Exportin-4 or XPO4 belongs to a large family of nucleoproteins that mediate the transport of proteins and other cargo between the nuclear and cytoplasmic compartments. Exportin-4 is a RanGTP-binding protein and functions as a receptor for nuclear export of EIF-5A and also may have a role as an adapter in RNA export. Exportin-4 has been reported to be involved in nuclear export of Smad3 and thereby regulation of Smad signaling. Diseases associated with XPO4 include pinguecula. This protein has ubiquitously expressed.