Abstract
Spinster homolog 2 (SPNS2) exports the bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P) out of cells to regulate processes important for health and diseases. However, the molecular mechanism underlying SPNS2 transport functions and its precise physiological roles are not fully understood. Here, through a series of complementary approaches in mice, cellular assays, and particularly with in vitro cell-free binding and transport assays, we show that SPNS2 has antiporter-like activity, transporting S1P out of cells and glucose in. We demonstrate that SPNS2 directly binds glucose and transports it and identify key amino acid residues of SPNS2 involved in glucose engagement and import. Our data reveal that S1P, which enters from the cytosolic side of SPNS2 facilitates conformational changes, enabling extracellular glucose to move inward through the central cavity. Thus, we identify a mechanism that dynamically contributes to glucose homeostasis in response to metabolic and sphingolipid cues with clinical and pathophysiological implications.