Journal
EMBO JOURNAL
Volume 41, Issue 2, Pages -Publisher
WILEY
DOI: 10.15252/embj.2020106837
Keywords
lipid transport; membrane contact sites; membrane lipid homeostasis; membrane lipid unsaturation; mitochondria
Categories
Funding
- Division of Chemical Sciences in the Netherlands
- Netherlands Organization for Scientific Research (NWO) [711-013-004]
- China Scholarship Council [201204910146]
- Barth Syndrome Foundation (BSF)
- Federation of European Biochemical Societies (FEBS)
- Villum Fonden (Villum Foundation) [VKR023439]
- VILLUM Center for Bioanalytical Sciences [VKR023179]
- Lundbeckfonden (Lundbeck Foundation) [R54-A5858]
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Our study reveals the importance of ERMES and Vps39p in mediating the transfer of di-unsaturated phospholipids to mitochondria. This supports the concept that lipid flow between membranes is limited by molecular species-dependent lipid efflux and concentration gradients between membranes.
Mitochondria depend on the import of phospholipid precursors for the biosynthesis of phosphatidylethanolamine (PE) and cardiolipin, yet the mechanism of their transport remains elusive. A dynamic lipidomics approach revealed that mitochondria preferentially import di-unsaturated phosphatidylserine (PS) for subsequent conversion to PE by the mitochondrial PS decarboxylase Psd1p. Several protein complexes tethering mitochondria to the endomembrane system have been implicated in lipid transport in yeast, including the endoplasmic reticulum (ER)-mitochondrial encounter structure (ERMES), ER-membrane complex (EMC), and the vacuole and mitochondria patch (vCLAMP). By limiting the availability of unsaturated phospholipids, we created conditions to investigate the mechanism of lipid transfer and the contributions of the tethering complexes in vivo. Under these conditions, inactivation of ERMES components or of the vCLAMP component Vps39p exacerbated accumulation of saturated lipid acyl chains, indicating that ERMES and Vps39p contribute to the mitochondrial sink for unsaturated acyl chains by mediating transfer of di-unsaturated phospholipids. These results support the concept that intermembrane lipid flow is rate-limited by molecular species-dependent lipid efflux from the donor membrane and driven by the lipid species' concentration gradient between donor and acceptor membrane.
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