Differential requirements for cyclase-associated protein (CAP) in actin-dependent processes of Toxoplasma gondii
Abstract
Toxoplasma gondii contains a limited subset of actin binding proteins. Here we show that the putative actin regulator cyclase-associated protein (CAP) is present in two different isoforms and its deletion leads to significant defects in some but not all actin dependent processes. We observe defects in cell-cell communication, daughter cell orientation and the juxtanuclear accumulation of actin, but only modest defects in synchronicity of division and no defect in the replication of the apicoplast. 3D electron microscopy reveals that loss of CAP results in a defect in formation of a normal central residual body, but parasites remain connected within the vacuole. This dissociates synchronicity of division and parasite rosetting and reveals that establishment and maintenance of the residual body may be more complex than previously thought. These results highlight the different spatial requirements for F-actin regulation in Toxoplasma which appear to be achieved by partially overlapping functions of actin regulators.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 4, 5, 6, 8 and 10. Data Availability: Raw data for FIB SEM supporting movies will be uploaded to EMPIAR. Raw data for FIB SEM supporting movies have been deposited to EMPIAR.
Article and author information
Author details
Funding
Francis Crick Institute (FC001189)
- Lucy Collinson
NIH Office of the Director (AI121885)
- Romain Carmeille
- Aoife Heaslip
NIH Office of the Director (AI139201)
- Robyn Kent
- Gary E Ward
Francis Crick Institute (FC001999)
- Matthew Robert Geoffrey Russell
- Christopher J Peddie
- Lucy Collinson
NIH Office of the Director (AI137767)
- Robyn Kent
- Gary E Ward
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All experiments were performed in accordance with UK Home Office regulations (PPL 80/2616) and approved by the ethical review panel at the Francis Crick Institute.
Reviewing Editor
- Friedrich Frischknecht, Medical School Heidelberg, Germany
Publication history
- Received: July 30, 2019
- Accepted: September 26, 2019
- Accepted Manuscript published: October 2, 2019 (version 1)
- Version of Record published: October 9, 2019 (version 2)
Copyright
© 2019, Hunt et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 1,764
- Page views
-
- 268
- Downloads
-
- 25
- Citations
Article citation count generated by polling the highest count across the following sources: Scopus, Crossref, PubMed Central.
Download links
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Further reading
-
- Evolutionary Biology
- Microbiology and Infectious Disease
Many bacterial genomes carry prophages whose induction can eliminate competitors. In response, bacteria may become resistant by modifying surface receptors, by lysogenization, or by other poorly known processes. All these mechanisms affect bacterial fitness and population dynamics. To understand the evolution of phage resistance, we co-cultivated a phage-sensitive strain (BJ1) and a poly-lysogenic Klebsiella pneumoniae strain (ST14) under different phage pressures. The population yield remained stable after 30 days. Surprisingly, the initially sensitive strain remained in all populations and its frequency was highest when phage pressure was strongest. Resistance to phages in these populations emerged initially through mutations preventing capsule biosynthesis. Protection through lysogeny was rarely observed because the lysogens have increased death rates due to prophage induction. Unexpectedly, the adaptation process changed at longer time scales the frequency of capsulated cells in BJ1 populations increased again, because the production of capsule was fine-tuned, reducing the ability of phage to absorb. Contrary to the lysogens, these capsulated resistant clones are pan-resistant to a large panel of phages. Intriguingly, some clones exhibited transient non-genetic resistance to phages, suggesting an important role of phenotypic resistance in coevolving populations. Our results show that interactions between lysogens and sensitive strains are shaped by antagonistic co-evolution between phages and bacteria. These processes may involve key physiological traits, such as the capsule, and depend on the time frame of the evolutionary process. At short time scales, simple and costly inactivating mutations are adaptive, but in the long-term, changes drawing more favorable trade-offs between resistance to phages and cell fitness become prevalent.
-
- Immunology and Inflammation
- Microbiology and Infectious Disease
Hantaviruses are high-priority emerging pathogens carried by rodents and transmitted to humans by aerosolized excreta or, in rare cases, person-to-person contact. While infections in humans are relatively rare, mortality rates range from 1 to 40% depending on the hantavirus species. There are currently no FDA-approved vaccines or therapeutics for hantaviruses, and the only treatment for infection is supportive care for respiratory or kidney failure. Additionally, the human humoral immune response to hantavirus infection is incompletely understood, especially the location of major antigenic sites on the viral glycoproteins and conserved neutralizing epitopes. Here, we report antigenic mapping and functional characterization for four neutralizing hantavirus antibodies. The broadly neutralizing antibody SNV-53 targets an interface between Gn/Gc, neutralizes through fusion inhibition and cross-protects against the Old World hantavirus species Hantaan virus when administered pre- or post-exposure. Another broad antibody, SNV-24, also neutralizes through fusion inhibition but targets domain I of Gc and demonstrates weak neutralizing activity to authentic hantaviruses. ANDV-specific, neutralizing antibodies (ANDV-5 and ANDV-34) neutralize through attachment blocking and protect against hantavirus cardiopulmonary syndrome (HCPS) in animals but target two different antigenic faces on the head domain of Gn. Determining the antigenic sites for neutralizing antibodies will contribute to further therapeutic development for hantavirus-related diseases and inform the design of new broadly protective hantavirus vaccines.