The ufmylation cascade controls COPII recruitment, anterograde transport, and sorting of nascent GPCRs at ER.

Ufmylation is implicated in multiple cellular processes, but little is known about its functions and regulation in protein trafficking. Here, we demonstrate that the genetic depletion of core components of the ufmylation cascade, including ubiquitin-fold modifier 1 (UFM1), UFM1 activation enzyme 5, UFM1-specific ligase 1 (UFL1), UFM1-specific protease 2, and UFM1-binding protein 1 (UFBP1) each markedly inhibits the endoplasmic reticulum (ER)-Golgi transport, surface delivery, and recruitment to COPII vesicles of a subset of G protein-coupled receptors (GPCRs) and UFBP1's function partially relies on UFM1 conjugation. We also show that UFBP1 and UFL1 interact with GPCRs and UFBP1 localizes at COPII vesicles coated with specific Sec24 isoforms. Furthermore, the UFBP1/UFL1-binding domain identified in the receptors effectively converts non-GPCR protein transport into the ufmylation-dependent pathway. Collectively, these data reveal important functions for the ufmylation system in GPCR recruitment to COPII vesicles, biosynthetic transport, and sorting at ER via UFBP1 ufmylation and interaction directly.

Gßγ translocation to the Golgi apparatus activates ARF1 to spatiotemporally regulate G protein-coupled receptor signaling to MAPK.

After activation of G protein-coupled receptors, G protein ßγ dimers may translocate from the plasma membrane to the Golgi apparatus (GA). We recently report that this translocation activates extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) via PI3Kγ; however, how Gßγ-PI3Kγ activates the ERK1/2 pathway is unclear. Here, we demonstrate that chemokine receptor CXCR4 activates ADP-ribosylation factor 1 (ARF1), a small GTPase important for vesicle-mediated membrane trafficking. This activation is blocked by CRISPR-Cas9-mediated knockout of the GA-translocating Gγ9 subunit. Inducible targeting of different Gßγ dimers to the GA can directly activate ARF1. CXCR4 activation and constitutive Gßγ recruitment to the GA also enhance ARF1 translocation to the GA. We further demonstrate that pharmacological inhibition and CRISPR-Cas9-mediated knockout of PI3Kγ markedly inhibit CXCR4-mediated and Gßγ translocation-mediated ARF1 activation. We also show that depletion of ARF1 by siRNA and CRISPR-Cas9 and inhibition of GA-localized ARF1 activation abolish ERK1/2 activation by CXCR4 and Gßγ translocation to the GA and suppress prostate cancer PC3 cell migration and invasion. Collectively, our data reveal a novel function for Gßγ translocation to the GA to activate ARF1 and identify GA-localized ARF1 as an effector acting downstream of Gßγ-PI3Kγ to spatiotemporally regulate G protein-coupled receptor signaling to mitogen-activated protein kinases.