| Autor: |
Wirth, Christine Clara |
| Přispěvatelé: |
Pradel, Gabriele, Spehr, Marc |
| Jazyk: |
němčina |
| Rok vydání: |
2016 |
| Předmět: |
|
| Zdroj: |
Aachen 1 Online-Ressource (106 Seiten) : Illustrationen, Diagramme (2016). = Dissertation, RWTH Aachen, 2016 |
| Popis: |
The obligate intracellular malaria parasite Plasmodium falciparum undergoes several changes of host cells during its intraerythrocytic blood cycle in the human host as well as during its sexual phase in the Anopheles vector. Of particular interest in this area is the egress of activated mature gametocytes from the host erythrocyte upon transmission to the mosquito midgut. This process marks the beginning of the sexual phase and is essential for the transmission of the malaria parasite. Host cell egress is actively regulated by the parasite and starts with rupture of the parasitophorous vacuole membrane (PVM) followed by the erythrocyte membrane (EM). Detailled knowledge about P. falciparum midgut stages is a prerequisite for development of transmission blocking strategies as part of malaria prevention. The aim of this thesis therefore was the analysis of five plasmodial perforin-like proteins (PPLP1 to 5) regarding their potential role during gametocyte egress.First of all, the expression pattern of PPLP1 to 5 in blood schizonts and activated gametocytes was investigated. Using immunofluorescence assays (IFA), simultaneous expression of several members of the PPLP family was detected for both parasite stages. However, characterization of PPLP2 and PPLP4 using reverse genetics showed that only PPLP2, not PPLP4, is essential for gametocyte egress. Participation of PPLP2 in EM permeabilization prior to membrane rupture was successfully demonstrated by quantification of hemoglobine release and electron microscopy. Although activated PPLP2-deficient gametocytes were able to initiate PVM rupture, the fully developed gamete remained trapped inside the host cell, therefore blocking parasite transmission to the mosquito.Regarding PPLP4, IFAs revealed female specific expression of the protein in gametocytes. PPLP4-deficient gametocytes complete gametogenesis but standard membrane feeding assays using Anopheles mosquitoes revealed a severely reduced formation of oocysts, while ookinetes accumulate in the mosquito midgut. These results point to an essential role of PPLP4 in the infection of the mosquito vector.It has therefore been shown for PPLP2 and PPLP4 that both perforin-like proteins play independent roles in transmission of the malaria parasite to the Anopheles vector. These results complete the initial functional characterization of all five plasmodial perforins and provide evidence for a strict stage specific mode of action of the PPLPs. Basic molecular principles of different functions and regulation processes displayed by the PPLPS will be subject to future research projects.The identification of PPLP2 and PPLP4 as essential factors for progress of the P. falciparum life cycle upon transmission to the mosquito midgut contributed to a better understanding of the molecular mechanisms during transmission of the malaria parasite. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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