PNPase knockout results in mtDNA loss and an altered metabolic gene expression program.

Polynucleotide phosphorylase (PNPase) is an essential mitochondria-localized exoribonuclease implicated in multiple biological processes and human disorders. To reveal role(s) for PNPase in mitochondria, we established PNPase knockout (PKO) systems by first shifting culture conditions to enable cell growth with defective respiration. Interestingly, PKO established in mouse embryonic fibroblasts (MEFs) resulted in the loss of mitochondrial DNA (mtDNA).

Mitochondria-targeted RNA import.

The import of a modest number of nucleus-encoded RNAs into mitochondria has been reported in species ranging from yeast to human. With the advent of high-throughput RNA sequencing, additional nucleus-encoded mitochondrial RNAs are being identified. Confirming the mitochondrial localization of candidate RNAs of interest (e.

The metabolite α-ketoglutarate extends lifespan by inhibiting ATP synthase and TOR.

Metabolism and ageing are intimately linked. Compared with ad libitum feeding, dietary restriction consistently extends lifespan and delays age-related diseases in evolutionarily diverse organisms. Similar conditions of nutrient limitation and genetic or pharmacological perturbations of nutrient or energy metabolism also have longevity benefits.

Proteomic analysis and molecular modelling characterize the iron-regulatory protein haemojuvelin/repulsive guidance molecule c.

HJV (haemojuvelin) plays a key role in iron metabolism in mammals by regulating expression of the liver-derived hormone hepcidin, which controls systemic iron uptake and release. Mutations in HJV cause juvenile haemochromatosis, a rapidly progressing iron overload disorder in humans. HJV, also known as RGMc (repulsive guidance molecule c), is a member of the three-protein RGM family.

Defining the disulfide bonds of insulin-like growth factor-binding protein-5 by tandem mass spectrometry with electron transfer dissociation and collision-induced dissociation.

The six high-affinity insulin-like growth factor-binding proteins (IGFBPs) comprise a conserved family of secreted molecules that modulate IGF actions by regulating their half-life and access to signaling receptors, and also exert biological effects that are independent of IGF binding. IGFBPs are composed of cysteine-rich amino- (N-) and carboxyl- (C-) terminal domains, along with a cysteine-poor central linker segment. IGFBP-5 is the most conserved IGFBP, and contains 18 cysteines, but only 2 of 9 putative disulfide bonds have been mapped to date.

Soluble repulsive guidance molecule c/hemojuvelin is a broad spectrum bone morphogenetic protein (BMP) antagonist and inhibits both BMP2- and BMP6-mediated signaling and gene expression.

Inactivating mutations in hemojuvelin/repulsive guidance molecule c (HJV/RGMc) cause juvenile hemochromatosis (JH), a rapidly progressive iron overload disorder in which expression of hepcidin, a key liver-derived iron-regulatory hormone, is severely diminished. Several growth factors in the bone morphogenetic protein (BMP) family, including BMP2 and BMP6, can stimulate production of hepcidin, a biological effect that may be modified by RGMc. Here we demonstrate that soluble RGMc proteins are potent BMP inhibitors.

Pro-protein convertases control the maturation and processing of the iron-regulatory protein, RGMc/hemojuvelin.

Background: Repulsive guidance molecule c (RGMc or hemojuvelin), a glycosylphosphatidylinositol-linked glycoprotein expressed in liver and striated muscle, plays a central role in systemic iron balance. Inactivating mutations in the RGMc gene cause juvenile hemochromatosis (JH), a rapidly progressing iron storage disorder with severe systemic manifestations. RGMc undergoes complex biosynthetic steps leading to membrane-bound and soluble forms of the protein, including both 50 and 40 kDa single-chain species.

Selective binding of RGMc/hemojuvelin, a key protein in systemic iron metabolism, to BMP-2 and neogenin.

Juvenile hemochromatosis is a severe and rapidly progressing hereditary disorder of iron overload, and it is caused primarily by defects in the gene encoding repulsive guidance molecule c/hemojuvelin (RGMc/HJV), a recently identified protein that undergoes a complicated biosynthetic pathway in muscle and liver, leading to cell membrane-linked single-chain and heterodimeric species, and two secreted single-chain isoforms. RGMc modulates expression of the hepatic iron regulatory factor, hepcidin, potentially through effects on signaling by the bone morphogenetic protein (BMP) family of soluble growth factors. To date, little is known about specific pathogenic defects in disease-causing RGMc/HJV proteins.

Cardiomyopathic tropomyosin mutations that increase thin filament Ca2+ sensitivity and tropomyosin N-domain flexibility.

The relationship between tropomyosin thermal stability and thin filament activation was explored using two N-domain mutants of alpha-striated muscle tropomyosin, A63V and K70T, each previously implicated in familial hypertrophic cardiomyopathy. Both mutations had prominent effects on tropomyosin thermal stability as monitored by circular dichroism. Wild type tropomyosin unfolded in two transitions, separated by 10 degrees C.

Phosphorylation or glutamic acid substitution at protein kinase C sites on cardiac troponin I differentially depress myofilament tension and shortening velocity.

There is evidence that multi-site phosphorylation of cardiac troponin I (cTnI) by protein kinase C is important in both long- and short-term regulation of cardiac function. To determine the specific functional effects of these phosphorylation sites (Ser-43, Ser-45, and Thr-144), we measured tension and sliding speed of thin filaments in reconstituted preparations in which endogenous cTnI was replaced with cTnI phosphorylated by protein kinase C-epsilon or mutated to cTnI-S43E/S45E/T144E, cTnI-S43E/S45E, or cTnI-T144E. We used detergent-skinned mouse cardiac fiber bundles to measure changes in Ca(2+)-dependence of force.

Chemical decoupling of ATPase activation and force production from the contractile cycle in myosin by steric hindrance of lever-arm movement.

The myosin motor protein generates force in muscle by hydrolyzing Adenosine 5'-triphosphate (ATP) while interacting transiently with actin. Structural evidence suggests the myosin globular head (subfragment 1 or S1) is articulated with semi-rigid catalytic and lever-arm domains joined by a flexible converter domain. According to the prevailing hypothesis for energy transduction, ATP binding and hydrolysis in the catalytic domain drives the relative movement of the lever arm.