Figure 2.

Antigen crosslinks IgE/FcεRI complexes to initiate a tyrosine phosphorylation cascade that results in the activation of both PLCγ and Cdc42. Hydrolysis of PIP₂ by PLCγ produces IP₃, which mediates Ca²⁺ release from ER stores to stimulate SOCE that is necessary for degranulation. Activation of Cdc42 is important for sustained Ca²⁺ responses, including sustained Ca²⁺ oscillations, possibly because it promotes PIP5-kinase-mediated synthesis of PIP₂ via a mechanism that involves activation of protein kinase C. Modified from (23).