Effect of SPNS1 on lipid metabolism in mice
Accumulation of sphingolipids, especially sphingosines, in the lysosomes is attributed to the pathogenesis of several lysosomal storage diseases. In searching for a lysosomal protein that mediates the release of sphingosines, we identified SPNS1 which shares the highest homology to SPNS2, a sphingosine-1-phosphate (S1P) transporter. We generated knockout cells and mice for Spns1 and employed lipidomics and metabolomics to identify SPNS1 ligands. We found that knockouts of Spns1 resulted in the accumulation of sphingolipids including sphingosines in embryonic brains and cell lines. These results suggest that deficiency of SPNS1 affects the clearance of sphingolipids in lysosomes. Biochemical assays demonstrated that sphingosines released from lysosomes required SPNS1. Postnatal deletion of Spns1 in mice causes lipid accumulation in the lysosomes and pathological conditions that are reminiscent of sphingolipid lysosomal storage diseases. These results reveal a critical molecular role of SPNS1 as a transporter for lysosphingolipids and lysoglyerophospholipids from the lysosomes and link its physiological roles with lysosomal storage diseases. Overall design: To investigate the role of SPNS1 in lipid metabolism, SPNS1 has been knocked out in mice.