Linard, Dominique
[UCL]
(eng)
Cyclophilin-D (CyP-D) is a peptidyl prolyl cis/trans isomerase located in the mitochondrial matrix of mammalian cells. The subcellular localization of the protein is determined by the presence of a mitochondrial targeting presequence. In the first part of this work, we characterized human CyP-D presequence allowing the protein translocation into mitochondria. We showed that the 16 first amino acid of the presequence are necessary and sufficient to form a functional presequence and to address hCyP-D into mitochondria. One of the main physiological roles of CyP-D is to activate the mitochondrial permeability transition pore (mPTP) opening. The mPTP is a protein complex formed during oxidative stress and leading to cell necrosis. Thus, CyP-D may be considered as a necrosis inductor. Nevertheless, several studies have also shown that CyP-D exhibits a protective role toward apoptosis induced by oxidative stress. However, the mechanism implicated in the cellular protection conferred by CyP-D is not yet known. Recently, the redox sensitivity of several CyPs has been highlighted. In this work, we show that recombinant hCyP-D is redox sensitive. Indeed, hCyP-D oxidation leads to conformational changes of the enzyme and to a partial loss of its activity. Moreover, we show also that Cys203 residue appears to be the main target of the CyP-D oxidation. Furthermore, we confirm hCyP-D redox-sensitivity in human SH-SY5Y cells. These results suggest that hCyP-D could act as a redox sensor. Several CyPs are able to increase the peroxidase activity of some peroxiredoxins (PRDXs). Here, we show in vitro, the binding between hCyP-D and hPRDX5, a mitochondrial PRDX. Interactions between hPRDX5 and hCyP-D appeared to have a dual role on enzyme activities. First, hCyP-D induces an increase of the peroxidatic activity of hPRDX5. Moreover, CyP-D is also able to reduce PRDX5. We show that PRDX reduction by CyP is not thioredoxin-dependent. Interestingly, interactions between hPRDX5 and hCyP-D also confer the ability to hPRDX5 to regenerate the activity of oxidized CyP-D. Furthermore, CyP-D expression is increased in cells overexpressing PRDX5 suggesting a physiological role of these interactions in cells. Our results suggest that the conformational changes of CyP-D and its interaction with PRDX5 could play an important role in cell death. Indeed, protein interactions may protect mammalian cells against apoptosis induced by a low oxidative stress whereas a high oxidative stress may induce a conformational change of CyP-D leading to mPTP opening and cell necrosis.
Bibliographic reference |
Linard, Dominique. Characterization of the redox state of human cyclophilin-D and its interactions with peroxiredoxin 5. Prom. : Knoops, Bernard |
Permanent URL |
http://hdl.handle.net/2078.1/20884 |