Spns1 is a lysophospholipid transporter mediating lysosomal phospholipid salvage

M He, ACY Kuk, M Ding, CF Chin… - Proceedings of the …, 2022 - National Acad Sciences
M He, ACY Kuk, M Ding, CF Chin, DLA Galam, JM Nah, BC Tan, HL Yeo, GL Chua…
Proceedings of the National Academy of Sciences, 2022National Acad Sciences
The lysosome is central to the degradation of proteins, carbohydrates, and lipids and their
salvage back to the cytosol for reutilization. Lysosomal transporters for amino acids, sugars,
and cholesterol have been identified, and the metabolic fates of these molecules in the
cytoplasm have been elucidated. Remarkably, it is not known whether lysosomal salvage
exists for glycerophospholipids, the major constituents of cellular membranes. By using a
transport assay screen against orphan lysosomal transporters, we identified the major …
The lysosome is central to the degradation of proteins, carbohydrates, and lipids and their salvage back to the cytosol for reutilization. Lysosomal transporters for amino acids, sugars, and cholesterol have been identified, and the metabolic fates of these molecules in the cytoplasm have been elucidated. Remarkably, it is not known whether lysosomal salvage exists for glycerophospholipids, the major constituents of cellular membranes. By using a transport assay screen against orphan lysosomal transporters, we identified the major facilitator superfamily protein Spns1 that is ubiquitously expressed in all tissues as a proton-dependent lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) transporter, with LPC and LPE being the lysosomal breakdown products of the most abundant eukaryotic phospholipids, phosphatidylcholine and phosphatidylethanolamine, respectively. Spns1 deficiency in cells, zebrafish embryos, and mouse liver resulted in lysosomal accumulation of LPC and LPE species with pathological consequences on lysosomal function. Flux analysis using stable isotope-labeled phospholipid apolipoprotein E nanodiscs targeted to lysosomes showed that LPC was transported out of lysosomes in an Spns1-dependent manner and re-esterified back into the cytoplasmic pools of phosphatidylcholine. Our findings identify a phospholipid salvage pathway from lysosomes to the cytosol that is dependent on Spns1 and critical for maintaining normal lysosomal function.
National Acad Sciences