De novo evolved lipid transport and processing mechanisms interfacing human cells

ABSTRACT Mammals, including humans, evolved complex lipid transport and processing machinery to acquire and produce lipids and fatty acids to be used as building material for membranes, fats for energy storage or molecules for cell-cell signaling. Our deep knowledge of the physiology of lipid transport and processing is central to our understanding of human physiology but also cardiovascular disease, regulation of hormones, energy homeostasis or cancer. While humans evolved one version of lipid transport and processing machinery there exist a plethora of alternatives realized in non-model organisms. As a whole they can provide us with a breadth of general concepts that can be exploited to manipulate lipid transport and processing to improve human health. Plasmodium has evolved to replace the lipid transport and processing systems that its host-Red Blood Cell has removed in the process of specialization on oxygen transport. As the Red Blood Cell lost its lipid transporting and processing organelles, endoplasmic reticulum, Golgi apparatus and mitochondria, Plasmodium exapted (evolved to work in a new environment) its own proteins to take on new functions in the human host cell. Plasmodium thus features an independently evolved lipid transport and processing machinery compatible with human physiology. Our goal is to identify and characterize function of these analogous proteins, unrecognizable in sequence when compared to known analogues. To understand the range of lipids transported by Plasmodium, we will quantify lipid uptake dynamics of fluorescent lipid analogs. This allows us to construct a lipid uptake matrix (compartment vs lipid) that can be used identify activity of lipid transport and processing proteins. Novel lipid transport and processing proteins will be identified using the structural lipid interacting pocket predictor and proximity biotinylation of proteins at membrane contact site regions implicated in lipid transport. Proteins will be functionally characterized in vivo for their role in Plasmodium’s ability to transport and process lipids supported by in vitro characterization of lipid binding using recombinant proteins. Finally, the identified lipid transport and processing proteins will be characterized in a human cell line by localization to organelles and quantification of their impact on the cell’s lipid metabolism. In summary, our work identifies and characterizes an alternative version of the human lipid transport and processing machinery allowing us to recognize and conceptualize general principles of lipid handling to understand human physiology and expanding the design space to manipulate the human lipidome.