dictyNews
Electronic Edition
Volume 39, number 9
March 29, 2013

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Abstracts
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Ndufaf5 deficiency in the Dictyostelium model: new roles in 
autophagy and development

Sergio Carilla-Latorre, Sarah J. Annesley, Sandra 
Muñoz-Braceras, Paul R. Fisher, and Ricardo Escalante

Molecular Biology of the Cell, in press

Ndufaf5 (also known as C20orf7) is a mitochondrial complex I 
(CI) assembly factor whose mutations lead to human 
mitochondrial disease. Little is known about the function 
of the protein and the cytopathological consequences of the 
mutations. Disruption of Dictyostelium Ndufaf5 leads to CI 
deficiency and defects in growth and development. The 
predicted sequence of Ndufaf5 contains a putative 
methyltransferase domain. Site-directed mutagenesis indicates 
that the methyltransferase motif is essential for its 
function. Pathological mutations were recreated in the 
Dictyostelium protein and expressed in the mutant background. 
These proteins were unable to complement the phenotypes, 
which further validates Dictyostelium as a model of the 
disease. Chronic activation of AMP-activated protein kinase 
(AMPK) has been proposed to play a role in Dictyostelium and 
human cytopathology in mitochondrial diseases. However, 
inhibition of the expression of AMPK gene in the Ndufaf5 
null mutant does not rescue the phenotypes associated with 
the lack of Ndufaf5 suggesting that novel AMPK-independent 
pathways are responsible of Ndufaf5 cytopathology.  
Interestingly, the Ndufaf5 deficient strain shows an increase 
in autophagy. This phenomenon was also observed in a 
Dictyostelium mutant lacking MidA (C2orf56/PRO1853/Ndufaf7), 
another CI assembly factor, suggesting that autophagy 
activation might be a common feature in mitochondrial 
CI dysfunction.

 
Submitted by Ricardo Escalante [[log in to unmask]]
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