Ufmylation System: Novel Control of GPCR Biosynthetic Trafficking and Therapeutic Targets

G protein-coupled receptors (GPCRs) constitute the largest family of membrane receptors that regulate a vast variety of cellular functions and serve as important therapeutic targets. A fundamental but poorly addressed question in GPCR biology is how individual receptors are efficiently delivered to their functional destinations following synthesis in the endoplasmic reticulum (ER). Ufmylation is a ubiquitination-like post-translational modification in which ubiquitin-fold modifier 1 is conjugated to target proteins. Compared with ubiquitination, the physiological and pathological significance of ufmylation is much less defined. Recent studies, however, have revealed crucial functions of the ufmylation system in maintaining ER homeostasis and directing GPCR export from the ER. In this review, we succinctly summarize recent advances in understanding the ufmylation system, discuss its role in the biosynthetic transport and segregation of nascent GPCRs at ER-derived COPII vesicles, and explore the therapeutic potential of targeting ufmylation-mediated GPCR trafficking.