CHP1 Regulates Compartmentalized Glycerolipid Synthesis by Activating GPAT4

• DOI: 10.1016/j.molcel.2019.01.037
• Publication Date: 2019-03-04T18:10:13Z
• Authors: Xiphias Ge Zhu; Shirony Nicholson...; Yihui Shen; Konnor La; Can Ozlu; Tim Wang; Diana Klompstra; Yetis Gultekin; Jingyi Chi; Justine Fidelin; Tao Peng; Henrik Molina; Howard C. Hang; Wei Min; Kıvanç Birsoy
• Keywords: 0301 basic medicine; Lipogenesis; Calcium-Binding Proteins; 3T3 Cells; Hep G2 Cells; Endoplasmic Reticulum; Gene Expression Regulation, Enzymologic; Glycerides; Enzyme Activation; Jurkat Cells; 03 medical and health sciences; Drosophila melanogaster; HEK293 Cells; Glycerol-3-Phosphate O-Acyltransferase; Animals; Drosophila Proteins; Humans; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Acyltransferases; Cell Proliferation; HeLa Cells

Cells require a constant supply of fatty acids to survive and proliferate. Fatty acids incorporate into membrane and storage glycerolipids through a series of endoplasmic reticulum (ER) enzymes, but how these enzymes are regulated is not well understood. Here, using a combination of CRISPR-based genetic screens and unbiased lipidomics, we identified calcineurin B homologous protein 1 (CHP1) as a major regulator of ER glycerolipid synthesis. Loss of CHP1 severely reduces fatty acid incorporation and storage in mammalian cells and invertebrates. Mechanistically, CHP1 binds and activates GPAT4, which catalyzes the initial rate-limiting step in glycerolipid synthesis. GPAT4 activity requires CHP1 to be N-myristoylated, forming a key molecular interface between the two proteins. Interestingly, upon CHP1 loss, the peroxisomal enzyme, GNPAT, partially compensates for the loss of ER lipid synthesis, enabling cell proliferation. Thus, our work identifies a conserved regulator of glycerolipid metabolism and reveals plasticity in lipid synthesis of proliferating cells.