Abstract text
1. Introduction
The liver stage of Plasmodium berghei is marked by extensive growth of a few sporozoites to produce thousands of progeny and establish the blood-stage infection. To ensure the fast growth, the parasite needs to acquire nutrients from within the host cells. Although late endosomes and the Golgi apparatus have been shown to associate with the parasitophorous vacuole in which the parasite resides, we hypothesize that additional host membrane compartments contribute to a successful liver stage infection.
2. Objectives
In our study, we wanted to identify membrane trafficking pathways that interact with the parasitophorous vacuole. To this end, we investigated the localization of host Rab GTPases during the infection. Rab GTPases are key regulators of specific trafficking events, which might be altered by the parasite. Other intracellular parasites have been shown to target specific Rab proteins to ensure their survival.
3. Materials & Methods
We infected hepatoma cells expressing tagged Rab GTPases and infected them with P. berghei. Through microscopy, we observed the localization of the different Rab proteins in infected cells at various time points during the infection. With additional immunofluorescence staining we determined the arrangement of additional host and parasite structures.
4. Results
Our initial screening of different Rab proteins showed association of Rab-labelled membranes with the parasite. Amongst predicted candidates like late endosomes, additional specific membrane compartments were observed accumulating in close proximity to the parasitophorous vacuole. Intriguingly, we identified a host Rab protein that not only accumulates near the parasite but is present on the parasitophorous vacuole. It showed clear colocalization with the parasitophorous vacuole membrane marker UIS4 throughout the development of the parasite.
5. Conclusions
Our data demonstrate that specific host membranes can be found in close proximity to the parasite-containing vacuole during infection. The presence of a host Rab on the membrane surrounding the parasite suggests this particular candidate is relevant to the infection. The localization of this Rab and of the neighboring host vesicles suggests some interplay between host Rab GTPases and the growing parasites.