Quantitative Studies on the Soluble Compartments of Light and Heavy Mitochondria from Rat Liver

Hepatitis B Virus X protein elevates Parkin-mediated mitophagy through Lon Peptidase in starvation

Hepatocellular Carcinoma (HCC) is the fifth most prevalent cancer worldwide. Specially, Hepatitis B viurs X protein (HBx) is a leading factor in the progression of Hepatitis B viurs-related HCC. Nutrient-deprived tumor microenvironment also contributes to tumor development. However, the role of HBx in nutrient-deprived HCC has received little investigation. Here, we show that HBx elevates PINK1-Parkin mediating mitophagy in starvation. HBx not only increases the PINK1/Parkin gene expression but also accelerates Parkin recruitment to partial mitochondria. Further analysis indicates that, HBx either promotes mitochondrial unfolded protein response, with remarkable mitochondrial LONP1 increases, or reduces LONP1 expression in cytosol inducing LONP1-Parkin pathway, both consequently enhancing mitophagy. Moreover, the enhanced mitophagy lowers mitochondrial apoptosis in starved hepatoma cells, and Bax is implied in the machinery. In addition, we define differential centrifuge, 3000 g or 12,000 g to pellet mitochondria, as an effective method to obtain distinct mitochondria. In collect, HBx regulates diverse aspects of LONP1 and Parkin, enhancing mitophagy in starvation. This study may shed new insights into the machinery development of hepatocellular carcinoma.

Intramitochondrial location of the molecular forms of chicken liver mitochondrial malate dehydrogenase

1. The two molecular forms of mitochondrial malate dehydrogenase are partly bound to the mitochondrial membranes. 2. The A form is located on the outer surface of the inner mitochondrial membrane and also in the intermembrane space. 3. The B form of the enzyme appears in the matrix and bound in part, probably, to the inner surface of the inner mitochondrial membrane. 4. Glutamate dehydrogenase, glutamate oxaloacetate transaminase, fumarase and lactate dehydrogenase are bound, to a greater or lesser extent, to the mitochondrial membranes, the fumarase having the highest degree of binding.

Oxidation-reduction midpoint potentials of mitochondrial flavoproteins and their intramitochondrial localization

Spectrophotometric and fluorimetric substrate couple titrations and potentiometric spectrophotometric titrations were used to determine the oxidation-reduction potentials of components showing absorbance or fluorescence at the wavelengths attributable to the flavoproteins of mitochondria fractionated using digitonin together with sonication. A pure mitoplast fraction devoid of cytochrome b5 contamination could be obtained using 230 micrograms digitonin/mg of mitochondrial protein. The digitonin-soluble fraction contained a species having Em7.4 = -123 mV and probably represents the outer membrane flavoproteins. The inner membrane-matrix fraction, treated with ultrasound, provided evidence of a flavoprotein species with redox potential (Em7.4 = -302 mV) in the matrix fraction. The -302 mV component is probably lipoamide dehydrogenase. A high redox potential species with Em7.4 = +19 mV in titrations with the succinate fumarate couple was located in the inner membrane vesicles and is probably identical with succinate dehydrogenase. The electron-transferring flavoprotein (ETF) was isolated from bovine heart mitochondria and its Em7.4 = -74 mV determined. The component in the matrix fraction with an apparent Em7.4 = -56 mV probably represents ETF, and that in the inner membrane fraction with an apparent Em7.4 = -43 mV the NADH dehydrogenase flavoprotein. A component in an apparently low concentration with Em7.4 = +30 mV was detected in the inner membrane fraction. This probably represents the ETF-dehydrogenase flavoprotein. The origin of the flavoprotein fluorescence of mitochondria and intact tissues is discussed.