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:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have purified and characterized two kinds of GTP-binding proteins with Mr of 22,000 in human platelet membrane (main; m22KG(I), minor; m22KG(II)) (Nagata, K. and Nozawa, Y. (1988) FEBS Lett. 238, 90-94). In this study, the main GTP-binding protein (m22KG(I)) was found to be phosphorylated by cyclic AMP-dependent protein kinase (A-kinase), but not by protein kinase C. About 0.5 mol of phosphate was maximally incorporated into one mol of the protein and this phosphorylation was inhibited in the presence of A-kinase inhibitor. Phosphorylation of m22KG(I) did not alter either its GTP-binding or GTPase activity. When m22KG(I) was incubated alone or in the presence of 100 microM guanosine 5'-(3-O-thio)triphosphate (GTP gamma S) and then exposed to A-kinase, no significant changes in the level of phosphorylation were observed. On the other hand, the most abundant GTP-binding protein with Mr of 21,000 (c21KG) in human platelet cytosol, which was identified as a transformation suppressor gene product (rap 1 protein, smg p21 and Krev-1 protein), was not phosphorylated by A-kinase under the same condition. However, c21KG was phosphorylated by A-kinase after pretreatment with alkaline phosphatase.
...
PMID:Low Mr GTP-binding proteins in human platelets: cyclic AMP-dependent protein kinase phosphorylates m22KG(I) in membrane but not c21KG in cytosol. 254 Jul 45

The T cell antigen receptor is composed of at least seven chains derived from six different gene products. Upon stimulation, several chains can be phosphorylated. Two of these, CD3-gamma and CD3-epsilon are phosphorylated on serine residues. In addition, a 21-kDa nonglycosylated receptor component is phosphorylated, upon activation, on tyrosine residues. We have referred to this phosphoprotein as p21 because we have previously not been able to assign the tyrosine phosphorylation to any of the described receptor subunits (Samelson, L. E., Patel, M. D., Weissman, A. M., Harford, J. B., and Klausner, R. D. (1986) Cell 46, 1083-1090). In this paper, we demonstrate that it is the 16-kDa zeta chain which is the tyrosine phosphorylated subunit, and thus the p21 nomenclature can be replaced. This phosphorylation results in a shift of the apparent Mr of zeta to 21 kDa. Proof that p21 is tyrosine phosphorylated zeta was afforded by a number of approaches. Specific anti-zeta antibodies directly precipitated phospho-p21. Metabolically labeled protein corresponding to p21 could only be observed after activation. When this 21-kDa band was isolated after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reanalyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after treatment with alkaline phosphatase, its migration was identical with that of zeta. Furthermore, peptide mapping of metabolically labeled p21 (after gel isolation and dephosphorylation) showed it to be indistinguishable from p21. Thus, one of the early events of T cell activation is the tyrosine phosphorylation of the zeta chain of the T cell antigen receptor.
...
PMID:The T cell antigen receptor zeta chain is tyrosine phosphorylated upon activation. 314 73

CCRF-CEM T-lymphoblastoid cells have been exposed to an asymmetric electromagnetic signal pulsed at 72 Hz for up to 28 hr. Following exposure, cells were lysed and extracted, and the extract was electrophoresed on SDS-polyacrylamide gels. Proteins were electroblotted onto nitrocellulose membranes and the product of the ras proto-oncogenes, p21, was identified and quantitated by successive treatment with pan ras p21 antibody, second antibody-alkaline phosphatase conjugate, and enzyme substrate. No changes in p21 levels were observed for the first 6 h of electromagnetic field exposure as compared to unexposed control cells. However, from 6-16 h exposure, p21 levels in exposed cells decreased linearly to only 30% of control values. From 16-28 h exposure, p21 levels in exposed cells increased nearly linearly to control cell values. Slot-blot analysis indicated that altered p21 protein expression is a result, at least in part, of changes in the levels of N-ras mRNA. No concomitant changes were detected in either cyclic AMP levels or in the expression of cell surface markers. While the significance of the marked reduction in cellular p21 is unclear, it does not appear to be related to cell differentiation.
...
PMID:Effect of 72 Hz pulsed magnetic field exposure on ras p21 expression in CCRF-CEM cells. 811 31

The myc gene family has been implicated in multiple cell processes including proliferation, differentiation, tumorigenesis, and apoptosis. For its cellular growth promoting function, Myc must heterodimerize with Max. To study the effect of Myc inactivation on the growth and differentiation properties of epithelial tumor cells, we transfected the H-630 human colon cancer cell line with bm-max, a mutant Max protein in which DNA-binding activity has been abolished. Cells expressing high levels of bm-Max grow poorly, and the morphology of both colonies and single cells is altered. Moreover, increased bm-Max expression results in a prolonged G alpha/G1 phase accompanied by induced expression of p21 (WAF1/CIP1), elevated levels of alkaline phosphatase (ALP) activity, and accumulation of large fat granuli within the cells. These distinctive cell characteristics are associated with differentiation processes in numerous malignant cell lines. The results of this study support a model in which sequestering of endogenous Myc and Max proteins into "basic mutant" dimers lacking DNA-binding activity is sufficient both to inhibit proliferation and to induce changes in cell behavior consistent with differentiation.
...
PMID:c-Myc inactivation by mutant Max alters growth and morphology of NCI-H-630 colon cancer cells. 884 36

The eukaryotic cell cycle is regulated by a complex network of many proteins. Effective reprogramming of this complex regulatory apparatus to achieve bioprocess goals, such as cessation of proliferation at high cell density to allow an extended period of high production, can require coordinated manipulation of multiple genes. Previous efforts to establish inducible cell-cycle arrest of Chinese hamster ovary (CHO) cells by regulated expression of the cyclin-dependent kinase inhibitor (CDI) p21 failed. By tetracycline-regulated coexpression of p21 and the differentiation factor CCAAT/enhancer-binding protein alpha (which both stabilizes and induces p21), we have achieved effective cell-cycle arrest. Production of a model heterologous protein (secreted alkaline phosphatase; SEAP) has been increased 10-15 times, on a per cell basis, relative to an isogenic control cell line. Because activation of apoptosis response is a possible complication in a proliferation-arrested culture, the survival gene bcl-xL was coexpressed with another CDI, p27, found to enable CHO cell-cycle arrest predominantly in G1 phase. CHO cells stably transfected with a tricistronic construct containing the genes for these proteins and for SEAP showed 30-fold higher SEAP expression than controls.
...
PMID:Controlled proliferation by multigene metabolic engineering enhances the productivity of Chinese hamster ovary cells. 959 85

The cyclin-dependent kinase inhibitor p21(WAF1,CIP1,SDI1) plays a critical role in cell differentiation, and it has been shown to confer resistance to apoptosis. Based on this, and on evidence that activation of the gp130/signal transducer and activator of transcription (STAT) signal transduction pathway by interleukin (IL)-6 type cytokines promotes differentiation and prevents apoptosis in osteoblastic cells, we have investigated the possibility that p21 is a downstream effector of this signaling pathway in osteoblasts. We report that either oncostatin M (OSM) or IL-6 plus soluble IL-6 receptor increased the levels of p21 mRNA and protein in the osteoblast-like human osteosarcoma cell line MG63 and stimulated the activity of a 2.4-kilobase pair segment of the human p21 gene promoter. Further, nuclear extracts from cytokine-stimulated MG63 cells formed protein-DNA complexes with a 19-base pair nucleotide fragment of the p21 promoter containing a single STAT response element. The identity of the binding proteins as Stat3 and Stat1 was demonstrated with specific antibodies. In addition, and in support of a mediating role of STATs in the activation of the p21 promoter, overexpression of Stat3 potentiated the cytokine effect on the p21 promoter; whereas a dominant negative Stat3, or a mutation of the STAT response element on the promoter, significantly reduced the cytokine effect. Finally, antisense oligonucleotides complementary to p21 mRNA inhibited OSM-induced stimulation of alkaline phosphatase expression and antagonized the protective effect of OSM on anti-Fas-induced apoptosis. These results demonstrate that p21 is a downstream effector of gp130/Stat3 activation and a critical mediator of the pro-differentiating and anti-apoptotic effects of IL-6 type cytokines on human osteoblastic cells.
...
PMID:Transcriptional activation of the p21(WAF1,CIP1,SDI1) gene by interleukin-6 type cytokines. A prerequisite for their pro-differentiating and anti-apoptotic effects on human osteoblastic cells. 969 69

We constructed stable Chinese hamster ovary (CHO) cell lines which conditionally and coordinately express the model product gene secreted alkaline phosphatase (SEAP) and one of the cytostatic genes p21, p27, and p53175P, a p53 mutant deficient in apoptotic but not cell-cycle arrest function. The use of dicistronic expression technology allowed the conditional expression of the model product gene and the cytostatic gene in a coordinated fashion from a single expression unit under the control of the tetracycline-responsive promoter PhCMV-1. Due to the presence of a cytostatic gene in the multicistronic expression unit, the growth behavior of the engineered CHO cell lines could be controlled by the addition or withdrawal of the exogenous agent tetracycline to or from the cell culture medium. Withdrawal of tetracycline resulted in sustained growth arrest of the stable cell lines for a prolonged period. The growth arrest of such cell lines was found to be accompanied by a 10-15-fold increase in their production of SEAP per cell. This controlled proliferation technology allows the design of a novel two-stage production process which consists of a proliferation phase leading to the desired cell density, followed by an extended production phase during which the cells remain growth-arrested and increase cell-specific production of a heterologous protein.
...
PMID:Higher productivity of growth-arrested Chinese hamster ovary cells expressing the cyclin-dependent kinase inhibitor p27. 975 59

The cellular mechanisms regulating intestinal proliferation and differentiation remain largely undefined. Previously, we showed an early induction of the cyclin-dependent kinase (CDK) inhibitor p21(Waf1/Cip1) in Caco-2 cells, a human colon cancer line that spontaneously differentiates into a small bowel phenotype. The purpose of our present study was to assess the timing of cell cycle arrest in relation to differentiation in Caco-2 cells and to examine the mechanisms responsible for CDK inactivation. Caco-2 cells undergo a relative G1/S block and cease to proliferate at day 3 postconfluency; an increase in the activity of terminally differentiated brush-border enzymes (sucrase and alkaline phosphatase) was noted at day 6 postconfluency. Cell cycle block was associated with suppression of both CDK2 and CDK4 activities, which are important for G1/S progression. Treatment of the CDK immune complexes with the detergent deoxycholate (DOC) resulted in restoration of CDK2, but not CDK4, activity at day 3 postconfluency, suggesting the presence of inhibitory protein(s) binding to the cyclin/CDK2 complex at this time point. An increased binding of p21(Waf1/Cip1) to CDK2 complexes at day 3 postconfluency was noted, suggesting a potential role for p21(Waf1/Cip1) in CDK2 inactivation; however, immunodepletion of p21(Waf1/Cip1) from Caco-2 protein extracts demonstrated that p21(Waf1/Cip1) is only partially responsible for CDK2 suppression at day 3 postconfluency. A decrease in the cyclin E/CDK2 complex appears to contribute to the CDK2 inactivation noted at days 6 and 12 postconfluency. Taken together, our results suggest that multiple mechanisms contribute to CDK suppression during Caco-2 cell differentiation. Inhibition of CDK2 and CDK4 leads to G1 arrest and inhibition of proliferation that precede Caco-2 cell differentiation.
...
PMID:Caco-2 intestinal cell differentiation is associated with G1 arrest and suppression of CDK2 and CDK4. 981 65

The p53-inducible gene product p21(WAF1/CIP1) plays a critical role in regulating the rate of tumor incidence, and identifying mechanisms of its post-translational regulation will define key pathways that link growth control to p21-dependent tumor suppression. A eukaryotic cell model system has been developed to determine whether protein kinase signaling pathways that phosphorylate human p21 exist in vivo and whether such pathways regulate the binding of p21 to one of its key target proteins, proliferating cell nuclear antigen (PCNA). Although human p21 expressed in Sf9 cells is able to form a complex with human PCNA, the inclusion of cell-permeable phosphatase inhibitors renders p21 protein inactive for PCNA binding. The treatment of this inactive isoform of p21 with alkaline phosphatase restores its binding to PCNA, suggesting that p21 expressed in Sf9 cells is subject to reversible phosphorylation at a key regulatory site(s). A biochemical approach was subsequently used to map the phosphorylation sites within p21, whose modification in vitro can inhibit p21-PCNA complex formation, to the C-terminal domain at residues Thr(145) or Ser(146). A phospho-specific antibody was developed that only bound to full-length p21 protein after phosphorylation in vitro at Ser(146), and this reagent was further used to demonstrate that the inactive isoform of p21 recovered from Sf9 cells treated with phosphatase inhibitors had been phosphorylated in vivo at Ser(146). These data identify the first phosphorylation site within the C-terminal regulatory domain of p21 whose modification in vivo modulates p21-PCNA interactions and define a eukaryotic cell model that can be used to study post-translational signaling pathways that regulate p21.
...
PMID:Reversible phosphorylation at the C-terminal regulatory domain of p21(Waf1/Cip1) modulates proliferating cell nuclear antigen binding. 1075 73

Jaagsiekte sheep retrovirus (JSRV) is a type D retrovirus associated with a contagious lung tumor of sheep, ovine pulmonary carcinoma. Other than sheep, JSRV is known to infect goats, but there is no evidence of human infection. Until now it has not been possible to study the host range for JSRV because of the inability to grow this virus in culture. Here we show that the JSRV envelope protein (Env) can be used to pseudotype Moloney murine leukemia virus (MoMLV)-based retrovirus vectors and that such vectors can transduce human cells in culture. We constructed hybrid retrovirus packaging cells that express the JSRV Env and the MoMLV Gag-Pol proteins and can produce JSRV-pseudotype vectors at titers of up to 10(6) alkaline phosphatase-positive focus-forming units/ml. Using this high-titer virus, we have studied the host range for JSRV, which includes sheep, human, monkey, bovine, dog, and rabbit cells but not mouse, rat, or hamster cells. Considering the inability of the JSRV-pseudotype vector to transduce hamster cells, we used the hamster cell line-based Stanford G3 panel of whole human genome radiation hybrids to phenotypically map the JSRV receptor (JVR) gene within the p21.3 region of human chromosome 3. JVR is likely a new retrovirus receptor, as none of the previously identified retrovirus receptors localizes to the same position. Several chemokine receptors that have been shown to serve as coreceptors for lentivirus infection are clustered in the same region of chromosome 3; however, careful examination shows that the JSRV receptor does not colocalize with any of these genes.
...
PMID:Retrovirus vectors bearing jaagsiekte sheep retrovirus Env transduce human cells by using a new receptor localized to chromosome 3p21.3. 1077 7


1 2 3 4 5 Next >>

---