JM4 is a 178 amino acid endosomal multi-pass membrane protein involved in vesicular trafficking and Endoplasmic reticulum/Golgi transport. As a member of the PRA1 family, JM4 contains four putative transmembrane (TM) domains, interacts with the CC chemokine receptor 5 (CCR5) and colocalizes with Calnexin in the ER and mannose 6-phosphate receptor (CD-MPR) in the Golgi apparatus. While ubiquitously expressed, JM4 has been found at high levels in small intestine, lung, pancreas, spleen, Purkinje cells of the cerebellum and in neuronal cells of the hippocampus, cerebral cortex and lateral ventricles of the brain. JM4 plays a proapoptic role in cerulenin-induced neuroblastoma apoptosis and has been implicated in human cancer. JM4, which serves as a candidate prognostic marker in neuroblastoma, is encoded by a gene that maps to human chromosome Xp11.23