Protein Phosphatase 2C of Toxoplasma Gondii Interacts with Human SSRP1 and Negatively Regulates Cell Apoptosis.
OBJECTIVE
The protozoan Toxoplasma gondii expresses large amounts of a 37 kDa Type 2C serine-threonine phosphatase, the so-called TgPP2C which has been suggested to contribute to parasite growth regulation. Ectopic expression in mammalian cells also indicated that the enzyme could regulate growth and survival. In this study, we aimed to investigate the interaction of TgPP2C with human SSRP1 (structure-specific recognition protein 1) and the effects of TgPP2C on cell viability.


METHODS
The yeast two hybrid system, His-tag pull-down and co-immunoprecipitation assays were used to confirm the interaction of TgPP2C with SSRP1 and determine the binding domain on SSRP1. The evaluation of cell apoptosis was performed using cleaved caspase-3 antibody and Annexin-V/PI kit combined with flow cytometry.


RESULTS
We identified human SSRP1 as an interacting partner of TgPP2C. The C-terminal region of SSRP1 including the amino acids 471 to 538 was specifically mapped as the region responsible for interaction with TgPP2C. The overexpression of TgPP2C down-regulated cell apoptosis and negatively regulated apoptosis induced by DRB, casein kinase II (CKII) inhibitor, through enhanced interaction with SSRP1.


CONCLUSIONS
TgPP2C may be a parasitic factor capable of promoting cell survival through interaction with the host protein SSRP1, thereby creating a favorable environment for parasite growth.
Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, Guangdong, China.
Xue Juan
XJ
Gao
Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, Guangdong, China.
Jun Xia
JX
Feng
Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, Guangdong, China.
Sen
S
Zhu
Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, Guangdong, China.
Xiao Hui
XH
Liu
Institut Cochin, Université Descartes, Team FRM 'Barriers and Pathogens', 22 Rue Méchain, Paris 75014, France.
Isabelle
I
Tardieux
Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, Guangdong, China.
Lang Xia
LX
Liu
D017209:Apoptosis; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D006367:HeLa Cells; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D000071636:Protein Phosphatase 2C; D014122:Toxoplasma / Q000201:enzymology*; D035602:Transcriptional Elongation Factors / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; C073537:SSRP1 protein, human; D035602:Transcriptional Elongation Factors; C000607456:PPM1A protein, human; C000607457:PPM1B protein, human; C000607460:PPM1G protein, human; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C
Apoptosis; SSRP1; TgPP2C; Toxoplasma gondii