Mitochondrial targeting of human NADH dehydrogenase (ubiquinone) flavoprotein 2 (NDUFV2) and its association with early-onset hypertrophic cardiomyopathy and encephalopathy

Abstract

BackgroundNADH dehydrogenase (ubiquinone) flavoprotein 2 (NDUFV2), containing one iron sulfur cluster ([2Fe-2S] binuclear cluster N1a), is one of the core nuclear-encoded subunits existing in human mitochondrial complex I. Defects in this subunit have been associated with Parkinson's disease, Alzheimer's disease, Bipolar disorder, and Schizophrenia. The aim of this study is to examine the mitochondrial targeting of NDUFV2 and dissect the pathogenetic mechanism of one human deletion mutation present in patients with early-onset hypertrophic cardiomyopathy and encephalopathy.MethodsA series of deletion and point-mutated constructs with the c-myc epitope tag were generated to identify the location and sequence features of mitochondrial targeting sequence for NDUFV2 in human cells using the confocal microscopy. In addition, various lengths of the NDUFV2 N-terminal and C-terminal fragments were fused with enhanced green fluorescent protein to investigate the minimal region required for correct mitochondrial import. Finally, a deletion construct that mimicked the IVS2+5_+8delGTAA mutation in NDUFV2 gene and would eventually produce a shortened NDUFV2 lacking 19-40 residues was generated to explore the connection between human gene mutation and disease.ResultsWe identified that the cleavage site of NDUFV2 was located around amino acid 32 of the precursor protein, and the first 22 residues of NDUFV2 were enough to function as an efficient mitochondrial targeting sequence to carry the passenger protein into mitochondria. A site-directed mutagenesis study showed that none of the single-point mutations derived from basic, hydroxylated and hydrophobic residues in the NDUFV2 presequence had a significant effect on mitochondrial targeting, while increasing number of mutations in basic and hydrophobic residues gradually decreased the mitochondrial import efficacy of the protein. The deletion mutant mimicking the human early-onset hypertrophic cardiomyopathy and encephalopathy lacked 19-40 residues in NDUFV2 and exhibited a significant reduction in its mitochondrial targeting ability.ConclusionsThe mitochondrial targeting sequence of NDUFV2 is located at the N-terminus of the precursor protein. Maintaining a net positive charge and an amphiphilic structure with the overall balance and distribution of basic and hydrophobic amino acids in the N-terminus of NDUFV2 is important for mitochondrial targeting. The results of human disease cell model established that the impairment of mitochondrial localization of NDUFV2 as a mechanistic basis for early-onset hypertrophic cardiomyopathy and encephalopathy.

Exome sequencing identifies complex I NDUFV2 mutations as a novel cause of Leigh syndrome

“…52 The mutation is predicted to result in a truncated transcript with an altered mitochondrial targeting sequence. 99 Western blot analysis demonstrated a residual protein level of 25% in mitochondria in our family with the compound heterozygous mutation, which is comparable to that seen in a published patient with the same homozygous mutation. 53 Some full length protein may be produced due to read-through of the c.IVS2 þ 1delGTAA splice site mutation.…”

Identification of genes associated with the effect of inflammation on the neurotransmission of vascular smooth muscle cell

“…NDUFV2 , which is located on chromosome 18p11.31-p11.2, has been named as a causative gene in neurological diseases, such as schizophrenia, Parkinson's disease, and bipolar disorder (24,25). A human disease cell model has revealed that the injury of mitochondrial localization of NDUFV2 is related to the pathogenesis of early-onset hypertrophic cardiomyopathy and encephalopathy (26). Therefore, the expression of NDUFV2 may be involved in the effect of inflammation on neurotransmission of VSMC.…”

Potential hippocampal genes and pathways involved in Alzheimer’s disease: a bioinformatic analysis

“…NDUFB3 is also an accessory subunit of complex I that is not believed to be involved in catalysis. A study of Liu et al (2011) indicated that defects in NDUFV2 are closely related to AD and other encephalopathies. COX7B is one of the nuclear-encoded polypeptide chains of cytochrome c oxidase (complex IV), the terminal oxidase in mitochondrial electron transport.…”