Lysophosphatidic acid acyltransferase 3 tunes the membrane status of germ cells by incorporating docosahexaenoic acid during spermatogenesis

摘要

Docosahexaenoic acid (DHA) is one of the essential ω-3 polyunsaturated fatty acids with a wide range of physiological roles important for human health. For example, DHA renders cell membranes more flexible and is therefore important for cellular function, but information on the mechanisms that control DHA levels in membranes is limited. Specifically, it is unclear which factors determine DHA incorporation into cell membranes and how DHA exerts biological effects. We found that lysophosphatidic acid acyltransferase 3 (LPAAT3) is required for producing DHA-containing phospholipids in various tissues, such as the testes and retina. In this study, we report that LPAAT3-KO mice display severe male infertility with abnormal sperm morphology. During germ cell differentiation, the expression of LPAAT3 was induced, and germ cells obtained more DHA-containing phospholipids. Loss of LPAAT3 caused drastic reduction of DHA-containing phospholipids in spermatids that led to excess cytoplasm around its head, which is normally removed by surrounding Sertoli cells via endocytosis at the final stage of spermatogenesis. In vitro liposome filtration assay raised the possibility that DHA in phospholipids promotes membrane deformation that is required for the rapid endocytosis. These data suggest that decreased membrane flexibility in LPAAT3-KO sperm impaired the efficient removal of sperm content through endocytosis. We conclude that LPAAT3-mediated enrichment of cell membranes with DHA-containing phospholipids endows these membranes with physicochemical properties needed for normal cellular processes, as exemplified by spermatogenesis.