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bioRxiv · 10.64898/2026.04.14.718606

A PROPPIN links V-ATPase assembly to endocytic membrane dynamics in malaria parasites

Schmitz, Y.·Sengupta, M.·Schneider, C.·Ziesmann, T.·Hellmold, F.·Distler, U.·Reimer, R.·Matz, J. M.
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Abstract

Malaria parasites replicate inside red blood cells, degrading hemoglobin within a specialized digestive vacuole. Efficient hemoglobin processing is essential for parasite survival and influences antimalarial drug susceptibility. The vacuole constantly fuses with incoming hemoglobin-filled vesicles, yet the mechanisms that balance cargo influx with membrane homeostasis remain unclear. Here, using conditional reverse genetics, quantitative live-cell imaging, and 3D electron microscopy, we characterize the autophagy-related protein 18 of Plasmodium falciparum (PfATG18) as a key regulator of vacuolar membrane dynamics. Loss of PfATG18 caused vacuole fragmentation, accumulation of hemoglobin-filled vesicles, and parasite death. These defects were preceded by broad architectural destabilization of the parasites V-ATPase, a proton pump controlling organelle acidification and the vacuoles fusion-fission equilibrium. Direct interference with its membrane sector phenocopied PfATG18 deficiency. We found that PfATG18 does not interact directly with the proton pump but instead associates with a putative V-ATPase assembly factor and with complexes regulating phosphoinositide balance and vesicle trafficking. The breadth of these interactions indicates a multifaceted role at the vacuolar membrane and a regulatory influence on V-ATPase mediated through associated protein machinery. Although a point mutation in PfATG18 has been linked to artemisinin resistance, its complete knockout did not decrease sensitivity, but rather hypersensitized ring-stage parasites to dihydroartemisinin. Together, these findings establish PfATG18 as a central regulator of endocytic membrane homeostasis, essential for V-ATPase function and asexual parasite proliferation in the human blood.

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Schmitz, Y., Sengupta, M., Schneider, C., Ziesmann, T., Hellmold, F., Distler, U., Reimer, R., Matz, J. M.. 2026-04-15. A PROPPIN links V-ATPase assembly to endocytic membrane dynamics in malaria parasites. https://doi.org/10.64898/2026.04.14.718606

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