The molecular mechanism of B cell activation by toll-like receptor protein RP-105

Abstract

The B cell–specific transmembrane protein RP-105 belongs to the family of Drosophila toll-like

proteins which are likely to trigger innate immune responses in mice and man. Here we demonstrate

that the Src-family protein tyrosine kinase Lyn, protein kinase C

b I/II (PKC

bI/II),

and Erk2-specific mitogen-activated protein (MAP) kinase kinase (MEK) are essential and

probably functionally connected elements of the RP-105–mediated signaling cascade in B cells.

We also find that negative regulation of RP-105–mediated activation of MAP kinases by membrane

immunoglobulin may account for the phenomenon of antigen receptor–mediated arrest

of RP-105–mediated B cell proliferation.