The critical role of <i>Toxoplasma gondii</i> GRA1 in nutrient salvage

<i>Toxoplasma gondii</i> critically relies on host nutrients for growth, but the underlying mechanisms are largely unknown. Here, we discovered that the secretory protein GRA1 in <i>Toxoplasma</i> played a crucial role in scavenging host nutrients to support parasite proliferation. GRA1 is the first reported GRA protein, but its function remains enigmatic since its discovery in 1989. GRA1 is secreted to the PV from the dense granules, which harbor many proteins that traffic to PV, PVM, and even host cells to perform diverse functions, including forming channels on the PVM to take up host nutrients to establish parasitism. GRA1 disruption impaired the structure of IVN and abolished the targeting of other GRA proteins to their destinations, which compromised the parasite's ability to import nutrients from the hosts. These findings reveal the functional mode of GRA1 in <i>T. gondii</i> and highlight its potential as a target for developing new interventions against toxoplasmosis.