Lysophospholipase PNPLA7 is a critical checkpoint of phosphatidylcholine catabolism and turnover for skeletal muscle homeostasis.

Abstract

Current evidence suggests that disturbed phosphatidylcholine (PC) turnover causes skeletal muscle dysfunction. However, the enzyme that converts lysophosphatidylcholine (LPC) to glycerophosphocholine (GPC), an irreversible checkpoint in PC catabolism, in skeletal muscle has remained unidentified. Here we show that PNPLA7, a patatin-like phospholipase isoform, is responsible for this process. Pnpla7 deletion in myoblasts impedes the conversion of LPC to GPC and then to choline. Quadriceps muscles in global Pnpla7-deficient mice display thinner muscle fibers with aberrant mitochondrial morphology, reduced endurance capacity, and decreased expression of genes related to fatty acid β-oxidation, mitochondrial functions, and slow-twitch fibers with age. These abnormalities are preceded by alterations in phospholipid composition, with decreases in docosahexaenoic acid-containing PC and mitochondrial cardiolipin. Moreover, skeletal muscle-specific Pnpla7 deficiency results in muscle phenotypes similar to its global deficiency. Identification of the lysophospholipase PNPLA7 aids further understanding of the role of PC turnover in skeletal muscle homeostasis.