Host cell Ca2+ and protein kinase C regulate innate recognition of Toxoplasma gondii.
In healthy hosts, acute infection with the opportunistic pathogen Toxoplasma gondii is controlled by innate production of IL-12, a key cytokine crucial for the development of protective immunity. Previous work has established that the mitogen-activated protein kinases (MAPK), particularly p38 and ERK1/2, are important regulators of T. gondii-induced IL-12 synthesis. Here we report that host cell Ca(2+) is required for activation of MAPK by T. gondii, as well as LPS and CpG, and for parasite-induced synthesis of IL-12. In addition, pharmacological mobilization of Ca(2+) stores in macrophages treated with parasites or LPS enhanced MAPK phosphorylation initiated by these stimuli. Investigation of the upstream mechanism by which Ca(2+) regulates MAPK activation revealed that T. gondii induced acute activation of conventional, Ca(2+)-dependent PKCalpha and PKCbeta, which are required for infection-induced MAPK activation and production of IL-12. Despite these findings, neither acute parasite infection nor LPS initiated a measurable Ca(2+) response in macrophages, suggesting that low levels of Ca(2+) are permissive for initiation of pro-inflammatory signaling. Together these data identify host cell Ca(2+) and PKC as crucial regulators of the innate immune response to microbial stimuli, including T. gondii.
Masek
Katherine S
KS
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
Fiore
Jim
J
Leitges
Michael
M
Yan
Shi-Fang
SF
Freedman
Bruce D
BD
Hunter
Christopher A
CA
D000818:Animals; D001853:Bone Marrow / Q000276:immunology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D018664:Interleukin-12 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport; D015398:Signal Transduction; D014122:Toxoplasma / Q000276:immunology* / Q000502:physiology; D014124:Toxoplasmosis, Animal / Q000276:immunology / Q000378:metabolism
D008070:Lipopolysaccharides; D018664:Interleukin-12; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium