FIG. 8.

EGFR inhibition blocks cell proliferation and calcium signaling. (a) H4 cells were pretreated with DMSO or lapatinib (1 μM) for 1 h and subsequently treated with CHPG at the indicated doses for 10 min. Calcium mobilization was assayed using the Fluo4NW kit (Invitrogen). Error bars indicate the standard deviations (n = 3). (b) H4 cells were pretreated with DMSO, lapatinib, gefitinib, or compound A (Cmpd A) (1 μM each) for 1 h and subsequently treated with glutamate (Glu; 400 μM), CHPG (200 μM), or EGF (100 ng/ml) for 24 h. Cell metabolic activity was measured using a colorimetric assay (Promega). Error bars indicate the standard deviations (n = 4). (c) Model for glutamate signaling to NF-κB. Glutamate binding to mGluR5 triggers association with and transactivation of the EGFR leading to calcium mobilization, calcium-dependent IKKα/β phosphorylation, and dissociation of the p65-IκBα complexes. Glutamate also leads to p65 phosphorylation and enhanced p65 transcriptional activation. Circled P, Phosphorylation sites.