ARF4

ARF4, or ADP-ribosylation factor 4, is a member of the ARF family of small GTPases that regulate vesicular trafficking in eukaryotic cells. Like other GTPases, ARF4 acts as a molecular switch, cycling between GDP-bound inactive and GTP-bound active states. Guanine nucleotide exchange factors (GEFs) promote the active state, and GTPase-activating proteins (GAPs) stimulate inactivation. In its GTP-bound form, ARF4 associates with membranes and recruits coat protein complexes to budding vesicles, helping to drive formation and cargo sorting. It is most closely linked to COPI-mediated transport at the Golgi and along endomembrane routes to endosomes and the plasma membrane.

ARF4 localizes primarily to the Golgi and post-Golgi compartments, and it participates in maintaining Golgi structure and membrane identity. Its activity is coordinated with phospholipid interactions and with other trafficking regulators. As with other ARF family members, ARF4 functions within a network of GEFs, GAPs, and effectors that ensure correct cargo delivery and organelle organization.

ARF4 homologs are found across eukaryotes, including plants and animals, where they contribute to conserved aspects of vesicle trafficking as well as organism-specific roles. The ARF family as a whole comprises small GTPases that regulate vesicle budding, coat recruitment, and membrane trafficking in the secretory pathway.