GPIankerlipiden

GPIankerlipiden are the lipid components of glycosylphosphatidylinositol (GPI) anchors, which teth­er certain proteins to the exterior of the cell membrane. The lipid moiety embeds in the outer leaflet of the lipid bilayer, while the attached protein projects into the extracellular space via a glycan bridge and a short peptide linkage.

The lipid portion is based on a phosphatidylinositol core, typically formed as a diacylglycerol linked to an inositol ring. This lipid backbone is connected to a glycan core that attaches to the protein through an ethanolamine phosphate group. Lipid composition can vary between species and tissues, and remodeling after attachment can influence membrane localization and raft association.

Biosynthesis and attachment occur in the endoplasmic reticulum. A nascent protein bearing a C-terminal GPI signal is transferred to the preassembled GPI anchor by a GPI transamidase complex, covalently linking the protein to the lipid via the ethanolamine phosphate. The GPI-anchored protein is then trafficked through the secretory pathway to the plasma membrane, where the lipid portion remains embedded.

Function and significance are broad. GPIankerlipiden regulate protein localization, trafficking, and function, and they influence processes such as signal transduction and cell adhesion. GPI-anchored proteins participate in immune recognition, enzymatic activity, and developmental signaling. Across eukaryotes, many enzymes, receptors, and regulatory proteins are GPI-anchored.

Clinical and research relevance includes defects in GPI biosynthesis, caused by mutations in PIG and related genes, which lead to congenital disorders. In research, enzymatic release of GPI-anchored proteins by phosphatidylinositol-specific phospholipase C is used to study their properties and membrane organization.