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Nucléoside diphosphate kinase D : une protéine mitochondriale bifonctionnelle

Abstract : The nucleoside diphosphate kinases (NDPK) are essential for generation of nucleoside triphosphates (NTPs) using ATP and NDPs. The mitochondrial NDPK isoform (NDPK-D) located in the mitochondrial intermembrane space is found to have two modes of function. First, the phosphotransfer mode in which the protein has a kinase activity like other NDPK enzymes. In this mode, NDPK-D produces GTP for the optic atrophy 1 protein (OPA1), a GTPase involved in mitochondrial fusion, and ADP for the adenylate translocator (ANT) and the mitochondrial ATPase for ATP regeneration. The second mode of function is called lipid transfer and is related to the capacity of NDPK-D to bind anionic phospholipids, especially cardiolipin (CL). In this mode, the protein can cross-link the two mitochondrial membranes and transfer CL from the inner to the outer mitochondrial membrane, which can serve as a signal for mitophagy and apoptosis. This work aims to study these NDPK-D functions in more detail. With the use of HeLa cells stably expressing the wild-type, kinase inactive (H151N mutation) or lipid binding deficient (R90D mutation) NDPK-D and mouse lung epithelial cells, we show (i) the close proximity between NDPK-D and OPA1 that leads to GTP channeling from NDPK-D to OPA1, (ii) the essential role of NDPK-D for CL externalization to the mitochondrial surface during mitophagy, serving as a recognition signal for LC3-II-autophagosomes to eliminate damaged mitochondria, (iii) the possible inhibition of CL externalization due to the presence of NDPK-D/OPA1 complexes, and (iv) a pro-metastatic phenotype of HeLa cells expressing either of the NDPK-D mutants (H151N or R90D), characterized by high invasive and migratory potential, altered proteomic profile and changed mitochondrial network structure and function. Finally, a first bacterial expression and purification strategy for full-length OPA1 has been established for future in vitro studies of NDPK-D/OPA1 complexes.
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Céline Desbourdes. Nucléoside diphosphate kinase D : une protéine mitochondriale bifonctionnelle. Sciences agricoles. Université Grenoble Alpes, 2017. Français. ⟨NNT : 2017GREAV004⟩. ⟨tel-01685622⟩

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