# PTPA Governs Stress-Responsive Differentiation and Metabolic Homeostasis in Toxoplasma gondii

## TL;DR

This study reveals that PTPA regulates stress responses and metabolism in Toxoplasma gondii, a parasite that causes lifelong infections in hosts.

## Contribution

The study identifies PTPA as a key regulator of PP2A activity, linking it to both acute and chronic stages of Toxoplasma gondii infection.

## Key findings

- PTPA forms a complex with PP2A subunits and is essential for tachyzoite proliferation and invasion.
- PTPA depletion disrupts bradyzoite cyst formation and causes metabolic changes like amylopectin accumulation.
- The PP2A inhibitor LB-100 mimics PTPA depletion, suggesting PTPA–PP2A as a drug target for antitoxoplasmosis.

## Abstract

The protozoan parasite Toxoplasma gondii transitions between acute (tachyzoite) and chronic (bradyzoite) stages, enabling lifelong persistence in hosts. Iron depletion triggers bradyzoite differentiation, with the phosphotyrosyl phosphatase activator (PTPA) identified as a key regulator. Here, we define PTPA’s role in T. gondii pathogenesis. PTPA forms a ternary complex with PP2A A/C subunits, validated by reciprocal pull-down assays. Depleting PTPA impaired tachyzoite proliferation, invasion, and gliding motility, while stress-induced bradyzoites exhibited defective cyst formation and vacuolar swelling. Metabolic dysregulation included amylopectin accumulation and lipid droplet proliferation. The PP2A inhibitor LB-100 phenocopied PTPA depletion, suppressing tachyzoite growth and bradyzoite differentiation. TgPTPA emerges as a linchpin coordinating PP2A activity, metabolic flux, and lifecycle transitions. Its dual roles in acute virulence and chronic persistence, combined with LB-100’s efficacy, position the PTPA–PP2A axis as a promising target for antitoxoplasmosis strategies.