MidA is a putative methyltransferase that is required for mitochondrial complex I function

Abstract

SummaryDictyostelium 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.

Complex I deficiency: clinical features, biochemistry and molecular genetics

“…C20ORF7 contains a predicted S-adenosyl methionine-dependent fold, suggesting that it may methylate proteins, RNA or DNA within mitochondria 13 14. Only two complex I subunits are known to be methylated:15 NDUFS2 (methylated arginine R323) and NDUFB3 (contains two or three highly conserved methylated histidines) 16. Like ND1, NDUFB3 is located in the membrane arm, suggesting that post-translational methylation may play a role in the assembly or stability of the membrane arm.…”

Mutations in Complex I Assembly Factor TMEM126B Result in Muscle Weakness and Isolated Complex I Deficiency

“…[14][15][16][17][18][19][20][21][22][23][24] Only a few CI assembly factors have been identified by functional studies in normal cellular models. [25][26][27][28][29][30][31] One of these is TMEM126B, a mitochondrial transmembrane protein. Deficiency of this protein has been shown to reduce the total amount of CI in a cellular model system.…”

“…His height and weight were 1.49 m and 37.7 kg, respectively. Metabolic investigations showed permanent hyperlactacidemia (2.8-7.4 mmol/L), elevated lactate/pyruvate ratios (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32), hyperalaninemia (702 mmol/L; normal range ¼ 274 5 50 mmol/L), and elevated lactate levels in urine (2,775 mmol/mmol creatinine; control values < 84 mmol/mmol creatinine). Ophthalmological and cardiac examination was normal.…”

Mutations in the Gene Encoding C8orf38 Block Complex I Assembly by Inhibiting Production of the Mitochondria-Encoded Subunit ND1

“…16 To date, mutations in nine nuclear genes that cause complex I enzymatic deficiency due to impaired assembly have been described; these are CIA30/NDUFAF1, [17][18][19] B17.2L/NDUFAF2, [20][21][22] C6orf66/NDUFAF4, 23 C20orf7, [24][25][26] C3orf60/NDUFAF3, 27 FOXRED1, 16,28 NUBPL, 16 C8orf38, 29 and ACAD9. [30][31][32] In addition, ECSIT (an evolutionary conserved signaling intermediate in Toll pathways), which is found in intermediates with NDUFAF1, 33 and MidA, which interacts with the complex I subunit NDUFS2, 34 are also involved in various aspects of complex I biogenesis; however, human pathogenic gene mutations have not been identified.…”