Exploring the composition and the function of CHCHD2-CHCHD10 protein complex and its involvement in neurodegenerative diseases

Impaired mitochondrial function and dynamics are known to be involved in the pathogenesis and/or the progression of various neurodegenerative diseases. Recently, mutations in coiled-coil helix coiled coil helix domain 2 (CHCHD2) and 10 (CHCHD10) have been identified in patients affected by Parkinson’s Disease (PD), frontotemporal dementia (FTD) or amyotrophic later sclerosis (ALS). Previous in vitro studies have shown that CHCHD2 and CHCHD10 are primarily located in the mitochondrial intermembrane space (IMS) and partially organized in a large complex. However in vivo function and composition of this complex in mitochondria remains unclear. This research project aims to define by the molecular interactomes of CHCHD2 and CHCHD10 the composition of CHCHD2-CHCHD10 complex and the physiological function of these two proteins. Thus, we performed immunoprecipitation experiments of endogenous CHCHD2 and CHCHD10 in mitochondria isolated from mouse tissues and human cells. Western blot and mass spectrometry analyses of pulldown experiments demonstrate a very strong interaction between CHCHD2 and CHCHD10 in vitro and in vivo. Furthermore, we show that both proteins share the large majority of interacting partners, suggesting collaborative and partially overlapping functions. Interestingly, we found that CHCHD2 and CHCHD10 do not interact with MICOS machinery but interact with components of the Prohibitin complex (PHB1, PHB2) and SPY complex (STOML2, PARL and YME1L), involved in mitochondrial inner membrane organization. In addition, computational and experimental approaches performed, show an increase in the steady-state levels of CHCHD2 and CHCHD10 in mouse models with severe mitochondrial dysfunction, with no regulation at the transcriptional level. Notably, two-dimensional electrophoresis analysis demonstrate that both size and abundance of CHCHD2-CHCHD10 complex increased in response to mitochondrial damage. Overall, our results suggest that CHCHD2 and CHCHD10 together form a novel large mitochondrial protein complex, which might be involved in the organization of mitochondrial structure and is upregulated in response to mitochondrial dysfunction.