Regulation of Starch Stores by a Ca2+-Dependent Protein Kinase Is Essential for Viable Cyst Development in Toxoplasma gondii

• Published in: Cell host & microbe Vol. 18; no. 6; pp. 670 - 681
• Main Authors: Uboldi, Alessandro D., McCoy, James M., Blume, Martin, Gerlic, Motti, Ferguson, David J.P., Dagley, Laura F., Beahan, Cherie T., Stapleton, David I., Gooley, Paul R., Bacic, Antony, Masters, Seth L., Webb, Andrew I., McConville, Malcolm J., Tonkin, Christopher J.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 09.12.2015
• ISSN: 1931-3128; 1934-6069
• DOI: 10.1016/j.chom.2015.11.004

Transmissible stages of Toxoplasma gondii store energy in the form of the carbohydrate amylopectin. Here, we show that the Ca2+-dependent protein kinase CDPK2 is a critical regulator of amylopectin metabolism. Increased synthesis and loss of degradation of amylopectin in CDPK2 deficient parasites results in the hyperaccumulation of this sugar polymer. A carbohydrate-binding module 20 (CBM20) targets CDPK2 to amylopectin stores, while the EF-hands regulate CDPK2 kinase activity in response to Ca2+ to modulate amylopectin levels. We identify enzymes involved in amylopectin turnover whose phosphorylation is dependent on CDPK2 activity. Strikingly, accumulation of massive amylopectin granules in CDPK2-deficient bradyzoite stages leads to gross morphological defects and complete ablation of cyst formation in a mouse model. Together these data show that Ca2+ signaling regulates carbohydrate metabolism in Toxoplasma and that the post-translational control of this pathway is required for normal cyst development. [Display omitted] •The Toxoplasma kinase CDPK2 has functional Ca2+- and carbohydrate-binding domains•CDPK2 deficiency causes unchecked accumulation of starch in Toxoplasma parasites•Phosphorylation of several starch-metabolic enzymes relies on CDPK2 activity•Loss of CDPK2 results in starch hyperaccumulation and death of chronic-stage parasites Encysted lifecycle stages of Toxoplasma gondii produce and store starch. Uboldi et al. show that the kinase CDPK2 is targeted to starch stores and regulates starch turnover in a Ca2+-dependent manner. CDPK2 defiency leads to unchecked starch accumulation and death of parasite tissue cysts.