Biology subjects

Periz, J.

Publications and source records attributed to Periz, J..

6 recordsLinked to original sources

bioRxiv2025

Tracking maternal proteins uncovers a central role for the residual body in organelle recycling during Toxoplasma gondii replication

Toxoplasma gondii replicates through endodyogeny, an unconventional form of internal budding in which two daughter cells are assembled within a single mother cell. During this process, daughter cells must acquire a full complement of organelles, which may be inherited from the mother, formed de novo, or assembled through a combination of both mechanisms. To date, the fate of maternal components during replication remains poorly understood. We previously showed that F-actin driven dynamics generate an intravacuolar network, associated with the residual body (RB) and facilitates the recycling of microneme proteins. However, the inheritance and recycling of other organelles have not been systematically analysed. To address this, we employed a dual HaloTag-based pulse-chase fluorescence labelling strategy to distinguish between de novo-synthesized and maternally inherited proteins in replicating tachyzoites. This approach reveals three distinct modes of organelle inheritance: (1) inheritance of intact maternal organelles (e.g., rhoptries and micronemes), (2) expansion and division of pre-existing maternal organelles with incorporation of newly synthesized components (e.g., Golgi apparatus and apicoplast), and (3) degradation of maternal structures followed by de novo assembly (e.g., inner membrane complex). Furthermore, we identify Myosin F (MyoF) as an important factor in the redistribution of maternal micronemes and rhoptries. In the absence of MyoF, these organelles accumulate in the RB, while restoration of MyoF permits accumulated maternal micronemes to redistribute to daughter parasites. Together, these findings support a role for the RB as a dynamic compartment in the recycling and redistribution of maternal organelles.

cell biology↗

bioRxiv2025

Localisation of Apicomplexa motor Myosin A with axial nanometric precision using graphene energy transfer

Migration in Apicomplexan parasites, a phylum that includes Plasmodium spp. responsible for malaria and the zoonotic Toxoplasma, is explained by the linear migration motor model. This model predicts that Myosin A is confined beneath the plasma membrane and above the inner membrane complex (IMC), a membranous barrier separating the cell membrane and the cytoplasm. Cumulative data, using mutant cell lines and biochemical data support this model. Paradoxically, a proof of the precise localization of Myosin A is still lacking due to limitations in resolving the motor with nanometric precision within the space comprising the membrane and the IMC. Here, we implement graphene energy transfer (GET), a novel axial nanometric ruler with a resolution of [~]1 nm, to determine the relative axial position of Myosin A and IMC1 (a reference protein defining IMC position). Using GET, we estimate the IMC dimensions with precision matching electron microscopy (EM) data and the added advantage of identifying specific bauplan proteins. We complement these measurements with 2D STED microscopy in MIRA confiners, uExMIC, and cryo-immunolabeling. Our data present the first direct localization of Myosin A populations with nanometric resolution in the third dimension, which is compatible with the linear motor model. One sentence summaryUsing the novel GET method, this study presents the first direct localization of Myosin A populations in Toxoplasma gondii with 1-4 nm axial precision, supporting the linear model.

biophysics↗

bioRxiv2024

Hijacked Immune Cells Traverse Microenvironmental Barriers by Positioning and Pushing their Intracellular Parasite Cargo

Cell migration is fundamental to development, homeostasis, and immunity, and requires cells to traverse space-limited microenvironments by deforming intracellular organelles such as the nucleus. Although nuclear mechanics are established as a rate-limiting factor during confined migration, how cells transport bulky foreign cargo remains unclear. Here, using Toxoplasma gondii, a disease-causing parasite that hijacks motile immune cells for dissemination while replicating into large intracellular assemblies, we discover that parasitic cargoes exceed the size and stiffness of host nuclei, and therefore constitute a primary bottleneck for migration. We uncover a mechanoadaptive response to parasite size, characterized by size-dependent intracellular repositioning, myosin-II contractility, and bleb-based protrusions. This reprogramming of forces and subcellular architecture enables the transport of oversized, mechanically rigid cargo through space-limited microenvironments. These findings establish a mechanobiological principle of how cells size-dependently adapt forces and their subcellular architecture to accommodate intracellular objects that challenge the physical limits of cell migration.

cell biology↗

bioRxiv2021

A phenotypic screen using splitCas9 identifies essential genes required for actin regulation during host cell egress and invasion by Toxoplasma gondii

Apicomplexan parasites, such as Toxoplasma gondii, possess unique organelles, cytoskeletal structures, signalling cascades, replicate by internal budding within a specialised compartment and actively invade and exit the host cell, to name a few aspects of the unique biology that characterise this phylum. Due to their huge phylogenetic distance from well established model organisms, such as opisthokonts, comparative genomics has a limited capacity to infer gene functions and conserved proteins can fulfil different roles in apicomplexans. Indeed, approximately 30% of all genes are annotated as hypothetical and many had a crucial role during the asexual life cycle in genome-wide screens. While the current CRISPR/Cas9-based screens allow the identification of fitness conferring genes, only little information about the respective functions can be obtained. To overcome this limitation, and to group genes of interest into functional groups, we established a conditional Cas9-system in T. gondii that allows phenotypic screens. Using an indicator strain for F-actin dynamics and apicoplast segregation, we identified critical genes required for defined steps during the asexual life cycle. The detailed characterisation of two of these candidates revealed them to be critical for host cell egress and invasion and to act at different time points in the disassembly of the intravacuolar F-actin network. While the signalling linking factor (SLF) is an integral part of a signalling complex required for early induction of egress, a novel conoid protein (conoid gliding protein, CGP) acts late during egress and is required for the activation of gliding motility.

microbiology↗

bioRxiv2019

Rab11A regulates the constitutive secretory pathway during Toxoplasma gondii invasion of host cells and parasite replication.

Toxoplasma gondii possesses an armada of secreted virulent factors that enable parasite invasion and survival into host cells. These factors are contained in specific secretory organelles, the rhoptries, micronemes and dense granules that release their content upon host cell recognition. Dense granules are secreted in a constitutive manner during parasite replication and play a crucial role in modulating host metabolic and immune responses. While the molecular mechanisms triggering rhoptry and microneme release upon host cell adhesion have been well studied, constitutive secretion remains a poorly explored aspect of T. gondii vesicular trafficking. Here, we investigated the role of the small GTPase Rab11A, a known regulator of exocytosis in eukaryotic cells. Our data revealed an essential role of Rab11A in promoting the cytoskeleton driven transport of DG and the release of their content into the vacuolar space. Rab11A also regulates transmembrane protein trafficking and localization during parasite replication, indicating a broader role of Rab11A in cargo exocytosis at the plasma membrane. Moreover, we found that Rab11A also regulates extracellular parasite motility and adhesion to host cells. In line with these findings, MIC2 secretion was altered in Rab11A-defective parasites, which also exhibited severe morphological defects. Strikingly, by live imaging we observed a polarized accumulation of Rab11A-positive vesicles and dense granules at the apical pole of extracellular motile parasites suggesting that a Rab11A-dependent apically polarized transport of cargo regulates parasite motility.

microbiology↗

bioRxiv2019

Apicomplexan F-actin is required for efficient nuclear entry during host cell invasion

The obligate intracellular parasites Toxoplasma gondii and Plasmodium spp. invade host cells by injecting a protein complex into the membrane of the targeted cell that bridges the two cells through the assembly of a ring-like junction. This circular junction stretches while the parasites applies a traction force to pass through; a step that typically concurs with transient constriction of the parasite body. Here we show that the junction can oppose resistance to the passage of the parasites nucleus. Super-resolution microscopy and real time imaging highlighted an F-actin pool at the apex of pre-invading parasite, an F-actin ring at the junction area during invasion but also networks of perinuclear and posteriorly localized F-actin. Mutant parasites with dysfunctional acto-myosin showed significant decrease of junctional and perinuclear F-actin and are coincidently affected in nuclear passage through the junction. We propose that the F-actin machinery eases nuclear passage by stabilising the junction and pushing the nucleus through the constriction, providing first evidence for a dual contribution of actin-forces during host cell invasion by apicomplexan parasites.

cell biology↗