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Biochim Biophys Acta Biomembr. 2019 Sep 12:183064. doi: 10.1016/j.bbamem.2019.183064. [Epub ahead of print]

Tau-induced mitochondrial membrane perturbation is dependent upon cardiolipin.

Author information

1
Department of Physiology and Biochemistry, Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta.
2
MODAG GmbH, Wendelsheim, Germany.
3
Center for Neuropathology and Prion Research, Ludwig-Maximilians-University, Munich, Germany.
4
Biomedical Center-BMC, Metabolic Biochemistry, Ludwig-Maximilians-University, Munich, Germany.
5
MODAG GmbH, Wendelsheim, Germany; Department of NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
6
Department of NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
7
Department of Physiology and Biochemistry, Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta. Electronic address: neville.vassallo@um.edu.mt.

Abstract

Misfolding and aggregate formation by the tau protein has been closely related with neurotoxicity in a large group of human neurodegenerative disorders, which includes Alzheimer's disease. Here, we investigate the membrane-active properties of tau oligomers on mitochondrial membranes, using minimalist in vitro model systems. Thus, exposure of isolated mitochondria to oligomeric tau evoked a disruption of mitochondrial membrane integrity, as evidenced by a combination of organelle swelling, efflux of cytochrome c and loss of the mitochondrial membrane potential. Tau-induced mitochondrial dysfunction occurred independently of the mitochondrial permeability transition (mPT) pore complex. Notably, mitochondria were rescued by pre-incubation with 10-N-nonyl acridine orange (NAO), a molecule that specifically binds cardiolipin (CL), the signature phospholipid of mitochondrial membranes. Additionally, NAO prevented direct binding of tau oligomers to isolated mitochondria. At the same time, tau proteins exhibited high affinity to CL-enriched membranes, whilst permeabilisation of lipid vesicles also strongly correlated with CL content. Intriguingly, using single-channel electrophysiology, we could demonstrate the formation of non-selective ion-conducting tau nanopores exhibiting multilevel conductances in mito-mimetic bilayers. Taken together, the data presented here advances a scenario in which toxic cytosolic entities of tau protein would target mitochondrial organelles by associating with their CL-rich membrane domains, leading to membrane poration and compromised mitochondrial structural integrity.

KEYWORDS:

Cardiolipin; Membrane permeabilisation; Mitochondria; Nanopores; Oligomers; Tau

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