Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two controversial aspects in the mechanism of human vitamin D receptor (hVDR) action are the possible significance of VDR homodimers and the functional role of receptor phosphorylation. To address these issues, milligram quantities of baculovirus-expressed hVDR were purified to 97% homogeneity, and then tested for binding to the rat osteocalcin vitamin D responsive element (VDRE) via electrophoretic mobility shift and half-site competition assays in the presence or absence of a CV-1 nuclear extract containing retinoid X receptor (RXR). Methylation interference analysis revealed that both the hVDR homodimer and the VDR-RXR heterodimer display similar patterns of VDRE G-base protection. However, in competition studies, the relative dissociation of the homodimeric hVDR complex from the VDRE was extremely rapid (t1/2 < 30 s) compared to the dissociation of the heteromeric complex (t1/2 > 5 min), thus illustrating the relative instability and low affinity of homodimeric VDR binding to DNA. These results indicate that VDR-RXR heterodimers are the preferred VDRE binding species. Further, two dimensional gel electrophoresis of hVDR demonstrated several isoelectric forms of the receptor, suggesting that it is subject to multiple phosphorylation events. In vitro kinase assays confirmed that purified hVDR is an efficient substrate for protein kinases A and Cbeta, as well as casein kinase II. In vivo studies of the expressed receptor in intact cells, namely baculovirus vector infected Sf9 insect cells and transfected mammalian COS-7 cells, demonstrated that hVDR was phosphorylated in a hormone-enhanced fashion. Functional consequences of hVDR phosphorylation were suggested by the observations that: (i) potato acid phosphatase (PAP)-treated hVDR no longer interacted with the VDRE as either a homodimer or a heteromeric complex with RXR, and (ii) treatment of transfected COS-7 cells with a phosphatase inhibitor (okadaic acid) along with 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) resulted in a synergistic enhancement of both hVDR phosphorylation and transactivation of a VDRE-linked reporter gene, compared to the effect of treatment with either agent alone. These studies point to a significant role for phosphorylation of VDR in regulating high-affinity VDR-RXR interactions with VDREs, and also in modulating 1,25(OH)2D3-elicited transcriptional activation in target cells.
...
PMID:Isolation of baculovirus-expressed human vitamin D receptor: DNA responsive element interactions and phosphorylation of the purified receptor. 1194 98

Yeast regulatory factor PHO85, which is a cyclin-dependent kinase (DCK), participates in the regulation of the cell cycle and the expression of the acid phosphatase gene. Using PHO85 as target, we have cloned from the yeast two-hybrid genomic library a novel gene (PAP1) with product which can asscociate with the PHO85 protein. The PAP1 gene including the 5apo; and 3apo; flanking sequence was cloned and sequenced. It codes for a protein composed of 284 amino acids, which contains a cyclin conservative region (150-263 aa), and shares 63% similarity with the conservative region of PHO80. The N-terminal of the PAP1 protein abounds in PEST sequence, which is believed to be common to rapidly degraded proteins. Using the yeast two-hybrid system, we demonstrated that both the full-length PAP1 protein and the C-terminal (99-285 aa) can interact with PHO85. The coding sequence of the PAP1 gene was cloned and sequenced, then arranged under the control of the P(L) promoter, and expressed in E. coli BL21 (DE3) pLysS. After heat induction at 42 degrees, protein band of approximately 32 kD was observed in the SDS-PAGE, which fits the molecular size of the hypothetical PAP1 protein. The 10 N-terminal amino acids of the 32 kD protein agreed with the deduced PAP1 amino acid sequence. The protein was found as inclusion body in E. coli, and accounted for 50% of the precipitant after purification.
...
PMID:Cloning and Expression of a Novel PHO85 Associated Protein PAP1 Gene of Saccharomyces cerevisiae. 1217 91

Semenogelins I and II are the quantitatively dominating proteins in human semen. They comprise the major part of the sperm-entrapping gel formed at ejaculation, which subsequently liquefies due to proteolysis of the gel-forming proteins by prostate-specific antigen (PSA). The mechanism behind gel formation and its physiological significance is not known. We have studied phosphorylation and dephosphorylation of human semenogelins. Both were phosphorylated by protein kinases A and C (PKA and PKC, respectively) at a rate about 5 times less than that of histone. For PKA, incorporated ((32)P)phosphate into semenogelin approached a maximum above 1 mol/mol. Corresponding values for phosphorylation of the semenogelins with PKC were greater than 10. There was no change in the sensitivity of phosphosemenogelins to proteolysis by PSA. Serine (PKA) and serine and threonine (PKC) were the phosphate-accepting amino acid residues, and all incorporated ((32)P)phosphate could be removed from the semenogelins with human acid phosphatase. Nil or very little phosphate could be detected in purified semenogelins isolated from seminal plasma. In vivo, about half the protein kinase activity in seminal plasma was bound to prostasomes. PKA but not PKC purified from prostasomes could phosphorylate specific substrates, but they could phosphorylate either of the semenogelins.
...
PMID:Exogenous protein kinases A and C, but not endogenous prostasome-associated protein kinase, phosphorylate semenogelins I and II from human semen. 1239 26

The Pho85-Pho80 cyclin-CDK (cyclin-dependent protein kinase) complex of Saccharomyces cerevisiae functions as a key regulator of the phosphate-repressible acid phosphatase system. We have further characterized the Pho85-Pho80 kinase complex and identified the Pho80 cyclin subunit and the Pho81 CDK inhibitor as substrates of the Pho85 protein kinase. The phosphorylation sites within Pho80 have been identified at Ser234 and Ser267. Of the two sites, phosphorylation of Ser234 is required for Pho80 function, to form an active kinase complex and repress acid phosphatase expression. Evidence suggests that the activity of Pho81 is regulated by a post-translational modification and therefore that Pho85-mediated phosphorylation of Pho81 may alter its ability to function as a CDK inhibitor. Thus, the control of acid phosphatase expression involves the phosphorylation of several of the regulatory components of the system.
...
PMID:The yeast Pho80-Pho85 cyclin-CDK complex has multiple substrates. 1505 67

Cyclins, cyclin-dependent kinases (CDK) and their inhibitors play a critical role in many biological processes. In yeast, the ankyrin repeat protein Pho81p, by being an inhibitor of the Pho85p-Pho80p cyclin-dependent protein kinase complex, transcriptionally regulates the production of repressible acid phosphatase, encoded by the PHO5 gene. Recent studies in our laboratory showed that Pho81p is phosphorylated by the Pho80p-Pho85p CDK complex in vitro; and, to determine the significance of the phosphorylation, we used site-directed mutagenesis to alter the potential phosphorylation sites for this kinase complex. The resulting mutations were introduced into a yeast strain containing a deletion of PHO81 and the effect of the mutation on PHO5 expression was assayed. Results suggest that phosphorylation of particular residues within Pho81p is crucial for its activity as an inhibitor. Studies using a green fluorescent protein-Pho81p fusion and Western analysis indicate that the localization and half-life of the mutants are similar to wild-type Pho81 proteins. However, an in vivo binding assay indicates that the mutant Pho81p is deficient in binding to the Pho80p-Pho85p kinase complex. These findings support the observation that the mutant fails to inhibit kinase activity in low phosphate. These studies provide insight into the mechanism of regulation of CDK inhibitor activity.
...
PMID:Regulation by phosphorylation of Pho81p, a cyclin-dependent kinase inhibitor in Saccharomyces cerevisiae. 1512 25

In response to phosphate limitation, Saccharomyces cerevisiae induces transcription of a set of genes important for survival. One of these genes is PHO5, which encodes a secreted acid phosphatase. A phosphate-responsive signal transduction pathway (the PHO pathway) mediates this response through three central components: a cyclin-dependent kinase (CDK), Pho85; a cyclin, Pho80; and a CDK inhibitor (CKI), Pho81. While signaling downstream of the Pho81/Pho80/Pho85 complex to PHO5 expression has been well characterized, little is known about factors acting upstream of these components. To identify missing factors involved in the PHO pathway, we carried out a high-throughput, quantitative enzymatic screen of a yeast deletion collection, searching for novel mutants defective in expression of PHO5. As a result of this study, we have identified at least nine genes that were previously not known to regulate PHO5 expression. The functional diversity of these genes suggests that the PHO pathway is networked with other important cellular signaling pathways. Among these genes, ADK1 and ADO1, encoding an adenylate kinase and an adenosine kinase, respectively, negatively regulate PHO5 expression and appear to function upstream of PHO81.
...
PMID:A systematic high-throughput screen of a yeast deletion collection for mutants defective in PHO5 regulation. 1569 58

In Saccharomyces cerevisiae, the phosphate signal transduction PHO pathway is involved in regulating several phosphate-responsive genes such as PHO5, which encodes repressible acid phosphatase. In this pathway, a cyclin-dependent kinase inhibitor (Pho81p) regulates the kinase activity of the cyclin-cyclin-dependent kinase complex Pho80p-Pho85p, which phosphorylates the transcription factor Pho4p in response to intracellular phosphate levels. However, how cells sense phosphate availability and transduce the phosphate signal to Pho81p remains unknown. To identify additional components of the PHO pathway, we have screened a collection of yeast deletion strains. We found that disruptants of PLC1, ARG82, and KCS1, which are involved in the synthesis of inositol polyphosphate, and ADK1, which encodes adenylate kinase, constitutively express PHO5. Each of these factors functions upstream of Pho81p and negatively regulates the PHO pathway independently of intracellular orthophosphate levels. Overexpression of KCS1, but not of the other genes, suppressed PHO5 expression in the wild-type strain under low phosphate conditions. These results raise the possibility that diphosphoinositol tetrakisphosphate and/or bisdiphosphoinositol triphosphate may be essential for regulation of the PHO pathway. Furthermore, the Deltaplc1, Deltaarg82, and Deltakcs1 deletion strains, but not the Deltaipk1 deletion strain, had significantly reduced intracellular polyphosphate levels, suggesting that enzymes involved in inositol pyrophosphate synthesis are also required for polyphosphate accumulation.
...
PMID:Plc1p, Arg82p, and Kcs1p, enzymes involved in inositol pyrophosphate synthesis, are essential for phosphate regulation and polyphosphate accumulation in Saccharomyces cerevisiae. 1586 81

The active oxygen species (AOS) that arise from normal metabolic processes are kept under tight control by various antioxidant mechanisms. AOS are important signal molecules that regulate many physiological processes, including environmental stress responses. In this work, we have investigated the effect of lowered cytosolic ascorbate peroxidase (APX) activity in transgenic tobacco BY-2 cells, using two transformed BY-2 cell lines, cAPX-S2 and cAPX-S3, resulting from co-suppression by expression of Arabidopsis APX1 cDNA under the cauliflower mosaic virus (CaMV) 35S promoter. cAPX-S2 and cAPX-S3 possessed 50 and 75% lower cytosolic APX activity, respectively, compared with that in the untransformed cells. Chemical fluorescence analysis indicated that the AOS levels were markedly higher in the two APX-suppressed cell lines than in the wild-type cells. However, there were no substantial differences in the activity levels of the various other antioxidant enzymes. Interestingly, the APX-suppressed cells showed different responses and tolerances to environmental stresses, such as heat and salinity. Suppression subtractive hybridization revealed that several heat- and salt stress-inducible genes were up-regulated in cAPX-S3 cells. HSP70, DnaJ-like protein and purple acid phosphatase were among the constitutively induced genes. An in-gel kinase assay suggested that a mitogen-activated protein (MAP) kinase of approximately 46 kDa was predominantly active in the APX-suppressed cells, and transcript levels of both nicotiana protein kinase 1 (NPK1) and nucleoside diphosphate kinase 2 (NDPK2) were up-regulated. These data suggest the possibility that MAP kinase cascades are activated by subtle imbalances in the homeostasis of the cellular redox status caused by lowered cytosolic APX activity.
...
PMID:Acclimation to diverse environmental stresses caused by a suppression of cytosolic ascorbate peroxidase in tobacco BY-2 cells. 1591 70

Aromatization of testosterone into oestradiol plays a key role in the activation of male sexual behaviour in many vertebrate species. Rapid changes in brain aromatase activity have recently been identified and the resulting changes in local oestrogen bioavailability could modulate fast behavioural responses to oestrogens. In quail hypothalamic homogenates, aromatase activity is down-regulated within minutes by calcium-dependent phosphorylations in the presence of ATP, MgCl2 and CaCl2 (ATP/Mg/Ca). Three kinases (protein kinases A and C and calmodulin kinase; PKA, PKC and CAMK) are potentially implicated in this process. If kinases decrease aromatase activity in a reversible manner, then it would be expected that the enzymatic activity would increase and/or return to baseline levels in the presence of phosphatases. We showed previously that 0.1 mM vanadate (a general inhibitor of protein phosphatases) significantly decreases aromatase activity but specific protein phosphatases that could up-regulate aromatase activity have not been identified to date. The reversibility of aromatase activity inhibition by phosphorylations was investigated in the present study using alkaline and acid phosphatase (Alk and Ac PPase). Unexpectedly, Alk PPase inhibited aromatase activity in a dose-dependent manner in the presence, as well as in the absence, of ATP/Mg/Ca. By contrast, Ac PPase completely blocked the inhibitory effects of ATP/Mg/Ca on aromatase activity, even if it moderately inhibited aromatase activity in the absence of ATP/Mg/Ca. However, the addition of Ac PPase was unable to restore aromatase activity after it had been inhibited by exposure to ATP/Mg/Ca. Taken together, these data suggest that, amongst the 15 potential consensus phosphorylation sites identified on the quail aromatase sequence, some must be constitutively phosphorylated for the enzyme to be active whereas phosphorylation of the others is involved in the rapid inhibition of aromatase activity by the competitive effects of protein kinases and phosphatases. Two out of these 15 putative phosphorylation sites occur in an environment corresponding to the consensus sites for PKC, PKA (and possibly a CAMK) and, in all probability, represent the sites whose phosphorylation rapidly blocks enzyme activity.
...
PMID:Interactions between kinases and phosphatases in the rapid control of brain aromatase. 1610 93

The switch from budding to filamentous growth is a key aspect of invasive growth and virulence for the fungal phytopathogen Ustilago maydis. The cyclic AMP (cAMP) signaling pathway regulates dimorphism in U. maydis, as demonstrated by the phenotypes of mutants with defects in protein kinase A (PKA). Specifically, a mutant lacking the regulatory subunit of PKA encoded by the ubc1 gene displays a multiple-budded phenotype and fails to incite disease symptoms, although proliferation does occur in the plant host. A mutant with a defect in a catalytic subunit of PKA, encoded by adr1, has a constitutively filamentous phenotype and is nonpathogenic. We employed serial analysis of gene expression to examine the transcriptomes of a wild-type strain and the ubc1 and adr1 mutants to further define the role of PKA in U. maydis. The mutants displayed changes in the transcript levels for genes encoding ribosomal proteins, genes regulated by the b mating-type proteins, and genes for metabolic functions. Importantly, the ubc1 mutant displayed elevated transcript levels for genes involved in phosphate acquisition and storage, thus revealing a connection between cAMP and phosphate metabolism. Further experimentation indicated a phosphate storage defect and elevated acid phosphatase activity for the ubc1 mutant. Elevated phosphate levels in culture media also enhanced the filamentous growth of wild-type cells in response to lipids, a finding consistent with PKA regulation of morphogenesis in U. maydis. Overall, these findings extend our understanding of cAMP signaling in U. maydis and reveal a link between phosphate metabolism and morphogenesis.
...
PMID:Serial analysis of gene expression reveals conserved links between protein kinase A, ribosome biogenesis, and phosphate metabolism in Ustilago maydis. 1633 21


<< Previous 1 2 3 4 5 6 7 8 9 Next >>

---