Figure 7. UVB induces β-catenin signaling in keratinocytes.
Our proposed pathway: UVB exposure leads to increased COX-2 expression which results in increased PGE2 production. PGE2 binds and activates its G-protein coupled receptor, EP2. Upon the binding of PGE2, Gαs binds to Axin resulting in the release of GSK3β from the phosphorylation/destruction complex. Concurrently, the Gβγ subunits stimulate Akt, through PI3K, leading to the phosphorylation and inactivation of GSK3β. This allows for stabilization and accumulation of β-catenin which translocates to the nucleus and activates transcription of target genes, such as AXIN2. Activation of β-catenin signaling could contribute to the proliferative response of keratinocytes to UVB radiation.