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

Abstract

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 β-arrestin-2 (βarr2) expression. However, subsequent studies reveal that CREB activation in CF cells is independent of protein kinase- A (PKA). The goal of this study is to test the hypothesis that elevated βarr2 expression leads to increased CREB activation in a PKA-independent mechanism. βarr2-GFP expressing tracheal epithelial cells (βarr2-GFP) exhibit an increase of pCREB content and subsequent CRE activation compared to GFP expressing control cells. βarr2 activation of the ERK cascade represents a candidate mechanism leading to CREB activation. ERK exhibits increased activation in βarr2-GFP cells compared to cont-GFP cells and ERK inhibition diminishes CRE activation in both GFP and βarr2-GFP cells. To test directly whether CREB regulation in CF is βarr2-dependent, nasal epithelium excised from wt mice (Cftr +/+; βarr2 +/+), CF mice (Cftr −/−; βarr2 +/+), and DKO mice (Cftr −/−; βarr2 −/−) were analyzed for pCREB protein content. Removal of βarr2 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 βarr2 expression via the ERK pathway.

β-Arrestin Recruitment and G Protein Signaling by the Atypical Human Chemokine Decoy Receptor CCX-CKR

“…Interestingly, all ligands are ϳ30 -100-fold less potent to stimulate CRE activity in comparison to recruiting ␤-arrestins, which might suggest that ␤-arrestin is not involved in CRE activation in PTX-treated CCX-CKR-expressing cells by interacting with the transcription factor cAMPresponse element-binding protein and the histone acetyltransferase p300 as previously observed for the ␦-opioid receptor (43). Moreover, the absence of CCL19-induced ERK1/2 phosphorylation in CCX-CKR-expressing cells indicates that CRE activation is also not induced via a ␤-arrestin-and ERK1/2-dependent pathway, which has been recently described in tracheal epithelial cells (44). FIGURE 9.…”

Regulatory role of β-arrestin-2 in cholesterol processing in cystic fibrosis epithelial cells

“…These cells also show a colocalization of the expressed ␤ arr2-GFP and unesterifi ed cholesterol. Previous studies demonstrated that total ␤ arr2 expression in ␤ arr2-GFP cells was comparable to CF model cells ( 22 ).…”

“…Cftr/ ␤ arr2 double knockout (DKO) mice were developed as recently published ( 22 ) and utilized to directly examine the effect of ␤ arr2 on aspects of cholesterol processing and signaling. We previously demonstrated that CF mice exhibit increased de novo cholesterol synthesis in the liver compared with sibling WT mice ( 11 ).…”

β-Arrestins in the Immune System

“…Nasal epithelium excised from Cftr and β-arrestin 2 double knockout mice exhibit reduced pCREB and pERK levels compared to Cftr −/− mice, but similar to WT mice. Thus, β-arrestin 2 directly regulates cystic fibrosis induced CREB activation through the ERK signaling pathway 164 .…”