Trans-Golgi Network (TGN) as a regulatory node for ?1-adrenergic receptor (?1AR) down-modulation and recycling.

ABSTRACT: Receptor down-modulation is the key mechanism by which G protein-coupled receptors (GPCRs) prevent excessive receptor signaling in response to agonist stimulation. Recently, the trans-Golgi network (TGN) has been implicated as a key checkpoint for receptor endocytosis and degradation. Here, we investigated the involvement of the TGN in down-modulation of ?1-adrenergic receptor in response to persistent isoprotenerol stimulation. Immunofluorescent staining showed that ~50% of endocytosed ?1AR colocalized with TGN-46 at 5 h. Disruption of the TGN by brefeldin A (BFA) led to the robust accumulation of endocytosed ?1AR in Rab11(+) recycling endosomes, inhibited ?1AR entry into LAMP1(+) lysosomes, and as a result enhanced ?1AR recycling to the plasma membrane. The lysosomotropic agent, chloroquine, arrested the majority of endocytosed ?1AR in the TGN by 4 h. Immunoblot analysis showed that either disruption of the TGN or blockage of the lysosome prevented ?1AR degradation. Co-expression of GFP-arrestin-3 in ?1AR cells increased the endocytosis of ?1AR and facilitated its entry to the TGN but inhibited recycling to the plasma membrane. Arrestin-3-induced inhibition of ?1AR recycling was reversed by BFA treatment, whereas chloroquine induced the accumulation of arrestin-3 with ?1AR in the TGN. These results demonstrate for the first time that the TGN acts as a checkpoint for both the recycling and down-regulation of ?1AR and that arrestin-3 not only mediates ?1AR endocytosis but also its recycling through the TGN.

SUBMITTER: Cheng SB 

PROVIDER: S-EPMC3340205 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature