Figure 2.

Trichoplein promotes cell proliferation through suppression of ciliogenesis in the presence of EGF. A) EGF activates USP8 through phosphorylation. Activated USP8 deubiquitinates and stabilizes trichoplein at the mother centriole. Trichoplein suppresses ciliogenesis through activation of Aurora A kinase, which stimulates cell proliferation. B) In the absence of EGF signaling, USP8 is not activated. Unphosphorylated USP8 (inactive USP8) allows for the polyubiquitination of TCHP by CRL3-KCTD17, which culminates in TCHP degradation and primary cilium formation. Cell cycle arrest occurs after formation of the primary cilium.