Biology subjects

Maco, B.

Publications and source records attributed to Maco, B..

6 recordsLinked to original sources

bioRxiv2026

A transporter essential for apical secretory organelles homeostasis in Toxoplasma gondii

Apicomplexan parasites rely on the rhoptries and micronemes to coordinate egress, motility, and host cell invasion. In Toxoplasma gondii, mechanistic insights into the control of these organelles lipid composition remain sparse. Although nearly 60 T. gondii Major Facilitator Superfamily (MFS) are predicted, many remain functionally uncharacterized. The MFS protein HAP12 was previously annotated as an apicoplast protein contributing to invasion and organelle inheritance. Based on localization and phylogenetic analyses, we show that HAP12 (renamed TFP5), is predominantly associated with the Golgi, with additional signal in the ELC and apical compartments, without convincing evidence of a major apicoplast-associated pool. Furthermore, TFP5 clusters with a subgroup of MFS transporter facilitator proteins (TFPs) involved in the morphological integrity of secretory apical organelles. TFP5 depletion results in defective microneme secretion and pronounced alterations in rhoptry morphology and positioning. Structural analyses revealed that TFP5 is strongly similar to MFSD2-like lipid transporters, while lipidomic analyses showed substantial changes in parasite lipid composition following TFP5 depletion. Together, these findings support a model in which TFP5 regulates lipid homeostasis required for the function of apical secretory organelles, thereby critically contributing to parasite virulence.

microbiology↗

bioRxiv2026

Human airway organoids as a high-throughput screening platform for antiviral natural products discovery

Antiviral drug discovery for respiratory viruses is hindered by the lack of scalable physiologically relevant systems. Here, we report the first high-throughput screen of 764 natural plant extracts against respiratory syncytial virus (RSV) using human primary airway organoids as a relevant model. A parallel screen conducted in A549 cells allowed the identification of 70 extracts with organoid-specific antiviral activity from which 45 active phytocompounds were purified. We identified early- and late-acting antiviral compounds and demonstrated a polarization-dependent activity for some of them. Collectively, our results establish the use of airway organoids as a scalable first-line platform for high-throughput antiviral discovery and exploit the plant-derived chemical space as an underexplored source of RSV inhibitors.

microbiology↗

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↗

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↗

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↗

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↗