Compound heterozygosity for severe and hypomorphic mutations cause non-syndromic LHON-like optic neuropathy.

Background: Non-syndromic hereditary optic neuropathy (HON) has been ascribed to mutations in mitochondrial fusion/fission dynamics genes, nuclear and mitochondrial DNA-encoded respiratory enzyme genes or nuclear genes of poorly known mitochondrial function. However, the disease causing gene remains unknown in many families. The objective of the present study was to identify the molecular cause of non-syndromic LHON-like disease in siblings born to non-consanguineous parents of French origin.

Loss of HIF-1α in macrophages attenuates AhR/ARNT-mediated tumorigenesis in a PAH-driven tumor model.

Activation of hypoxia-inducible factor (HIF) and macrophage infiltration of solid tumors independently promote tumor progression. As little is known how myeloid HIF affects tumor development, we injected the polycyclic aromatic hydrocarbon (PAH) and procarcinogen 3-methylcholanthrene (MCA; 100 μg/100 μl) subcutaneously into myeloid-specific Hif-1α and Hif-2α knockout mice (C57BL/6J) to induce fibrosarcomas (n = 16). Deletion of Hif-1α but not Hif-2α in macrophages diminished tumor outgrowth in the MCA-model.

Inactivation of tristetraprolin in chronic hypoxia provokes the expression of cathepsin B.

Macrophages play important roles in many diseases and are frequently found in hypoxic areas. A chronic hypoxic microenvironment alters global cellular protein expression, but molecular details remain poorly understood. Although hypoxia-inducible factor (HIF) is an established transcription factor allowing adaption to acute hypoxia, responses to chronic hypoxia are more complex.

Small single transmembrane domain (STMD) proteins organize the hydrophobic subunits of large membrane protein complexes.

The large membrane protein complexes of mitochondrial oxidative phosphorylation are composed of central subunits that are essential for their bioenergetic core function and accessory subunits that may assist in regulation, assembly or stabilization. Although sequence conservation is low, a significant proportion of the accessory subunits is characterized by a common single transmembrane (STMD) topology. The STMD signature is also found in subunits of other membrane protein complexes.

Chapter 27 An improved method for introducing point mutations into the mitochondrial cytochrome B gene to facilitate studying the role of cytochrome B in the formation of reactive oxygen species.

Cytochrome b is a pivotal protein subunit of the cytochrome bc(1) complex and forms the ubiquinol oxidation site in the enzyme that is generally thought to be the primary site where electrons are aberrantly diverted from the enzyme, reacting with oxygen to form superoxide anion. In addition, recent studies have shown that mutations in cytochrome b can substantially increase rates of oxygen radical formation by the bc(1) complex. It would, thus, be advantageous to be able to manipulate cytochrome b by mutagenesis of the cytochrome b gene to better understand the role of cytochrome b in oxygen radical formation.

Combining Inhibitor Resistance-conferring Mutations in Cytochrome b Creates Conditional Synthetic Lethality in Saccharomyces cerevisiae.

The mitochondrial cytochrome bc(1) complex is an essential respiratory enzyme in oxygen-utilizing eukaryotic cells. Its core subunit, cytochrome b, contains two sites, center P and center N, that participate in the electron transfer activity of the bc(1) complex and that can be blocked by specific inhibitors. In yeast, there are various point mutations that confer inhibitor resistance at center P or center N.

Introduction of cytochrome b mutations in Saccharomyces cerevisiae by a method that allows selection for both functional and non-functional cytochrome b proteins.

We have previously used inhibitors interacting with the Qn site of the yeast cytochrome bc(1) complex to obtain yeast strains with resistance-conferring mutations in cytochrome b as a means to investigate the effects of amino acid substitutions on Qn site enzymatic activity [M.G. Ding, J.

Differential efficacy of inhibition of mitochondrial and bacterial cytochrome bc1 complexes by center N inhibitors antimycin, ilicicolin H and funiculosin.

We have compared the efficacy of inhibition of the cytochrome bc1 complexes from yeast and bovine heart mitochondria and Paracoccus denitrificans by antimycin, ilicicolin H, and funiculosin, three inhibitors that act at the quinone reduction site at center N of the enzyme. Although the three inhibitors have some structural features in common, they differ significantly in their patterns of inhibition. Also, while the overall folding pattern of cytochrome b around center N is similar in the enzymes from the three species, amino acid sequence differences create sufficient structural differences so that there are striking differences in the inhibitors binding to the three enzymes.

Investigating the Qn site of the cytochrome bc1 complex in Saccharomyces cerevisiae with mutants resistant to ilicicolin H, a novel Qn site inhibitor.

The cytochrome bc1 complex resides in the inner membrane of mitochondria and transfers electrons from ubiquinol to cytochrome c. This electron transfer is coupled to the translocation of protons across the membrane by the protonmotive Q cycle mechanism. This mechanism topographically separates reduction of quinone and reoxidation of quinol at sites on opposite sites of the membrane, referred to as center N (Qn site) and center P (Qp site), respectively.

The antioxidant systems in Toxoplasma gondii and the role of cytosolic catalase in defence against oxidative injury.

Superoxide dismutase, catalase, glutathione peroxidase and peroxiredoxins form an antioxidant network protecting cells against reactive oxygen species (ROS). Catalase is a potent H2O2-detoxifying enzyme, which is unexpectedly absent in some members of the Kinetoplastida and Apicomplexa, but present in Toxoplasma gondii. In T.

Expression of the human RNA-binding protein HuR in Trypanosoma brucei increases the abundance of mRNAs containing AU-rich regulatory elements.

The salivarian trypanosome Trypanosoma brucei infects mammals and is transmitted by tsetse flies. The mammalian 'bloodstream form' trypanosome has a variant surface glycoprotein coat and relies on glycolysis while the procyclic form from tsetse flies has EP protein on the surface and has a more developed mitochondrion. We show here that the mRNA for the procyclic-specific cytosolic phosphoglycerate kinase PGKB, like that for EP proteins, contains a regulatory AU-rich element (ARE) that destabilises the mRNA in bloodstream forms.