Glycophosphatidylinositol
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753
Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [2] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Glycosylphosphatidylinositol (GPI anchor ) is a glycolipid that can be attached to the C-terminus of a protein during posttranslational modification. It is composed of a hydrophobic phosphatidylinositol group linked through a carbohydrate containing linker (glucosamine and mannose glycosidically bound to the inositol residue) to the C-terminal amino acid of a mature protein. The two fatty acids within the hydrophobic phosphatidyl-inositol group anchor the protein to the cell membrane.
Glypiated proteins contain a signal peptide, thus directing them into the endoplasmic reticulum (ER). The C-terminus is composed of hydrophobic amino acids which stay inserted in the ER membrane. The hydrophobic end is then cleaved off and replaced by the GPI-anchor. As the protein processes through the secretory pathway, it is transferred via vesicles to the Golgi apparatus and finally to the extracellular space where it remains attached to the exterior leaflet of the cell membrane. Since the glypiation is the sole means of attachment of such proteins to the membrane, cleavage of the group by phospholipases will result in controlled release of the protein from the membrane. The latter mechanism is used in vitro, i.e. the membrane proteins released from the membranes in the enzymatic assay are glypiated protein.
Phospholipase C (PLC) is an enzyme that is known to cleave the phospho-glycerol bond found in GPI-anchored proteins. Treatment with PLC will cause release of GPI-linked proteins from the outer cell membrane. The T-cell marker Thy-1, acetylcholinesterase, as well as both intestinal and placental alkaline phosphatase are known to be GPI-linked and are released by treatment with PLC. GPI-linked proteins are thought to be preferentially located in lipid rafts, suggesting a high level of organization within microdomains plasma membrane.
Defects of GPI anchors occur in the rare disease paroxysmal nocturnal hemoglobinuria.
External links
Lipids: phospholipids | |
|---|---|
| Glycerol backbone (Glycerophospholipids/ Phosphoglycerides) | Phosphatidyl-: -ethanolamine/cephalin - -choline/lechithin (dipalmitoyl-) - -serine - -glycerol - -inositol (glyco-)
phosphatidylinositol phosphates: PIP1 - PIP2 (3,4, 3,5, 4,5) - PIP3 Ether lipids: Plasmalogen (Platelet-activating factor) |
| Sphingosine backbone | Sphingomyelin |
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
