Single Mutation in the NFU1 Gene Metabolically Reprograms Pulmonary Artery Smooth Muscle Cells

Abstract

Objective: NFU1 is a mitochondrial iron-sulfur scaffold protein, involved in iron-sulfur assembly and transfer to complex II and LAS (lipoic acid synthase). Patients with the point mutation NFU1 G208C and CRISPR/CAS9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat–associated 9)-generated rats develop mitochondrial dysfunction leading to pulmonary arterial hypertension. However, the mechanistic understanding of pulmonary vascular proliferation due to a single mutation in NFU1 remains unresolved. Approach and Results: Quantitative proteomics of isolated mitochondria showed the entire phenotypic transformation of NFU1 G206C rats with a disturbed mitochondrial proteomic landscape, involving significant changes in the expression of 208 mitochondrial proteins. The NFU1 mutation deranged the expression pattern of electron transport proteins, resulting in a significant decrease in mitochondrial respiration. Reduced reliance on mitochondrial respiration amplified glycolysis in pulmonary artery smooth muscle cell (PASMC) and activated GPD (glycerol-3-phosphate dehydrogenase), linking glycolysis to oxidative phosphorylation and lipid metabolism. Decreased PDH (pyruvate dehydrogenase) activity due to the lipoic acid shortage is compensated by increased fatty acid metabolism and oxidation. PASMC became dependent on extracellular fatty acid sources due to upregulated transporters such as CD36 (cluster of differentiation 36) and CPT (carnitine palmitoyltransferase)-1. Finally, the NFU1 mutation produced a dysregulated antioxidant system in the mitochondria, leading to increased reactive oxygen species levels. PASMC from NFU1 rats showed apoptosis resistance, increased anaplerosis, and attained a highly proliferative phenotype. Attenuation of mitochondrial reactive oxygen species by mitochondrial-targeted antioxidant significantly decreased PASMC proliferation. Conclusions: The alteration in iron-sulfur metabolism completely transforms the proteomic landscape of the mitochondria, leading toward metabolic plasticity and redistribution of energy sources to the acquisition of a proliferative phenotype by the PASMC.

Allele-specific mitochondrial stress induced by Multiple Mitochondrial Dysfunctions Syndrome 1 pathogenic mutations modeled in Caenorhabditis elegans

“…deliver ISCs to CI and CII [12,13,70] precludes normal ETC function. This conclusion is in agreement with the recent rodent model of MMDS1 [41,85]. Given that the ETC is responsible for maintaining Δψ m , the TMRE data supports this conclusion (Fig 3D and 3E).…”

“…Multiple lines of evidence presented herein indicate that oxidative stress contributes to the phenotypes observed in the nfu-1 mutants as well as the corroborating evidence in a rodent MMDS1 model [85]. The most direct of these is the elevated fluorescence observed in the Gly147Arg, Gly148Arg and Cys168Phe mutants in the H 2 DCFDA assay (Fig 4B and 4B').…”

“…Yet, the phenotypic presentation of these mutants is not always identical, especially with the Gly166Cys mutant, indicating auxiliary stresses or dysfunctions. Recent work with a rodent model of the human NFU1 Gly208Cys mutant has also shown similarly complex phenotypes to the orthologous C. elegans Gly166Cys mutant including decreased ETC function, oxidative stress, and mitohormesis [85]. While some of these findings are unique to the Gly166Cys mutant, many are shared with the Gly148Arg and Cys168Phe mutants as well, further illustrating complexity beyond reduced protein lipoylation.…”

“…Such a concept is pertinent given the neurodegenerative nature of MMDS1 and the potential for neuronal dysfunction to impact nonneuronal tissues. Nearly all MMDS1 individuals present with neurodegenerative symptoms which are likely to affect, if not be causative of, both the hypotonia and pulmonary hypertension that are also characteristic of MMDS1 [41,85]. Thus C. elegans could provide an excellent model in which to parse the nuances of these stress-response relationships further.…”

Recent advancements in pulmonary arterial hypertension and right heart failure research: overview of selected abstracts from ATS2020 and emerging COVID‐19 research

“… 43 At the ATS2020 Conference, James and colleagues investigated targeting the iron-sulfur (Fe-S) scaffold protein NFU1 G206C mutation as a therapeutic target to reverse PH. 44 The function of the mitochondrial Fe-S cluster assembly protein NFU1 is largely unknown; however, individuals with mutations in NFU1 develop PH, neurological issue, early death, and multiple mitochondrial dysfunction syndrome (MMDS1). 45 NFU1 G206C mutant rats have been shown to spontaneously develop PH with increased pulmonary artery thickness, pulmonary pressure, and Fulton index.…”