PT - JOURNAL ARTICLE AU - Jonathan Munera Lopez AU - Isadonna F. Tengganu AU - Jun Liu AU - John Murray AU - Luisa F. Arias Padilla AU - Ying Zhang AU - Laurence Florens AU - Ke Hu TI - An apical protein, Pcr2, is required for persistent movement by the human parasite <em>Toxoplasma gondii</em> AID - 10.1101/2022.05.20.492694 DP - 2022 Jan 01 TA - bioRxiv PG - 2022.05.20.492694 4099 - http://biorxiv.org/content/early/2022/05/20/2022.05.20.492694.short 4100 - http://biorxiv.org/content/early/2022/05/20/2022.05.20.492694.full AB - The phylum Apicomplexa includes thousands of species of unicellular parasites that cause a wide range of human and animal diseases such as malaria and toxoplasmosis. To infect, the parasite must first initiate active movement to disseminate through tissue and invade into a host cell, and then cease moving once inside. The parasite moves by gliding on a surface, propelled by an internal cortical actomyosin-based motility apparatus. One of the most effective invaders in Apicomplexa is Toxoplasma gondii, which can infect any nucleated cell and any warm-blooded animal. During invasion, the parasite first makes contact with the host cell “head-on” with the apical complex, which features an elaborate cytoskeletal apparatus and associated structures. Here we report the identification and characterization of a new component of its apical complex, Preconoidal region protein 2 (Pcr2). Pcr2 knockout parasites replicate normally, but they are severely diminished in their capacity for host tissue destruction due to significantly impaired invasion and egress, two vital steps in the lytic cycle. When stimulated for calcium-induced egress, Pcr2 knockout parasites become active, and secrete effectors to lyse the host cell. Calcium-induced secretion of the major adhesin, MIC2, also appears to be normal. However, the movement of the Pcr2 knockout parasite is spasmodic and unproductive, which drastically compromises egress. In addition to faulty motility, the ability of the Pcr2 knockout parasite to assemble the moving junction is impaired. Both defects likely contribute to the poor efficiency of invasion. Interestingly, actomyosin activity, as indicated by the motion of mEmerald tagged actin chromobody, appears to be largely unperturbed in the absence of Pcr2, raising the possibility that Pcr2 may act downstream of or in parallel with the actomyosin machinery.Competing Interest StatementThe authors have declared no competing interest.