Identification of endoplasmic reticulum export motifs for G protein-coupled receptors.

Coat protein complex II (COPII) vesicle-mediated protein export from the endoplasmic reticulum (ER) can be controlled by linear, independent motifs embedded within the cargo. ER export motifs directly interact with selective components of COPII vesicles and enhance cargo recruitment onto COPII vesicles. Moreover, ER export motifs are able to confer their transport abilities to other proteins. We have recently identified a novel ER export motif for α(2B)-adrenergic receptor (α(2B)-AR). This motif selectively interacts with Sec24C/D isoforms of COPII vesicles and facilitates α(2B)-AR export from the ER as well as transport to the cell surface. This motif can also mediate CD8 glycoprotein transport. These studies indicate that ER export of nascent G protein-coupled receptors (GPCRs) may be directed by specific codes that mediate receptor interaction with the ER-derived COPII vesicles. In this chapter, I discuss experimental approaches to identify ER export motifs for GPCRs by using α(2B)-AR as a model.