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Sensing of Host Cell Contact by the Pseudomonas aeruginosa Type III Secretion System

Armentrout, Erin I
http://orcid.org/0000-0002-7502-5427
http://rave.ohiolink.edu/etdc/view?acc_num=case1499965816504161

Abstract Details

2017, Doctor of Philosophy, Case Western Reserve University, Molecular Biology and Microbiology.
Pseudomonas aeruginosa uses a type III secretion system (T3SS), a syringe-like apparatus, to inject bacterial effector proteins into the host cell cytoplasm. Upon cell contact the T3SS assembles the translocon, which is essential for effector injection. The translocon creates a conduit for effectors to pass from the bacterium to the host cell and consists of three proteins: PopB and PopD, pore-forming translocators, and PcrV, the needle tip. Mismatch studies with Yersinia translocators identified interactions between PopD and PcrV, as well as PopB and PopD. The PopD-PcrV interaction was confirmed by covalently crosslinking the interacting proteins during cell contact. We demonstrated that PopB and PopD also form homo-dimers. Tethering the PopD dimer or disrupting the PopD-PcrV interaction interferes with triggering of effector secretion. These data support the model that cell-contact is sensed by the translocation pore. The signal is then transmitted to the needle tip and from there propagated down the needle to initiate of effector secretion. The host cell component that mediates sensing of the host cell contact has not yet been identified. Preliminary data from the lab suggested that the phagosome causes constant triggering of translocation, which may be related to membrane curvature. We aimed to identify this aspect using a three-pronged approach. First, we attempted to recapitulate in vitro the membrane curvature that the bacterium experiences during phagocytosis. A curved membrane composed of only phosphatidylserine and phosphatidylcholine did not cause triggering of effector secretion, suggesting that there must be additional factors involved in sensing of host cell contact. Second, we demonstrated that blocking membrane damage repair-related endocytosis decreased the level of effectors translocated. However, this decrease was minor and implies that the membrane damage repair response is not solely responsible for triggering of effector secretion. Third, because ExoS can regulate its own translocation into host cells through its catalytic function, we aimed to identify cellular components that contribute to translocation by detecting targets of ExoS. We found that localization of ExoS, as well as both the GTPase activating protein- and the ADP-ribosyltransferase domains contribute to proper regulation of translocation.
Arne Rietsch, Ph.D. (Advisor)
Piet de Boer, Ph.D. (Committee Chair)
Liem Nguyen, Ph.D. (Committee Member)
Pieter de Haseth, Ph.D. (Committee Member)
116 p.
Microbiology; Molecular Biology
Pseudomonas aeruginosa; type III secretion; T3SS; translocator; PopB; PopD; PcrV, ExoS; membrane damage repair; endocytosis; feedback inhibition;

Recommended Citations

Citations

  • Armentrout, E. I. (2017). Sensing of Host Cell Contact by the Pseudomonas aeruginosa Type III Secretion System [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1499965816504161

    APA Style (7th edition)

  • Armentrout, Erin. Sensing of Host Cell Contact by the Pseudomonas aeruginosa Type III Secretion System. 2017. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1499965816504161.

    MLA Style (8th edition)

  • Armentrout, Erin. "Sensing of Host Cell Contact by the Pseudomonas aeruginosa Type III Secretion System." Doctoral dissertation, Case Western Reserve University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1499965816504161

    Chicago Manual of Style (17th edition)

case1499965816504161
301
© 2017, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.