Article

A peptide containing residues 26-44 of tau protein impairs mitochondrial oxidative phosphorylation acting at the level of the adenine nucleotide translocator.

Institute of Biomembranes and Bioenergetics, CNR, Bari, Italy.
Biochimica et Biophysica Acta (Impact Factor: 4.66). 09/2008; 1777(10):1289-300. DOI: 10.1016/j.bbabio.2008.07.004
Source: PubMed

ABSTRACT Having confirmed that adenovirus-mediated overexpression of NH(2)-tau fragment lacking the first 25 aminoacids evokes a potent neurotoxic effect, sustained by protracted stimulation of NMDA receptors, in primary neuronal cultures we investigated whether and how chemically synthesized NH(2)-derived tau peptides, i.e. NH(2)-26-44 and NH(2)-1-25 fragments, affect mitochondrial function. We tested both fragments on each step of the processes leading to ATP synthesis via oxidative phosphorylation: i) electron flow via the respiratory chain from physiological substrates to oxygen with the activity of each individual complex of the respiratory chain investigated in some detail, ii) membrane potential generation arising from externally added succinate and iii) the activity of both the adenine nucleotide translocator and iv) ATP synthase. Oxidative phosphorylation is not affected by NH(2)-1-25 tau fragment, but dramatically impaired by NH(2)-26-44 tau fragment. Both cytochrome c oxidase and the adenine nucleotide translocator are targets of NH(2)-26-44 tau fragment, but adenine nucleotide translocator is the unique mitochondrial target responsible for impairment of oxidative phosphorylation by the NH(2)-26-44 tau fragment, which then exerts deleterious effects on cellular availability of ATP synthesized into mitochondria.

0 Bookmarks
 · 
85 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Although amyloid beta (Aβ) peptide can promote tau pathology and its toxicity is concurrently tau-dependent, the underlying mechanisms of the in vivo interplay of these proteins remain unsolved. Structural and functional mitochondrial alterations play an early, precipitating role in synaptic failure of Alzheimer's disease (AD) pathogenesis and an aggravated mitochondrial impairment has been described in triple APP/PS/tau transgenic mice carrying both plaques and tangles, if compared with mice overexpressing tau or amyloid precursor protein (APP) alone. Here, we show that a neurotoxic aminoterminal (NH(2))-derived tau fragment mapping between 26 and 230 amino acids of the human tau40 isoform (441 amino acids)-but not the physiological full-length protein-preferentially interacts with Aβ peptide(s) in human AD synapses in association with mitochondrial adenine nucleotide translocator-1 (ANT-1) and cyclophilin D. The two peptides-Aβ 1-42 and the smaller and more potent NH(2)-26-44 peptide of the longest 20-22 kDa NH(2)-tau fragment-inhibit the ANT-1-dependent adenosine diphosphate-adenosine triphosphate (ADP/ATP) exchange in a noncompetitive and competitive manner, respectively, and together further aggravate the mitochondrial dysfunction by exacerbating the ANT-1 impairment. Taken together, these data establish a common, direct and synergistic toxicity of pathological APP and tau products on synaptic mitochondria and suggest potential, new pathway(s) and target(s) for a combined, more efficient therapeutic intervention of early synaptic dysfunction in AD.
    Neurobiology of aging 09/2011; 33(4):833.e1-25. · 5.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Apoptosis in neuronal tissue is an efficient mechanism which contributes to both normal cell development and pathological cell death. The present study explores the effects of extracellular ADP on low [K(+)]-induced apoptosis in rat cerebellar granule cells. ADP, released into the extracellular space in brain by multiple mechanisms, can interact with its receptor or be converted, through the actions of ectoenzymes, to adenosine. The findings reported in this paper demonstrate that ADP inhibits the proapoptotic stimulus supposedly via: i) inhibition of ROS production during early stages of apoptosis, an effect mediated by its interaction with cell receptor/s. This conclusion is validated by the increase in SOD and Catalase activities as well as by the GSSG/GSH ratio value decrease, in conjunction with the drop of ROS level and the prevention of the ADP protective effect by pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), a novel functionally selective antagonist of purine receptor; ii) safeguard of the functionality of the mitochondrial adeninnucleotide-1 translocator (ANT-1), which is early impaired during apoptosis. This effect is mediated by its plausible internalization into cell occurring as such or after its hydrolysis, by means of plasma membrane nucleotide metabolizing enzymes, and resynthesis into the cell. Moreover, the findings that ADP also protects ANT-1 from the toxic action of the two Alzheimer disease peptides, i.e. Aβ1-42 and NH2htau, which are known to be produced in apoptotic cerebellar neurons, further corroborate the molecular mechanism of neuroprotection by ADP, herein proposed.
    Biochimica et Biophysica Acta 04/2014; · 4.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Functional as well as structural alterations in mitochondria size, shape and distribution are precipitating, early events in progression of Alzheimer's Disease (AD). We reported that a 20–22 kDa NH2-tau fragment (aka NH2htau), mapping between 26 and 230 amino acids of the longest human tau isoform, is detected in cellular and animal AD models and is neurotoxic in hippocampal neurons. The NH2htau –but not the physiological full-length protein– interacts with Aβ at human AD synapses and cooperates with it in inhibiting the mitochondrial ANT-1-dependent ADP/ATP exchange. Here we show that the NH2htau also adversely affects the interplay between the mitochondria dynamics and their selective autophagic clearance. Fragmentation and perinuclear mislocalization of mitochondria with smaller size and density are early found in dying NH2htau-expressing neurons. The specific effect of NH2htau on quality control of mitochondria is accompanied by (i) net reduction in their mass in correlation with a general Parkin-mediated remodeling of membrane proteome; (ii) their extensive association with LC3 and LAMP1 autophagic markers; (iii) bioenergetic deficits and (iv) in vitro synaptic pathology. These results suggest that NH2htau can compromise the mitochondrial biology thereby contributing to AD synaptic deficits not only by ANT-1 inactivation but also, indirectly, by impairing the quality control mechanism of these organelles.
    Neurobiology of Disease 01/2014; 62:489–507. · 5.62 Impact Factor

Full-text (2 Sources)

View
24 Downloads
Available from
May 20, 2014