Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transforming growth factor beta 1 (TGF-beta 1) exerts a positive effect on the transcription of genes coding for several extracellular matrix-related products, including collagen I. We have previously identified a strong TGF-beta 1-responsive element (TbRE) in the upstream promoter sequence of the alpha 2(I) collagen (COL1A2) gene. Our experiments have shown that TGF-beta 1 stimulates COL1A2 transcription by increasing binding of an Sp1-containing complex (TbRC) to the TbRE. They have also suggested that the change occurs via posttranslational modification of a protein(s) directly or indirectly interacting with Sp1. Here, we provide evidence showing that tyrosine dephosphorylation of nuclear proteins mimics the stimulation of COL1A2 transcription by the TGF-beta 1-activated signaling pathway. Preincubation of nuclear extracts with protein tyrosine phosphatase (PTPase) but not with protein phosphatase type 2A (PP2A), a serine/threonine phosphatase, enhanced binding of the TbRC to the same degree as culturing cells in TGF-beta 1. Consistent with these in vitro findings, genistein, a tyrosine kinase inhibitor, led to markedly increased COL1A2 gene expression, whereas sodium orthovanadate, a tyrosine phosphatase inhibitor, decreased it substantially. These results were supported by transfection experiments showing that genistein and sodium orthovanadate have opposite effects on TbRE-mediated transcription. Moreover, nuclear proteins isolated from genistein-treated cells were found to interact with the TbRE significantly more than those from untreated cells. Furthermore, pretreatment of cells with sodium orthovanadate virtually abrogated nuclear protein binding to the TbRE, but not to a neighboring cis-acting element unresponsive to TGF-beta 1. The results of this study, therefore, provide the first correlation between tyrosine dephosphorylation, increased binding of a transcriptional complex, and TGF-beta 1 stimulation of gene expression.
Mol Cell Biol 1995 Dec
PMID:Tyrosine dephosphorylation of nuclear proteins mimics transforming growth factor beta 1 stimulation of alpha 2(I) collagen gene expression. 852 47

The current studies were undertaken to determine whether embryonic myoblasts or myogenic satellite cells undergoing differentiation and fusion contained endogenous modulators of protein kinase C (PKC). Clonal-derived turkey embryonic myoblast and satellite cell cultures were harvested at confluency and at approximately 40% fusion (embryonic myoblasts) or 75% fusion (satellite cells). PKC activity in cystosolic preparations of the cells and myotubes was undetectable. Cytosolic extracts (0.065 mg protein) of confluent and fused satellite cell cultures and confluent embryonic myoblasts had no effect on control PKC activity (control: 14.9 pmol/min, control + cytosols: 15.2, 13.9 and 13.5 pmol/min, respectively). Cytosolic preparations (0.065 mg protein) of embryonic myoblast-derived myotubes inhibited control PKC activity (4.0 pmol/min). In a time-course study, PKC-inhibitory activity was present in embryonic myoblasts at the earliest time point examined (30% fusion). Additionally, protein phosphatase activity correlated with PKC inhibitory activity. Thus, PKC-inhibitory activity appears as embryonic myoblasts begin to undergo fusion to form myotubes, but is not present in differentiating satellite cells.
Comp Biochem Physiol B Biochem Mol Biol 1995 Nov
PMID:Production of an endogenous inhibitor of protein kinase C by embryonic myoblasts undergoing differentiation. 852 31

Calcineurin is a serine/threonine protein phosphatase which catalyzes the hydrolysis of both phosphoseryl/phosphothreonyl and phosphotyrosyl proteins as well as low molecular weight compounds such as p-nitrophenyl phosphate. It is a hetero-dimeric protein consisting of a 60 kDa A chain and 19 kDa B chain. Calcineurin A is organized into functionally distinct domains such as a catalytic domain, a calcineurin B binding domain, a calmodulin-binding domain, and an inhibitory domain. Calcineurin B has four EF-hand calcium binding domains with a secondary structure that is homologous to calmodulin but its metal binding properties are more similar to troponin-C. The N-terminal myristoyl group of calcineurin B might play a role in the interaction between subunits A and B during phosphorylation/dephosphorylation processes. Crystals of size 0.125 x 0.07 x 0.03 mm and 0.7 x 0.03 x 0.02 mm have been obtained for calcineurin and the A subunit respectively. Crystals of calcineurin show strong diffraction to 5.3 A and weak diffraction to 3.0 A on rotating anode operated at 50 kV and 100 mA. Further work is in progress to improve the X-ray diffraction quality of these crystals and to obtain well diffracting crystals of calcineurin B.
Mol Cell Biochem
PMID:Preliminary crystallization studies of calmodulin-dependent protein phosphatase (calcineurin) from bovine brain. 856 21

Glycogen synthase, the regulatory enzyme of glycogen synthesis undergoes multisite phosphorylation leading to its inactivation. The kinases responsible for this covalent modification (ex. cAMP-dependent protein kinase, protein kinase C and glycogen synthase kinase-3) are controlled by the second messengers generated by different hormones. The isolated hepatocytes has been used as one of the experimental models for studying this complex regulatory process. Inactivation of glycogen synthase by glucagon and vasopressin has been shown to be accompanied with incorporation of phosphate into the enzyme protein. Insulin has been shown to activate glycogen synthase by inhibition of kinases and activation of synthase phosphatase. Glycogen synthase is activated by several gluconeogenic substrates, in addition to glucose. Studies in hepatocytes with activators and inhibitors of protein kinase C show that this enzyme negatively controls glycogen synthase. The differential effects of the phosphatase inhibitors, calyculin A and okadaic acid in liver cells provide supporting evidence that protein phosphatase type-1 plays a major role in the regulation of glycogen synthase. Hepatocytes isolated from diabetic rats of both types (insulin-dependent and non-insulin-dependent) mimic the defective glycogen synthase activation seen in vivo.
Mol Cell Biochem
PMID:Regulation of glycogen synthase activation in isolated hepatocytes. 856 54

A soluble protein phosphatase from the promastigote form of the parasitic protozoan Leishmania donovani was partially purified using Sephadex G-100, DEAE-cellulose and again Sephadex G-100 columns. The partially purified enzyme showed a native molecular weight of about 42,000 in both Sephadex G-100 and sucrose density gradient centrifugation. The sedimentation constant, stokes radius and frictional ratio were found to be 3.43S, 2.8 nm and 1.20 respectively. The enzyme preferentially utilized phosphohistone as the best exogenous substrate. Mg2+ ions were essential for enzyme activity; among other metal ions Mn2+ can replace Mg2+ to a certain extent whereas Ca2+, Co2+ and Zn2+ could not substitute for Mg2+. The pH optimum of the enzyme was 6.5-7.5 and the temperature optimum 37 degrees C. The apparent Km for phosphohistone was 7.14 microM. ATP, ADP, inorganic phosphate and pyrophosphate had inhibitory effect on the enzyme activity whereas no inhibition was observed with sodium tartrate and okadaic acid. These results suggest that L. donovani promastigotes possess a protein phosphatase which has similar characteristics with the mammalian protein phosphatase 2C.
Mol Cell Biochem 1995 Jul 19
PMID:Partial purification and characterization of a soluble protein phosphatase from Leishmania donovani promastigotes. 859 23

Complementary and genomic DNA clones coding for aldolase C-1, the fourth-type isozyme of aldolase in rice Oryza sativa L., have been characterized. The organization of the gene is quite similar to those encoding rice aldolase C-a and a maize cytoplasmic-type aldolase, in that introns are located in the same position. Amino acid sequences are highly conserved among cytoplasmic aldolases in plants. Expression of the gene in rice callus is activated by a protein phosphatase inhibitor okadaic acid, and is inhibited in the presence of thapsigargin, a reagent which increases calcium influx into the cytoplasm. The inhibition is rescued by the simultaneous addition of protein kinase inhibitor H-7. Thus, it is suggested that expression of the aldolase C-1 gene is regulated through a signal transduction pathway involving a Ca 2+ -mediated protein kinase-protein phosphatase system.
Plant Mol Biol 1996 Jan
PMID:Genomic structure of the rice aldolase isozyme C-1 gene and its regulation through a Ca 2+ -mediated protein kinase-phosphatase pathway. 861 63

The C heterogeneous ribonucleoprotein particle (hnRNP) protein bind to nascent pre-mRNA and may participate in assembly of the early prespliceosome. Ser/Thr phosphorylation of the C1 hnRNP protein in HeLa nuclear extracts regulates its binding to pre-mRNA (S. H. Mayrand, P. Dwen, and T. Pederson, Proc. Natl. Acad. Sci. USA 90:7764-7768, 1993). We have now further investigated the phosphorylation cycle of the C1 hnRNP protein, with emphasis on its regulation. Pretreatment of nuclear extracts with micrococcal nuclease eliminated the phosphorylation of C1 hnRNP protein, but pretreatment with DNase did not, suggesting a dependence on RNA. Oligodeoxynucleotide-targeted RNase H cleavage of U1, U2, and U4 small nuclear RNAs did not affect the phosphorylation of C1 hnRNP protein. However, cleavage of nucleotides 78 to 95, but not other regions, of U6 small nuclear RNA resulted in an inhibition of the dephosphorylation step of the C1 hnRNP protein phosphorylation cycle. This inhibition was as pronounced as that seen with the serine/threonine protein phosphatase inhibitor okadaic acid. C1 hnRNP protein dephosphorylation could be completely restored by the addition of intact U6 RNA. Add-back experiments with mutant RNAs further delineated the minimal region essential for C1 protein dephosphorylation as residing in nucleotides 85 to 92 of U6 RNA. These results illuminate a hitherto unanticipated function of U6 RNA: the modulation of a phosphorylation-dephosphorylation cycle of C1 hnRNP protein that influences the binding affinity of this protein for pre-mRNA. This newly revealed function of U6 RNA is likely to play a very early role in the prespliceosome assembly pathway, prior to U6 RNA's entry into the mature spliceosome's active center.
Mol Cell Biol 1996 Mar
PMID:A discrete 3' region of U6 small nuclear RNA modulates the phosphorylation cycle of the C1 heterogeneous nuclear ribonucleoprotein particle protein. 862 68

The PMC1 gene in Saccharomyces cerevisiae encodes a vacuolar Ca2+ ATPase required for growth in high-Ca2+ conditions. Previous work showed that Ca2+ tolerance can be restored to pmc1 mutants by inactivation of calcineurin, a Ca2+/calmodulin-dependent protein phosphatase sensitive to the immunosuppressive drug FK506. We now report that calcineurin decreases Ca2+ tolerance of pmc1 mutants by inhibiting the function of VCX1, which encodes a vacuolar H+/Ca2+ exchanger related to vertebrate Na+/Ca2+ exchangers. The contribution of VCX1 in Ca2+ tolerance is low in strains with a functional calcineurin and is high in strains which lack calcineurin activity. In contrast, the contribution of PMC1 to Ca2+ tolerance is augmented by calcineurin activation. Consistent with these positive and negative roles of calcineurin, expression of a vcx1::lacZ reporter was slightly diminished and a pmc1::lacZ reporter was induced up to 500-fold by processes dependent on calcineurin, calmodulin, and Ca2+. It is likely that calcineurin inhibits VCX1 function mainly by posttranslational mechanisms. Activities of VCX1 and PMC1 help to control cytosolic free Ca2+ concentrations because their function can decrease pmc1::lacZ induction by calcineurin. Additional studies with reporter genes and mutants indicate that PMR1 and PMR2A, encoding P-type ion pumps required for Mn2+ and Na+ tolerance, may also be induced physiologically in response to high-Mn2+ and -Na+ conditions through calcineurin-dependent mechanisms. In these situations, inhibition of VCX1 function may be important for the production of Ca2+ signals. We propose that elevated cytosolic free Ca2+ concentrations, calmodulin, and calcineurin regulate at least four ion transporters in S. cerevisiae in response to several environmental conditions.
Mol Cell Biol 1996 May
PMID:Calcineurin inhibits VCX1-dependent H+/Ca2+ exchange and induces Ca2+ ATPases in Saccharomyces cerevisiae. 862 89

SIT4 is the catalytic subunit of a type 2A-related protein phosphatase in Saccharomyces cerevisiae that is required for G1 cyclin transcription and for bud formation. SIT4 associates with several high-molecular-mass proteins in a cell cycle-dependent fashion. We purified two SIT4-associated proteins, SAP155 and SAP190, and cloned the corresponding genes. By sequence homology, we isolated two additional SAP genes, SAP185 and SAP4. Through such an association is not yet proven for SAP4, each of SAP155, SAP185, and SAP190 physically associates with SIT4 in separate complexes. The SAPs function positively with SIT4, and by several criteria, the loss of all four SAPs is equivalent to the loss of SIT4. The data suggest that the SAPs are not functional in the absence of SIT4 and likewise that SIT4 is not functional in the absence of the SAPs. The SAPs are hyperphoshorylated in cells lacking SIT4, raising the possibility that the SAPs are substrates of SIT4. By sequence similarity, the SAPs fall into two groups, the SAP4/SAP155 group and the SAP185/SAP190 group. Overexpression of a SAP from one group does not suppress the defects due to the loss of the other group. These findings and others indicate that the SAPs have distinct functions.
Mol Cell Biol 1996 Jun
PMID:The SAP, a new family of proteins, associate and function positively with the SIT4 phosphatase. 864 82

Calcineurin, or PP2B, plays a critical role in mediating Ca2+-dependent signaling in many cell types. In yeast cells, this highly conserved protein phosphatase regulates aspects of ion homeostasis and cell wall synthesis. We show that calcineurin mutants are sensitive to high concentrations of Mn2+ and identify two genes, CCC1 and HUM1, that, at high dosages, increase the Mn2+ tolerance of calcineurin mutants. CCC1 was previously identified by complementation of a Ca2+-sensitive (csg1) mutant. HUM1 (for "high copy number undoes manganese") is a novel gene whose predicted protein product shows similarity to mammalian Na+/Ca2+ exchangers. hum1 mutations confer Mn2+ sensitivity in some genetic backgrounds and exacerbate the Mn2+ sensitivity of calcineurin mutants. Furthermore, disruption of HUM1 in a calcineurin mutant strain results in a Ca2+-sensitive phenotype. We investigated the effect of disrupting HUM1 in other strains with defects in Ca2+ homeostasis. The Ca2+ sensitivity of pmc1 mutants, which lack a P-type ATPase presumed to transport Ca2+ into the vacuole, is exacerbated in a hum1 mutant strain background. Also, the Ca2+ content of hum1 pmc1 cells is less than that of pmc1 cells. In contrast, the Ca2+ sensitivity of vph1 mutants, which are specifically defective in vacuolar acidification, is not significantly altered by disruption of Hum1p function. These genetic interactions suggest that Hum1p may participate in vacuolar Ca2+/H+ exchange. Therefore, we prepared vacuolar membrane vesicles from wild-type and hum1 cells and compared their Ca2+ transport properties. Vacuolar membrane vesicles from hum1 mutants lack all Ca2+/H+ antiport activity, demonstrating that Hum1p catalyzes the exchange of Ca2+ for H+ across the yeast vacuolar membrane.
Mol Cell Biol 1996 Jul
PMID:The product of HUM1, a novel yeast gene, is required for vacuolar Ca2+/H+ exchange and is related to mammalian Na+/Ca2+ exchangers. 866 90


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