Figure 3.

A contemporary view of antigen-binding-induced activation of BCR signaling pathways. A highly simplified version of the view of BCR signaling pathways is given. Early biochemical studies indicated that PTKs from three different families, including Lyn, Syk and Btk, are activated following BCR and antigen recognition, forming the typical membrane-proximal signalosome. Such signalosome complex is further stabilized by the involvement of a series of adaptor proteins including BLNK and GRB2. Upon the recruitment of PI3K and PLCγ2 to these membrane-proximal signalosome complexes, these two signaling molecules are activated, the former leading to the production of PIP₃ from PIP₂, while the latter resulting in the production of IP₃ and DAG from PIP₂. Starting from this point, BCR signaling gets quite diverse and triggers at least four different downstream signaling cascades^22,23, toward the transcriptional activation or regulation of NF-κB, NF-AT, FoxO and MAPK pathways.