|peptidylprolyl isomerase A (cyclophilin A)|
Ribbon diagram of cyclophilin A in complex with ciclosporin (yellow). From .
|Locus||Chr. 7 p13|
|File:PDB 1w74 EBI.jpg|
x-ray structure of peptidyl-prolyl cis-trans isomerase a, ppia, rv0009, from mycobacterium tuberculosis.
Cyclophilins are a family of proteins from vertebrates and other organisms that bind to ciclosporin (cyclosporin A), an immunosuppressant which is usually used to suppress rejection after internal organ transplants. These proteins have peptidyl prolyl isomerase activity, which catalyzes the isomerization of peptide bonds from trans form to cis form at proline residues and facilitates protein folding.
Cyclophilin A is a cytosolic and highly abundant protein. The protein belongs to a family of isozymes, including cyclophilins B and C, and natural killer cell cyclophilin-related protein. Major isoforms have been found within single cells, including inside the Endoplasmic reticulum, and some are even secreted.
Cyclophilin A (CypA)
Cyclophilin A also known as peptidylprolyl isomerase A, which is found in the cytosol, has a beta barrel structure with two alpha helices and a beta-sheet. Other cyclophilins have similar structures to cyclophilin A. The cyclosporin-cyclophilin A complex inhibits a calcium/calmodulin-dependent phosphatase, calcineurin, the inhibition of which is thought to suppress organ rejection by halting the production of the pro-inflammatory molecules TNF alpha and interleukin 2.
Cyclophilin D, which is located in the matrix of mitochondria, is only a modulatory, but may or may not be a structural component of the mitochondrial permeability transition pore. The pore opening raises the permeability of the mitochondrial inner membrane, allows influx of cytosolic molecules into the mitochondrial matrix, increases the matrix volume, and disrupts the mitochondrial outer membrane. As a result, the mitochondria fall into a functional disorder, so the opening of the pore plays an important role in cell death. Cyclophilin D is thought to regulate the opening of the pore because cyclosporin A, which binds to CyP-D, inhibits the pore opening.
Cyclophilins as drug targets
This section needs expansion. You can help by adding to it. (December 2015)
Human genes encoding proteins containing the cyclophilin type peptidyl-prolyl cis-trans isomerase domain include:
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- Doczi J, Turiák L, Vajda S, et al. (February 2011). "Complex contribution of cyclophilin D to Ca2+-induced permeability transition in brain mitochondria, with relation to the bioenergetic state". J. Biol. Chem. 286 (8): 6345–53. doi:10.1074/jbc.M110.196600. PMC 3057831. PMID 21173147.
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- Nigro, P; Pompilio, G; Capogrossi, M C (2013). "Cyclophilin A: a key player for human disease". Cell Death and Disease. 4.
- J&J targets degenerative diseases in cyclophilin inhibitor partnership. Dan Stanton. 08-Dec-2015
- "Cyclophilin inhibition as potential therapy for liver diseases". Journal of Hepatology. 61 (5): 1166–1174. November 2014.