"Cyclophilin D" redirects here. Not to be confused with peptidyl-prolyl cis-trans isomerase, mitochondrial (PPIF), which may also be referred to as Cyclophilin D.
Peptidylprolyl isomerase D (cyclophilin D), also known as PPID, is an enzyme which in humans is encoded by the PPIDgene on chromosome 4. As a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family, this protein catalyzes the cis-transisomerization of proline imidic peptide bonds, which allows it to facilitate folding or repair of proteins.[5] In addition, PPID participates in many biological processes, including mitochondrial metabolism, apoptosis, redox, and inflammation, as well as in related diseases and conditions, such as ischemic reperfusion injury, AIDS, and cancer.[6][7][8][9]
Structure
Like other cyclophilins, PPID forms a β-barrel structure with a hydrophobic core. This β-barrel is composed of eight anti-parallel β-strands and capped by two α-helices at the top and bottom. In addition, the β-turns and loops in the strands contribute to the flexibility of the barrel.[8] PPID in particular is composed of 370 residues and shares structural homology with PPIF, FKBP4, and FKBP5, including an N-terminal immunophilin-like domain and a C-terminaltetratricopeptide repeat (TPR) domain.[10]
Function
The protein encoded by this gene is a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and accelerate the folding of proteins.[5] Generally, PPIases are found in all eubacteria and eukaryotes, as well as in a few archaea, and thus are highly conserved.[6][11] The PPIase family is further divided into three structurally distinct subfamilies: cyclophilin (CyP), FK506-binding protein (FKBP), and parvulin (Pvn).[6][8] As a cyclophilin, PPID binds cyclosporin A (CsA) and can be found within the cell or secreted by the cell.[7] In eukaryotes, cyclophilins localize ubiquitously to many cell and tissue types.[7][8] In addition to PPIase and protein chaperone activities, cyclophilins also function in mitochondrial metabolism, apoptosis, immunological response, inflammation, and cell growth and proliferation.[6][7][8] PPID in particular helps chaperone the assembly of heat shock protein Hsp90, as well as the nuclear localization of glucocorticoid, estrogen and progesterone receptors. Along with PPIF, PPID regulates mitochondrial apoptosis. In response to elevated reactive oxygen species (ROS) and calcium ion levels, PPID interacts with Bax to promote mitochondrial pore formation, thus releasing pro-apoptotic factors such as cytochrome C and AIF.[10]
Clinical Significance
As a cyclophilin, PPID binds the immunosuppressive drug CsA to form a CsA-cyclophilin complex, which then targets calcineurin to inhibit the signaling pathway for T-cell activation.
In cardiac myogenic cells, cyclophilins have been observed to be activated by heat shock and hypoxia-reoxygenation as well as complex with heat shock proteins. Thus, cyclophilins may function in cardioprotection during ischemia-reperfusion injury.
Currently, cyclophilin expression is highly correlated with cancer pathogenesis, but the specific mechanisms remain to be elucidated.[7] Studies have shown that PPID protects human keratinocytes from UVA-induced apoptosis, so medication and therapies that inhibit PPID, such as CsA, may inadvertently aid skin cancer development. Conversely, treatments promoting PPID activity may improve patient outcomes when paired with UVA therapies against cancer.[10]
^ abcdeWang T, Yun CH, Gu SY, Chang WR, Liang DC (Aug 2005). "1.88 A crystal structure of the C domain of hCyP33: a novel domain of peptidyl-prolyl cis-trans isomerase". Biochemical and Biophysical Research Communications. 333 (3): 845–9. doi:10.1016/j.bbrc.2005.06.006. PMID15963461.
Hoffmann K, Kakalis LT, Anderson KS, Armitage IM, Handschumacher RE (Apr 1995). "Expression of human cyclophilin-40 and the effect of the His141-->Trp mutation on catalysis and cyclosporin A binding". European Journal of Biochemistry. 229 (1): 188–93. doi:10.1111/j.1432-1033.1995.tb20454.x. PMID7744028.
Yokoi H, Shimizu Y, Anazawa H, Lefebvre CA, Korneluk RG, Ikeda JE (Aug 1996). "The structure and complete nucleotide sequence of the human cyclophilin 40 (PPID) gene". Genomics. 35 (3): 448–55. doi:10.1006/geno.1996.0384. PMID8812478.
Gevaert K, Goethals M, Martens L, Van Damme J, Staes A, Thomas GR, Vandekerckhove J (May 2003). "Exploring proteomes and analyzing protein processing by mass spectrometric identification of sorted N-terminal peptides". Nature Biotechnology. 21 (5): 566–9. doi:10.1038/nbt810. PMID12665801. S2CID23783563.
Machida K, Osada H (Dec 2003). "Molecular interaction between cyclophilin D and adenine nucleotide translocase in cytochrome c release: does it determine whether cytochrome c release is dependent on permeability transition or not?". Annals of the New York Academy of Sciences. 1010 (1): 182–5. Bibcode:2003NYASA1010..182M. doi:10.1196/annals.1299.031. PMID15033717. S2CID1034903.
Barrios-Rodiles M, Brown KR, Ozdamar B, Bose R, Liu Z, Donovan RS, Shinjo F, Liu Y, Dembowy J, Taylor IW, Luga V, Przulj N, Robinson M, Suzuki H, Hayashizaki Y, Jurisica I, Wrana JL (Mar 2005). "High-throughput mapping of a dynamic signaling network in mammalian cells". Science. 307 (5715): 1621–5. Bibcode:2005Sci...307.1621B. doi:10.1126/science.1105776. PMID15761153. S2CID39457788.