Actin dynamics is controlled by a casein kinase II and phosphatase 2C interplay on Toxoplasma gondii Toxofilin.

Abstract

Actin polymerization in Apicomplexa protozoa is central to parasite motility and host cell invasion. Toxofilin has been characterized as a protein that sequesters actin monomers and caps actin filaments in Toxoplasma gondii. Herein, we show that Toxofilin properties in vivo as in vitro depend on its phosphorylation. We identify a novel parasitic type 2C phosphatase that binds the Toxofilin/G-actin complex and a casein kinase II-like activity in the cytosol, both of which modulate the phosphorylation status of Toxofilin serine53. The interplay of these two molecules controls Toxofilin binding of G-actin as well as actin dynamics in vivo. Such functional interactions should play a major role in actin sequestration, a central feature of actin dynamics in Apicomplexa that underlies the spectacular speed and nature of parasite gliding motility.