B Cell Receptor Cross-Talk: Exposure to Lipopolysaccharide Induces an Alternate Pathway for B Cell Receptor-Induced Erk Phosphorylation and Nf-B Activation

Dye, J.R.; Palvanov, A.; Guo, B.; Rothstein, T.L.

The Journal of Immunology 179(1): 229-235


DOI: 10.4049/jimmunol.179.1.229
Accession: 068490636

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BCR signaling in naive B cells depends on the function of signalosome mediators; however, prior engagement of CD40 or of IL-4R produces an alternate signaling pathway in which Bruton's tyrosine kinase, PI3K, phospholipase Cgamma2, and protein kinase Cbeta are no longer required for BCR-induced downstream events. To explore the range of mediators capable of producing such an alternate pathway for BCR signaling, we examined the TLR4 agonist, LPS. B cell treatment with LPS at relatively low doses altered subsequent BCR signaling such that ERK phosphorylation and NF-kappaB activation occurred in a PI3K-independent manner. This effect of LPS extended to MEK phosphorylation and IkappaBalpha degradation, and it developed slowly over a period of 16-24 h. The involvement of TLRs is suggested by similar effects observed with a structurally distinct TLR agonist, PAM3CSK4 and by the need for MyD88 for induction of alternate BCR signaling by LPS. Thus, LPS-mediated TLR engagement produces an alternate pathway for BCR-triggered signal propagation that differs from the classical, signalosome-dependent pathway.