β-Arrestin-2 Regulation of the cAMP Response Element Binding Protein

Previous work demonstrated that cystic fibrosis (CF) cells exhibit an increase in cAMP-mediated signaling as a characteristic response to lost CFTR function. Evidence for increased cAMP-mediated signaling in CF included increased phosphorylation of the cAMP response element binding protein (CREB) and elevated beta-arrestin-2 (beta arr2) expression. However, subsequent studies reveal that CREB activation in CF cells is independent of protein kinase-A (PICA). The goal of this study is to test the hypothesis that elevated beta arr2 expression leads to increased CREB activation in a PICA-independent mechanism. beta arr2-GFP expressing tracheal epithelial cells (beta arr2-GFP) exhibit an increase of pCREB content and subsequent CRE activation compared to GFP expressing control cells. beta arr2 activation of the ERK cascade represents a candidate mechanism leading to CREB activation. ERK exhibits increased activation in beta arr2-GFP cells compared to cont-GFP cells, and ERK inhibition diminishes CRE activation in both GFP and beta arr2-GFP cells. To test directly whether CREB regulation in CF is beta arr2-dependent, nasal epithelium excised from wt mice (Cftr +/+; beta arr2 +/+), CF mice (Cftr -/-; beta arr2 +/+), and DKO mice (Cftr -/-; beta arr2 -/-) were analyzed for pCREB protein content. Removal of beta arr2 expression from CF mice reduces both pCREB and pERK content to wt levels. These data indicate that CF-related CREB regulation is mediated directly through beta arr2 expression via the ERK pathway.