Biology subjects

Dos Santos Pacheco, N.

Publications and source records attributed to Dos Santos Pacheco, N..

8 recordsLinked to original sources

bioRxiv2026

MyoL-Dependent Coupling of Preconoidal Rings to Conoid Is Required for Motility in Toxoplasma gondii

Apicomplexan parasites are unified by their apical complex, a structure of cytoskeletal elements and secretory organelles. At its core lies the conoid, made of spiraling tubulin fibers essential for parasite motility and invasion. In Toxoplasma gondii, conoid extrusion and retraction through the apical polar ring is powered by Myosin H, ultimately regulating gliding motility. The conoid is capped by three preconoidal rings (PCRs), critical for extrusion and motility as they anchor formin 1, which produces filamentous actin needed for both processes. We demonstrate here that PCR composition and stability differ between daughter and mature cells and that Pcr2 and Pcr3 adopt a half-ring localization. The non-functional head containing Myosin-like protein MyoL, a previously unrecognized PCR component, is essential for gliding motility and invasion. Its depletion partially detaches PCRs from the conoid, highlighting its role as a mechanical tether. Targeted mutagenesis identifies the neck and tail regions of MyoL as critical for localization and function. Together, these findings illuminate the architecture and functional organization of the PCR in T. gondii, a structure conserved across several Apicomplexa.

microbiology↗

bioRxiv2025

The spatial proteome of the Plasmodium falciparum schizont illuminates the composition and evolutionary trajectories of its organelles

Malaria is caused by apicomplexan parasites of the genus Plasmodium, with all malaria symptoms and pathology caused by parasite stages that develop within, or transit between, host erythrocytes. The ability of Plasmodium cells to parasitise erythrocytes depends on distinctive intracellular compartments associated with invasion, as well as the development of unique cellular niches within the infected host cell. However, our understanding of the biology of the malaria parasite is limited by the fact that a large proportion of the parasites proteome has no known cellular location or function. To address this problem, we have generated comprehensive high-resolution maps of protein subcellular localisation for the invasive stage of the erythrocytic life cycle of Plasmodium falciparum, the major cause of malaria mortality. Using the spatial proteomics technique hyperplexed Localisation of Organelle Proteins by Isotopic Tagging (hyperLOPIT) we generated data for 3000 P. falciparum proteins expressed in late schizont stages. Our hyperLOPIT data resolved 24 distinct cellular niches, and using supervised machine-learning we can classify 1646 proteins into one of these compartments including exported sites within the host cell. Through comparative genomic analyses our data resolve the spatial patterns of cell evolution that have shaped the development of Plasmodium species and ongoing adaptive pressures and responses that challenge our efforts to manage these major disease-causing organisms.

microbiology↗

bioRxiv2024

RNG2 tethers the conoid to the apical polar ring in Toxoplasma gondii: a key mechanism in parasite motility and invasion

In Toxoplasma gondii, the conoid is a dynamic organelle composed of spiraling tubulin fibers that extrudes during egress, gliding motility, and invasion. This organelle traverses the apical polar ring (APR) in response to calcium waves and plays a critical role in controlling parasite motility. While the actomyosin-dependent extrusion of the conoid is beginning to be understood, the mechanism by which it is anchored apically to the APR remains unclear. RNG2, a protein localized at both the conoid and the APR, has emerged as a key candidate for this function. By combining iterative ultrastructure expansion microscopy and immunoelectron microscopy we discovered that RNG2 forms 22 tethers between the APR and the conoid. The unique biochemical properties of RNG2, including several proteolytic processing events and its ability to form concatenations, enable it to function as a dynamic bridge between these structures. Conditional depletion of RNG2 resulted in the conoid organelle detaching from the APR without compromising the integrity of its structure, thereby confirming RNG2 essential tethering role. Although microneme secretion remains normal, parasites lacking RNG2 were unable to move and impaired in rhoptry discharge, highlighting the conoids crucial role in parasite motility and invasion. RNG2 is a pivotal protein that ensures conoid functionality in Coccidia.

microbiology↗

bioRxiv2023

Structural and regulatory insights into the glideosome-associated connector from Toxoplasma gondii

The phylum of Apicomplexa groups intracellular parasites that employ substratedependent gliding motility to invade host cells, egress from the infected cells and cross biological barriers. The glideosome associated connector (GAC) is a conserved protein essential to this process. GAC facilitates the association of actin filaments with surface transmembrane adhesins and the efficient transmission of the force generated by myosin translocation of actin to the cell surface substrate. Here, we present the crystal structure of Toxoplasma gondii GAC and reveal a unique, supercoiled armadillo repeat region that adopts a closed ring conformation. Characterisation of the membrane binding interface within the C-terminal PH domain as well as an N-terminal fragment necessary for association with F-actin suggest that GAC adopts multiple conformations. A multi-conformational model for assembly of GAC within the glideosome is proposed.

biochemistry↗

bioRxiv2022

Conoid extrusion serves as gatekeeper for entry of glideosome components into the pellicular space to control motility and invasion in Apicomplexa

Members of the Apicomplexa are defined by apical cytoskeletal structures and secretory or-ganelles, tailored for motility and invasion. Gliding is powered by actomyosin-dependent rearward translocation of apically secreted transmembrane adhesins. In Toxoplasma gondii, the conoid, composed of a cone of spiraling tubulin fibers and apposed preconoidal rings (PCRs), is an enigmatic, dynamic organelle of undefined function. Here we mapped five new components of the PCRs and deduce that the structure serves as a pivotal hub for actin polymerization and glideosome assembly. F-actin produced by Formin1 on the PCRs is used by Myosin H to generate the force for conoid extrusion. A set of B-box-type zinc finger domain containing proteins conserved in Apicomplexa is indispensable for PCRs formation, conoid extrusion and motility in Toxoplasma and Plasmodium. Conoid dynamics directs the flux of F-actin to the pellicular space, acting as dynamic gatekeeper to tightly control parasite motility during invasion and egress.

microbiology↗

bioRxiv2021

Organization and composition of apicomplexan kinetochores reveals plasticity in chromosome segregation across parasite modes of division

Kinetochores are multiprotein assemblies directing mitotic spindle attachment and chromosome segregation. In apicomplexan parasites, most known kinetochore components and associated regulators are apparently missing, suggesting a minimal structure with limited control over chromosome segregation. In this study, we use interactomics combined with deep homology searches to identify six divergent eukaryotic components, in addition to a set of eight apicomplexan kinetochore proteins (AKiTs) that bear no detectable sequence similarity to known proteins. The nanoscale organization of the apicomplexan kinetochore includes four subdomains, each displaying different evolutionary rates across the phylum. Functional analyses confirm AKiTs are essential for mitosis and reveal architectures parallel to biorientation at metaphase. Furthermore, we identify a homolog of MAD1 at the apicomplexan kinetochore, suggesting conserved spindle assembly checkpoint signaling. Finally, we show unexpected plasticity in kinetochore composition and segregation throughout the parasite lifecycle, indicating diverse requirements to maintain fidelity of chromosome segregation across apicomplexan modes of division.

microbiology↗

bioRxiv2021

Revisiting the role of Toxoplasma gondii ERK7 in the maintenance and stability of the apical complex

Toxoplasma gondii ERK7 is known to contribute to the integrity of the apical complex and to be involved only in the final step of the conoid biogenesis. In the absence of ERK7, mature parasites lose their conoid complex and are unable to glide, invade or egress from host cells. In contrast to a previous report, we show here that depletion of ERK7 phenocopies the depletion of the apical cap proteins AC9 or AC10. The absence of ERK7 leads to the loss of the apical polar ring, the disorganization of the basket of subpellicular microtubules and an impairment in micronemes secretion. Ultra-expansion microscopy (U-ExM) coupled to NHS-Ester staining on intracellular parasites offers an unprecedented level of resolution and highlights the disorganization of the rhoptries as well as the dilated plasma membrane at the apical pole in the absence of ERK7. Comparative proteomics analysis of wild-type and ERK7 or AC9 depleted parasites led to the disappearance of known, predicted, as well as putative novel components of the apical complex. In contrast, the absence of ERK7 led to an accumulation of microneme proteins, resulting from the defect in exocytosis of the organelles. ImportanceThe conoid is an enigmatic, dynamic organelle positioned at the apical tip of the coccidian subgroup of the Apicomplexa, close to the apical polar ring (APR) from which the subpellicular microtubules (SPTMs) emerge and at the site of microneme and rhoptry secretory organelles exocytosis. In Toxoplasma gondii, the conoid protrudes concomitantly to microneme secretion, during egress, motility and invasion. The conditional depletion of the apical cap structural protein AC9 or AC10 leads to a disorganization of SPTMs as well as the loss of APR and conoid that result in microneme secretion defect and block in motility, invasion and egress. We show here that depletion of the kinase ERK7 phenocopies completely AC9 and AC10 mutants. Moreover, the combination of ultrastructure expansion microscopy with an NHS ester staining revealed that ERK7 depleted parasites exhibit a dilated apical plasma membrane and a mis-positioning of the rhoptry organelles.

microbiology↗

bioRxiv2020

Two alveolin network proteins are essential for the subpellicular microtubules assembly and conoid anchoring to the apical pole of mature Toxoplasma gondii

Toxoplasma gondii belongs to the coccidian sub-group of Apicomplexa that possess an apical complex harboring a conoid, made of unique tubulin polymer fibers. This enigmatic and dynamic organelle extrudes in extracellular invasive parasites and is associated to the apical polar ring (APR), a microtubule-organizing center for the 22 subpellicular microtubules (SPMTs). The SPMTs are linked to the Inner Membrane Complex (IMC), a patchwork of flattened vesicles, via an intricate network of small filaments composed of alveolins proteins. Here, we capitalize on super-resolution techniques including stimulated emission depletion (STED) microscopy and ultrastructure expansion microscopy (U-ExM) to localize the Apical Cap protein 9 (AC9) and its close partner AC10, identified by BioID, to the alveolin network and intercalated between the SPMTs. Conditional depletion of AC9 or AC10 using the Auxin-induced Degron (AiD) system uncovered a severe loss of fitness. Parasites lacking AC9 or AC10 replicate normally but are defective in microneme secretion and hence fail to invade and egress from infected cells. Remarkably, a series of crucial apical complex proteins (MyoH, AKMT, FRM1, CPH1, ICMAP1 and RNG2) are lost in the mature parasites although they are still present in the forming daughter cells. Electron microscopy on intracellular or deoxycholate-extracted parasites revealed that the mature parasite mutants are conoidless. Closer examination of the SPMTs by U-ExM highlighted the disassembly of the SPMTs in the apical cap region that is presumably at the origin of the catastrophic loss of APR and conoid. AC9 and AC10 are two critical components of the alveolin network that ensure the integrity of the whole apical complex in T. gondii and likely other coccidians.

microbiology↗