RALBP1 is a multifunctional membrane protein with dual roles in xenobiotic transport and small GTPase signaling. As an ATP-dependent transporter, it actively exports glutathione conjugates of electrophilic compounds and chemotherapy agents including doxorubicin out of cells, contributing to multidrug resistance. The protein also binds the small GTPase RalA and possesses GTPase-activating protein activity toward CDC42 and Rac1, linking Ras/Ral signaling to cytoskeletal regulation. RALBP1 is overexpressed in multiple human malignancies, including lung, ovarian carcinomas, and melanomas 1, and aberrant RALBP1 expression is considered a fundamental hallmark of carcinogenesis and drug/radiation resistance 2. Loss of RALBP1 increases sensitivity to radiation and chemotherapy 1. In gastric cancer, elevated RALBP1 promotes tumorigenesis through PI3K/Akt/mTOR signaling 3. At the blood-brain barrier, RALBP1 expression is induced by inflammation and modulates barrier permeability, linking it to neurodegenerative diseases 4. Recent evidence suggests RALBP1 also regulates surface protein homeostasis through stabilization of GTP-bound RalA in the exocytic pathway 5, pointing to broader cellular functions beyond xenobiotic transport.