TY - JOUR
T1 - Toxoplasma GRA7 effector increases turnover of immunity-related GTPases and contributes to acute virulence in the mouse
AU - Alaganan, Aditi
AU - Fentress, Sarah J.
AU - Tang, Keliang
AU - Wang, Qiuling
AU - Sibley, L. David
PY - 2014/1/21
Y1 - 2014/1/21
N2 - The intracellular parasite Toxoplasma gondii enjoys a wide host range and is adept at surviving in both naive and activated macrophages. Previous studies have emphasized the importance of the active serine-threonine protein kinase rhoptry protein 18(ROP18), which targets immunity-related GTPases (IRGs), in mediating macrophage survival and acute virulence of T. gondii in mice. Here, we demonstrate that ROP18 exists in a complex with the pseudokinases rhoptry proteins 8 and 2 (ROP8/2) and dense granule protein 7 (GRA7). Individual deletion mutant Δgra7 or Δrop18 was partially attenuated for virulence in mice, whereas the combined Δgra7Δrop18 mutant was avirulent, suggesting these proteins act together in the same pathway. The virulence defect of the double mutant was mirrored by increased recruitment of IRGs and clearance of the parasite in IFN-γ-activated macrophages in vitro. GRA7 was shown to recognize a conserved feature of IRGs, binding directly to the active dimer of immunity-related GTPase a6 in a GTP-dependent manner. Binding of GRA7 to immunity-related GTPase a6 led to enhanced polymerization, rapid turnover, and eventual disassembly. Collectively, these studies suggest that ROP18 and GRA7 act in a complex to target IRGs by distinct mechanisms that are synergistic.
AB - The intracellular parasite Toxoplasma gondii enjoys a wide host range and is adept at surviving in both naive and activated macrophages. Previous studies have emphasized the importance of the active serine-threonine protein kinase rhoptry protein 18(ROP18), which targets immunity-related GTPases (IRGs), in mediating macrophage survival and acute virulence of T. gondii in mice. Here, we demonstrate that ROP18 exists in a complex with the pseudokinases rhoptry proteins 8 and 2 (ROP8/2) and dense granule protein 7 (GRA7). Individual deletion mutant Δgra7 or Δrop18 was partially attenuated for virulence in mice, whereas the combined Δgra7Δrop18 mutant was avirulent, suggesting these proteins act together in the same pathway. The virulence defect of the double mutant was mirrored by increased recruitment of IRGs and clearance of the parasite in IFN-γ-activated macrophages in vitro. GRA7 was shown to recognize a conserved feature of IRGs, binding directly to the active dimer of immunity-related GTPase a6 in a GTP-dependent manner. Binding of GRA7 to immunity-related GTPase a6 led to enhanced polymerization, rapid turnover, and eventual disassembly. Collectively, these studies suggest that ROP18 and GRA7 act in a complex to target IRGs by distinct mechanisms that are synergistic.
KW - Cooperative polymerization
KW - Innate immunity
KW - Pathogenesis
UR - http://www.scopus.com/inward/record.url?scp=84892910206&partnerID=8YFLogxK
U2 - 10.1073/pnas.1313501111
DO - 10.1073/pnas.1313501111
M3 - Article
C2 - 24390541
AN - SCOPUS:84892910206
SN - 0027-8424
VL - 111
SP - 1126
EP - 1131
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 3
ER -