In vivo structure-function analysis of beta-arrestin Kurtz
Kurtz (Krz), a homolog of mammalian β-arrestins, is the only non-visual β-arrestin in Drosophila and has been implicated in the regulation of cellular signaling pathways such as G-protein coupled receptor (GPCR) and mitogen associated protein kinase (MAPK). Dysregulation of these pathways results in severe developmental abnormalities, many of which have been implicated in various diseases. It is important to understand which specific residues on arrestins are functionally important for GPCR desensitization, and while numerous mammalian in-vitro studies have focused on the direct association between GPCRs and arrestins, few, if any, have tested their in vivo functionality. Mutations in arginine to alanine (R66A), lysine to alanine (K51A and K52A) and valine and leucine to alanine (V111A and L112A), have been found to alter arrestin-GPCR binding. In order to study the role of Krz in fruit fly development, we have performed genetic studies which show that mutations of the Krz residues in which individual binding sites were lost do not alter Krz’s ability to rescue lethality associated with complete loss of krz function, while a combination of mutations such as KK/A and VL/A completely impairs Krz’s ability to rescue homozygous krz mutants. Understanding the mechanisms by which β-arrestins regulate cell-signaling networks presents great hopes for understanding multiple signaling networks and developing therapies for developmental and behavioral disorders.