Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.5.1.18 (glutathione S-transferase)
 22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Stimulation of p21-activated kinase-1 (Pak1) signaling promotes motility, invasiveness, anchorage-independent growth and abnormal mitotic assembly in human breast cancer cells. Here, we provide new evidence that, before the onset of mitosis, activated Pak1 is specifically localized with the chromosomes during prophase and on the centrosomes in metaphase and moves to the contraction ring during cytokinesis. To identify mitosis-specific substrates of Pak1, we screened a synchronized G2-M expression library by using a glutathione transferase Pak1 solid-phase-based kinase reaction. This analysis identified histone H3 as a substrate of Pak1 both in vitro and in vivo, and it specifically interacted with Pak1 but not Pak2 or Pak3. Site-directed mutagenesis indicated that Pak1 phosphorylates histone H3 on Ser10. Expressions of the wild-type, or catalytically active, Pak1 caused it to appear at the poles corresponding to mitotic centrosomes in a variety of mammalian cells. Together, these results suggest for the first time that Pak1 interacts with and phosphorylates histone H3 and may thus influence the Pak1-histone H3 pathway, which in turn may influence mitotic events in breast cancer cells.
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PMID:p21-activated kinase 1 interacts with and phosphorylates histone H3 in breast cancer cells. 1215 36

The p21-activated protein kinases (Paks) are serine/threonine protein kinases activated by binding to Rho family small GTPases, Rac and Cdc42. Recently, Pak family members have been subdivided into two groups, I and II. Group II Paks, including Pak4, Pak5, and Pak6, does not contain the highly conserved autoinhibitory domain that is found in the group I Paks members, i.e. Pak1, Pak2, and Pak3. In the present study, we have purified the glutathione S-transferase fusion form of Pak5 and shown for the first time that Pak5 autophosphorylation can be activated by GTP bound form of Cdc42. Mutation of histidine residues 19 and 22 to leucine on the p21-binding domain of Pak5 completely abolished the binding of Cdc42 and the Cdc42-mediated autophosphorylation. On the other hand, mutation of tyrosine 40 to cysteine of Cdc42 did not knockout the binding of Pak5. Analysis of C-terminal deletion mutants has identified an autoinhibitory fragment of Pak5 that is absent from other group II Pak family members. Taken together, these results suggest that Pak5, like Pak1, contains an autoinhibitory domain and its activity is regulated by Cdc42.
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PMID:Identification of an autoinhibitory domain of p21-activated protein kinase 5. 1286 Sep 98

Pak2, a member of the p21-activated protein kinase (Pak) family, is activated in response to a variety of stresses and is directly involved in the induction of cytostasis. At the molecular level Pak2 binds Cdc42(GTP), translocating Pak2 to the endoplasmic reticulum where it is autophosphorylated and activated. Pak2 is autophosphorylated at eight sites; Ser-141 and Ser-165 in the regulatory domain and Thr-402 in the activation loop are identified as key sites in activation of the protein kinase. The function of phosphorylation of Ser-141 and Ser-165 on the activation was analyzed with wild-type (WT) and mutants of Pak2. With S141A, the level of autophosphorylation was reduced to 65% as compared with that of WT and S141D with a concomitant 45% reduction in substrate phosphorylation, indicating that phosphorylation at Ser-141 is required for optimal activity. Autophosphorylation inhibited the interaction between WT Pak2 and Cdc42(GTP). In 293T cells, WT Pak2, S141A, and S141D formed a stable complex with the constitutively active mutant Cdc42 L61, but not with the dominant negative Cdc42 N17. As shown in glutathione S-transferase pull-down assays, S141A bound to Cdc42(GTP) at a 6-fold higher level than that of S141D. In contrast, the S165A and S165D mutants had no effect on autophosphorylation, binding to Cdc42, or activation of Pak2. In summary, autophosphorylation of Ser-141 was required for activation of Pak2 and down-regulated the interaction of Pak2 with Cdc42. A model is proposed suggesting that binding of Cdc42 localizes Pak2 to the endoplasmic reticulum, where autophosphorylation alters association of the two proteins.
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PMID:Regulation of the interaction of Pak2 with Cdc42 via autophosphorylation of serine 141. 1620 30

Atypical RhoV GTPase (Chp/Wrch-2) is a member of the human Rho GTPase family, which belongs to the superfamily of Ras-related small GTPases. The biological functions of RhoV, regulation of its activity, and mechanisms of its action remain largely unexplored. Rho GTPases regulate a wide range of cellular processes by interacting with protein targets called effectors. Several putative RhoV effectors have been identified, including protein kinases of the Pak (p21-activated kinase) family: Pak1, Pak2, Pak4, and Pak6. RhoV GTPase activates Pak1 protein kinase and simultaneously induces its ubiquitin-dependent degradation. Pak1 regulates E-cadherin localization at adherens junctions downstream of RhoV during gastrulation in fish. The effector domain of RhoV mediates its binding to the CRIB (Cdc42/Rac1 interactive binding) motif in the N-terminal p21-binding domain (PBD) of Pak6 protein kinase. The role of the RhoV effector domain in mediating interaction with Pak1 has not been studied. This study has identified mutations in the effector domain of RhoV GTPase (Y60K, T63A, L65A, and D66A) that impair its interaction with Pak1 in the GST-PAK-PBD pull-down assay and coimmunoprecipitation. Our results suggest that the effector domain of RhoV mediates its binding to Pak1, complementing the current view of the molecular basics of RhoV binding to effectors of the Pak family. These data lay the basis for further studies on the role of Pak1 in RhoV-activated signaling pathways and cellular processes.
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PMID:[Mutations in the Effector Domain of RhoV GTPase Impair Its Binding to Pak1 Protein Kinase]. 3011 35