This is the C-terminal domain of Armadillo-like helical domain-containing protein 3 (ARMH3), the previously uncharacterised peripheral Golgi protein C10orf76. ARMH3 interacts with and is involved in GBF1 recruitment, Golgi maintenance and protein secretion [, ]. C10orf76 associates with the lipid kinase PI4KB that increases phosphatidylinositol 4-phosphate (PI4P) levels at the Golgi, being essential for the viral replication of specific enteroviruses []. The function of this domain is unknown.
Arf GTPases are involved in the formation of coated carrier vesicles by recruiting coat proteins. This entry includes Arf1, Arf2, Arf3, Arf4, Arf5, and related proteins. Each contains an N-terminal myristoylated amphipathic helix that is folded into the protein in the GDP-bound state. GDP/GTP exchange exposes the helix, which anchors to the membrane. Following GTP hydrolysis, the helix dissociates from the membrane and folds back into the protein. A general feature of Arf1-5 signaling may be the cooperation of two Arfs at the same site. Arfs1-5 are generally considered to be interchangeable in function and location, but some specific functions have been assigned []. Arf1 localizes to the early/cis-Golgi, where it is activated by GBF1 and recruits the coat protein COPI. It also localizes to the trans-Golgi network (TGN), where it is activated by BIG1/BIG2 and recruits the AP1, AP3, AP4, and GGA proteins []. Humans, but not rodents and other lower eukaryotes, lack Arf2. Human Arf3 shares 96% sequence identity with Arf1 and is believed to generally function interchangeably with Arf1. Human Arf4 in the activated (GTP-bound) state has been shown to interact with the cytoplasmic domain of epidermal growth factor receptor (EGFR) and mediate the EGF-dependent activation of phospholipase D2 (PLD2), leading to activation of the activator protein 1 (AP-1) transcription factor []. Arf4 has also been shown to recognise the C-terminal sorting signal of rhodopsin and regulate its incorporation into specialised post-Golgi rhodopsin transport carriers (RTCs) []. There is some evidence that Arf5 functions at the early-Golgi and the trans-Golgi to affect Golgi-associated alpha-adaptin homology Arf-binding proteins (GGAs) [].
