MidA is a putative methyltransferase that is required for mitochondrial complex I function.
Dictyostelium and human MidA are homologous proteins that belong to a family of proteins of unknown function called DUF185. Using yeast two-hybrid screening and pull-down experiments, we showed that both proteins interact with the mitochondrial complex I subunit NDUFS2. Consistent with this, Dictyostelium cells lacking MidA showed a specific defect in complex I activity, and knockdown of human MidA in HEK293T cells resulted in reduced levels of assembled complex I. These results indicate a role for MidA in complex I assembly or stability. A structural bioinformatics analysis suggested the presence of a methyltransferase domain; this was further supported by site-directed mutagenesis of specific residues from the putative catalytic site. Interestingly, this complex I deficiency in a Dictyostelium midA(-) mutant causes a complex phenotypic outcome, which includes phototaxis and thermotaxis defects. We found that these aspects of the phenotype are mediated by a chronic activation of AMPK, revealing a possible role of AMPK signaling in complex I cytopathology.
Carilla-Latorre
Sergio
S
Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM), Arturo Duperier 4, 28029 Madrid, Spain.
Gallardo
M Esther
ME
Annesley
Sarah J
SJ
Calvo-Garrido
Javier
J
Graña
Osvaldo
O
Accari
Sandra L
SL
Smith
Paige K
PK
Valencia
Alfonso
A
Garesse
Rafael
R
Fisher
Paul R
PR
Escalante
Ricardo
R
D000091162:AMP-Activated Protein Kinase Kinases; D020134:Catalytic Domain / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D019295:Computational Biology; D004023:Dictyostelium; D042967:Electron Transport Complex I / Q000378:metabolism; D006801:Humans; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D009245:NADH Dehydrogenase / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D020798:Two-Hybrid System Techniques
C000598027:NDUFAF7 protein, human; D015800:Protozoan Proteins; D034741:RNA, Small Interfering; D009245:NADH Dehydrogenase; D008780:Methyltransferases; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases; D042967:Electron Transport Complex I; C496411:NDUFS2 protein, human