Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent genetic and functional evidence suggests that the amino terminus of the retinoblastoma (Rb) protein plays an important role in Rb-mediated growth suppression. To explore the mechanism(s) by which this portion of Rb may regulate cell growth, we have sought to characterize cellular proteins that associate with the Rb amino terminus using an in vitro protein-binding assay. Here we report that at least one such protein is a cell cycle-regulated Rb/histone H1 kinase (RbK) whose enzymatic and/or Rb association activity is most prevalent in G2/M phases of cells. In contrast to previously characterized cyclin-dependent and Rb-associated kinases, such as cdk1 (cdc2) and cdk2, G2/M RbK 1) is not depleted by incubation with p13suc-beads, 2) is not detected with antisera against several Rb-associated cyclins-cdks, and 3) associated with Rb via the Rb amino terminus, a region that is dispensable for interaction with other Rb-associated kinases. RbK is clearly distinct from previously characterized mitotic cdks since cyclin A-cdc2, cyclin A-cdk2, cyclin B-cdc2, and cyclin B-cdk2 did not associate with the Rb amino terminus. Coprecipitation experiments with Rb antisera confirmed the association of Rb with a RbK-like kinase in metaphase-arrested cells in vivo. Interestingly, G2/M RbK did not appreciably associate with an analogous portion of p107, a Rb-related protein. Taken together, these data indicate that the Rb amino terminus specifically associates with a novel cell cycle-regulated kinase in late cell cycle stages.
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PMID:Detection of a novel cell cycle-regulated kinase activity that associates with the amino terminus of the retinoblastoma protein in G2/M phases. 772 48

Neurofilament (NF) protein [high molecular mass (NF-H)] is extensively phosphorylated in vivo. The phosphorylation occurs mainly in its characteristic KSP (Lys-Ser-Pro) repeat motifs. There are two major types of KSP motifs in the NF-H tail domain: KSPXKX and KSPXXX. Recent studies by two different laboratories have demonstrated the presence of a cdc2-like kinase [cyclin-dependent kinase-5 (cdk5)] in nervous tissue that selectively phosphorylates KSPXKX and XS/TXK motifs in NF-H and lysine-rich histone (H1). This article describes the identification of phosphatases dephosphorylating three different substrates: histone (H1), NF-H in a NF preparation, and a bacterially expressed C-terminal tail domain of NF-H, each containing KSPXKX repeats phosphorylated in vitro by cdk5. Among various phosphatases identified, protein phosphatase (PP) 2A from rabbit skeletal muscle appeared to be the most effective phosphatase in in vitro assays. Three phosphatase activity peaks--P1, P2, and P3--were partially purified from frozen rat spinal cord by ion exchange and size exclusion column chromatography and then characterized on the basis of biochemical, pharmacological, and immunochemical studies. One of the three peaks was identified as PP2A, whereas the others were mixtures of both PP2A and PP1. These three peaks could dephosphorylate cdk5-phosphorylated 32P-histone (H1), 32P-NF-H in the NF preparation, and 32P-NF-H tail fusion protein. These studies suggest the involvement of PP2A or a PP2A-like activity in the regulation of the phosphorylation state of KSPXKX motifs in NF-H.
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PMID:Neuronal cyclin-dependent kinase-5 phosphorylation sites in neurofilament protein (NF-H) are dephosphorylated by protein phosphatase 2A. 776 48

Neurofilament proteins and the neuron-specific microtubule-associated protein tau are phosphorylated in vivo at sites conforming to the phosphorylation consensus motif of the cell-cycle-control protein kinase, p34cdc2-cyclin. Abnormalities in the phosphorylation of these proteins are associated with neurodegenerative disorders, such as amylotrophic lateral sclerosis and Alzheimer's disease. A cdc2-like kinase composed of cyclin-dependent kinase 5 (cdk5) and a brain-specific regulatory subunit is proposed to be responsible for the cdc2-like phosphorylation of these neuronal proteins.
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PMID:Neuronal cdc2-like kinase. 787 42

We have identified mutations in the Drosophila cdc2 gene. The recessive lethality of these mutant alleles was rescued after P-element-mediated transformation with a genomic cdc2 fragment. Sequence analysis of amorphic alleles revealed non-conservative exchanges in evolutionary conserved positions. These alleles caused lethality at the larval-pupal interphase due to the absence of imaginal tissues. Embryonic lethality resulted when the maternal Dm cdc2 contribution was reduced through the use of a temperature-sensitive allele. Dm cdc2 function, therefore, is essential for cell proliferation throughout development. Dm cdc2 function is clearly required for mitosis, but no evidence for a requirement in S-phase was obtained. The reversible block of the mitotic proliferation which was observed in the PNS of mutant embryos occurred exclusively in the G2-phase. Moreover, while the mitotic proliferation of imaginal cells was blocked in the amorphic mutant larvae, non-imaginal larval cells continued to grow and endoreplicate their DNA. The Dm cdc2 mutant phenotype could neither be rescued with Dm cdc2c (encoding a cdc2-like kinase) nor enhanced by a reduction of the Dm cdc2c gene dose. These results indicate that the Dm cdc2- and Dm cdc2c-kinases control different processes.
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PMID:Genetic analysis of the Drosophila cdc2 homolog. 822 48

We have shown earlier that certain proline-directed kinases such as MAP kinase or GSK-3 can phosphorylate tau protein in an abnormal manner reminiscent of tau from Alzheimer paired helical filaments [Drewes et al. (1992); Mandelkow et al. (1992)]. Both kinases are abundant in brain tissue and associate physically with microtubules through several cycles of assembly and disassembly. In this report we show that cdk2/cyclin A incorporates = 5 Pi into recombinant tau, and that it also induces the MR shift and antibody reactivity typical of Alzheimer tau. However, since there is no cdk2 in brain [Meyerson et al. (1992)] we looked for other members of this family of kinases. Using an antibody against the conserved N-terminus we isolated a cdk-like kinase from brain which was capable of inducing the Alzheimer-like characteristics in tau by phosphorylation. Its size (31 kDa), target specificity (proline-directed), chromatographic behavior, and abundance in brain suggest that this kinase is similar or identical to the neuronal cdc2-like kinase nclk alias PSSARLE or cdk5 [Hellmich et al. (1992); Meyerson et al. (1992); Xiong et al. (1992); Tsai et al. (1993)]. This was confirmed by an antibody specific for cdk5. Like MAP kinase and GSK-3, this kinase is physically associated with microtubules and can be enriched by cycles of microtubule assembly and disassembly. Thus, cdk5 should be regarded as another kinase that could be held responsible for the changes in tau protein during Alzheimer disease progression.
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PMID:Abnormal Alzheimer-like phosphorylation of tau-protein by cyclin-dependent kinases cdk2 and cdk5. 828 4

A protein kinase that phosphorylates a specific KSP sequence [K(S/T)PXK], which is abundant in high molecular weight neurofilament (NF) proteins, was identified and isolated from rat spinal cord. Characterization of this enzyme activity revealed a close relationship with p34cdc2 kinase with respect to its molecular mass (32.5 kDa by SDS/PAGE) and substrate specificities. It could phosphorylate a synthetic peptide analog of the simian virus 40 large tumor antigen, reportedly a specific substrate for p34cdc2 kinase. Histone (H1) and peptide analogs of the KSP sequence present in the C-terminal end of rat and mouse neurofilament proteins were phosphorylated. This kinase did not phosphorylate alpha-casein and peptide substrates of other known second messenger-dependent or -independent kinases. Dephosphorylated rat NF protein NF-H was strongly phosphorylated by the purified enzyme; NF proteins NF-M and native NF-H, but not NF-L, were slightly phosphorylated. Studies on synthetic peptide analogs of KSP repeats with substitution of specific residues, known to be present in the C-terminal regions of NF-H, revealed a consensus sequence of X(S/T)PXK, characteristic of the p34cdc2 kinase substrate. On Western blots, the enzyme was immunoreactive with antibody against the C-terminal end of cdc2 kinase (mouse) and neuronal cdc2-like kinase from rat but not with an antibody against the conserved PSTAIRE region of the p34cdc2 kinase. The antibody against the C-terminal end of cdc2 kinase could immunoprecipitate (immunodeplete) the purified kinase activity. Since the adult nervous system is composed primarily of postmitotic cells, the present observations indicate a nonmitotic role for this cdc2-like kinase activity. The effective phosphorylation of NF-H by this kinase suggests a function in axonal structure.
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PMID:cdc2-like kinase from rat spinal cord specifically phosphorylates KSPXK motifs in neurofilament proteins: isolation and characterization. 834 7

A serine/threonine kinase from bovine brain has been purified (Lew, J., Beaudette, K. N., Litwin, C. M. E., and Wang, J. H. (1992) J. Biol. Chem. 267, 13383-13390) and found to consist of a 33-kDa catalytic subunit having high sequence homology to p34cdc2 and cdk2 (Lew, J., Winkfein, R. J., Paudel, H., and Wang, J. H. (1992) J. Biol. Chem. 267, 25922-25926). Substrate specificity determinants for this cdc2-like kinase were examined using synthetic peptide substrates derived from the in vitro p34cdc2 phosphorylation sites of histone H1. The peptide P-K-T-P-K-K-A-K-K-L was found to be an excellent substrate for the bovine cdc2-like kinase, having a Km value in the micromolar range. Important determinants for efficient substrate phosphorylation of this peptide were found both within the proposed substrate consensus motif (S/T-P-X-K/R) of p34cdc2 kinase and outside of this sequence. In addition to the absolute requirement for a proline residue immediately COOH-terminal to the phosphorylatable residue (+1) and a basic residue at the +3 position, a basic amino acid at the +2 position was greatly preferred over an acidic amino acid. A proline residue at the -2 position and a cluster of basic amino acids further COOH-terminal to the consensus motif were also found to be important for substrate binding. HeLa cell p34cdc2 kinase displays similar specificity to that of the bovine cdc2-like kinase, as the additional determinants outside of the consensus motif that contribute to the efficient phosphorylation of the histone peptide by this novel enzyme also appear to be important for p34cdc2-catalyzed phosphorylation.
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PMID:Substrate specificity characterization of a cdc2-like protein kinase purified from bovine brain. 840 12

Neuronal cdc2-like kinase, nclk, is a heterodimer of cyclin dependent protein kinase 5, cdk5, and a 25 kDa subunit derived from a novel, neuron-specific, 35 kDa protein: p35. The characterization and regulation of nclk will be summarized in this minireview. The activity of nclk appears to be governed by highly complex regulatory mechanisms including protein-protein interaction, protein phosphorylation and isoforms. The histone H1 kinase activity of nclk is absolutely dependent of the interaction between the 25 kDa subunit and the catalytic subunit, cdk5. In addition, nclk interacts with other cellular proteins to form macromolecular complexes. The kinase activity of nclk is inhibited in vitro by the phosphorylation reactions of a weel-like protein tyrosine kinase and a protein serine/threonine kinase from bovine thymus. Northern blot analysis has revealed the existence of two populations of p35 mRNA of 2 and 4 kb. A novel cDNA encoding a p35 homologous protein has been obtained from a human hippocampus library.
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PMID:Regulatory properties of neuronal cdc2-like kinase. 856 47

Neuronal cdc2-like kinase (Nclk) purified from bovine brain is a heterodimer of Cdk5 and an essential 25-kDa regulatory subunit (Lew, J., and Wang, J. H. (1995) Trends Biochem. Sci. 20, 33-37). The regulatory subunit is an N-terminal truncated derivative of a 35-kDa protein expressed specifically in brain, hence the name neuronal Cdk5 activator, p25/p35nck5a. In this study, we probe the relationship between the two different forms of Nck5a and their interaction with and activation of Cdk5 in bovine brain extract. Using protein fractionation procedures in combination with Western blot analysis and protein kinase assay, three forms of Cdk5 have been detected in bovine brain: a monomeric Cdk5 that can be activated by bacterially expressed GST-p21nck5a, a heterodimer of Cdk5 and p25nck5a that displays high kinase activity, and a Cdk5.p35nck5a complex that is inactive and refractory to GST-p21nck5a activation. Analysis of the Cdk5.p35nck5a complex by gel filtration chromatography indicated that the complex was part of a macromolecular structure with a molecular mass of approximately 670 kDa. When the macromolecular complex was subjected to gel filtration chromatography in the presence of 10% ethylene glycol, the fractions containing both p35nck5a and Cdk5, although eluting at the same position as control, displayed high kinase activity. The result is compatible with the suggestion that the macromolecular complex contained a kinase inhibitory factor that dissociated from the complex in 10% ethylene glycol.
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PMID:Interaction of cyclin-dependent kinase 5 (Cdk5) and neuronal Cdk5 activator in bovine brain. 857 50

We report the isolation of a large cyclophilin protein containing RS (arginine-serine) repeats from a yeast two-hybrid screen using ClK (CDC28/cdc2-like kinase) as a probe. This Clk associating RS-cyclophilin (CARS-Cyp) possesses 39% homology to the NK-TR1 (natural killer tumor recognition protein-1) we have previously characterized (Anderson et al. (1993) Proc. Natl. Acad. Sci. USA 90 (1993) 542-546). CARS-Cyp is expressed in a variety of tissues and cell types, and codes for a protein with a predicted mass of 89 kDa containing a cyclophilin-related domain, two Nopp140 (nucleolar phosphoprotein of 140 kDa)-related domains, and a large RS domain. The RS-cyclophilins, a novel class of proteins, may play an important role in the regulation of pre-mRNA splicing.
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PMID:RS cyclophilins: identification of an NK-TR1-related cyclophilin. 897 60


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