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Are Required for TLR2-Mediated Gene Transcription1
Departments of Immunology and Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037
The Rho GTPases are molecular switches that regulate many essential cellular processes, including actin dynamics, gene transcription, cell cycle progression, cell adhesion, and motility. In this study, we report that stimulation of TLR2 in human epithelial and monocytic cells leads to rapid and transient activation of RhoA. RhoA cooperated with the canonical I-
B kinase-mediated pathway that induces the release of NF-B, in regulating the trans activation of the NF-B subunit p65/RelA by affecting Ser311 phosphorylation, and subsequent cytokine production. Another consequence of TLR2 stimulation by bacterial derived products was the activation of atypical protein kinase C (PKC) 
and association of this protein kinase with RhoA. Inhibition of PKC decreased NF-B activation and p65/RelA trans activation without affecting I-B
degradation. The observation of a transient, stimulus-dependent association of RhoA with PKC suggests that RhoA mediates at least partially its effect on gene transcription through atypical PKC. In contrast to previous studies, identifying Rac1-PI3K as an upstream element in TLR2-initiated response to NF-B, PI3K signaling was not required for RhoA or PKC activity. These results indicate that multiple GTPase-regulated pathways emerge from stimulated Toll receptors, controlling different aspects of NF-B-mediated gene transcription.
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