1-deoxysphingolipids dysregulate membrane properties and cargo trafficking in the early secretory pathway.

1-Deoxysphingolipids are non-canonical sphingolipids linked to several diseases, yet their cellular effects are poorly understood. Here, we utilize lipid chemical biology approaches to investigate the role of 1-deoxysphingolipid metabolism on the properties and functions of secretory membranes. We applied organelle-specific bioorthogonal labeling to visualize the subcellular distribution of metabolically tagged sphingolipids. We observed that 1-deoxysphingolipids are retained in the endoplasmic reticulum (ER) and specifically in ER exit sites (ERESs), suggesting that they do not efficiently sort into vesicular carriers. Cell lines expressing disease-associated variants of serine palmitoyl-CoA transferase accumulated 1-deoxysphingolipids, which were accompanied by a reduction in ER membrane fluidity and enlargement of ERES. We found that the rates of membrane protein release from the ER were altered in response to 1-deoxysphingolipid metabolism in a manner dependent on the protein's affinity for ordered or disordered membranes. The dysregulation of sphingolipid metabolism can thus alter secretory membrane properties and affect protein trafficking.