 Creo-electron microscopy structures reveal that the apo form of human SLC-15A4 is in an outward-facing conformation, while the dimeric form involves four cholesterol molecules. The TASL bound complex shows an unprecedented interaction mode with solute carriers and undergoes a conformational change to form a binding pocket for TASL insertion. These findings provide insights into the molecular basis of regulatory switch involving a human solute carrier and offer an important framework for structure-guided drug discovery targeting SLC-15A4-TASL-related human autoimmune diseases. This article was authored by Su Dong Chen, Min It-Sie, Sen Sen Jong, and others.