Receptor for the leucine-rich nuclear export signal (NES) (PubMed:10636888, PubMed:14638854, PubMed:16103875). Binds cooperatively to the NES on its target protein and to the small GTPase Ran in its active GTP-bound form (PubMed:10636888, PubMed:14638854). Involved in the export of dl, RpS2 and the pre-40S ribosome from the nucleus to the cytoplasm (PubMed:14638854, PubMed:25858587, PubMed:17032737). Plays an important role in nuclear pore assembly by mediating nucleoporin condensation and biogenesis of annulate lamellae (PubMed:31626769). Required for the function or maintenance of certain tissues such as brain and gut (PubMed:10924475). Interacts with Clbn (via its N-terminus) (PubMed:16103875). Associates with the nuclear pore complex via interaction with mbo and Nup214 (PubMed:14638854, PubMed:17032737). Interacts with target proteins containing NES sequences such as actin and dl (PubMed:10924475, PubMed:14638854, PubMed:17032737). Localization to the nuclear pore complex is promoted by Nup214. High expression observed in the developing embryonic brain, hind gut and posterior spiracles shortly before dorsal closure; and in the ventral nerve cord, midgut and somatic musculature shortly after dorsal closure. Expression increases when the tissue is well developed. Expressed in the larva (at protein level) (PubMed:14638854). Highly expressed both maternally and zygotically (PubMed:10924475). RNAi-mediated knockdown results in defects in nuclear export resulting in accumulation of RpS2 and pre-40S ribosome in the nucleus (PubMed:25858587). During oogenesis, mislocalizes Nup358-containing granules to nurse cells and abolishes the formation of annulate lamellae (PubMed:31626769). Activity inhibited by leptomycin B, which disrupts interaction with the NES and RanGTP. Belongs to the exportin family.