Résumé :
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Charcot-Marie-Tooth disease (CMT) is a frequent, genetically heterogeneous group of peripheral neuropathies. Mutation of the MFN2 gene provoke CMT2A, and probably represent the commonest cause of CMT2. The deficiencies provoked by MFN2-mutations and the physiopathological mechanisms of CMT2A remain unknown. In order to advance in the understanding of mitofusin function and CMT2A physiopathology, we setup to identify partners of Mfn2 and Mfn1, two ubiquitous GTPases of the mitochondrial outer membrane that are required for mitochondrial fusion and display 60% sequence identity. We have demonstrated by immunoprecipitation that Mfn2 and Mfn1 interact with each other and with OPA1, another mitochondrial GTPase involved in fusion (1). In addition, others have identified putative mitofusin-partners (Mfn2-binding Stoml2 and Mfn1-binding MIB) using proteomic approaches (2,3). We engineered soluble forms of Mfn2 and Mfn1 and used them as baits in yeast-two-hybrid (Y2H) screens. Surprisingly, none of these known partners was “fished” in our Y2H-screens. The Mfn1-NT being toxic to yeast cells, this Y2H-screen was performed with an inducible promoter. It yielded a high number of clones (>80). The high proportion of clones that were out of frame or in antisense orientation point to unspecific interactions with the toxic (misfolded?) bait. A first Mfn2-screen yielded 3 clones encoding a predicted protein of unknown function (hypothetical Mitofusin2 binding protein - hM2BP). We have cloned hM2BP and are currently investigating its localization and properties. A second Mfn2-screen yielded 3 independent clones of a second putative partner (2PP) reported to be involved in the maintenance of mitochondrial morphology and in mitochondrial apoptotis. We pursue the study of 2PP-Mfn interactions and their putative role in mitochondrial dynamics. 1. Guillery et al. (2008) Biol Cell in press. 2. Hajek et al. (2007) J Biol Chem 282(8), 5670-5681 3. Eura et al. (2006) J Cell Sci 119(Pt 23), 4913-4925
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