GPCR binding and JNK3 activation by arrestin-3 have different structural requirements

Abstract

Arrestins bind active phosphorylated G protein-coupled receptors (GPCRs). Among the four mammalian subtypes, only arrestin-3 facilitates the activation of JNK3 in cells. In available structures, Lys-295 in the lariat loop of arrestin-3 and its homologue Lys-294 in arrestin-2 di-rectly interact with the activator-attached phosphates. We compared the role of arrestin-3 con-formational equilibrium and of Lys-295 in GPCR binding and JNK3 activation. Several mutants with enhanced ability to bind GPCRs showed much lower activity towards JNK3, whereas a mutant that does not bind GPCRs was more active. Subcellular distribution of mutants did not correlate with GPCR recruitment or JNK3 activation. Charge neutralization and reversal muta-tions of Lys-295 differentially affected receptor binding on different backgrounds, but had virtu-ally no effect on JNK3 activation. Thus, GPCR binding and arrestin-3-assisted JNK3 activation have distinct structural requirements, suggesting that facilitation of JNK3 activation is the func-tion of arrestin-3 that is not bound to a GPCR.

Arrestin-3-assisted activation of JNK3 mediates dopaminergic behavioral and signaling plasticity in vivo

“…This is perfectly correct for the arrestin-dependent regulation of ERK1/2, as only arrestins bound to activated phosphorylated GPCRs have high affinity for ERK (Luttrell et al, 2001;Song et al, 2009) and facilitate ERK1/2 activation (Breitman et al, 2012;Luttrell et al, 2001). In contrast, the JNK pathway is regulated by a non-receptor bound Arr3 (Breitman et al, 2012;Miller et al, 2001;Song et al, 2009;Zhan et al, 2016;Zheng et al, 2023). This leaves open the question about a link between the stimulation of DA receptors and Arr3-dependent JNK3 activation.…”