Involved in cellular auxin homeostasis by regulating auxin metabolism. Regulates intracellular auxin accumulation at the endoplasmic reticulum and thus auxin availability for nuclear auxin signaling. Expressed in seedlings, rosette and cauline leaves, stems, flowers and siliques. Up-regulated by auxin application. Belongs to the auxin efflux carrier (TC 2.A.69.2) family.