PROJECT SUMMARY
Malaria is an important global cause of morbidity and mortality. Most of this disease burden falls on children
and pregnant women and is caused by infection with Plasmodium falciparum. The signs and symptoms of
human malaria result from the exponential expansion of parasite biomass that occurs during asexual
replication of parasites in human red blood cells. During this clinically important blood stage, P. falciparum
parasites divide by schizogony – a process wherein components for several daughter cells are produced
within a common cytoplasm prior to a complex and synchronized cytokinesis known as segmentation.
Cytokinesis via segmentation is highly divergent from the process of cell division in human cells. The
generation of the invasive daughter parasites, known as merozoites, occurs with high fidelity, ensuring that
each daughter has a single nucleus and the required organelles. The fundamental molecular mechanisms
that facilitate segmentation are incompletely understand, and this is a significant knowledge gap.
Successful segmentation requires two parasite-specific structures, the inner membrane complex (IMC) and
the basal complex. The IMC is a double lipid bilayer with associated proteins that, together with an
underlying cytoskeletal network, dictates parasite shape and rigidity. The basal complex is a group of
proteins at the posterior (i.e., basal) end of the IMC. This multi-protein molecular machine is essential for
parasite cell division and is hypothesized to facilitate proper biogenesis of the IMC, likely to contribute to cell
shape, and to mediate the final abscission step of cytokinesis. In the current proposal, we will move
stepwise towards a molecular understanding of basal complex function. We have a high-confidence list of
basal complex components, and our preliminary data demonstrate that individual proteins define
subcompartments within the complex and dynamically join and depart the complex. In the first aim, we will
utilize high-resolution live-cell time lapse microscopy to determine the precise order of assembly and
disassembly of the basal complex. In the second aim, we will utilize super-resolution ultrastructure
expansion microscopy to localize individual proteins into subcompartments of the basal complex and
proximity labeling to identify novel components within these compartments. In the third aim, we evaluate the
requirement for the remaining basal complex components for segmentation and determine the minimal core
of proteins that are essential for basal complex function. In summary, the basal complex is essential for
asexual replication of P. falciparum, is insufficiently understood, and is not targeted by any current
therapeutics. The studies in this proposal will narrow the significant knowledge gap around the molecular
mechanisms of basal complex function and may identify important targets for future antimalarials.