ABHD12 and LPCAT3 Interplay Regulates a Lyso-phosphatidylserine-C20:4 Phosphatidylserine Lipid Network Implicated in Neurological Disease.

PHARC (polyneuropathy, hearing loss, cerebellar ataxia, retinitis pigmentosa, and cataract) is a human neurological disorder caused by deleterious mutations in the ABHD12 gene, which encodes an integral membrane lyso-phosphatidylserine (lyso-PS) lipase. Pharmacological or genetic disruption of ABHD12 leads to higher levels of lyso-PS lipids in human cells and the central nervous system (CNS) of mice. ABHD12 loss also causes rapid rewiring of PS content, resulting in selective increases in the level of arachidonoyl (C20:4) PS and decreases in the levels of other PS species. The biochemical basis for ABHD12-dependent PS remodeling and its pathophysiological significance remain unknown. Here, we show that genetic deletion of the lysophospholipid acyltransferase LPCAT3 blocks accumulation of brain C20:4 PS in mice lacking ABHD12 and concurrently produces hyper-increases in the level of lyso-PS in these animals. These lipid changes correlate with exacerbated auditory dysfunction and brain microgliosis in mice lacking both ABHD12 and LPCAT3. Taken together, our findings reveal that ABHD12 and LPCAT3 coordinately regulate lyso-PS and C20:4 PS content in the CNS and point to lyso-PS lipids as the likely bioactive metabolites contributing to PHARC-related neuropathologies.