Alterations in mitochondrial function and energy metabolism-related properties in thyroid cancer stem cells

Increasing evidence indicates that cancer stem cells (CSCs) are initiators of the occurrence, development, and recurrence of malignant tumors. Mitochondria are important organelles in eukaryotic cells, not only responsible for converting part of energy released during nutrients oxidation into the energy-yielding molecule adenosine triphosphate (ATP) to fuel the activities of cell, but also play essential roles in processes such as cell apoptosis and cellular proliferation. The mitochondrial-related abnormalities have also been considered to have an important role in the origin and development of tumors. This study aimed at testing the abnormalities in mitochondrial function and energy/metabolism-related phenotypes in thyroid cancer stem cells (TCSCs). TCSCs were isolated and identified from MDA-T32 thyroid carcinoma cell line. The mitochondrial mass and mitochondrial arrangement, amount of mitochondrial DNA (mtDNA), mitochondrial membrane potential (MMP), oxygen/glucose consumption, and intracellular concentrations of reactive oxygen species (ROS) and ATP levels were examined. Perinuclear mitochondrial distribution, low amount of mtDNA and oxygen/glucose consumption, high MMP, and low intracellular ROS and ATP concentrations were observed in TCSCs. Alterations in mitochondrial function and cellular energy metabolism may be used as novel indicators of thyroid cancer.

A Role for Cell Polarity in Lifespan and Mitochondrial Quality Control in the Budding Yeast Saccharomyces cerevisiae

SummaryBabies are born young, largely independent of the age of their mothers. Mother-daughter age asymmetry in yeast is achieved, in part, by inheritance of higher-functioning mitochondria by daughter cells and retention of some high-functioning mitochondria in mother cells. The mitochondrial F-box protein, Mfb1p, tethers mitochondria at both poles in a cell cycle-regulated manner: it localizes to and anchors mitochondria to the mother cell tip throughout the cell cycle, and to the bud tip prior to cytokinesis. Here, we report that cell polarity and polarized localization of Mfb1p decline with age in S. cerevisiae. Moreover, deletion of BUD1/RSR1, a Ras protein required for cytoskeletal polarization during asymmetric yeast cell division, results in depolarized Mfb1p localization, defects in mitochondrial distribution and quality control, and reduced replicative lifespan. Our results demonstrate a role for the polarity machinery in lifespan through modulating Mfb1 function in asymmetric inheritance of mitochondria during yeast cell division.

A Mitochondria-Cluster At The Proximal Axon Initial Segment Controls Axodendritic TAU Trafficking In Rodent Primary And Human iPSCderived Neurons

Loss of neuronal polarity and missorting of the axonal microtubule-associated protein TAU are hallmarks of Alzheimer’s disease (AD) and related tauopathies. Impairment of mitochondrial function is causative for various neurogenetic mitochondriopathies, but the role of mitochondria in tauopathies and in axonal TAU-sorting is still unclear. The axon initial segment (AIS) is vital for maintaining neuronal polarity and proper sorting of TAU. Here, we aimed to investigate the role of mitochondria in the AIS regarding the maintenance of TAU polarity. Using global mitochondria impairment, but also live-cell-imaging and photoactivation methods, we specifically tracked and selectively impaired mitochondria in the AIS in primary mouse and human iPSC-derived neurons, and measured the subsequent missorting of TAU. We observed that global application of mitochondrial toxins efficiently induced tauopathy-like missorting, indicating involvement of mitochondria in TAU polarity. Mitochondria show a biased distribution within the AIS, with a proximal cluster and relative absence in the central AIS. The mitochondria of this cluster are largely immobile and only sparsely participate in axonal mitochondria-trafficking. Locally constricted impairment of only the AIS-mitochondria-cluster leads to detectable increases of somatic TAU, reminiscent of AD-like TAU-missorting. Here, we provide first evidence that the mitochondrial distribution within the proximal axon is biased towards the proximal AIS and that proper function of this newly described mitochondrial cluster may be essential for the maintenance of TAU neuronal polarity. This strengthens the role of mitochondrial impairment as an upstream event and therapeutic target in the pathological cascade leading to TAU missorting and consequent neuronal dysfunction.

Hexestrol Deteriorates Oocyte Quality via Perturbation of Mitochondrial Dynamics and Function

Hexestrol (HES) is a synthetic non-steroidal estrogen that was widely used illegally to boost the growth rate in livestock production and aquaculture. HES can also be transferred to humans from treated animals and the environment. HES has been shown to have an adverse effect on ovarian function and oogenesis, but the potential mechanism has not been clearly defined. To understand the potential mechanisms regarding how HES affect female ovarian function, we assessed oocyte quality by examining the critical events during oocyte maturation. We found that HES has an adverse effect on oocyte quality, indicated by the decreased capacity of oocyte maturation and early embryo development competency. Specifically, HES-exposed oocytes exhibited aberrant microtubule nucleation and spindle assembly, resulting in meiotic arrest. In addition, HES exposure disrupted mitochondrial distribution and the balance of mitochondrial fission and fusion, leading to aberrant mitochondrial membrane potential and accumulation of reactive oxygen species. Lastly, we found that HES exposure can increase cytosolic Ca2+ levels and induce DNA damage and early apoptosis. In summary, these results demonstrate that mitochondrial dysfunction and perturbation of normal mitochondrial fission and fusion dynamics could be major causes of reduced oocyte quality after HES exposure.

Mitochondrial Transport, Partitioning and Quality Control at the Heart of Cell Proliferation and Fate Acquisition

Mitochondria are essential to cell homeostasis, and alterations in mitochondrial distribution, segregation or turnover have been linked to complex pathologies such as neurodegenerative diseases or cancer. Understanding how these functions are coordinated in specific cell types is a major challenge to discover how mitochondria globally shape cell functionality. In this review, we will first describe how mitochondrial transport and dynamics are regulated throughout the cell cycle in yeast and in mammals. Second, we will explore the functional consequences of mitochondrial transport and partitioning on cell proliferation, fate acquisition, stemness, and on the way cells adapt their metabolism. Last, we will focus on how mitochondrial clearance programs represent a further layer of complexity for cell differentiation, or in the maintenance of stemness. Defining how mitochondrial transport, dynamics and clearance are mutually orchestrated in specific cell types may help our understanding of how cells can transition from a physiological to a pathological state.

Exposure to Copper Compromises the Maturational Competency of Porcine Oocytes by Impairing Mitochondrial Function

Copper (Cu) is an essential trace element for animals, and also an important nutritional component for the normal physiology and metabolism of animal reproductive systems. An excess or lack of Cu will directly or indirectly affect animal reproductive activities. However, the effect of Cu, in particular excessive Cu, on the reproductive performance of sows has not been studied. Here, we report that excessive Cu had negative effects on oocyte maturation and organelle functions. We showed that Cu exposure perturbed porcine oocyte meiotic maturation and impaired spindle/chromosome structure, resulting in a defective spindle assembly, as well as the abnormal distribution of actin dynamics and cortical granules. In addition, single-cell transcriptome analysis identified the target effectors of Cu actions in porcine oocytes, further demonstrating that Cu exposure affects the mitochondrial distribution and function, leading to the high levels of reactive oxygen species, DNA damage, and early apoptosis of porcine oocytes. These findings demonstrate that Cu exposure causes abnormalities in the mitochondrial distribution and function, resulting in the increased oxidative stress and levels of reactive oxygen species, DNA damage, and apoptosis, ultimately leading to a decreased porcine oocyte quality.

Dysregulation of mitochondria-lysosome contacts by GBA1 dysfunction in dopaminergic neuronal models of Parkinson’s disease

Mitochondria-lysosome contacts are recently identified sites for mediating crosstalk between both organelles, but their role in normal and diseased human neurons remains unknown. In this study, we demonstrate that mitochondria-lysosome contacts can dynamically form in the soma, axons, and dendrites of human neurons, allowing for their bidirectional crosstalk. Parkinson’s disease patient derived neurons harboring mutant GBA1 exhibited prolonged mitochondria-lysosome contacts due to defective modulation of the untethering protein TBC1D15, which mediates Rab7 GTP hydrolysis for contact untethering. This dysregulation was due to decreased GBA1 (β-glucocerebrosidase (GCase)) lysosomal enzyme activity in patient derived neurons, and could be rescued by increasing enzyme activity with a GCase modulator. These defects resulted in disrupted mitochondrial distribution and function, and could be further rescued by TBC1D15 in Parkinson’s patient derived GBA1-linked neurons. Together, our work demonstrates a potential role of mitochondria-lysosome contacts as an upstream regulator of mitochondrial function and dynamics in midbrain dopaminergic neurons in GBA1-linked Parkinson’s disease.