Suppression of epidermal growth factor receptor signaling by protein kinase C-α activation requires CD82, caveolin-1, and ganglioside

Activation of protein kinase C (PKC)-α decreases normal and neoplastic cell proliferation by inhibiting epidermal growth factor receptor (EGFR)-related signaling. The molecular interactions upstream to PKC-α that influence its suppression of EGFR, however, are poorly understood. We have found that caveolin-1, tetraspanin CD82, and ganglioside GM3 enable the association of EGFR with PKC-α, ultimately leading to inhibition of EGFR signaling. GM3- and CD82-induced inhibition of EGFR signaling requires PKC-α translocation and serine/threonine phosphorylation, which eventually triggers EGFR Thr⁶⁵⁴ phosphorylation and receptor internalization. Within this ordered complex of signaling molecules, the ability of CD82 to associate with PKC-α requires the presence of caveolin-1, whereas the interaction of caveolin-1 or PKC-α with EGFR requires the presence of CD82 and ganglioside GM3. Disruption of the membrane with methyl-β-cyclodextrin dissociates the EGFR/GM3/caveolin-1/CD82/PKC-α complex and prevents the inhibitory effect of PKC-α on EGFR phosphorylation, suggesting that caveolin-1, CD82, and ganglioside interact with EGFR and PKC-α within intact cholesterol-enriched membrane microdomains. Given the role of these membrane molecules in suppressing EGFR signaling, upregulation of GM3, caveolin-1, and CD82 function may be an effective adjunctive therapy for treating epithelial cell malignancies.