RANBP9 is a multifunctional scaffolding protein that serves as a core component of the CTLH E3 ubiquitin-protein ligase complex 1. Its primary roles include mediating cell spreading and actin cytoskeleton rearrangement 2, enhancing HGF-MET signaling through Sos recruitment and Ras pathway activation 3, and regulating transcription factor activity including stabilization of TP73 alpha and enhancement of androgen receptor transactivation 4. RANBP9 inhibits DYRK1A/1B kinase activity and FMR1 RNA binding 5. The protein functions as part of a regulatory rheostat with RANBP10, where their relative expression ratio controls CTLH complex ubiquitylation output and cell proliferation 6. RANBP9 participates in DNA damage response signaling through ATM pathway involvement 7 and regulates AMPK activity via ubiquitination 8. Elevated RANBP9 expression is associated with poor prognosis in breast cancer 9 and correlates with reduced lenvatinib sensitivity in hepatocellular carcinoma through MFN2 regulation 10. In neurodegeneration, RANBP9 enhances tau pathology through interaction with Hsp90/Hsc70 chaperone complexes 11.