cdc25 family of phosphatases (Cdc25A, Cdc25B, and Cdc25C). These enzymes catalyze the removal of inhibitory phosphate residues from cyclin-dependent kinases (Cdks), allowing their activation. In particular, Cdc25A primarily functions at the G1/S transition to dephosphorylate Cdk2 at Thr 14 and Tyr 15, thus positively regulating the Cdk2-cyclin E complex for S-phase entry. Cdc25A also has mitotic functions. Phosphorylation of Cdc25A at Ser125 by Chk1 leads to Cdc25A ubiquitination and degradation, thus inhibiting DNA replication origin firing. In contrast, Cdc25B and Cdc25C regulate the onset of mitosis through dephosphorylation and activation of Cdk1-cyclin B complexes. In response to replication stress, Chk1 phosphorylates Cdc25B and Cdc25C leading to Cdc25B/C complex formation with 14-3-3 proteins. As these complexes are sequestered in the cytoplasm, they are unable to activate the nuclear Cdk1-cyclin B complex for mitotic entry.

These events are outlined in the figure. Persistent single-stranded DNA associated with RPA binds claspin (A) and ATR:ATRIP (B), leading to claspin phosphorylation (C). In parallel, the same single-stranded DNA:RPA complex binds RAD17:RFC (D), enabling the loading of RAD9:HUS1:RAD1 (9-1-1) complex onto the DNA (E). The resulting complex of proteins can then repeatedly bind (F) and phosphorylate (G) CHK1, activating multiple copies of CHK1.

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