No abstract

The mammalian mitochondrial proteome is under dual genomic control, with 99% of proteins encoded by the nuclear genome and 13 originating from the mitochondrial DNA (mtDNA). We previously developed MitoCarta, a catalogue of over 1000 genes encoding the mammalian mitochondrial proteome. This catalogue was compiled using a Bayesian integration of multiple sequence features and experimental datasets, notably protein mass spectrometry of mitochondria isolated from fourteen murine tissues. Here, we introduce MitoCarta3.0. Beginning with the MitoCarta2.0 inventory, we performed manual review to remove 100 genes and introduce 78 additional genes, arriving at an updated inventory of 1136 human genes. We now include manually curated annotations of sub-mitochondrial localization (matrix, inner membrane, intermembrane space, outer membrane) as well as assignment to 149 hierarchical ‘MitoPathways’ spanning seven broad functional categories relevant to mitochondria. MitoCarta3.0, including sub-mitochondrial localization and MitoPathway annotations, is freely available at http://www.broadinstitute.org/mitocarta and should serve as a continued community resource for mitochondrial biology and medicine.

Mitochondrial dysfunction is associated with a spectrum of human disorders, ranging from rare, inborn errors of metabolism to common, age-associated diseases such as neurodegeneration. How these lesions give rise to diverse pathology is not well understood, partly because their proximal consequences have not been well-studied in mammalian cells. Here we provide two lines of evidence that mitochondrial respiratory chain dysfunction leads to alterations in one-carbon metabolism pathways. First, using hypothesis-generating metabolic, proteomic, and transcriptional profiling, followed by confirmatory experiments, we report that mitochondrial DNA depletion leads to an ATF4-mediated increase in serine biosynthesis and transsulfuration. Second, we show that lesioning the respiratory chain impairs mitochondrial production of formate from serine, and that in some cells, respiratory chain inhibition leads to growth defects upon serine withdrawal that are rescuable with purine or formate supplementation. Our work underscores the connection between the respiratory chain and one-carbon metabolism with implications for understanding mitochondrial pathogenesis.DOI: http://dx.doi.org/10.7554/eLife.10575.001

Generalized obesity is associated with postoperative wound infections after pancreaticoduodenectomy. The degree of visceral fat on preoperative cross-sectional imaging is associated with significantly higher rates of overall complications and pancreatic fistula.

Over the past few years, the NCCN Guidelines for Melanoma: Cutaneous have been expanded to include pathways for treatment of microscopic satellitosis (added in v2.2020), and the following Principles sections: Molecular Testing (added in v2.2019), Systemic Therapy Considerations (added in v2.2020), and Brain Metastases Management (added in v3.2020). The v1.2021 update included additional modifications of these sections and notable revisions to Principles of: Pathology, Surgical Margins for Wide Excision of Primary Melanoma, Sentinel Lymph Node Biopsy, Completion/Therapeutic Lymph Node Dissection, and Radiation Therapy. These NCCN Guidelines Insights discuss the important changes to pathology and surgery recommendations, as well as additions to systemic therapy options for patients with advanced disease.

Mitochondrial dysfunction is associated with activation of the integrated stress response (ISR) but the underlying triggers remain unclear. We systematically combined acute mitochondrial inhibitors with genetic tools for compartment-specific NADH oxidation to trace mechanisms linking different forms of mitochondrial dysfunction to the ISR in proliferating mouse myoblasts and in differentiated myotubes. In myoblasts, we find that impaired NADH oxidation upon electron transport chain (ETC) inhibition depletes asparagine, activating the ISR via the eIF2α kinase GCN2. In myotubes, however, impaired NADH oxidation following ETC inhibition neither depletes asparagine nor activates the ISR, reflecting an altered metabolic state. ATP synthase inhibition in myotubes triggers the ISR via a distinct mechanism related to mitochondrial inner-membrane hyperpolarization. Our work dispels the notion of a universal path linking mitochondrial dysfunction to the ISR, instead revealing multiple paths that depend both on the nature of the mitochondrial defect and on the metabolic state of the cell.

The cellular NADH/NAD + ratio is fundamental to biochemistry but the extent to which it reflects versus drives metabolic physiology in vivo is poorly understood. Here, we report the in vivo application of Lb NOX 1 , a bacterial water-forming NADH oxidase, to assess the metabolic consequences of directly lowering the hepatic cytosolic NADH/NAD + ratio in mice. By combining this genetic tool with metabolomics, we identify circulating α-hydroxybutyrate (αHB) as a robust marker of elevated hepatic cytosolic NADH/NAD + ratio, also known as reductive stress. In humans, elevations in circulating αHB levels have previously been associated with impaired glucose tolerance 2 , insulin resistance 3 , and mitochondrial disease 4 , and are associated with a common genetic variant in GCKR 5 , which has previously been associated with many seemingly disparate metabolic traits. Using Lb NOX, we demonstrate NADH reductive stress mediates the effects of GCKR variation on many metabolic traits including circulating triglycerides, glucose tolerance, and FGF21 levels. Our work identifies elevated hepatic NADH/NAD + as a latent metabolic parameter that is shaped by human genetic variation and contributes causally to key metabolic traits and diseases. Moreover, it undescores the utility of genetic tools such as Lb NOX to empower studies of “causal metabolism.”

Conflict of interest:VKM is on the scientific advisory board and receives equity from Janssen Pharmaceuticals and 5AM Ventures. VKM is an inventor on a patent application filed by Massachusetts General Hospital on novel therapeutic approaches targeting reductive stress ("Extracellular Redox Enzyme System to Alleviate Disease," no. 16/769,319). OSS is a paid consultant for Proteinaceous Inc. MH is a paid consultant for Zogenix and Entrada Therapeutics. DCDV is a paid consultant for Biogen and AveXis Therapeutics. RS holds equity in BlueBird Bio.