Beta-arrestin signaling and regulation of transcription.

Beta-arrestin 1 and beta-arrestin 2 are well-known negative regulators of G-protein-coupled receptor (GPCR) signaling. Upon GPCR activation, beta-arrestins translocate to the cell membrane and bind to the agonist-occupied receptors. This uncouples these receptors from G proteins and promotes their internalization, thus causing desensitization. However, accumulating evidence indicates that beta-arrestins also function as scaffold proteins that interact with several cytoplasmic proteins and link GPCRs to intracellular signaling pathways such as MAPK cascades. Recent work has also revealed that, in response to activation of certain GPCRs, beta-arrestins translocate from the cytoplasm to the nucleus and associate with transcription cofactors such as p300 and cAMP-response element-binding protein (CREB) at the promoters of target genes to promote transcription. They also interact with regulators of transcription factors, such as IkappaBalpha and MDM2, in the cytoplasm and regulate transcription indirectly. This beta-arrestin-mediated regulation of transcription appears to play important roles in cell growth, apoptosis and modulation of immune functions.