Glycosylphosphatidylinositol (GPI)-anchored proteins are long and firmly embed within the membrane and leave an extension out over the surface of the membrane. One end of the protein stays embedded firmly within the cell membrane and the other end can attach to a variety of important molecules such as enzymes and antigens. The enzyme or antigen is held above the cell membrane in a position that makes it available to be activated on the cell surface.
The phosphatidylinositol end is lipid (oil or fat) based and dissolves well in the fatty acid rich environment found within the membrane. The glyco- or sugar part of the molecule is able to dissolve in water or form bonds with other proteins or carbohydrates and is found on the end of the molecule that sticks out over the surface of the membrane.
GPI anchor proteins are essential for life. Mice that were experimentally made to lack the gene thought to encode for GPI anchor proteins did not survive. Experimental “knockout” mice are usually observed to see what types of function the knocked out gene might have performed. The experiment showed that GPI anchors were necessary for basic survival of baby mice. (Ref. 1, Brooks, Dwek, Schumacher, 2002, p 225) When a protein is found to be so essential that a “knockout” mouse doesn’t survive than more minor differences are attempted to be made in order to try to find out what types of functions are changed or are missing from the more slightly modified “knockout” mice.
Background information: GPI anchors are found in some types of G-protein couple receptors and may have importance within the cannabinoid receptor system which has been found to play early and essential roles in implantation of the newly fertilized egg within the mother’s uterus.
/Disclosure: This information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes./
- Brooks SA, Dwek MV, Schumacher U., Functional and Molecular Glycobiology, (Bios, 2002, Oxford, UK)
- Landry Y, Niederhoffer N, Sick E, Gies JP., Heptahelical and other G-protein-coupled receptors (GPCRs) signaling., Curr Med Chem. 2006;13(1):51-63. [ncbi.nlm.nih.gov/pubmed/16457639]
- Maccarrone M, Bernardi G, […], and Centonze D., Cannabinoid receptor signalling in neurodegenerative diseases: a potential role for membrane fluidity disturbance., Br J Pharmacol. 2011 August; 163(7): 1379-1390 [ncbi.nlm.nih.gov/pmc/articles/PMC3165948/]
Additional note on GPI anchors:
- Fujita M, Kinoshita T. “GPI-anchor remodeling: potential functions of GPI-anchors in intracellular trafficking and membrane dynamics.” Biochim Biophys Acta. 2012 Aug;1821(8):1050-8. doi: 10.1016/j.bbalip.2012.01.004. Epub 2012 Jan 11. Abstract: [http://www.ncbi.nlm.nih.gov/pubmed/22265715] “and discuss how GPI-anchors regulate protein sorting, trafficking, and dynamics.”
/Disclosure: This information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes./GPI anchors are cell membrane glycoproteins by Jenny