Juliane Küchenhoff (Aachen / DE), Juliane Sassmannshausen (Aachen / DE), Dr. Sandra Bennink (Aachen / DE), Dr. Ute Distler (Mainz / DE), Dr. Paul-Christian Burda (Hamburg / DE), Prof. Stefan Tenzer (Mainz / DE), Prof. Tim Wolf Gilberger (Hamburg / DE), Prof. Gabriele Pradel (Aachen / DE)
Abstract text
Introduction
Malaria tropica, caused by protozoan parasite Plasmodium falciparum remains an important health threat. Molecular understanding of P. falciparum gametocytes and their egress from the host cell is crucial for the development of transmission-blocking strategies, which are needed for malaria eradication and antimalarial resistance control. Following uptake by the mosquito vector, gametocytes become activated through environmental stimuli, which triggers their inside-out egress from the red blood cell. At least two types of specialized secretory vesicles are essential for this process. Initially, the parasitophorous vacuole membrane ruptures after exocytosis of osmiophilic bodies (OB) followed by lysis of the erythrocyte membrane, which is associated with exocytosis of g-exonemes. Known components of OBs are G377 and MDV1, while for g-exonemes only PPLP2 has as yet been identified as a constituent.
Material and Methods
To unveil the proteomes of OBs and g-exonemes, we employed BioID methods. BioID/TurboID lines for G377, MDV1 and PPLP2 were generated to identify possible interaction partners and biotinylated proteins of all three lines were successfully analysed via mass spectrometry (MS).
Results
For selected putative vesicle components as identified by MS, HA-tagged parasite lines were generated using the pSLI-HA-glmS knockdown system. Among others, two unknown conserved proteins, PF3D7_1319900 and PF3D7_0811600, and the secreted ookinete protein PSOP1 were shown to localized to vesicular structures in gametocytes. The lines are currently being phenotypically characterized by means of immunohistochemical techniques and cell-based assays to investigate their role in egress-related vesicle dynamics.
Conclusion
The results help to unveil the interactome of egress-related vesicles of P. falciparum gametocytes, providing insights into the immense molecular machinery involved in mediating egress of malaria parasites from erythrocytes during gametogenesis.