CD59

CD59 or Protectin is a protein that in humans is encoded by the CD59 gene. CD59 is a cell surface glycoprotein that regulates complement-mediated cell lysis, and it is involved in lymphocyte signal transduction. This protein is a potent inhibitor of the complement membrane attack complex, whereby it binds complement C8 and/or C9 during the assembly of this complex, thereby inhibiting the incorporation of multiple copies of C9 into the complex, which is necessary for osmolytic pore formation.

Function

CD59 is a small (18-20 kDa) glycoprotein widely expressed on cells in the body. The protein inhibits the formation of the membrane attack complex (MAC). This complex forms a pore in the plasma membrane of cells to which complement proteins have bound through the classical or alternative complement pathways. The MAC is composed of the complement proteins C5b, C6, C7, C8, and multiple copies of C9. The insertion of MAC into the cell membrane forms a pore which disrupts the membrane and can lead to cell lysis.

Clinical significance

Deficiency of this protein is associated with a variety of clinical disorders, including paroxysmal nocturnal hemoglobinuria (PNH), hemolytic anemia, and thrombosis. Mutations in this gene have been associated with stroke, Hemolytic-uremic syndrome (HUS), and nephrotic syndrome. Two transcript variants encoding different isoforms have been found for this gene.

See also

• Cluster of differentiation
• Complement system
• Paroxysmal nocturnal hemoglobinuria

External links

• Human Gene CD59 (uc002kve.4) description and Page link to gene location from the National Center for Biotechnology Information
• CD59 at the Universal Protein Resource (UniProt)