GPI anchor biosynthesis. (A) Core structure of the GPI anchor. The inositol-phospholipid (PI) is anchors into the lipid bilayer of the plasma membrane. The glycan core consists of a molecule of N-glucosamine, 3 manose molecules (Man), and a molecule of ethanolamine phosphate. The protein is covalently attached through an amide bond to an ethanolamine on the terminal mannose. (B) GPI anchor biosynthesis takes place in the endoplasmic reticulum. PIGA is 1 of 7 subunits involved in the first step of GPI anchor biosynthesis. There are ≥10 additional steps and >25 genes involved. After the protein is attached to the GPI anchor, the mature GPI-anchored protein goes to the Golgi, where fatty acid remodeling occurs and (C) eventually the GPI anchored protein is transported to the plasma membrane.