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)

The immunosuppressive drugs FK506 and cyclosporin A block T-lymphocyte proliferation by inhibiting calcineurin, a critical signaling molecule for activation. Multiple intracellular receptors (immunophilins) for these drugs that specifically bind either FK506 and rapamycin (FK506-binding proteins [FKBPs]) or cyclosporin A (cyclophilins) have been identified. We report the cloning and characterization of a new 51-kDa member of the FKBP family from murine T cells. The novel immunophilin, FKBP51, is distinct from the previously isolated and sequenced 52-kDa murine FKBP, demonstrating 53% identity overall. Importantly, Western blot (immunoblot) analysis showed that unlike all other FKBPs characterized to date, FKBP51 expression was largely restricted to T cells. Drug binding to recombinant FKBP51 was demonstrated by inhibition of peptidyl prolyl isomerase activity. As judged from peptidyl prolyl isomerase activity, FKBP51 had a slightly higher affinity for rapamycin than for FK520, an FK506 analog. FKBP51, when complexed with FK520, was capable of inhibiting calcineurin phosphatase activity in an in vitro assay system. Inhibition of calcineurin phosphatase activity has been implicated both in the mechanism of immunosuppression and in the observed toxic side effects of FK506 in nonlymphoid cells. Identification of a new FKBP that can mediate calcineurin inhibition and is restricted in its expression to T cells suggests that new immunosuppressive drugs may be identified that, by virtue of their specific interaction with FKBP51, would be targeted in their site of action.
Mol Cell Biol 1995 Aug
PMID:FKBP51, a novel T-cell-specific immunophilin capable of calcineurin inhibition. 754 43

Protein phosphatases regulate the activity of signal transduction mechanisms by dephosphorylating activated components. By utilizing selective inhibitors of these phosphatases, we investigated their role in regulating cAMP accumulation in the UMR 106 osteoblast-like tumor cell line. PTHrP, PTH and PGE2 stimulated cAMP accumulation up to 100-fold. Calyculin A, a potent inhibitor of protein phosphatase type 1 (PP1) and type 2A (PP2A), did not affect basal levels of cAMP, but concentrations of 10(-11) M to 10(-8) M increased PTHrP-, PTH-, and PGE2-stimulated cAMP accumulation up to 1.7-fold, and this increase was concentration-dependent. Similar results were obtained with tautomycin, another potent inhibitor of PP1 and PP2A. In contrast, okadaic acid, a potent inhibitor of PP2A which inhibited PP1 less potently, did not enhance PTHrP-, PTH-, or PGE2-stimulated cAMP accumulation. The effect of calyculin A on agonist-stimulated cAMP accumulation persisted in cells treated with isobutyl methylxanthine, a phosphodiesterase inhibitor. When the effect of calyculin A was compared with that of 4 beta-phorbol 12-myristate 13-acetate (PMA), it was found that while PMA enhanced both the receptor and forskolin-stimulated cAMP accumulation, calyculin A had no effect on the forskolin-stimulated cAMP accumulation. The effect of calyculin A on PTHrP- and PTH-stimulated cAMP accumulation persisted in cells treated with PMA. These results suggest that protein phosphatases play an important role in agonist-stimulated cAMP accumulation in osteoblast-like cells, and that PP1 but not PP2A may be the major phosphatase involved. In contrast to activation by protein kinase C, the site of action for the phosphatase appears to be predominantly at a step prior to the activation of adenylyl cyclase in the cAMP signal transduction pathway.
Mol Cell Endocrinol 1995 Apr 28
PMID:Inhibition of serine/threonine protein phosphatases enhances agonist-stimulated cAMP accumulation in UMR 106 osteoblast-like cells. 754 25

Levels of the mRNA encoding the catalytic subunit of protein phosphatase type-1 (PP-1cat) were reduced in skeletal muscle but not liver in response to short-term (2h) chow refeeding after prolonged (40h) starvation in the rat. This reduction did not appear to be mediated by insulin per se since streptozotocin-induced diabetes was associated with a reduction in PP-1cat levels in skeletal muscle. It is suggested that glucose levels may be one factor that modulates skeletal muscle PP-1cat mRNA levels. Despite the changes in PP-1cat mRNA levels in skeletal muscle, total protein phosphatase-1 catalytic activity was not altered by either chow refeeding or streptozotocin-diabetes. By contrast, although total hepatic PP-1cat mRNA levels were not altered in response to chow refeeding, there was a marked reduction in glycogen phosphorylase phosphatase activity in the cytosol but not in the glycogen/microsomal fraction.
Biochem Mol Biol Int 1995 Apr
PMID:Protein phosphatase type-1 mRNA levels in response to starvation-refeeding and streptozotocin-diabetes. 754 40

Dynamic regulation of ion transport is essential for homeostasis as cells confront changes in their environment. The gene HAL3 encodes a novel component of this regulatory circuit in the yeast Saccharomyces cerevisiae. Overexpression of HAL3 improves growth of wild-type cells exposed to toxic concentrations of sodium and lithium and suppresses the salt sensitivity conferred by mutation of the calcium-dependent protein phosphatase calcineurin. Null mutants of HAL3 display salt sensitivity. The sequence of HAL3 gives little clue to its function. However, alterations in intracellular cation concentrations associated with changes in HAL3 expression suggest that HAL3 activity may directly increase cytoplasmic K+ and decrease Na+ and Li+. Cation efflux in S. cerevisiae is mediated by the P-type ATPase encoded by the ENA1/PMR24 gene, a putative plasma membrane Na+ pump whose expression is salt induced. Acting in concert with calcineurin, HAL3 is necessary for full activation of ENA1 expression. This functional complementarity is also reflected in the participation of both proteins in recovery from alpha-factor-induced growth arrest. Recently, HAL3 was isolated as a gene (named SIS2) which when overexpressed partially relieves loss of transcription of G1 cyclins in mutants lacking the protein phosphatase Sit4p. Therefore, HAL3 influences cell cycle control and ion homeostasis, acting in parallel to the protein phosphatases Sit4p and calcineurin.
Mol Cell Biol 1995 Oct
PMID:Regulation of cation transport in Saccharomyces cerevisiae by the salt tolerance gene HAL3. 756 98

1,3-beta-D-Glucan is a major structural polymer of yeast and fungal cell walls and is synthesized from UDP-glucose by the multisubunit enzyme 1,3-beta-D-glucan synthase. Previous work has shown that the FKS1 gene encodes a 215-kDa integral membrane protein (Fks1p) which mediates sensitivity to the echinocandin class of antifungal glucan synthase inhibitors and is a subunit of this enzyme. We have cloned and sequenced FKS2, a homolog of FKS1 encoding a 217-kDa integral membrane protein (Fks2p) which is 88% identical to Fks1p. The residual glucan synthase activity present in strains with deletions of fks1 is (i) immunodepleted by antibodies prepared against FKS2 peptides, demonstrating that Fks2p is also a component of the enzyme, and (ii) more sensitive to the echinocandin L-733,560, explaining the increased sensitivity of fks1 null mutants to this drug. Simultaneous disruption of FKS1 and FKS2 is lethal, suggesting that Fks1p and Fks2p are alternative subunits with essential overlapping function. Analysis of FKS1 and FKS2 expression reveals that transcription of FKS1 is regulated in the cell cycle and predominates during growth on glucose, while FKS2 is expressed in the absence of glucose. FKS2 is essential for sporulation, a process which occurs during nutritional starvation. FKS2 is induced by the addition of Ca2+ to the growth medium, and this induction is completely dependent on the Ca2+/calmodulin-dependent phosphoprotein phosphatase calcineurin. We have previously shown that growth of fks1 null mutants is highly sensitive to the calcineurin inhibitors FK506 and cyclosporin A. Expression of FKS2 from the heterologous ADH1 promoter results in FK506-resistant growth. Thus, the sensitivity of fks1 mutants to these drugs can be explained by the calcineurin-dependent transcription of FKS2. Moreover, FKS2 is also highly induced in response to pheromone in a calcineurin-dependent manner, suggesting that FKS2 may also play a role in the remodeling of the cell wall during the mating process.
Mol Cell Biol 1995 Oct
PMID:Differential expression and function of two homologous subunits of yeast 1,3-beta-D-glucan synthase. 756 18

The MPK1 (SLT2) gene of Saccharomyces cerevisiae encodes a mitogen-activated protein kinase that is regulated by a kinase cascade whose known elements are Pkc1 (a homolog of protein kinase C), Bck1 (Slk1) (a homolog of MEK kinase), and the functionally redundant Mpk1 activators Mkk1 and Mkk2 (homologs of MEK). An activated mutation of MKK1, MKK1P386, inhibits growth when overexpressed. This growth-inhibitory effect was suppressed by the mpk1 delta mutation, suggesting that hyperactivation of the Mpk1 pathway is toxic to cells. To search for genes that interact with the Mpk1 pathway, we isolated both chromosomal mutations and dosage suppressor genes that ameliorate the growth-inhibitory effect of overexpressed Mkk1P386. One of the genes identified by the analysis of chromosomal mutations is RLM1 (resistance to lethality of MKK1P386 overexpression), which encodes a protein homologous to a conserved domain of the MADS (Mcm1, Agamous, Deficiens, and serum response factor) box family of transcription factors. Although rlm1 delta cells grow normally at any temperature, they display a caffeine-sensitive phenotype similar to that observed in mutants defective in BCK1, MKK1/MKK2, or MPK1. A gene fusion that provides Rlm1 with a transcriptional activation domain of Gal4 suppresses bck1 delta and mpk1 delta. A screening for dosage suppressors yielded the MSG5 genes, which encode a dual-specificity protein phosphatase. Our results suggest that Rlm1 functions as a transcription factor downstream of Mpk1 that is subject to activation by the Mpk1 mitogen-activated protein kinase pathway.
Mol Cell Biol 1995 Oct
PMID:Yeast RLM1 encodes a serum response factor-like protein that may function downstream of the Mpk1 (Slt2) mitogen-activated protein kinase pathway. 756 26

The Ipl1 protein kinase is essential for proper chromosome segregation and cell viability in the budding yeast Saccharomyces cerevisiae. We have previously shown that the temperature-sensitive growth phenotype of conditional ipl1-1ts mutants can be suppressed by a partial loss-of-function mutation in the GLC7 gene, which encodes the catalytic subunit (PP1C) of protein phosphatase 1, thus suggesting that this enzyme acts in opposition to the Ipl1 protein kinase in regulating yeast chromosome segregation. We report here that the Glc8 protein, which is related in primary sequence to mammalian inhibitor 2, also participates in this regulation. Like inhibitor 2, the Glc8 protein is heat stable, exhibits anomalous electrophoretic mobility, and functions in vitro as an inhibitor of yeast as well as rabbit skeletal muscle PP1C. Interestingly, overexpression as well as deletion of the GLC8 gene results in a partial suppression of the temperature-sensitive growth phenotype of ipl1ts mutants and also moderately reduces the amount of protein phosphatase 1 activity which is assayable in crude yeast lysates. In addition, the chromosome missegregation phenotype caused by an increase in the dosage of GLC7 is totally suppressed by the glc8-delta 101::LEU2 deletion mutation. These findings together suggest that the Glc8 protein is involved in vivo in the activation of PP1C and that when the Glc8 protein is overproduced, it may also inhibit PP1C function. Furthermore, site-directed mutagenesis studies of GLC8 suggest that Thr-118 of the Glc8 protein, which is equivalent to Thr-72 of inhibitor 2, may play a central role in the ability of this protein to activate and/or inhibit PP1C in vivo.
Mol Cell Biol 1995 Nov
PMID:Regulation of chromosome segregation by Glc8p, a structural homolog of mammalian inhibitor 2 that functions as both an activator and an inhibitor of yeast protein phosphatase 1. 756 59

The regulatory G-subunit of the glycogen-associated form of protein phosphatase 1 (PP1) plays a crucial part in muscle tissue glycogen synthesis and breakdown. As impaired insulin stimulated glycogen synthesis in peripheral tissues is considered to be a pathogenic factor in subsets of non-insulin-dependent diabetes mellitus (NIDDM) and obesity, the G-subunit of PP1 should be viewed as a candidate gene for inherited insulin resistance. When applying heteroduplex formation analysis and nucleotide sequencing of PP1G-subunit cDNA from 30 insulin resistant white NIDDM patients two cases were identified as heterozygous carriers of an Asp905 --> Tyr substitution. The carrier prevalence of the PP1G-subunit variant was 18% in 150 healthy subjects and 13% in 313 NIDDM subjects (chi 2 = 1.94, p = 0.16). Twenty-seven healthy subjects volunteered for a 4 h euglycaemic, hyperinsulinaemic clamp in combination with indirect calorimetry in order to elucidate the potential impact of the Tyr905 substitution on the whole body glucose metabolism. Interestingly, the Tyr905 variant was associated with altered routing of glucose: a decreased insulin stimulated non-oxidative glucose metabolism of peripheral tissues (glycogen synthesis) (p < 0.04) and an increased basal glucose oxidation rate (p < 0.04) when compared with wild type carriers. A population-based sample of 380 unrelated young healthy Caucasians was examined during a combined intravenous glucose and tolbutamide test to address whether the Asp905/Tyr905 polymorphism was associated with alterations in insulin secretion which might be secondary to the insulin resistance of skeletal muscle.(ABSTRACT TRUNCATED AT 250 WORDS)
Hum Mol Genet 1995 Aug
PMID:A widespread amino acid polymorphism at codon 905 of the glycogen-associated regulatory subunit of protein phosphatase-1 is associated with insulin resistance and hypersecretion of insulin. 758 68

Stimulation of the T-cell antigen receptor (TCR) induces activation of multiple tyrosine kinases, resulting in phosphorylation of numerous intracellular substrates. One substrate is p95vav, which is expressed exclusively in hematopoietic and trophoblast cells. It contains a number of structural motifs, including Src homology 2, Src homology 3, and pleckstrin homology domains and a putative guanine nucleotide exchange domain. The role of p95vav in TCR-mediated signaling processes is unclear. Here, we show that overexpression of p95vav alone in Jurkat T cells leads to activation of the nuclear factors, including NFAT, involved in interleukin-2 expression. Furthermore, p95vav synergizes with TCR stimulation in inducing NFAT- and interleukin-2-dependent transcription. In contrast, NFAT activation by a G-protein-coupled receptor is not modulated by p95vav overexpression, suggesting that the effect is specific to the TCR signaling pathways. Although removal of the first 67 amino acids of p95vav activates its transforming potential in NIH 3T3 cells, this region appears to be required for its function in T cells. We further demonstrate that the p95vav-induced NFAT activation is not mimicked by Ras activation, though its function is dependent upon Ras and Raf. Furthermore, the activating function of p95vav is blocked by FK506, suggesting that its activity also depends on calcineurin. To further dissect p95vav involvement in TCR signaling, we analyzed various Jurkat mutants deficient in TCR signaling function or TCR expression and showed that an intact TCR signaling pathway is required for p95vav to function. However, overexpression of p95vav does not appear to influence TCR-induced protein tyrosine phosphorylation or increases in cytoplasmic free calcium. Taken together, our data suggest that p95vav plays an important role at an yet unidentified proximal position in the TCR signaling cascade.
Mol Cell Biol 1995 Aug
PMID:A functional T-cell receptor signaling pathway is required for p95vav activity. 762 28

The Cdc2 protein kinase is a key regulator of the G1-S and G2-M cell cycle transitions in the fission yeast Schizosaccharomyces pombe. The activation of Cdc2 at the G2-M transition is triggered by dephosphorylation at a conserved tyrosine residue Y15. The level of Y15 phosphorylation is controlled by the Wee1 and Mik1 protein kinases acting in opposition to the Cdc25 protein phosphatase. Here, we demonstrate that Wee1 overexpression leads to a high stoichiometry of phosphorylation at a previously undetected site in S. pombe Cdc2, T14. T14 phosphorylation was also detected in certain cell cycle mutants blocked in progression through S phase, indicating that T14 phosphorylation might normally occur at low stoichiometry during DNA replication or early G2. Strains in which the chromosomal copy of cdc2 was replaced with either a T14A or a T14S mutant allele were generated and the phenotypes of these strains are consistent with T14 phosphorylation playing an inhibitory role in the activation of Cdc2 as it does in higher eukaryotes. We have also obtained evidence that Wee1 but not Mik1 or Chk1 is required for phosphorylation at this site, that the Mik1 and Chk1 protein kinases are unable to drive T14 phosphorylation in vivo, that residue 14 phosphorylation requires previous phosphorylation at Y15, and that the T14A mutant, unlike Y15F, is recessive to wild-type Cdc2 activity. Finally, the normal duration of G2 delay after irradiation or hydroxyurea treatment in a T14A mutant strain indicates that T14 phosphorylation is not required for the DNA damage or replication checkpoint controls.
Mol Biol Cell 1995 Apr
PMID:The Wee1 protein kinase regulates T14 phosphorylation of fission yeast Cdc2. 762 4


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