IMC Compartmentalization and its role in maturation and transmission of P. falciparum gametocytes

Malaria is one of the most infectious diseases in the world with P.falciparum malaria responsible for the majority of cases. The recent efforts directed towards its eradication have highlighted the need to target the gametocyte stages of these parasites. The intraerythrocytic development of the gametocyte stage parasites involves sequential morphological changes. These occur in niches such as the bone marrow of the host where the gametocyte remain isolated from the host immune effectors. The morphological changes associated with alterations in the shape and deformability of the gametocyte cells enable effective mechanical sequestration during maturation, leading to the release of the mature late stages parasites into circulation. The Inner membrane complex (IMC), a series of flattened vesicles underlying the parasite plasma membrane and mediating interactions with numerous cytoskeletal structures is differentially associated through these developmental stages. The IMC protein components, their interactions and the specialized functions are largely unknown.

This study would 1) reveal the molecular components essential for IMC formation and its various functional roles during the development of P.falciparum gametocytes. 2) The interactions mediated by newly identified protein complexes of the IMC with the parasite cytoskeleton and membranes would be elucidated. 3) The phospho-signalling mechanisms at the IMC and its potential inhibitors would be identified. 4) The biophysical properties contributing to transmission would be evaluated upon disrupting the development of the gametocyte IMC. Firstly, to establish a comprehensive list of essential IMC components, co-immunoprecipitation, conditional gene knockdowns and localization based screens would be performed on transgenic parasites. Further, specialised post-translational modifications specific mass-spectrometry, fluorescence imaging techniques and differential cytoskeleton extractions would help map the essential protein interactions and signalling events at the IMC. Biophysical assays such as micropipette aspiration to measure the stage specific deformability, as well as the capillary flow characteristics would be investigated to measure the contribution of the identified essential interactions towards the physiological behaviours such as sequestration and margination capabilities. This proposal would therefore dissect the essential protein interactions and signalling mechanisms at the gametocyte IMC which confer the stage specific morphology and biophysical parameters mediating the sequestration at the bone marrow of immature gametocytes, the eventual release into the circulation, and the characteristic behaviour in the capillary blood flow leading to successful transmission of malaria. Prioritizing essential targets addresses a critical need to identify gametocyte stage molecular targets and suitable drug inhibitors as only 14% of all identified anti-Plasmodium drugs have gametocytocidal activity.