SLC35A4 is a Golgi membrane transporter that mediates CDP-ribitol import, a critical substrate for ribitol phosphate incorporation into α-dystroglycan glycans 1. The protein functions redundantly with SLC35A1 for CDP-ribitol transport, with its smaller binding pocket restricting substrate specificity compared to the promiscuous SLC35A1 1. SLC35A4 does not transport CMP-sialic acid, UDP-galactose, or UDP-N-acetylglucosamine 21. Beyond its canonical transporter role, SLC35A4 exhibits dual-coding capacity: its upstream ORF encodes a functional inner mitochondrial membrane microprotein (SLC35A4-MP) that regulates cellular respiration and ATP generation 3. An alternative ORF produces AltSLC35A4, also localized to the inner mitochondrial membrane 4. Both the reference SLC35A4 protein and AltSLC35A4 protect against oxidative stress, with SLC35A4 showing dramatic translational upregulation during sodium arsenite-induced oxidative stress via upstream ORF-dependent mechanisms 4. At the Golgi, SLC35A4 associates with nucleotide sugar transporters SLC35A2 and SLC35A3, modulating their subcellular distribution and forming multi-enzyme complexes that facilitate N-glycan synthesis 25.