Journal
MOLECULAR IMMUNOLOGY
Volume 45, Issue 10, Pages 3012-3021Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.molimm.2008.01.011
Keywords
Francisella; Syk; PI3K/Akt; Erk; phagocytosis
Categories
Funding
- NCI NIH HHS [P01 CA095426-060002, P01 CA 095246, T32 CA090223, T32 CA090223-05, T32 CA 090223, P01 CA095426] Funding Source: Medline
- NIAID NIH HHS [U54 AI057153, R01 AI 59406, R01 AI059406, R01 AI059406-01A1, U54 AI057153-04, 1U54 AI 057153] Funding Source: Medline
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Francisella tularensis is a highly infectious, Gram-negative intra-cellular pathogen that can cause the zoonotic disease tularemia. Although the receptors critical for internalization of Francisella by macrophages are beginning to be defined, the identity of the downstream signaling pathways essential for the engulfment are not yet identified. In this study we have tested the role of Syk in the phagocytosis of Francisella. We report that Syk is activated during Francisella infection and is critical for the uptake of the organisms. Pharmacologic inhibition of Syk almost completely abrogated uptake, whereas the overexpression of Syk significantly enhanced uptake. However, Syk appears to be dispensable during initial host-pathogen contact. Further analyses of the molecular mechanism of Syk influence on Francisella uptake revealed that the MAPK Erk but not the phosphatidylinositol 3 kinase (PI3K)/Akt pathway is the downstream effector of Syk. Thus, the inhibition of Erk in Syk-overexpressing cells or the inhibition of Syk in Erk-overexpressing cells led to a significant attenuation of uptake. Collectively, these data identify Syk and Erk as key players in the phagocytosis of Francisella. (C) 2008 Elsevier Ltd. All rights reserved.
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