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Published online before print September 27, 2006

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(Journal of Leukocyte Biology. 2006;80:1480-1490.)
© 2006 by Society for Leukocyte Biology

Mycobacteria directly induce cytoskeletal rearrangements for macrophage spreading and polarization through TLR2-dependent PI3K signaling

Elena B. Lasunskaia^*,1, Mariana N. N. Campos^*, Marcelle R. M. de Andrade^*, Renato A. DaMatta, Thereza L. Kipnis^*, Marcelo Einicker-Lamas and Wilmar D. Da Silva^*

^* Laboratório de Biologia do Reconhecer,
Laboratório de Biologia Celular e Tecidual, Universidade Estadual do Norte Fluminense, Rio de Janeiro, Brazil; and
Instituto de Biofísica Carlos Chagas Filho, Laboratório de Físico-Química Biológica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

¹ Correspondence: LBR, CBB, UENF, Av. Alberto Lamego, 2000 Campos/RJ, Rio de Janeiro 28013-600, Brazil. E-mail: elena@uenf.br

Macrophage migration and adhesion are important for the control of mycobacterial infection and are critically dependent on the reorganization of the cytoskeleton. Mycobacteria elicit rapid morphological changes, such as cell spreading, a process relevant to in vivo changes of macrophage shape during extravasation and migration. In this study, we investigated the BCG mycobacteria-induced signaling events leading to macrophage cytoskeletal rearrangements employing specific pharmacological inhibitors to suppress distinct kinase pathways known to be elicited by infection. Viable or lysed mycobacteria, as well as purified cell wall lipoprotein p19, TLR2 agonist, induced RAW264.7 cells to extend actin-rich pseudopods, which impart radial spreading within 3 h, leading later to persistent cell polarization. BCG induced rapid activation of phosphatidylinositol 3-kinase, PI3K, activation that was recruited to the activated TLR2 receptor. TLR2- neutralizing antibody inhibited macrophage spreading and PI3K activation induced by p19. Additionally, BCG induced spreading and polarization of bone marrow-derived macrophages from TLR2- expressing mice in contrast to their TLR2-knockout counterparts. Neither MEK1/ERK, p38 MAPK, nor NF-B activation were important for the early cytoskeletal rearrangements observed, although suppression of these pathways is known to inhibit chemokine secretion by activated macrophages. B2-integrins blockade with a corresponding antibody inhibited macrophage spreading and polarization but had no effect on pseudopodia protrusions demonstrating the downstream position of integrin-mediated adhesion in PI3K- dependent signaling pathway leading to the motility phenotype. The obtained data demonstrate that the direct effect of mycobacteria on macrophage shape might be mediated through TLR2-dependent PI3K activation.

Key Words: BCG • RAW264.7 macrophages • signal transduction

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