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. Author manuscript; available in PMC: 2023 May 1.
Published in final edited form as: Immunol Rev. 2022 Feb 6;307(1):27–42. doi: 10.1111/imr.13070

Figure 1. Regulation of BCR signaling.

Figure 1.

I) Upon BCR crosslinking Lyn phosphorylates the ITAMs of CD79A/CD79B resulting in the recruitment and activation of Syk. II) Lyn and Syk activate PI3K which phosphorylates PI(4,5)P2 to generate PI(3,4,5)P3. III) A signaling cascade activates multiple pathways important for B cell activation. PI(3,4,5)P3 plays an important role in facilitating activating signaling via the recruitment of key proteins that contain PH domains. IV) ITIM/ITSM-containing receptors come in proximity to actively signaling BCRs. Lyn phosphorylates the ITIM/ITSM tyrosine leading to the recruitment and activation of SHP-1 and SHIP-1. V) The tyrosine phosphatase SHP-1 inhibits signaling by dephosphorylating key tyrosines. VI) The inositol phosphatase SHIP-1 inhibits PI3K-dependent signaling by dephosphorylating PI(3,4,5)P3 to PI(3,4)P2. PTEN also counteracts PI3K signaling by dephosphorylating PI(3,4,5)P3 to PI(4,5)P2.