<p>Transgenic parasite lines used in this study.</p>

Direct interference with its membrane sector phenocopied <i>Pf</i>ATG18 deficiency. We found that <i>Pf</i>ATG18 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 <i>Pf</i>ATG18 has been linked to artemisinin resistance, its complete knockout did not decrease sensitivity. Instead, it rendered ring-stage parasites hypersensitive to dihydroartemisinin, while leaving their susceptibility to other antimalarial drugs unchanged. Together, these findings establish <i>Pf</i>ATG18 as a central regulator of endocytic membrane homeostasis, essential for V-ATPase function and asexual parasite proliferation in the human blood.</p></div>