Mutations in nuclear genes encoding for
mitochondrial proteins very long-chain acyl-CoA dehydrogenase (
VLCAD) and trifunctional
protein (TFP) cause rare autosomal recessive disorders. Studies in fibroblasts derived from patients with mutations in
VLCAD and TFP exhibit
mitochondrial defects. To gain insights on pathological changes that account for the mitochondrial deficits we performed quantitative proteomic, biochemical, and morphometric analyses in fibroblasts derived from subjects with three different
VLCAD and three different TFP mutations. Proteomic data that was corroborated by antibody-based detection, indicated reduced levels of
VLCAD and TFP
protein in cells with
VLCAD and TFP mutations respectively, which in part accounted for the diminished
fatty acid oxidation capacity. Decreased mitochondrial respiratory capacity in cells with
VLCAD and TFP mutations was quantified after
glucose removal and cells with TFP mutations had lower levels of
glycogen. Despite these energetic deficiencies, the cells with
VLCAD and TFP mutations did not exhibit changes in mitochondria morphology, distribution, fusion and fission, quantified by either confocal or transmission electron microscopy and corroborated by proteomic and antibody-based
protein analysis. Fibroblasts with
VLCAD and to a lesser extend cells with TFP mutations had increased levels of mitochondrial respiratory chain
proteins and
proteins that facilitate the assembly of respiratory complexes. With the exception of reduced levels of
catalase and
glutathione S-transferase theta-1 in cells with TFP mutations, the levels of 45
proteins across all major intracellular
antioxidant networks were similar between cells with
VLCAD and TFP mutations and non-disease controls. Collectively the data indicate that despite the metabolic deficits, cells with
VLCAD and TFP mutations maintain their proteomic integrity to preserve cellular and mitochondria architecture, support energy production and protect against oxidative stress.