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John D. York - One of the best experts on this subject based on the ideXlab platform.

  • Biochemical Analysis of Inositol Phosphate Kinases
    Methods in Enzymology, 2020
    Co-Authors: James C. Otto, Sashidhar Mulugu, Peter C. Fridy, Shean-tai Chiou, Blaine N. Armbruster, Anthony A. Ribeiro, John D. York
    Abstract:

    Abstract Lipid-derived Inositol Phosphates (IPs) are a complex group of second messengers generated by the sequential phosphorylation of Inositol 1,4,5-trisPhosphate (IP 3 ). Synthetic pathways leading from IP 3 to the formation of Inositol tetrakisPhosphate IP 4 , Inositol pentakisPhosphate IP 5 , Inositol hexakisPhosphate IP 6 , and Inositol pyroPhosphates PP-IPs have been elucidated in eukaryotes from yeast to human. Studies have attributed a variety of cellular functions to IPs, highlighting the importance of understanding how the pathways for their synthesis are regulated. This chapter summarizes experimental techniques for the biochemical characterization of the key Inositol Phosphate kinases IPKs necessary for producing the diverse array of IP species.

  • Inositol Phosphate multikinase dependent transcriptional control
    Advances in biological regulation, 2017
    Co-Authors: Ace J Hatch, John D. York, Audrey R Odom
    Abstract:

    Abstract Production of lipid-derived Inositol Phosphates including IP4 and IP5 is an evolutionarily conserved process essential for cellular adaptive responses that is dependent on both phospholipase C and the Inositol Phosphate multikinase Ipk2 (also known as Arg82 and IPMK). Studies of Ipk2, along with Arg82 prior to demonstrating its IP kinase activity, have provided an important link between control of gene expression and IP metabolism as both kinase dependent and independent functions are required for proper transcriptional complex function that enables cellular adaptation in response to extracellular queues such as nutrient availability. Here we define a promoter sequence cis-element, 5′-CCCTAAAAGG-3′, that mediates both kinase-dependent and independent functions of Ipk2. Using a synthetic biological strategy, we show that proper gene expression in cells lacking Ipk2 may be restored through add-back of two components: IP4/IP5 production and overproduction of the MADS box DNA binding protein, Mcm1. Our results are consistent with a mechanism by which Ipk2 harbors a dual functionality that stabilizes transcription factor levels and enzymatically produces a small molecule code, which together coordinate control of biological processes and gene expression.

  • Inositol Phosphate kinase 2 is required for imaginal disc development in drosophila
    Proceedings of the National Academy of Sciences of the United States of America, 2015
    Co-Authors: Andrew M Seeds, John D. York, Marco M Tsui, Christine M Sunu, Eric P Spana
    Abstract:

    Inositol Phosphate kinase 2 (Ipk2), also known as IP multikinase IPMK, is an evolutionarily conserved protein that initiates production of Inositol Phosphate intracellular messengers (IPs), which are critical for regulating nuclear and cytoplasmic processes. Here we report that Ipk2 kinase activity is required for the development of the adult fruit fly epidermis. Ipk2 mutants show impaired development of their imaginal discs, the primordial tissues that form the adult epidermis. Although disk tissue seems to specify normally during early embryogenesis, loss of Ipk2 activity results in increased apoptosis and impairment of proliferation during larval and pupal development. The proliferation defect is in part attributed to a reduction in JAK/STAT signaling, possibly by controlling production or secretion of the pathway’s activating ligand, Unpaired. Constitutive activation of the JAK/STAT pathway downstream of Unpaired partially rescues the disk growth defects in Ipk2 mutants. Thus, IP production is essential for proliferation of the imaginal discs, in part, by regulating JAK/STAT signaling. Our work demonstrates an essential role for Ipk2 in producing inositide messengers required for imaginal disk tissue maturation and subsequent formation of adult body structures and provides molecular insights to signaling pathways involved in tissue growth and stability during development.

  • structural studies and protein engineering of Inositol Phosphate multikinase
    Journal of Biological Chemistry, 2012
    Co-Authors: Stuart Endostreeter, Mankin Marco Tsui, Audrey R Odom, Jeremy Block, John D. York
    Abstract:

    Abstract Inositol Phosphates (IPs) regulate vital processes in eukaryotes, and their production downstream of phospholipase C activation is controlled through a network of evolutionarily conserved kinases and phosphatases. Inositol Phosphate multikinase (IPMK, also called Ipk2 and Arg82) accounts for phosphorylation of IP3 to IP5, as well as production of several other IP molecules. Here, we report the structure of Arabidopsis thaliana IPMKα at 2.9 A and find it is similar to the yeast homolog Ipk2, despite 17% sequence identity, as well as the active site architecture of human IP3 3-kinase. Structural comparison and substrate modeling were used to identify a putative basis for IPMK selectivity. To test this model, we re-engineered binding site residues predicted to have restricted substrate specificity. Using steady-state kinetics and in vivo metabolic labeling studies in modified yeast strains, we observed that K117W and K117W:K121W mutants exhibited nearly normal 6-kinase function but harbored significantly reduced 3-kinase activity. These mutants complemented conditional nutritional growth defects observed in ipmk null yeast and, remarkably, suppressed lethality observed in ipmk null flies. Our data are consistent with the hypothesis that IPMK 6-kinase activity and production of Ins(1,4,5,6)P4 are critical for cellular signaling. Overall, our studies provide new insights into the structure and function of IPMK and utilize a synthetic biological approach to redesign Inositol Phosphate signaling pathways.

  • Inositol Phosphate synthesis and the nuclear processes they affect
    Current Opinion in Cell Biology, 2010
    Co-Authors: Jessica P Monserrate, John D. York
    Abstract:

    Recent studies have implicated Inositol Phosphates, a highly charged family of lipid-derived metabolites, in a slue of cellular processes. However, it is their involvement in nuclear events that has attracted much attention. Several IP molecules have been linked to gene regulatory factors, chromatin-remodeling complexes, mRNA export, and DNA repair machinery, yet in many instances direct mechanistic roles remain elusive. The purpose of this review is to cover the latest data gathered regarding only the nuclear roles of the various Inositol Phosphates while simultaneously providing a step-by-step tour of IP synthesis in eukaryotes.

S. Dalsgaard - One of the best experts on this subject based on the ideXlab platform.

  • interactions of phytate and myo Inositol Phosphate esters ip1 5 including ip5 isomers with dietary protein and iron and inhibition of pepsin
    Journal of Animal Science, 2012
    Co-Authors: A. Cowieson, C. Gilbert, P. Plumstead, Shi Yu, S. Dalsgaard
    Abstract:

    Phytic acid (IP6) and myo-Inositol Phosphate esters (IP1-5), including IP5 isomers prepared chemically and enzymatically with bacterial and fungal phytases, were examined for their effects on protein aggregation of soy protein and beta-casein, interaction with Fe3+, and pepsin activity. The results indicated that the aggregating capabilities of IP esters (IP1-6) on the 2 proteins decreased dramatically from IP6 to IP5 and became negligible with IP1-4. Among the IP5 isomers tested, InsP(5)(1,2,3,4,5) produced by 6-phytase was slightly less powerful in aggregating protein than InsP(5)(1,2,4,5,6) produced by 3-phytase (P = 0.001). For protein hydrolysis, IP esters of IP3-4 still showed inhibition of pepsin though to a lesser extent than IP5-6. The in vitro data with IP1-5 generated with microbial 3- and 6-phytases indicate that, for complete alleviation of pepsin inhibition, IP6 needs to be broken down to IP1-2. In contrast to the aggregation with protein, the reactivity of IP1-6 toward Fe3+ decreased proportionally from IP6 to IP3. Based on the radical decrease in turbidity of IP6-protein complex observed, as a result of IP6 dephosphorylation to IP5, a novel qualitative and semi-quantitative phytase plate assay was established using IP6-protein complex incorporated into an agarose petri-dish as substrate. Phytase activity was shown as the development of clear halos on the agarose plate with time. This simple phytase plate assay method can be used at animal farms, control laboratories, and even for the screening of engineered phytase variants. The current study, thus, stresses the importance of the efficient hydrolysis of IP6 at lower pH range to alleviate the negative effect of phytic acid and its degradation products on protein and Fe3+ digestion. (Less)

  • Interactions of phytate and myo-Inositol Phosphate esters (IP1-5) including IP5isomers with dietary protein and iron and inhibition of pepsin
    Journal of Animal Science, 2012
    Co-Authors: Shuanghe Yu, A. Cowieson, C. Gilbert, P. Plumstead, S. Dalsgaard
    Abstract:

    Phytic acid (IP(6)) and myo-Inositol Phosphate esters (IP(1-5)), including IP(5) isomers prepared chemically and enzymatically with bacterial and fungal phytases, were examined for their effects on protein aggregation of soy protein and β-casein, interaction with Fe(3+), and pepsin activity. The results indicated that the aggregating capabilities of IP esters (IP(1-6)) on the 2 proteins decreased dramatically from IP(6) to IP(5) and became negligible with IP(1-4). Among the IP(5) isomers tested, InsP(5)(1,2,3,4,5) produced by 6-phytase was slightly less powerful in aggregating protein than InsP(5)(1,2,4,5,6) produced by 3-phytase (P = 0.001). For protein hydrolysis, IP esters of IP(3-4) still showed inhibition of pepsin though to a lesser extent than IP(5-6). The in vitro data with IP(1-5) generated with microbial 3- and 6-phytases indicate that, for complete alleviation of pepsin inhibition, IP(6) needs to be broken down to IP(1-2.) In contrast to the aggregation with protein, the reactivity of IP(1-6) toward Fe(3+) decreased proportionally from IP(6) to IP(3.) Based on the radical decrease in turbidity of IP(6) -protein complex observed, as a result of IP(6) dephosphorylation to IP(5), a novel qualitative and semi-quantitative phytase plate assay was established using IP(6)-protein complex incorporated into an agarose petri-dish as substrate. Phytase activity was shown as the development of clear halos on the agarose plate with time. This simple phytase plate assay method can be used at animal farms, control laboratories, and even for the screening of engineered phytase variants. The current study, thus, stresses the importance of the efficient hydrolysis of IP(6) at lower pH range to alleviate the negative effect of phytic acid and its degradation products on protein and Fe(3+) digestion.

Stephen B. Shears - One of the best experts on this subject based on the ideXlab platform.

  • Defining signal transduction by Inositol Phosphates.
    Sub-cellular biochemistry, 2020
    Co-Authors: Stephen B. Shears, Huanchen Wang, Sindura B. Ganapathi, Nikhil A. Gokhale, Tobias M. H. Schenk, Jeremy D. Weaver, Angelika Zaremba, Yixing Zhou
    Abstract:

    Ins(1,4,5)P3 is a classical intracellular messenger: stimulus-dependent changes in its levels elicits biological effects through its release of intracellular Ca2+ stores. The Ins(1,4,5)P3 response is “switched off” by its metabolism to a range of additional Inositol Phosphates. These metabolites have themselves come to be collectively described as a signaling “family”. The validity of that latter definition is critically examined in this review. That is, we assess the strength of the hypothesis that Ins(1,4,5)P3 metabolites are themselves “classical” signals. Put another way, what is the evidence that the biological function of a particular Inositol Phosphate depends upon stimulus dependent changes in its levels? In this assessment, examples of an Inositol Phosphate acting as a cofactor (i.e. its function is not stimulus-dependent) do not satisfy our signaling criteria. We conclude that Ins(3,4,5,6)P4 is, to date, the only Ins(1,4,5)P3 metabolite that has been validated to act as a second messenger.

  • Inositol Phosphate Kinases and Phosphatases
    Encyclopedia of Biological Chemistry, 2020
    Co-Authors: Stephen B. Shears
    Abstract:

    This article provides an initial guide for those encountering the field of Inositol Phosphate metabolism for the first time. Information is provided on the nomenclature deployed in this field, and the catalytic activities of the enzymes that metabolize Inositol Phosphates are briefly introduced.

  • a short historical perspective of methods in Inositol Phosphate research
    Methods of Molecular Biology, 2020
    Co-Authors: Stephen B. Shears
    Abstract:

    The multitudinous Inositol Phosphate family elicits a wide range of molecular effects that regulate countless biological responses. In this review, I provide a methodological viewpoint of the manner in which key advances in the field of Inositol Phosphate research were made. I also note some of the considerable challenges that still lie ahead.

  • Inositol Phosphate kinases expanding the biological significance of the universal core of the protein kinase fold
    Advances in biological regulation, 2019
    Co-Authors: Stephen B. Shears, Huanchen Wang
    Abstract:

    Abstract The protein kinase family is characterized by substantial conservation of architectural elements that are required for both ATP binding and phosphotransferase activity. Many of these structural features have also been identified in homologous enzymes that phosphorylate a variety of alternative, non-protein substrates. A comparative structural analysis of these different kinase sub-classes is a portal to a greater understanding of reaction mechanisms, enzyme regulation, inhibitor-development strategies, and superfamily-level evolutionary relationships. To serve such advances, we review structural elements of the protein kinase fold that are conserved in the subfamily of Inositol Phosphate kinases (InsPKs) that share a PxxxDxKxG catalytic signature: Inositol 1,4,5-trisPhosphate kinase (IP3K), Inositol hexakisPhosphate kinase (IP6K), and Inositol polyPhosphate multikinase (IPMK). We describe conservation of the fundamental two-lobe kinase architecture: an N-lobe constructed upon an anti-parallel β-strand scaffold, which is coupled to a largely helical C-lobe by a single, adenine-binding hinge. This equivalency also includes a G-loop that embraces the β/γ-Phosphates of ATP, a transition-state stabilizing residue (Lys/His), and a Mg-positioning aspartate residue within a catalytic triad. Furthermore, we expand this list of conserved structural features to include some not previously identified in InsPKs: a ‘gatekeeper’ residue in the N-lobe, and an ‘αF’-like helix in the C-lobe that anchors two structurally-stabilizing, hydrophobic spines, formed from non-consecutive residues that span the two lobes. We describe how this wide-ranging structural homology can be exploited to develop lead inhibitors of IP6K and IPMK, by using strategies similar to those that have generated ATP-competing inhibitors of protein-kinases. We provide several examples to illustrate how such an approach could benefit human health.

  • structural features of human Inositol Phosphate multikinase rationalize its Inositol Phosphate kinase and phosphoinositide 3 kinase activities
    Journal of Biological Chemistry, 2017
    Co-Authors: Huanchen Wang, Stephen B. Shears
    Abstract:

    Abstract Human Inositol Phosphate multikinase (HsIPMK) critically contributes to intracellular signaling through its Inositol-1,4,5-trisPhosphate (Ins(1,4,5)P3) 3-kinase and phosphatidylInositol 4,5-bisPhosphate (PtdIns(4,5)P2) 3-kinase activities. This catalytic profile is not conserved; orthologs from Arabidopsis thaliana and Saccharomyces cerevisiae are predominantly Ins(1,4,5)P3 6-kinases, and the plant enzyme cannot phosphorylate PtdIns(4,5)P2. Therefore, crystallographic analysis of the yeast and plant enzymes, without bound Inositol Phosphates, do not structurally rationalize HsIPMK activities. Here, we present 1.6-A resolution crystal structures of HsIPMK in complex with either Ins(1,4,5)P3 or PtdIns(4,5)P2. The Ins(1,4,5)P3 headgroup of PtdIns(4,5)P2 binds in precisely the same orientation as free Ins(1,4,5)P3 itself, indicative of evolutionary optimization of 3-kinase activities against both substrates. We report on nucleotide binding between the separate N- and C-lobes of HsIPMK. The N-lobe exhibits a remarkable degree of conservation with protein kinase A (root mean square deviation = 1.8 A), indicating common ancestry. We also describe structural features unique to HsIPMK. First, we observed a constrained, horseshoe-shaped substrate pocket, formed from an α-helix, a 310 helix, and a recently evolved tri-proline loop. We further found HsIPMK activities rely on a preponderance of Gln residues, in contrast to the larger Lys and Arg residues in yeast and plant orthologs. These conclusions are supported by analyzing 14 single-site HsIPMK mutants, some of which differentially affect 3-kinase and 6-kinase activities. Overall, we structurally rationalize phosphorylation of Ins(1,4,5)P3 and PtdIns(4,5)P2 by HsIPMK.

Helena Santos - One of the best experts on this subject based on the ideXlab platform.

  • thermococcus kodakarensis mutants deficient in di myo Inositol Phosphate use aspartate to cope with heat stress
    Journal of Bacteriology, 2010
    Co-Authors: Nuno Borges, Rie Matsumi, Tadayuki Imanaka, Haruyuki Atomi, Helena Santos
    Abstract:

    Many of the marine microorganisms which are adapted to grow at temperatures above 80°C accumulate di-myo-Inositol Phosphate (DIP) in response to heat stress. This led to the hypothesis that the solute plays a role in thermoprotection, but there is a lack of definitive experimental evidence. Mutant strains of Thermococcus kodakarensis (formerly Thermococcus kodakaraensis), manipulated in their ability to synthesize DIP, were constructed and used to investigate the involvement of DIP in thermoadaptation of this archaeon. The solute pool of the parental strain comprised DIP, aspartate, and α-glutamate. Under heat stress the level of DIP increased 20-fold compared to optimal conditions, whereas the pool of aspartate increased 4.3-fold in response to osmotic stress. Deleting the gene encoding the key enzyme in DIP synthesis, CTP:Inositol-1-Phosphate cytidylyltransferase/CDP-Inositol:Inositol-1-Phosphate transferase, abolished DIP synthesis. Conversely, overexpression of the same gene resulted in a mutant with restored ability to synthesize DIP. Despite the absence of DIP in the deletion mutant, this strain exhibited growth parameters similar to those of the parental strain, both at optimal (85°C) and supraoptimal (93.7°C) temperatures for growth. Analysis of the respective solute pools showed that DIP was replaced by aspartate. We conclude that DIP is part of the strategy used by T. kodakarensis to cope with heat stress, and aspartate can be used as an alternative solute of similar efficacy. This is the first study using mutants to demonstrate the involvement of compatible solutes in the thermoadaptation of (hyper)thermophilic organisms.

  • bifunctional ctp Inositol 1 Phosphate cytidylyltransferase cdp Inositol Inositol 1 Phosphate transferase the key enzyme for di myo Inositol Phosphate synthesis in several hyper thermophiles
    Journal of Bacteriology, 2007
    Co-Authors: Marta V Rodrigues, Nuno Borges, Mafalda Henriques, Pedro Lamosa, Rita Ventura, Chantal Fernandes, Nuno Empadinhas, Christopher D Maycock, Milton S Da Costa, Helena Santos
    Abstract:

    The pathway for the synthesis of di-myo-Inositol-Phosphate (DIP) was recently elucidated on the basis of the detection of the relevant activities in cell extracts of Archaeoglobus fulgidus and structural characterization of products by nuclear magnetic resonance (NMR) (N. Borges, L. G. Goncalves, M. V. Rodrigues, F. Siopa, R. Ventura, C. Maycock, P. Lamosa, and H. Santos, J. Bacteriol. 188:8128-8135, 2006). Here, a genomic approach was used to identify the genes involved in the synthesis of DIP. Cloning and expression in Escherichia coli of the putative genes for CTP:L-myo-Inositol-1-Phosphate cytidylyltransferase and DIPP (di-myo-Inositol-1,3- Phosphate-1-Phosphate, a phosphorylated form of DIP) synthase from several (hyper)thermophiles (A. fulgi- dus, Pyrococcus furiosus, Thermococcus kodakaraensis, Aquifex aeolicus, and Rubrobacter xylanophilus) confirmed the presence of those activities in the gene products. The DIPP synthase activity was part of a bifunctional enzyme that catalyzed the condensation of CTP and L-myo-Inositol-1-Phosphate into CDP-L-myo-Inositol, as well as the synthesis of DIPP from CDP-L-myo-Inositol and L-myo-Inositol-1-Phosphate. The cytidylyltrans- ferase was absolutely specific for CTP and L-myo-Inositol-1-P; the DIPP synthase domain used only L-myo- Inositol-1-Phosphate as an alcohol acceptor, but CDP-glycerol, as well as CDP-L-myo-Inositol and CDP-D-myo- Inositol, were recognized as alcohol donors. Genome analysis showed homologous genes in all organisms known to accumulate DIP and for which genome sequences were available. In most cases, the two activities (L-myo-Inositol-1-P cytidylyltransferase and DIPP synthase) were fused in a single gene product, but separate genes were predicted in Aeropyrum pernix, Thermotoga maritima, and Hyperthermus butylicus. Additionally, using L-myo-Inositol-1-Phosphate labeled on C-1 with carbon 13, the stereochemical configuration of all the metab- olites involved in DIP synthesis was established by NMR analysis. The two Inositol moieties in DIP had different stereochemical configurations, in contradiction of previous reports. The use of the designation di-myo-Inositol-1,3-Phosphate is recommended to facilitate tracing individual carbon atoms through meta- bolic pathways.

  • accumulation of mannosylglycerate and di myo Inositol Phosphate by pyrococcus furiosus in response to salinity and temperature
    Applied and Environmental Microbiology, 1995
    Co-Authors: Ligia O Martins, Helena Santos
    Abstract:

    (sup13)C and (sup1)H nuclear magnetic resonance spectroscopy was used to identify and quantify organic solutes accumulated by the hyperthermophilic archaeon Pyrococcus furiosus in response to temperature and salinity. Di-myo-Inositol-Phosphate and 2-O-(beta)-mannosylglycerate were the major organic solutes accumulated in these cells. The total intracellular organic solutes increased significantly in response either to an increase in temperature or to an increase in salinity, but (beta)-mannosylglycerate accumulated mainly at high salinities, whereas the concentration of di-myo-Inositol-Phosphate increased dramatically at supraoptimal growth temperatures. Glutamate was present at concentrations detectable by nuclear magnetic resonance only in cells grown in low-salinity media. The intracellular levels of K(sup+) are clearly dependent on the salinity of the medium, and the concentrations of this cation are high enough to counterbalance the negative charges of (beta)-mannosylglycerate and di-myo-Inositol-Phosphate in the cell. The results presented here together with those previously reported for Pyrococcus woesei (S. Scholz, J. Sonnenbichler, W. Schafer, and R. Hensel, FEBS Lett. 306:239-242, 1992) strongly support a role for di-myo-Inositol-Phosphate in thermoprotection.

Philip W Majerus - One of the best experts on this subject based on the ideXlab platform.

  • the human homolog of the rat Inositol Phosphate multikinase is an Inositol 1 3 4 6 tetrakisPhosphate 5 kinase
    Journal of Biological Chemistry, 2002
    Co-Authors: Shaochun Chang, A L Miller, Yucheng Feng, Susan R Wente, Philip W Majerus
    Abstract:

    Abstract We have demonstrated that the human homolog of the rat Inositol Phosphate multikinase is an Inositol 1,3,4,6-tetrakisPhosphate 5-kinase (InsP4 5-kinase). The cDNA of the human gene contained a putative open reading frame of 1251 bp encoding 416 amino acids with 83.6% identity compared with the rat protein. The substrate specificity of the recombinant human protein demonstrated preference for Ins(1,3,4,6)P4 with a catalytic efficiency (V max/Km ) 43-fold greater than that of Ins(1,3,4,5)P4 and 2-fold greater than that of Ins(1,4,5)P3. The apparentV max was 114 nmol of Ins(1,3,4,5,6)P5 formed/min/mg of protein, and the apparentKm was 0.3 μmIns(1,3,4,6)P4. The functional homolog in yeast is Ipk2p, and ipk2-null yeast strains do not synthesize Ins(1,3,4,5,6)P5 or InsP6. Synthesis of these compounds was restored by transformation with wild-type yeastIPK2 but not with human InsP4 5-kinase. Thus the human gene does not complement for the loss of the yeast gene because yeast cells do not contain the substrate Ins(1,3,4,6)P4, and the reaction of the human protein with Ins(1,3,4,5)P4 is insufficient to effect rescue or synthesis of InsP5 and InsP6. Therefore the major activity of human InsP4 5-kinase is phosphorylation at the D-5 position, and the pathways for synthesis of Ins(1,3,4,5,6)P5 in yeast versus humans are different.

  • sopb a protein required for virulence of salmonella dublin is an Inositol Phosphate phosphatase
    Proceedings of the National Academy of Sciences of the United States of America, 1998
    Co-Authors: F A Norris, Monita P Wilson, Timothy S Wallis, Edouard E Galyov, Philip W Majerus
    Abstract:

    Several proteins secreted by enteric bacteria are thought to contribute to virulence by disturbing the signal transduction of infected cells. Here, we report that SopB, a protein secreted by Salmonella dublin, has sequence homology to mammalian Inositol polyPhosphate 4-phosphatases and that recombinant SopB has Inositol Phosphate phosphatase activity in vitro. SopB hydrolyzes phosphatidylInositol 3,4,5-trisPhosphate, an inhibitor of Ca2+-dependent chloride secretion. In addition, SopB hydrolyzes Inositol 1,3,4,5,6 pentakisPhosphate to yield Inositol 1,4,5,6-tetrakisPhosphate, a signaling molecule that increases chloride secretion indirectly by antagonizing the inhibition of chloride secretion by phosphatidylInositol 3,4,5-trisPhosphate [Eckmann, L., Rudolf, M. T., Ptasznik, A., Schultz, C., Jiang, T., Wolfson, N., Tsien, R., Fierer, J., Shears, S. B., Kagnoff, M. F., et al. (1997) Proc. Natl. Acad. Sci. USA 94, 14456–14460]. Mutation of a conserved cysteine that abolishes phosphatase activity of SopB results in a mutant strain, S. dublin SB c/s, with decreased ability to induce fluid secretion in infected calf intestine loops. Moreover, HeLa cells infected with S. dublin SB c/s do not accumulate high levels of Inositol 1,4,5,6-tetrakisPhosphate that are characteristic of wild-type S. dublin-infected cells. Therefore, SopB mediates virulence by interdicting Inositol Phosphate signaling pathways.

  • Inositol Phosphate biochemistry
    Annual Review of Biochemistry, 1992
    Co-Authors: Philip W Majerus
    Abstract:

    PERSPECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 C ONVENTIONAL PHOSPHA TIDYLIN OSITOLS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 PHOSPHOLIPASE C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . 227 ACTIVATION Of PHOSPHOLIPASE C BY GaQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .. . 227 ACTIVATI ON OF PLCy BY TYR OSINE PHOSPHORYLATI ON . . . . . . . . . . . . . . . . . . . . . . . . 229 Inositol POLYPhosphate 5-PHOSPHATASE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1 INS ( 1 ,4,5)P3 3·KINASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 Inositol POLYPhosphate I·PHOSPHATASE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 Inositol POLYPhosphate 4·PHOSPHATASE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 Inositol P OLYPhosphate 3·PHOSPHATASE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 Inositol M ON OPHOSP HATA SE . . . . . . . . . . . .. . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 236 Inositol ( 1 :2 CYCLIC) Phosphate 2 PHOSPHOHYDROLASE AND IN OSITOL CYCLIC PhosphateS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 OTHER ENZYMES OF IN OSITOL Phosphate METAB OLISM . . . . . . . . . . . . . . . . . . . . . . . 238 IN OSITOL PENTAPhosphate AN D HE XAPhosphate METAB OLISM . . . . . . . . . . 238 IN OSITOL Phosphate-BIN DIN G PROTEINS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 PHOSPHATIDYLInositol 3·Phosphate PATHWAy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242