ABHD4 Regulates Multiple Classes of <i>N</i>‑Acyl Phospholipids in the Mammalian Central Nervous System

<i>N</i>-Acyl phospholipids are atypical components of cell membranes that bear three acyl chains and serve as potential biosynthetic precursors for lipid mediators such as endocannabinoids. Biochemical studies have implicated ABHD4 as a brain <i>N</i>-acyl phosphatidylethanolamine (NAPE) lipase, but <i>in vivo</i> evidence for this functional assignment is lacking. Here, we describe ABHD4<sup>–/–</sup> mice and their characterization using untargeted lipidomics to discover that ABHD4 regulates multiple classes of brain <i>N</i>-acyl phospholipids. In addition to showing reductions in brain glycerophospho-NAEs (GP-NAEs) and plasmalogen-based lyso-NAPEs (lyso-pNAPEs), ABHD4<sup>–/–</sup> mice exhibited decreases in a distinct set of brain lipids that were structurally characterized as <i>N</i>-acyl lysophosphatidylserines (lyso-NAPSs). Biochemical assays confirmed that NAPS lipids are direct substrates of ABHD4. These findings, taken together, designate ABHD4 as a principal regulator of <i>N</i>-acyl phospholipid metabolism in the mammalian nervous system.