Biology subjects

Tengganu, I. F.

Publications and source records attributed to Tengganu, I. F..

3 recordsLinked to original sources

bioRxiv2026

The human parasite, Toxoplasma gondii, is paralyzed without two components of the apical polar ring

The phylum Apicomplexa contains [~] 6000 known species of unicellular eukaryotic parasites. A unifying feature among the apicomplexans is the apical complex, which varies in complexity in different lineages, but always contains an annulus (a.k.a. the apical polar ring) into which the minus ends of an array of cortical microtubules are embedded. In Toxoplasma gondii, the apical complex also includes the conoid, which contains several signaling and structural proteins critical for parasite motility. The conoid extends and retracts through the apical polar ring in a calcium-dependent manner. Here we report the identification of several new apical polar ring components, including APR9, which is highly conserved among the apicomplexans and their free-living relative Chromera velia. The loss of APR9 alone has only a moderate impact on the parasite lytic cycle. However, the knockout of both APR9 and KinesinA (another apical polar ring component) paralyzes parasite and drastically impairs invasion, egress and the lytic cycle. The double-knockout displays multiple subcellular abnormalities, including the formation of an apical actin concentration, impaired conoid extension, and significantly reduced secretion of a major adhesin (MIC2) upon stimulation with a calcium ionophore. These findings reveal that the apical polar ring plays a critical role in parasite motility and contributes to multiple subcellular processes.

cell biology↗

bioRxiv2023

The cortical microtubules of Toxoplasma contribute to the helicity, but not the speed or persistence of parasite movement

Motility is essential for apicomplexan parasites to infect their hosts. In a three-dimensional (3-D) environment, the apicomplexan parasite Toxoplasma gondii moves along a helical path. The cortical microtubules, which are ultra-stable and spirally arranged, have been considered to be a structure that guides the long-distance movement of the parasite. Here we address the role of the cortical microtubules in parasite motility, invasion, and egress by utilizing a previously generated mutant (dubbed "TKO") in which these microtubules are destabilized in mature parasites. We found that the cortical microtubules in ~ 80% of the non-dividing (i.e. daughter-free) TKO parasites are much shorter than normal. The extent of depolymerization is further exacerbated upon commencement of daughter formation or cold treatment, but parasite replication is not affected. In a 3-D Matrigel matrix, the TKO mutant moves directionally over long distances, but along trajectories significantly more linear (i.e. less helical) than those of wild-type parasites. Interestingly, this change in trajectory does not impact either movement speed in the matrix or the speed and behavior of the parasites entry into and egress from the host cell.

cell biology↗

bioRxiv2022

An apical protein, Pcr2, is required for persistent movement by the human parasite Toxoplasma gondii

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 the 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, 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 by the loss of Pcr2, raising the possibility that Pcr2 may act downstream of or in parallel with the actomyosin machinery.

cell biology↗