Interplay between G protein-biased and arrestin-biased pathways in 5-HT2AR-mediated ERK activation

This study aimed to elucidate the interplay between G protein-biased and arrestin-biased signaling pathways in the context of 5-HT_2A receptor (5-HT_2AR)-mediated ERK activation. Subcellular fractionation analyses, shRNA-mediated knockdowns, and various pharmacological inhibitors were utilized to investigate the spatial dynamics and functional interactions between arrestin2, PKCβII, and ERK activation. Wild-type and mutant constructs of arrestin2 and PKCβII were employed to determine the necessity of their nuclear translocation and ubiquitination. It was shown that Mdm2-mediated ubiquitination of PKCβII and arrestin2 within the nucleus, triggered by 5-HT_2AR stimulation, is essential for ERK activation. Importantly, G protein signaling is necessary for the arrestin-biased pathway of 5-HT_2AR signaling, but not the Other way around. Gq signaling was observed to promote the nuclear entry of PKCβII in a Gβγ-dependent manner, followed by its ubiquitination in the nucleus. The ubiquitinated PKCβII then facilitates the nuclear import of arrestin2 via the importin complex, leading to arrestin2's ubiquitination in the nucleus. Conversely, arrestin2 is not required for the G protein signaling of 5-HT_2AR that leads to PKCβII activation. These results highlight the essential role of G protein signaling in facilitating arrestin-mediated pathways and unveil a hierarchical relationship between these signaling mechanisms.

5-HT(2A) receptor; Arrestin; Biased signaling; ERK; Mdm2; PKCβII.