Dokument: Characterization of effector proteins involved in the early Chlamydia pneumoniae infection
| Titel: | Characterization of effector proteins involved in the early Chlamydia pneumoniae infection | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=51583 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20191120-083511-6 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Braun, Corinna Ursula [Autor] | |||||||
| Dateien: |
| |||||||
| Beitragende: | Prof. Dr. Hegemann, Johannes [Gutachter] Prof. Dr. Klein, Thomas [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie | |||||||
| Beschreibung: | Chlamydia pneumoniae (C. pneumoniae) is one of the two major species of the Chlamydiaceae family that infects humans. C. pneumoniae causes infections in the upper and lower respiratory tract and is linked to a number of chronic diseases. The adhesion of the Chlamydiae to the human cell is the first essential step of the infection followed by the internalization and the establishment of a membrane-bound intracellular niche, termed the inclusion. Chlamydiae secrete effector proteins via the type III secretion system, whose purpose it is to facilitate the internalization, replication, survival and release of the bacteria from the host cell. One of the best-characterized secreted effector proteins is the C. trachomatis translocated actin recruiting phosphoprotein (TarP), which recruits and polymerizes actin at the entry site of the infectious chlamydial cell to support the internalization process. However, bacterial and human proteins involved in these early phases of the infection are ill-defined.
In the first part of this thesis, the C. pneumoniae TarP ortholog, CPn0572, was investigated. TarP orthologs from different species are quite diverse in their amino acid (aa) sequence but they share important domains, like the G-actin binding domain (ABD) or a proline-rich domain (PRD). In this work, early infection studies show that, upon bacterial invasion, CPn0572 is secreted into the host cell and associates with actin patches via the ABD conserved in TarP proteins. Ectopic expression of various GFP-CPn0572 deletion variants in human cells, as well as in Saccharomyces cerevisiae and Schizosaccharomyces pombe, revealed that association of CPn0572 to actin is not only mediated by the ABD. The C-terminus of CPn0572 without ABD binds to F-actin in vitro and associates with actin cables in human epithelial cells when ectopically expressed. Strikingly, the same assays revealed a possible inhibitory effect of the N-Terminus on the ABD. Furthermore, over bioinformatic and immunofluorescence microscopy a vinculin binding sequence (VBS) could be identified. Finally, in vitro actin filament binding assay showed that CPn0572 might have a stabilizing effect on actin, as it seems to displace cofilin from F-actin structures. In the second part of this thesis, a new C. pneumoniae-specific cluster of 13 genes (termed cee1-13) was characterized. A bioinformatic screen identified the hypothetical protein Cee1, because of a localized 27.9 % identity to the human Rab36 GTPase. Rab GTPases together with phosphoinositides (PtdIns) are key regulators of vesicular transport and membrane identity. The Cee cluster proteins share a 32.6 % overall identity and harbor up to two different domains of unknown function (DUF), DUF575 and DUF562. Moreover, in all proteins harboring a DUF domain, Ras-specific G1, G3- and G5 box motifs could be identified which are involved in guanine-triphosphate binding. In ectopic expression studies all DUF575 containing proteins show vesicle-like structures in human cells. Interestingly, Cee1 shows a G1 box motif-dependent association with early endosomes, endogenous, endocytosed EGFR and recycling-specific Rab11 and Rab14 proteins. Finally, during a C. pneumoniae infection specific antibodies against Cee1 and Cee4 detected both endogenous proteins associated with adhering EBs as early as 5 min post infection. Interestingly, recombinant Cee1 and Cee4 bind to membranes and interact with phosphatidylserine and PtdIns(4)P. These data suggest that the cluster proteins are effector proteins with a possible function as molecular mimic of Rab proteins during the early C. pneumoniae infection phase. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Funktionelle Genomforschung der Mikroorganismen | |||||||
| Dokument erstellt am: | 20.11.2019 | |||||||
| Dateien geändert am: | 20.11.2019 | |||||||
| Promotionsantrag am: | 31.08.2015 | |||||||
| Datum der Promotion: | 21.05.2019 |
