The function of RANBP9 (RAN binding protein 9, ENSG00000010017) is as follows. May act as scaffolding protein, and as adapter protein to couple membrane receptors to intracellular signaling pathways (Probable). Acts as a mediator of cell spreading and actin cytoskeleton rearrangement (PubMed:18710924). Core component of the CTLH E3 ubiquitin-protein ligase complex that selectively accepts ubiquitin from UBE2H and mediates ubiquitination and subsequent proteasomal degradation of the transcription factor HBP1 (PubMed:29911972). May be involved in signaling of ITGB2/LFA-1 and other integrins (PubMed:14722085). Enhances HGF-MET signaling by recruiting Sos and activating the Ras pathway (PubMed:12147692). Enhances dihydrotestosterone-induced transactivation activity of AR, as well as dexamethasone-induced transactivation activity of NR3C1, but not affect estrogen-induced transactivation (PubMed:12361945, PubMed:18222118). Stabilizes TP73 isoform Alpha, probably by inhibiting its ubiquitination, and increases its proapoptotic activity (PubMed:15558019). Inhibits the kinase activity of DYRK1A and DYRK1B. Inhibits FMR1 binding to RNA. {ECO:0000269|PubMed:12147692, ECO:0000269|PubMed:12361945, ECO:0000269|PubMed:14500717, ECO:0000269|PubMed:14722085, ECO:0000269|PubMed:15381419, ECO:0000269|PubMed:15558019, ECO:0000269|PubMed:18222118, ECO:0000269|PubMed:18710924, ECO:0000269|PubMed:29911972, ECO:0000305}.