Lipid-trap mass spectrometry identifies lipid–protein interactions in cells

Cells actively maintain complex lipidomes that encompass thousands of lipids; however, many of the roles of these lipids remain unexplored. Specific interactions between lipids and membrane proteins are a likely reason for lipidome complexity. Here we report the development of a technique, named lipid-trap mass spectrometry (LTMS), to systematically study lipid-protein interactions directly captured from mammalian cells. LTMS uses immunoprecipitation of GFP-tagged proteins expressed in HeLa cells, followed by lipidomic analysis of lipids bound to the GFP-tagged protein. We applied LTMS to cell division to illustrate the technique. We chose this process because membranes regulate their lipid composition as they undergo major changes during cytokinesis, and many cytokinetic proteins, including RACGAP1 and ESCRT-III components CHMP4B and CHMP2A, are membrane-associated. Using LTMS, we found that RACGAP1 and CHMP4B associate with specific lipid species in dividing compared with non-dividing cells. We expand our understanding of lipid diversity during cell division and present a general approach to explore lipid-protein interactions to further our knowledge of the roles of lipids in mammalian cells.