Lysosomal-associated transmembrane protein 4A (LAPTM4A), also known as Golgi 4-transmembrane spanning transporter MTP, is a 233 amino acid protein belonging to the LAPTM5/LAPTM5 transporter family. LAPTM4A is subcellularly localized to the intracytoplasmic membrane and has the potential to reside in intracellular membrane-bound compartments. LAPTM4A is thought to function as a transporter of nucleosides and/or nucleoside derivatives between the cytosol and the lumen of intracellular compartments. LAPTM4A is predicted to have four transmembrane domains, with the C-terminal domain being required for retention of the protein within intracellular membranes.