Discovering the molecular machinery for mitochondrial-derived vesicle formation linked to Parkinson's disease (PD)
Tim Koenig1, Thomas Stroh1, Michel Desjardins2 & Heidi M. McBride1 1Montreal Neurological Institute, McGill University, Montreal, QC, Canada 2Départment de Pathologie et Biologie Cellulaire, Université de Montréal, Montréal, Canada
Mitochondrial dysfunction is a hallmark of PD and impaired mitochondrial quality control through defective mitophagy by the PINK1/Parkin pathway is hypothesized to play a causal role in disease progression. Although PD mouse models of the well-established PINK1/Parkin mitophagy pathway are intensively studied, sporadic PD-like neurological symptoms are absent in these models. Independent of mitophagy, the McBride/Desjardin lab recently demonstrated a novel role of PINK1/Parkin-repressed mitochondrial-derived vesicles (MDVs) in activating the adaptive immune response, thus suggesting a role of autoimmunity in the pathogenesis of PD. These MDVs are stimulated upon mild heat stress or LPS treatment (fever/infection) carrying cargoes distinct from previously described MDVs and target the late endosome, where cargoes are processed and loaded on MHC class I proteins for presentation to cytotoxic CD8+ T-cells. Unpublished in vivo data from an expending collaboration remarkably establishes mitochondrial antigen presentation (MITAP) as a core contributor to PD pathology, providing a new therapeutic strategy for treatments that may arrest progression of the disease. However, before we can target this pathway we must fully understand the triggers and mechanistic details of MITAP. To identify key molecular components for MITAP, we have developed further a robust ß-galactosidase-based assay quantifying MITAP-induced T-cell activation combined with classical RNA-interference, thus allowing high-throughput genomic screening. This on-going screen will identify proteins within the entire MITAP pathway, from the signals downstream of cell surface receptors signaling vesicle formation, to the machinery budding the vesicles and proteins mediating fusion with late endosomes. Significant hits will further be validated via confocal microscopy and in-lab established state-of-the-art three-color super resolution STED microscopy using a newly generated fluorescently-tagged MDV cargo reporter cell line. This will advance our knowledge of the molecular mechanisms of MDV formation, their triggers and specific cargoes driving MITAP.
Credits: None available.
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