Identification of transporters essential for survival of Leishmania promastigotes in the digestive tract of sand flies
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Leishmania amastigotes ingested by female phlebotomine sand flies are exposed to a harsh and dynamic environment, markedly different from that of their mammalian host. Within the sand fly’s alimentary tract, these parasite forms encounter shifts in temperature, pH and nutrient availability, which trigger significant morphological and physiological adaptations. Membrane transporter proteins, channels and pumps play a crucial role in facilitating the movement of solutes across eukaryotic membranes. Previously, a systematic loss-of-function screen of the L. mexicana “transportome” identified forty transporter deletion mutants that caused significant loss of fitness in macrophage and mouse infections. Here, using an independently generated library of over 300 barcoded gene deletion mutants, we monitored their growth fitness for seven days in vitro and tested which transporters are required for Leishmania promastigotes to successfully colonise Lutzomyia longipalpis sand flies for nine days. Overall, fitness scores correlated between promastigotes from long-term in vitro culture and in vivo sand fly infections. More importantly, for 34 mutants, a significant loss of fitness was observed exclusively in vivo . Moreover, deletion of the vacuolar H + ATPase (V-ATPase) proved detrimental for parasite persistence and promastigote differentiation in the sand fly, uncovering a key role for the V-ATPase at different stages throughout the Leishmania life cycle.
Author Summary
Leishmania parasites cause leishmaniases - a group of neglected tropical diseases that affect millions of people worldwide. These parasites must survive in two radically different environments: inside a mammalian host and within the gut of a blood-feeding sand fly. To thrive in the sand fly, Leishmania undergo extensive physiological changes and depend on transporter proteins to move nutrients and other molecules across their cell membranes. In this study, we focused on identifying which of these transporters are critical for the parasite’s survival inside the sand fly. We used a genetically engineered library of Leishmania promastigotes - the parasite form adapted to the insect vector - to assess the importance of more than 300 different transporter genes. We discovered that 34 of these transporters are essential for successful colonization of the sand fly. Among them, one key protein complex - the vacuolar H + ATPase (V-ATPase) pump – was found to be crucial for parasite survival in the insect vector. Our findings deepen our understanding of how Leishmania adapts to life within the sand fly and highlight potential molecular targets for disrupting its transmission.
