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  1. Article: The

    Pha, Khavong / Mirrashidi, Katherine / Sherry, Jessica / Tran, Cuong Joseph / Herrera, Clara M / McMahon, Eleanor / Elwell, Cherilyn A / Engel, Joanne N

    bioRxiv : the preprint server for biology

    2024  

    Abstract: Chlamydia trachomatis, ...

    Abstract Chlamydia trachomatis,
    Language English
    Publishing date 2024-04-24
    Publishing country United States
    Document type Preprint
    DOI 10.1101/2024.04.23.590830
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: The

    Herrera, Clara M / McMahon, Eleanor / Swaney, Danielle L / Sherry, Jessica / Pha, Khavong / Adams-Boone, Kathleen / Johnson, Jeffrey R / Krogan, Nevan J / Stevers, Meredith / Solomon, David / Elwell, Cherilyn / Engel, Joanne

    bioRxiv : the preprint server for biology

    2024  

    Abstract: Chlamydia trachomatis: Importance: Chlamydia ... ...

    Abstract Chlamydia trachomatis
    Importance: Chlamydia trachomatis
    Language English
    Publishing date 2024-02-26
    Publishing country United States
    Document type Preprint
    DOI 10.1101/2024.02.26.581999
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: Yersinia type III effectors perturb host innate immune responses.

    Pha, Khavong / Navarro, Lorena

    World journal of biological chemistry

    2016  Volume 7, Issue 1, Page(s) 1–13

    Abstract: The innate immune system is the first line of defense against invading pathogens. Innate immune cells recognize molecular patterns from the pathogen and mount a response to resolve the infection. The production of proinflammatory cytokines and reactive ... ...

    Abstract The innate immune system is the first line of defense against invading pathogens. Innate immune cells recognize molecular patterns from the pathogen and mount a response to resolve the infection. The production of proinflammatory cytokines and reactive oxygen species, phagocytosis, and induced programmed cell death are processes initiated by innate immune cells in order to combat invading pathogens. However, pathogens have evolved various virulence mechanisms to subvert these responses. One strategy utilized by Gram-negative bacterial pathogens is the deployment of a complex machine termed the type III secretion system (T3SS). The T3SS is composed of a syringe-like needle structure and the effector proteins that are injected directly into a target host cell to disrupt a cellular response. The three human pathogenic Yersinia spp. (Y. pestis, Y. enterocolitica, and Y. pseudotuberculosis) are Gram-negative bacteria that share in common a 70 kb virulence plasmid which encodes the T3SS. Translocation of the Yersinia effector proteins (YopE, YopH, YopT, YopM, YpkA/YopO, and YopP/J) into the target host cell results in disruption of the actin cytoskeleton to inhibit phagocytosis, downregulation of proinflammatory cytokine/chemokine production, and induction of cellular apoptosis of the target cell. Over the past 25 years, studies on the Yersinia effector proteins have unveiled tremendous knowledge of how the effectors enhance Yersinia virulence. Recently, the long awaited crystal structure of YpkA has been solved providing further insights into the activation of the YpkA kinase domain. Multisite autophosphorylation by YpkA to activate its kinase domain was also shown and postulated to serve as a mechanism to bypass regulation by host phosphatases. In addition, novel Yersinia effector protein targets, such as caspase-1, and signaling pathways including activation of the inflammasome were identified. In this review, we summarize the recent discoveries made on Yersinia effector proteins and their contribution to Yersinia pathogenesis.
    Language English
    Publishing date 2016-03-15
    Publishing country United States
    Document type Journal Article ; Review
    ZDB-ID 2564793-3
    ISSN 1949-8454
    ISSN 1949-8454
    DOI 10.4331/wjbc.v7.i1.1
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Early development of the root-knot nematode Meloidogyne incognita.

    Calderón-Urrea, Alejandro / Vanholme, Bartel / Vangestel, Sandra / Kane, Saben M / Bahaji, Abdellatif / Pha, Khavong / Garcia, Miguel / Snider, Alyssa / Gheysen, Godelieve

    BMC developmental biology

    2016  Volume 16, Page(s) 10

    Abstract: Background: Detailed descriptions of the early development of parasitic nematodes are seldom available. The embryonic development of the plant-parasitic nematode Meloidogyne incognita was studied, focusing on the early events.: Results: A fixed ... ...

    Abstract Background: Detailed descriptions of the early development of parasitic nematodes are seldom available. The embryonic development of the plant-parasitic nematode Meloidogyne incognita was studied, focusing on the early events.
    Results: A fixed pattern of repeated cell cleavages was observed, resulting in the appearance of the six founder cells 3 days after the first cell division. Gastrulation, characterized by the translocation of cells from the ventral side to the center of the embryo, was seen 1 day later. Approximately 10 days after the first cell division a rapidly elongating two-fold stage was reached. The fully developed second stage juvenile hatched approximately 21 days after the first cell division.
    Conclusions: When compared to the development of the free-living nematode Caenorhabditis elegans, the development of M. incognita occurs approximately 35 times more slowly. Furthermore, M. incognita differs from C. elegans in the order of cell divisions, and the early cleavage patterns of the germ line cells. However, cytoplasmic ruffling and nuclear migration prior to the first cell division as well as the localization of microtubules are similar between C. elegans and M. incognita.
    MeSH term(s) Animals ; Cell Division ; Cell Lineage ; Cell Nucleus/metabolism ; Cytoskeleton/metabolism ; DNA/metabolism ; Embryo, Nonmammalian/cytology ; Embryo, Nonmammalian/metabolism ; Embryonic Development ; Female ; Gastrulation ; Ovum/cytology ; Phylogeny ; Plant Roots/parasitology ; Tylenchoidea/cytology ; Tylenchoidea/embryology
    Chemical Substances DNA (9007-49-2)
    Language English
    Publishing date 2016-04-28
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 2041492-4
    ISSN 1471-213X ; 1471-213X
    ISSN (online) 1471-213X
    ISSN 1471-213X
    DOI 10.1186/s12861-016-0109-x
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Regulation of Yersinia protein kinase A (YpkA) kinase activity by multisite autophosphorylation and identification of an N-terminal substrate-binding domain in YpkA.

    Pha, Khavong / Wright, Matthew E / Barr, Tasha M / Eigenheer, Richard A / Navarro, Lorena

    The Journal of biological chemistry

    2014  Volume 289, Issue 38, Page(s) 26167–26177

    Abstract: The serine/threonine protein kinase YpkA is an essential virulence factor produced by pathogenic Yersinia species. YpkA is delivered into host mammalian cells via a type III secretion system and localizes to the inner side of the plasma membrane. We have ...

    Abstract The serine/threonine protein kinase YpkA is an essential virulence factor produced by pathogenic Yersinia species. YpkA is delivered into host mammalian cells via a type III secretion system and localizes to the inner side of the plasma membrane. We have previously shown that YpkA binds to and phosphorylates the α subunit of the heterotrimeric G protein complex, Gαq, resulting in inhibition of Gαq signaling. To identify residues in YpkA involved in substrate binding activity we generated GFP-YpkA N-terminal deletion mutants and performed coimmunoprecipitation experiments. We located a substrate-binding domain on amino acids 40-49 of YpkA, which lies within the previously identified membrane localization domain on YpkA. Deletion of amino acids 40-49 on YpkA interfered with substrate binding, substrate phosphorylation and substrate inhibition. Autophosphorylation regulates the kinase activity of YpkA. To dissect the mechanism by which YpkA transmits signals, we performed nano liquid chromatography coupled to tandem mass spectrometry to map in vivo phosphorylation sites. Multiple serine phosphorylation sites were identified in the secretion/translocation region, kinase domain, and C-terminal region of YpkA. Using site-directed mutagenesis we generated multiple YpkA constructs harboring specific serine to alanine point mutations. Our results demonstrate that multiple autophosphorylation sites within the N terminus regulate YpkA kinase activation, whereas mutation of serine to alanine within the C terminus of YpkA had no effect on kinase activity. YpkA autophosphorylation on multiple sites may be a strategy used by pathogenic Yersinia to prevent inactivation of this important virulence protein by host proteins.
    MeSH term(s) Bacterial Proteins/chemistry ; Bacterial Proteins/metabolism ; Catalytic Domain ; GTP-Binding Protein alpha Subunits, Gq-G11/metabolism ; HEK293 Cells ; Host-Pathogen Interactions ; Humans ; Phosphorylation ; Protein Binding ; Protein Processing, Post-Translational ; Protein-Serine-Threonine Kinases/chemistry ; Protein-Serine-Threonine Kinases/metabolism ; Signal Transduction ; Yersinia enterocolitica/enzymology
    Chemical Substances Bacterial Proteins ; ypkA protein, Yersinia (EC 2.7.1.-) ; Protein-Serine-Threonine Kinases (EC 2.7.11.1) ; GTP-Binding Protein alpha Subunits, Gq-G11 (EC 3.6.5.1)
    Language English
    Publishing date 2014-08-01
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2997-x
    ISSN 1083-351X ; 0021-9258
    ISSN (online) 1083-351X
    ISSN 0021-9258
    DOI 10.1074/jbc.M114.601153
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article: Cloning and characterization of a microsomal epoxide hydrolase from Heliothis virescens

    Kamita, Shizuo G / Yamamoto, Kohji / Dadala, Mary M / Pha, Khavong / Morisseau, Christophe / Escaich, Aurélie / Hammock, Bruce D

    Insect biochemistry and molecular biology. 2013 Mar., v. 43, no. 3

    2013  

    Abstract: Epoxide hydrolases (EHs) are α/β-hydrolase fold superfamily enzymes that convert epoxides to 1,2-trans diols. In insects EHs play critical roles in the metabolism of toxic compounds and allelochemicals found in the diet and for the regulation of ... ...

    Abstract Epoxide hydrolases (EHs) are α/β-hydrolase fold superfamily enzymes that convert epoxides to 1,2-trans diols. In insects EHs play critical roles in the metabolism of toxic compounds and allelochemicals found in the diet and for the regulation of endogenous juvenile hormones (JHs). In this study we obtained a full-length cDNA, hvmeh1, from the generalist feeder Heliothis virescens that encoded a highly active EH, Hv-mEH1. Of the 10 different EH substrates that were tested, Hv-mEH1 showed the highest specific activity (1180 nmol min⁻¹ mg⁻¹) for a 1,2-disubstituted epoxide-containing fluorescent substrate. This specific activity was more than 25- and 3900-fold higher than that for the general EH substrates cis-stilbene oxide and trans-stilbene oxide, respectively. Although phylogenetic analysis placed Hv-mEH1 in a clade with some lepidopteran JH metabolizing EHs (JHEHs), JH III was a relatively poor substrate for Hv-mEH1. Hv-mEH1 showed a unique substrate selectivity profile for the substrates tested in comparison to those of MsJHEH, a well-characterized JHEH from Manduca sexta, and hmEH, a human microsomal EH. Hv-mEH1 also showed unique enzyme inhibition profiles to JH-like urea, JH-like secondary amide, JH-like primary amide, and non-JH-like primary amide compounds in comparison to MsJHEH and hmEH. Although Hv-mEH1 is capable of metabolizing JH III, our findings suggest that this enzymatic activity does not play a significant role in the metabolism of JH in the caterpillar. The ability of Hv-mEH1 to rapidly hydrolyze 1,2-disubstituted epoxides suggests that it may play roles in the metabolism of fatty acid epoxides such as those that are commonly found in the diet of Heliothis.
    Keywords Heliothis virescens ; Manduca sexta ; allelochemicals ; complementary DNA ; diet ; enzyme activity ; enzyme inhibition ; epoxide hydrolase ; epoxides ; fatty acid metabolism ; humans ; insects ; juvenile hormones ; phylogeny ; toxicity ; urea
    Language English
    Dates of publication 2013-03
    Size p. 219-228.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 1483248-3
    ISSN 1879-0240 ; 0965-1748
    ISSN (online) 1879-0240
    ISSN 0965-1748
    DOI 10.1016/j.ibmb.2012.12.002
    Database NAL-Catalogue (AGRICOLA)

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  7. Article ; Online: Cloning and characterization of a microsomal epoxide hydrolase from Heliothis virescens.

    Kamita, Shizuo G / Yamamoto, Kohji / Dadala, Mary M / Pha, Khavong / Morisseau, Christophe / Escaich, Aurélie / Hammock, Bruce D

    Insect biochemistry and molecular biology

    2012  Volume 43, Issue 3, Page(s) 219–228

    Abstract: Epoxide hydrolases (EHs) are α/β-hydrolase fold superfamily enzymes that convert epoxides to 1,2-trans diols. In insects EHs play critical roles in the metabolism of toxic compounds and allelochemicals found in the diet and for the regulation of ... ...

    Abstract Epoxide hydrolases (EHs) are α/β-hydrolase fold superfamily enzymes that convert epoxides to 1,2-trans diols. In insects EHs play critical roles in the metabolism of toxic compounds and allelochemicals found in the diet and for the regulation of endogenous juvenile hormones (JHs). In this study we obtained a full-length cDNA, hvmeh1, from the generalist feeder Heliothis virescens that encoded a highly active EH, Hv-mEH1. Of the 10 different EH substrates that were tested, Hv-mEH1 showed the highest specific activity (1180 nmol min(-1) mg(-1)) for a 1,2-disubstituted epoxide-containing fluorescent substrate. This specific activity was more than 25- and 3900-fold higher than that for the general EH substrates cis-stilbene oxide and trans-stilbene oxide, respectively. Although phylogenetic analysis placed Hv-mEH1 in a clade with some lepidopteran JH metabolizing EHs (JHEHs), JH III was a relatively poor substrate for Hv-mEH1. Hv-mEH1 showed a unique substrate selectivity profile for the substrates tested in comparison to those of MsJHEH, a well-characterized JHEH from Manduca sexta, and hmEH, a human microsomal EH. Hv-mEH1 also showed unique enzyme inhibition profiles to JH-like urea, JH-like secondary amide, JH-like primary amide, and non-JH-like primary amide compounds in comparison to MsJHEH and hmEH. Although Hv-mEH1 is capable of metabolizing JH III, our findings suggest that this enzymatic activity does not play a significant role in the metabolism of JH in the caterpillar. The ability of Hv-mEH1 to rapidly hydrolyze 1,2-disubstituted epoxides suggests that it may play roles in the metabolism of fatty acid epoxides such as those that are commonly found in the diet of Heliothis.
    MeSH term(s) Amino Acid Sequence ; Animals ; Base Sequence ; Cloning, Molecular ; Epoxide Hydrolases/isolation & purification ; Epoxide Hydrolases/metabolism ; Humans ; Insect Proteins/isolation & purification ; Insect Proteins/metabolism ; Juvenile Hormones/metabolism ; Larva/enzymology ; Molecular Sequence Data ; Moths/enzymology ; Radioligand Assay ; Recombinant Proteins/isolation & purification ; Recombinant Proteins/metabolism ; Sequence Analysis, DNA ; Sequence Homology, Amino Acid
    Chemical Substances Insect Proteins ; Juvenile Hormones ; Recombinant Proteins ; Epoxide Hydrolases (EC 3.3.2.-)
    Language English
    Publishing date 2012-12-28
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 1483248-3
    ISSN 1879-0240 ; 0965-1748
    ISSN (online) 1879-0240
    ISSN 0965-1748
    DOI 10.1016/j.ibmb.2012.12.002
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article: Cloning and characterization of a microsomal epoxide hydrolase from Heliothis virescens

    Kamita, Shizuo G. / Yamamoto, Kohji / Dadala, Mary M. / Pha, Khavong / Morisseau, Christophe / Escaich, Aurélie / Hammock, Bruce D.

    Insect biochemistry and molecular biology

    Volume v. 43,, Issue no. 3

    Abstract: Epoxide hydrolases (EHs) are α/β-hydrolase fold superfamily enzymes that convert epoxides to 1,2-trans diols. In insects EHs play critical roles in the metabolism of toxic compounds and allelochemicals found in the diet and for the regulation of ... ...

    Abstract Epoxide hydrolases (EHs) are α/β-hydrolase fold superfamily enzymes that convert epoxides to 1,2-trans diols. In insects EHs play critical roles in the metabolism of toxic compounds and allelochemicals found in the diet and for the regulation of endogenous juvenile hormones (JHs). In this study we obtained a full-length cDNA, hvmeh1, from the generalist feeder Heliothis virescens that encoded a highly active EH, Hv-mEH1. Of the 10 different EH substrates that were tested, Hv-mEH1 showed the highest specific activity (1180 nmol min⁻¹ mg⁻¹) for a 1,2-disubstituted epoxide-containing fluorescent substrate. This specific activity was more than 25- and 3900-fold higher than that for the general EH substrates cis-stilbene oxide and trans-stilbene oxide, respectively. Although phylogenetic analysis placed Hv-mEH1 in a clade with some lepidopteran JH metabolizing EHs (JHEHs), JH III was a relatively poor substrate for Hv-mEH1. Hv-mEH1 showed a unique substrate selectivity profile for the substrates tested in comparison to those of MsJHEH, a well-characterized JHEH from Manduca sexta, and hmEH, a human microsomal EH. Hv-mEH1 also showed unique enzyme inhibition profiles to JH-like urea, JH-like secondary amide, JH-like primary amide, and non-JH-like primary amide compounds in comparison to MsJHEH and hmEH. Although Hv-mEH1 is capable of metabolizing JH III, our findings suggest that this enzymatic activity does not play a significant role in the metabolism of JH in the caterpillar. The ability of Hv-mEH1 to rapidly hydrolyze 1,2-disubstituted epoxides suggests that it may play roles in the metabolism of fatty acid epoxides such as those that are commonly found in the diet of Heliothis.
    Keywords diet ; phylogeny ; Manduca sexta ; fatty acid metabolism ; humans ; enzyme inhibition ; insects ; juvenile hormones ; urea ; toxicity ; epoxides ; allelochemicals ; enzyme activity ; complementary DNA ; epoxide hydrolase ; Heliothis virescens
    Language English
    Document type Article
    ISSN 0965-1748
    Database AGRIS - International Information System for the Agricultural Sciences and Technology

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