Clathrin interactor 1 (CLINT1, also known as EpsinR) promotes Clathrin-coated vesicle formation at the trans-Golgi network and endosomes and thereby modulates Golgi-endosome trafficking []. It binds to the SNARE Protein vti1b []. Interestingly, one isoform of Drosophila EpsinR is a translational fusion with the only Tel2 coding sequences in Drosophila. In this fusion protein, Tel2 serves as a regulator of wingless signalling []. Human EpsinR is involved in endogenous MHC-II-restricted antigen presentation [].
Syntaxin 8 forms a complex with syntaxin 7 (Qa), Vti1b (Qb) and either VAMP7 or VAMP8 (R-SNARE) and is involved in the transport from early endosomes to the lysosome [, ]. Syntaxin 8 is a member of the Qc subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) that mediate the interactions between SNARE proteins, and a transmembrane domain []. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation []. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic centre layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle [].
