Small, rapidly dividing pluripotent stem cells (PSCs) have unique energetic and biosynthetic demands compared with typically larger, quiescent differentiated cells. Shifts between glycolysis and ...oxidative phosphorylation with PSC differentiation or reprogramming to pluripotency are accompanied by changes in cell cycle, biomass, metabolite levels, and redox state. PSC and cancer cell metabolism are overtly similar, with metabolite levels influencing epigenetic/genetic programs. Here, we discuss the emerging roles for metabolism in PSC self-renewal, differentiation, and reprogramming.
Cardiolipin, the signature phospholipid of mitochondria, is a lipid dimer that is important for a diverse range of mitochondrial activities beyond the process of ATP production. Thus not ...surprisingly, derangements in cardiolipin metabolism are now appreciated to contribute to an assortment of pathological conditions. A comprehensive inventory of enzymes involved in cardiolipin biosynthesis and remodeling was just recently obtained. Post-biosynthesis, the acyl chain composition of cardiolipin is modified by up to three distinct remodeling enzymes that produce either a homogeneous tissue-specific mature form of cardiolipin or alternatively ‘bad’ cardiolipin that has been linked to mitochondrial dysfunction. In this review, we initially focus on the newly identified players in cardiolipin metabolism and then shift our attention to how changes in cardiolipin metabolism contribute to human disease.
Most mitochondrial proteins are synthesized on cytosolic ribosomes and must be imported across one or both mitochondrial membranes. There is an amazingly versatile set of machineries and mechanisms, ...and at least four different pathways, for the importing and sorting of mitochondrial precursor proteins. The translocases that catalyze these processes are highly dynamic machines driven by the membrane potential, ATP, or redox reactions, and they cooperate with molecular chaperones and assembly complexes to direct mitochondrial proteins to their correct destinations. Here, we discuss recent insights into the importing and sorting of mitochondrial proteins and their contributions to mitochondrial biogenesis.
The formin-like protein INF2 is an important player in the polymerization of actin filaments. In this issue, Chakrabarti et al. (2018.
https://doi.org/10.1083/jcb.201709111) demonstrate that INF2 ...mediates actin polymerization at the endoplasmic reticulum (ER), resulting in increased ER-mitochondria contacts, calcium uptake by mitochondria, and mitochondrial division.
Mitochondria are essential regulators of cellular energy and metabolism, and have a crucial role in sustaining the growth and survival of cancer cells. A central function of mitochondria is the ...synthesis of ATP by oxidative phosphorylation, known as mitochondrial bioenergetics. Mitochondria maintain oxidative phosphorylation by creating a membrane potential gradient that is generated by the electron transport chain to drive the synthesis of ATP
. Mitochondria are essential for tumour initiation and maintaining tumour cell growth in cell culture and xenografts
. However, our understanding of oxidative mitochondrial metabolism in cancer is limited because most studies have been performed in vitro in cell culture models. This highlights a need for in vivo studies to better understand how oxidative metabolism supports tumour growth. Here we measure mitochondrial membrane potential in non-small-cell lung cancer in vivo using a voltage-sensitive, positron emission tomography (PET) radiotracer known as 4-
Ffluorobenzyl-triphenylphosphonium (
F-BnTP)
. By using PET imaging of
F-BnTP, we profile mitochondrial membrane potential in autochthonous mouse models of lung cancer, and find distinct functional mitochondrial heterogeneity within subtypes of lung tumours. The use of
F-BnTP PET imaging enabled us to functionally profile mitochondrial membrane potential in live tumours.
mtDNA sequence alterations are challenging to generate but desirable for basic studies and potential correction of mtDNA diseases. Here, we report a new method for transferring isolated mitochondria ...into somatic mammalian cells using a photothermal nanoblade, which bypasses endocytosis and cell fusion. The nanoblade rescued the pyrimidine auxotroph phenotype and respiration of ρ0 cells that lack mtDNA. Three stable isogenic nanoblade-rescued clones grown in uridine-free medium showed distinct bioenergetics profiles. Rescue lines 1 and 3 reestablished nucleus-encoded anapleurotic and catapleurotic enzyme gene expression patterns and had metabolite profiles similar to the parent cells from which the ρ0 recipient cells were derived. By contrast, rescue line 2 retained a ρ0 cell metabolic phenotype despite growth in uridine-free selection. The known influence of metabolite levels on cellular processes, including epigenome modifications and gene expression, suggests metabolite profiling can help assess the quality and function of mtDNA-modified cells.
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•Proof-of-principle photothermal nanoblade transfer of mitochondria is reported•Transfer into 143BTK− ρ0 cells generated rescue clones with recovered respiration•Mitochondrial transfer reset metabolic enzyme gene expression patterns•Two of three rescue clones showed metabolite profiles similar to 143BTK− parent cells
Optimizing mtDNA transfer into mammalian cells is an important step for basic studies and mitochondrial disease therapies. Using a photothermal nanoblade, Wu et al. are able to deliver isolated mitochondria into respiration-deficient cells. Rescued cell lines recover mitochondrial respiration and reset cellular metabolism to the parental cell level.
The mitochondrion has developed an elaborate translocation system for the import of nuclear-coded proteins and the export of proteins coded on the mitochondrial genome. Precursor proteins contain ...targeting and sorting information to reach the mitochondrion, whereas the translocons recognize the information and direct the precursor to the correct compartment. The outer membrane contains the TOM (translocase of the outer membrane) complex for translocation and the SAM (sorting and assembly machinery) complex for assembly of outer membrane proteins with complex topologies. At the inner membrane, the TIM23 (translocase of the inner membrane) mediates the import of mitochondrial proteins with a typical N-terminal targeting sequence, and the TIM22 complex mediates the import of polytopic inner membrane proteins. Based on its prokaryotic origin, the inner membrane also contains several components that mediate the export and assembly of proteins from within the matrix. Together the translocation and assembly complexes coordinate assembly of the mitochondrion.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Defined mutations in the mitochondrial ADP/ATP carrier (AAC) are associated with certain types of progressive external ophthalmoplegia. AAC is required for oxidative phosphorylation (OXPHOS), and ...dysregulation of AAC has been implicated in apoptosis. Little is known about the AAC interactome, aside from a known requirement for the phospholipid cardiolipin (CL) and that it is thought to function as a homodimer. Using a newly developed dual affinity tag, we demonstrate that yeast AAC2 physically participates in several protein complexes of distinct size and composition. The respiratory supercomplex and several smaller AAC2-containing complexes, including other members of the mitochondrial carrier family, are identified here. In the absence of CL, most of the defined interactions are destabilized or undetectable. The absence of CL and/or AAC2 results in distinct yet additive alterations in respiratory supercomplex structure and respiratory function. Thus, a single lipid can significantly alter the functional interactome of an individual protein.
It has been assumed, based largely on morphologic evidence, that human pluripotent stem cells (hPSCs) contain underdeveloped, bioenergetically inactive mitochondria. In contrast, differentiated cells ...harbour a branched mitochondrial network with oxidative phosphorylation as the main energy source. A role for mitochondria in hPSC bioenergetics and in cell differentiation therefore remains uncertain. Here, we show that hPSCs have functional respiratory complexes that are able to consume O2 at maximal capacity. Despite this, ATP generation in hPSCs is mainly by glycolysis and ATP is consumed by the F1F0 ATP synthase to partially maintain hPSC mitochondrial membrane potential and cell viability. Uncoupling protein 2 (UCP2) plays a regulating role in hPSC energy metabolism by preventing mitochondrial glucose oxidation and facilitating glycolysis via a substrate shunting mechanism. With early differentiation, hPSC proliferation slows, energy metabolism decreases, and UCP2 is repressed, resulting in decreased glycolysis and maintained or increased mitochondrial glucose oxidation. Ectopic UCP2 expression perturbs this metabolic transition and impairs hPSC differentiation. Overall, hPSCs contain active mitochondria and require UCP2 repression for full differentiation potential.
While studying metabolic fluxes in human pluripotent stem cells, this paper reveals UCP2 as metabolic switch from glycolysis to OXPHOS, facilitating early differentiation events.
Measurements of glycolysis and mitochondrial function are required to quantify energy metabolism in a wide variety of cellular contexts. In human pluripotent stem cells (hPSCs) and their ...differentiated progeny, this analysis can be challenging because of the unique cell properties, growth conditions and expense required to maintain these cell types. Here we provide protocols for analyzing energy metabolism in hPSCs and their early differentiated progenies that are generally applicable to mature cell types as well. Our approach has revealed distinct energy metabolism profiles used by hPSCs, differentiated cells, a variety of cancer cells and Rho-null cells. The protocols measure or estimate glycolysis on the basis of the extracellular acidification rate, and they measure or estimate oxidative phosphorylation on the basis of the oxygen consumption rate. Assays typically require 3 h after overnight sample preparation. Companion methods are also discussed and provided to aid researchers in developing more sophisticated experimental regimens for extended analyses of cellular bioenergetics.
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