Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.16 (calcineurin)
 17,112 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel serine/threonine protein phosphatase (PPase) designated PP7 was identified from cDNA produced from human retina RNA. PP7 has a molecular mass of approximately 75 kDa, and the deduced amino acid sequence of PP7 contains a phosphatase catalytic core domain that possesses all of the invariant motifs of the PP1, PP2A, PP2B, PP4, PP5, and PP6 gene family. However, PP7 has unique N- and C-terminal regions and shares < 35% identity with the other known PPases. The unique C-terminal region of PP7 contains multiple Ca2+ binding sites (i.e. EF-hand motifs). This region of PP7 is similar to the Drosophila retinal degeneration C gene product (rdgC), and PP7 and rdgC share 42.1% identity. Unlike the other known PPases, the expression of PP7 is not ubiquitous; PP7 was only detected in retina and retinal-derived Y-79 retinoblastoma cells. Expression of recombinant human PP7 in baculovirus-infected SF21 insect cells produces an active soluble enzyme that is capable of utilizing phosphohistone and p-nitrophenyl phosphate as substrates. The activity of recombinant PP7 is dependent on Mg2+ and is activated by calcium (IC50 approximately equal to 250 microM). PP7 is not affected by calmodulin and is insensitive to inhibition by okadaic acid, microcystin-LR, calyculin A, and cantharidin.
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PMID:Molecular cloning, expression, and characterization of a novel human serine/threonine protein phosphatase, PP7, that is homologous to Drosophila retinal degeneration C gene product (rdgC). 943 Jun 83

Over 100 distinct retinoschisis gene (RS1) mutations, of which approximately 10% are single exon deletions, have been described to date. In this paper we have characterized in detail two dissimilar RS1 gene deletions which are accountable for RS in one-third of Danish patients. First, a 136 kb deletion, spanning from the 5' region of the RS1 gene to intron 3, was identified. Unexpectedly this large deletion abolishes exons of three adjacent genes: serine-threonine phosphatase gene (PPEF-1)/serine-threonine protein phosphatase gene (PP7), retinoschisis gene (RS1), and serine-threonine kinase gene (STK9). We demonstrate that the RS1 and STK9 genes are partly overlapping and the sequences of the PP7 and PPEF-1 genes are identical. This is the first study which reports of retinoschisis patients who also suffer from deletions in genes adjacent to RS1. The 136 kb deletion is also the first gross deletion of the retinoschisis gene deleting three exons. It results from a recombination between two repetitive sequences of the Alu family, one in 5' region of the RS1 gene and the other in RS1 intron 3. The second alteration, the actual Danish RS founder mutation, is a 4.4 kb noncontiguous two-part deletion composed of two deleted 1.5 and 2.9 kb segments, separated by an intact 1.2 kb segment. It extends from the 5' flanking region of the retinoschisis gene to RS intron 1. RS1 gene deletions of this type have not been identified previously. Despite these two unique deletions, which either lead to severely defective transcription or total absence of the retinoschisin and PPEF-1 protein, all the patients have a typical retinoschisis phenotype.
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PMID:Characterization of two unusual RS1 gene deletions segregating in Danish retinoschisis families. 1101 41

Changes in the cytoplasmic inorganic phosphate (P(i)) concentrations are an important cue for the plant cells to regulate their metabolism and phosphate homeostasis. However, phosphate sensors/receptors involved in this regulation are largely unknown. P(i) is a common nonspecific competitive inhibitor of phosphatases, usually in millimolar range. Here we report a procedure to refold recombinant Arabidopsis thaliana protein Ser/Thr phosphatase PP7 and demonstrate that PP7 is inhibited by submillimolar P(i) concentrations (IC(50) = 0.66 +/- 0.14 mM) via a mainly noncompetitive mechanism. The results indicate that PP7 may possess a specific P(i)-binding site responsible for its allosteric regulation, and suggest a possible phosphate sensor function for this protein phosphatase.
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PMID:Noncompetitive inhibition of plant protein Ser/Thr phosphatase PP7 by phosphate. 1132 72

PP7, a recently identified protein Ser/Thr phosphatase of the PPP family distantly related to phosphatases PP5/PPT and PPEF/rdgC, was purified from cauliflower extracts to apparent homogeneity. Purified cauliflower PP7 and recombinant PP7 expressed in Escherichia coli exhibit light absorption in the visible range with a maximum at approximately 430 nm. Under nonreducing conditions, native PP7 exists as a mixture of monomer with an intramolecular disulfide bridge, disulfide-linked homodimer, and possibly disulfide-linked complexes with potential partner proteins. The activity of recombinant Arabidopsis thaliana PP7 is reversibly regulated by redox agents. The results demonstrate the existence of PP7 protein in planta and suggest a possibility of redox regulation of this protein phosphatase.
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PMID:Purification of plant protein phosphatase PP7 and evidence for its redox regulation. 1171 63

We have recently identified PP7, a novel group of plant protein Ser/Thr phosphatases, and hypothesized that PP7 may possess a calmodulin-binding site. To test this hypothesis, we assessed the effect of calmodulin on the activity of recombinant Arabidopsis thaliana PP7 and directly tested interaction between PP7 and calmodulin using surface plasmon resonance. Calmodulin exerted a moderate inhibitory effect on the phosphatase activity of PP7 with submicromolar affinity. PP7 specifically interacted with immobilized calmodulin (but not with recoverin, another EF hand Ca(2+)-binding protein) in a strictly Ca(2+)-dependent manner with nanomolar affinity. Deletion of an insert in the catalytic domain of PP7, predicted to function as a calmodulin-binding site, greatly decreased PP7 binding to calmodulin. These findings provide the first evidence for a plant protein phosphatase directly interacting with calmodulin and indicate that PP7 might be regulated by Ca(2+) levels in vivo.
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PMID:Interaction of plant protein Ser/Thr phosphatase PP7 with calmodulin. 1171 23

Regulation of protein dephosphorylation by cytoplasmic Ca(2+) levels and calmodulin (CaM) is well established and considered to be mediated solely by calcineurin. Yet, recent identification of protein phosphatases with EF-hand domains (PPEF/rdgC) point to the existence of another group of Ca(2+)-dependent protein phosphatases. We have recently hypothesised that PPEF/rdgC phosphatases might possess CaM-binding sites of the IQ-type in their N-terminal domains. We now employed yeast two-hybrid system and surface plasmon resonance (SPR) to test this hypothesis. We found that entire human PPEF2 interacts with CaM in the in vivo tests and that its N-terminal domain binds to CaM in a Ca(2+)-dependent manner with nanomolar affinity in vitro. The fragments corresponding to the second exons of PPEF1 and PPEF2, containing the IQ motifs, are sufficient for specific Ca(2+)-dependent interaction with CaM both in vivo and in vitro. These findings demonstrate the existence of mammalian CaM-binding protein Ser/Thr phosphatases distinct from calcineurin and suggest that the activity of PPEF phosphatases may be controlled by Ca(2+) in a dual way: via C-terminal Ca(2+)-binding domain and via interaction of the N-terminal domain with CaM.
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PMID:Protein Ser/Thr phosphatases PPEF interact with calmodulin. 1205 65

The psi2 mutant of Arabidopsis displays amplification of the responses controlled by the red/far red light photoreceptors phytochrome A (phyA) and phytochrome B (phyB) but no apparent defect in blue light perception. We found that loss-of-function alleles of the protein phosphatase 7 (AtPP7) are responsible for the light hypersensitivity in psi2 demonstrating that AtPP7 controls the levels of phytochrome signaling. Plants expressing reduced levels of AtPP7 mRNA display reduced blue-light induced cryptochrome signaling but no noticeable deficiency in phytochrome signaling. Our genetic analysis suggests that phytochrome signaling is enhanced in the AtPP7 loss of function alleles, including in blue light, which masks the reduced cryptochrome signaling. AtPP7 has been found to interact both in yeast and in planta assays with nucleotide-diphosphate kinase 2 (NDPK2), a positive regulator of phytochrome signals. Analysis of ndpk2-psi2 double mutants suggests that NDPK2 plays a critical role in the AtPP7 regulation of the phytochrome pathway and identifies NDPK2 as an upstream element involved in the modulation of the salicylic acid (SA)-dependent defense pathway by light. Thus, cryptochrome- and phytochrome-specific light signals synchronously control their relative contribution to the regulation of plant development. Interestingly, PP7 and NDPK are also components of animal light signaling systems.
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PMID:The protein phosphatase 7 regulates phytochrome signaling in Arabidopsis. 1862 57

PPP protein phosphatases are an important enzyme family involved in a variety of aspects of cellular signalling and metabolism. PPPs are ubiquitous in eukaryotes, and are also present in many bacteria. Canonical eukaryotic PPP phosphotases are represented by five major subfamilies (PP1, PP2A, calcineurin, PP5 and PPEF/PP7). We previously reported that three "bacterial-like" PPP groups span the prokaryote-eukaryote boundary, including "Shewanella-like" phosphatases (Shelphs), which are in the focus of this study. Here we predict possible biological functions and functional partners of Shelphs by examining composition of bacterial operons and expression data for eukaryotes available in public databases. In Arabidopsis thaliana, the predicted possible roles include light-dependent regulation of chloroplast functions, signalling between the nucleus and the chloroplast, and defence responses. In Plasmodium falciparum, Shelphs are predicted to be associated with host cell invasion. One isoform has been located in the apical complex, essential for the interaction with the host cell. This makes P. falciparum Shelphs obvious potential candidates for therapeutic targets. Shelphs are also present in bacteria that constitute a considerable proportion of symbiotic microflora in humans. The predicted involvement of bacterial Shelphs in sensing and import of nutrients and extrusion of toxins may be relevant to the links between physiology of humans and our symbionts. Thus, despite the absence of Shelphs in animals, including humans, they may have a direct relationship to human health. Some predicted biological processes and potential functional partners of Shelphs are common between different bacterial and/or eukaryotic lineages, suggesting evolutionary conservation of some Shelph regulatory modules.
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PMID:Prediction of biological functions of Shewanella-like protein phosphatases (Shelphs) across different domains of life. 2196 Feb 77

A "tug-of-war" between kinases and phosphatases establishes the phosphorylation states of proteins. While serine and threonine phosphorylation can be catalyzed by more than 400 protein kinases, the majority of serine and threonine dephosphorylation is carried out by seven phosphoprotein phosphatases (PPPs). The PPP family consists of protein phosphatases 1 (PP1), 2A (PP2A), 2B (PP2B), 4 (PP4), 5 (PP5), 6 (PP6), and 7 (PP7). The imbalance in numbers between serine- and threonine-directed kinases and phosphatases led to the early belief that PPPs are unspecific and that kinases are the primary determinants of protein phosphorylation. However, it is now clear that PPPs achieve specificity through association with noncatalytic subunits to form multimeric holoenzymes, which expands the number of functionally distinct signaling entities to several hundred. Although there has been great progress in deciphering signaling by kinases, much less is known about phosphatases.We have developed a chemical proteomic strategy for the systematic interrogation of endogenous PPP catalytic subunits and their interacting proteins, including regulatory and scaffolding subunits (the "PPPome"). PP1, PP2A, PP4, PP5, and PP6 were captured using an immobilized, specific but nonselective PPP inhibitor microcystin-LR (MCLR), followed by protein identification by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in a single analysis. Here, we combine this approach of phosphatase inhibitor bead profiling and mass spectrometry (PIB-MS) with label-free and tandem mass tag (TMT) quantification to map the PPPome in human cancer cell lines, mouse tissues, and yeast species, through which we identify cell- and tissue-type-specific PPP expression patterns and discover new PPP interacting proteins.
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PMID:A Quantitative Chemical Proteomic Strategy for Profiling Phosphoprotein Phosphatases from Yeast to Humans. 3022 94

Transposable elements (TEs) are DNA repeats that must remain silenced to ensure cell integrity. Several epigenetic pathways including DNA methylation and histone modifications are involved in the silencing of TEs, and in the regulation of gene expression. In Arabidopsis thaliana, the TE-derived plant mobile domain (PMD) proteins have been involved in TE silencing, genome stability, and control of developmental processes. Using a forward genetic screen, we found that the PMD protein MAINTENANCE OF MERISTEMS (MAIN) acts synergistically and redundantly with DNA methylation to silence TEs. We found that MAIN and its close homolog MAIN-LIKE 1 (MAIL1) interact together, as well as with the phosphoprotein phosphatase (PPP) PP7-like (PP7L). Remarkably, main, mail1, pp7l single and mail1 pp7l double mutants display similar developmental phenotypes, and share common subsets of upregulated TEs and misregulated genes. Finally, phylogenetic analyses of PMD and PP7-type PPP domains among the Eudicot lineage suggest neo-association processes between the two protein domains to potentially generate new protein function. We propose that, through this interaction, the PMD and PPP domains may constitute a functional protein module required for the proper expression of a common set of genes, and for silencing of TEs.
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PMID:The plant mobile domain proteins MAIN and MAIL1 interact with the phosphatase PP7L to regulate gene expression and silence transposable elements in Arabidopsis thaliana. 3228 71


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