scholarly journals Mitochondrial membrane tension governs fission

2018 ◽  
Author(s):  
Dora Mahecic ◽  
Lina Carlini ◽  
Tatjana Kleele ◽  
Adai Colom ◽  
Antoine Goujon ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Mitochondrial Membrane ◽  
Mitochondrial Fission ◽  
Outer Mitochondrial Membrane ◽  
Membrane Tension ◽  
Structured Illumination ◽  
Bending Energy ◽  
Structured Illumination Microscopy ◽  
Cellular Factors ◽  
Tension Sensor

AbstractDuring mitochondrial fission, key molecular and cellular factors assemble on the outer mitochondrial membrane, where they coordinate to generate constriction. Constriction sites can eventually divide, or reverse upon disassembly of the machinery. However, a role for membrane tension in mitochondrial fission, although speculated, has remained undefined. We captured the dynamics of constricting mitochondria in mammalian cells using live-cell structured illumination microscopy (SIM). By analyzing the diameters of tubules that emerge from mitochondria and implementing a fluorescence lifetime-based mitochondrial membrane tension sensor, we discovered that mitochondria are indeed under tension. Under perturbations that reduce mitochondrial tension, constrictions initiate at the same rate, but are less likely to divide. We propose a model based on our estimates of mitochondrial membrane tension and bending energy in living cells which accounts for the observed probability distribution for mitochondrial constrictions to divide.

scholarly journals Constriction and Dnm1p Recruitment Are Distinct Processes in Mitochondrial Fission

2003 ◽  
Vol 14 (5) ◽  
pp. 1953-1963 ◽  
Author(s):  
Aster Legesse-Miller ◽  
Ramiro H. Massol ◽  
Tom Kirchhausen
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fluorescence Imaging ◽  
Hot Spots ◽  
Mitochondrial Membrane ◽  
Mitochondrial Fission ◽  
Three Dimensional ◽  
Time Lapse ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Matrix ◽  
Different Shapes

Mitochondria undergo cycles of fusion and fission crucial for organelle homeostasis. Fission is regulated partially by recruitment of the large GTPase Dnm1p to the outer mitochondrial membrane. Using three-dimensional time-lapse fluorescence imaging of Saccharomyces cerevisiae cells, we found that Dnm1p-EGFP appears and disappears at “hot spots” along mitochondrial tubes. It forms patches that convert rapidly into different shapes regardless of whether mitochondrial fission ensues or not. Moreover, the thickness of the mitochondrial matrix displays frequent temporal fluctuations apparently unrelated to fission or to recruitment of Dnm1p-EGFP. These results suggest that mitochondrial fission requires coordination of at least two distinct processes.

scholarly journals PINK1 disables the anti-fission machinery to segregate damaged mitochondria for mitophagy

2016 ◽  
Vol 213 (2) ◽  
pp. 163-171 ◽  
Author(s):  
Kenneth R. Pryde ◽  
Heather L. Smith ◽  
Kai-Yin Chau ◽  
Anthony H.V. Schapira
Keyword(s):  
Protein Kinase ◽  
Parkinson Disease ◽  
Protein Kinase A ◽  
Mitochondrial Membrane ◽  
Mitochondrial Fission ◽  
Scaffold Protein ◽  
Outer Mitochondrial Membrane ◽  
Related Protein ◽  
Anchoring Protein ◽  
Kinase A

Mitochondrial fission is essential for the degradation of damaged mitochondria. It is currently unknown how the dynamin-related protein 1 (DRP1)–associated fission machinery is selectively targeted to segregate damaged mitochondria. We show that PTEN-induced putative kinase (PINK1) serves as a pro-fission signal, independently of Parkin. Normally, the scaffold protein AKAP1 recruits protein kinase A (PKA) to the outer mitochondrial membrane to phospho-inhibit DRP1. We reveal that after damage, PINK1 triggers PKA displacement from A-kinase anchoring protein 1. By ejecting PKA, PINK1 ensures the requisite fission of damaged mitochondria for organelle degradation. We propose that PINK1 functions as a master mitophagy regulator by activating Parkin and DRP1 in response to damage. We confirm that PINK1 mutations causing Parkinson disease interfere with the orchestration of selective fission and mitophagy by PINK1.

scholarly journals Mitochondrial RNA granules are fluid condensates, positioned by membrane dynamics

2019 ◽  
Author(s):  
Timo Rey ◽  
Sofia Zaganelli ◽  
Emilie Cuillery ◽  
Jean-Claude Martinou ◽  
Suliana Manley
Keyword(s):  
Dynamic Properties ◽  
Mitochondrial Fission ◽  
Super Resolution ◽  
Membrane Dynamics ◽  
Cellular Respiration ◽  
Mitochondrial Rna ◽  
Structured Illumination ◽  
Inner Mitochondrial Membrane ◽  
Structured Illumination Microscopy ◽  
Rna Granules

Mitochondria contain the genetic information and expression machinery to produce proteins essential for cellular respiration. Within the mitochondrial matrix, newly synthesized RNA, RNA processing proteins, and mitoribosome assembly factors are known to form punctate subcompartments referred to as mitochondrial RNA granules (MRGs) 1–3. Despite their proposed role in regulating gene expression, little is known about the structural and dynamic properties of MRGs. We investigated the organization of MRGs using fluorescence super-resolution localization microscopy and correlative electron microscopy techniques, obtaining ultrastructural details of their internal architecture. We find that MRGs are organized into nanoscale RNA cores surrounded by a protein shell. Using live-cell super-resolution structured illumination microscopy and photobleaching perturbations, we reveal that MRGs undergo fusion and rapidly exchange components, consistent with liquid-liquid phase separation (LLPS). Furthermore, MRGs associate with the inner mitochondrial membrane and their fusion coincides with membrane remodeling. Inhibition of mitochondrial fission leads to an aberrant distribution of MRGs into concentrated pockets, where they remain as distinct individual units despite their close apposition. Together, our results reveal a role for LLPS in concentrating RNA and its processing proteins into MRGs, which are positioned along mitochondria by membrane dynamics.

scholarly journals Identification of Novel Interaction Partners of AIF Protein on the Outer Mitochondrial Membrane

Acta Naturae ◽  
2018 ◽  
Vol 10 (4) ◽  
pp. 100-109 ◽  
Author(s):  
N. P. Fadeeva ◽  
N. V. Antipova ◽  
V. O. Shender ◽  
K. S. Anufrieva ◽  
G. A. Stepanov ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Mitochondrial Membrane ◽  
Bioinformatic Analysis ◽  
Amino Acid Sequences ◽  
Outer Mitochondrial Membrane ◽  
Apoptotic Pathway ◽  
Survival Prognosis ◽  
High Level

In response to the wide variety of external and internal signals, mammalian cells undergo apoptosis, programmed cell death. Dysregulation of apoptosis is involved in multiple human diseases, including cancer, autoimmunity, and ischemic injuries. Two types of apoptosis have been described: the caspase-dependent one, leading to digestion of cellular proteins, and caspase-independent apoptosis, resulting in DNA fragmentation. The latter type of apoptosis is executed by AIF protein and is believed to have appeared first during evolution. The key step in the caspase-independent apoptosis program is the dissociation of AIF from the outer mitochondrial membrane (OMM). However, the molecular mechanism of interaction between AIF and OMM remains poorly understood. In this study, we demonstrated that AIF can bind to OMM via mortalin protein. We confirmed interaction between AIF and mortalin both in vitro and in vivo and mapped the amino acid sequences that are important for the binding of these proteins. Next, we showed that apoptosis induction by chemotherapy leads to downregulation of AIF-mortalin interaction and dissociation of AIF from the OMM. Finally, a bioinformatic analysis demonstrated that a high level of mortalin expression correlates with a worse survival prognosis for glioma patients. Altogether, our data revealed that mortalin plays an important role in the regulation of the caspase-independent apoptotic pathway and allowed us to speculate that inhibition of AIF-mortalin interaction may induce a dissociation of AIF from the OMM and subsequent apoptosis of cancer cells.

scholarly journals Quantification of cristae architecture reveals time-dependent characteristics of individual mitochondria

2020 ◽  
Vol 3 (7) ◽  
pp. e201900620
Author(s):  
Mayuko Segawa ◽  
Dane M Wolf ◽  
Nan W Hultgren ◽  
David S Williams ◽  
Alexander M van der Bliek ◽  
...  
Keyword(s):  
Machine Learning ◽  
Mitochondrial Fission ◽  
Live Cell ◽  
Structured Illumination ◽  
Structured Illumination Microscopy ◽  
Fusion Event ◽  
New Strategy ◽  
Function Relationship ◽  
Relationship Of ◽  
Standard Techniques

Recent breakthroughs in live-cell imaging have enabled visualization of cristae, making it feasible to investigate the structure–function relationship of cristae in real time. However, quantifying live-cell images of cristae in an unbiased way remains challenging. Here, we present a novel, semi-automated approach to quantify cristae, using the machine-learning Trainable Weka Segmentation tool. Compared with standard techniques, our approach not only avoids the bias associated with manual thresholding but more efficiently segments cristae from Airyscan and structured illumination microscopy images. Using a cardiolipin-deficient cell line, as well as FCCP, we show that our approach is sufficiently sensitive to detect perturbations in cristae density, size, and shape. This approach, moreover, reveals that cristae are not uniformly distributed within the mitochondrion, and sites of mitochondrial fission are localized to areas of decreased cristae density. After a fusion event, individual cristae from the two mitochondria, at the site of fusion, merge into one object with distinct architectural values. Overall, our study shows that machine learning represents a compelling new strategy for quantifying cristae in living cells.

A Platinum(II) Based Correlative Probe for Bacteria

2019 ◽  
Author(s):  
Anna Maria Ranieri ◽  
Kathryn Leslie ◽  
Song Huang ◽  
Stefano Stagni ◽  
Denis Jacquemin ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Super Resolution ◽  
Molecular Probes ◽  
Live Cells ◽  
Structured Illumination ◽  
Luminescent Probe ◽  
Structured Illumination Microscopy ◽  
Cellular Localisation ◽  
Super Resolution Microscopy ◽  
Nanosims Analysis

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. This is especially so for correlative probes, which are proving to be powerful tools for enhancing the imaging of live cells. In this work a platinum(II)-naphthalimide molecule has been developed to extend small molecule correlative probes to bacterial imaging. The probe was designed to exploit the naphthalimide moiety as a luminescent probe for super-resolution microscopy, with the platinum(II) centre enabling visualisation of the complex with ion nanoscopy. Photophysical characterisation and theoretical studies confirmed that the emission properties of the naphthalimide are not altered by the platinum(II) centre. Structured illumination microscopy (SIM) imaging on live <i>Bacillus cereus</i>revealed that the platinum(II) centre does not change the sub-cellular localisation of the naphthalimide, and confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis of the sample was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the correlative action of the probe. The successful combination of these two probe moieties with no perturbation of their individual detection introduces a platform for a versatile range of new correlative probes for bacteria.

scholarly journals Receptor-mediated Drp1 oligomerization on endoplasmic reticulum

2017 ◽  
Author(s):  
Wei-Ke Ji ◽  
Rajarshi Chakrabarti ◽  
Xintao Fan ◽  
Lori Schoenfeld ◽  
Stefan Strack ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mammalian Cells ◽  
Actin Polymerization ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Division ◽  
Knock Out ◽  
Multiple Factors ◽  
Latrunculin A

AbstractDrpl is a dynamin GTPase important for mitochondrial and peroxisomal division. Drp1 oligomerization and mitochondrial recruitment are regulated by multiple factors, including interaction with mitochondrial receptors such as Mff, MiD49, MiD51 and Fis. In addition, both endoplasmic reticulum (ER) and actin filaments play positive roles in mitochondrial division, but mechanisms for their roles are poorly defined. Here, we find that a population of Drp1 oligomers is ER-associated in mammalian cells, and is distinct from mitochondrial or peroxisomal Drp1 populations. Sub-populations of Mff and Fis1, which are tail-anchored proteins, also localize to ER. Drp1 oligomers assemble on ER, from which they can transfer to mitochondria. Suppression of Mff or inhibition of actin polymerization through the formin INF2 significantly reduces all Drp1 oligomer populations (mitochondrial, peroxisomal, ER-bound) and mitochondrial division, while Mff targeting to ER has a stimulatory effect on division. Our results suggest that ER can function as a platform for Drp1 oligomerization, and that ER-associated Drp1 contributes to mitochondrial division.SummaryAssembly of the dynamin GTPase Drp1 into constriction-competent oligomers is a key event in mitochondrial division. Here, Ji et al show that Drp1 oligomerization can occur on endoplasmic reticulum through an ER-bound population of the tail-anchored protein Mff.Abbreviations used in this paper: Drp1, dynamin-related protein 1; Fis1, mitochondrial fission 1 protein; INF2, inverted formin 2; KD, siRNA-mediated knock down; KI, CRISPR-mediated knock in; KO, CRISPR-mediated knock out; LatA, Latrunculin A; MDV, mitochondrially-derived vesicle; Mff, mitochondrial fission factor; MiD49 and MiD51, mitochondrial dynamics protein of 49 and 51 kDa; OMM, outer mitochondrial membrane; TA, tail-anchored.

scholarly journals Distinct molecular signatures of fission predict mitochondrial degradation or proliferation

2020 ◽  
Author(s):  
Tatjana Kleele ◽  
Timo Rey ◽  
Julius Winter ◽  
Sofia Zaganelli ◽  
Dora Mahecic ◽  
...  
Keyword(s):  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Adaptor Proteins ◽  
Cellular Level ◽  
Mitochondrial Activity ◽  
Mitochondrial Morphology ◽  
Structured Illumination ◽  
Structured Illumination Microscopy ◽  
Downstream Effects ◽  
Fate Determinants

SUMMARYMitochondrial fission is a highly regulated process which, when disrupted, can alter metabolism, proliferation and apoptosis1–3. The downstream effects have implications for many diseases, from neurodegeneration4–6 to cardiovascular disease7,8 and cancer9,10. Key components of the fission machinery have been identified: constriction sites are initiated by the endoplasmic reticulum (ER)11 and actin12 before dynamin-related protein 1 (Drp1)13 is recruited to the outer mitochondrial membrane via adaptor proteins14–17, where it drives constriction and scission of the membrane18. In the life cycle of mitochondria, fission is important for the biogenesis of new mitochondria as well as the clearance of dysfunctional mitochondria via mitophagy3,19. Global regulation of fission on the cellular level is insufficient to explain how fate decisions are made at the single organelle level, so it is unknown how those dual functions arise, blocking progress in developing therapies that target mitochondrial activity. However, systematically studying mitochondrial division to uncover fate determinants is challenging, since fission is unpredictable, and mitochondrial morphology is extremely heterogeneous. Furthermore, because their ultrastructure lies below the diffraction limit, the dynamic organization of mitochondria and their interaction partners are hard to study at the single organelle level. We used live-cell structured illumination microscopy (SIM) and instant SIM20 for fast multi-colour acquisition of mitochondrial dynamics in Cos-7 cells and mouse cardiomyocytes. We analysed hundreds of fission events, and discovered two functionally and mechanistically distinct types of fission. Mitochondria divide peripherally to shed damaged material into smaller daughter mitochondria that subsequently undergo mitophagy, whereas healthy mitochondria proliferate via midzone division. Both types are Drp1-mediated, but they rely on different membrane adaptors to recruit Drp1, and ER and actin mediated pre-constriction is only involved in midzone fission.

scholarly journals A novel motif in the yeast mitochondrial dynamin Dnm1 is essential for adaptor binding and membrane recruitment

2012 ◽  
Vol 199 (4) ◽  
pp. 613-622 ◽  
Author(s):  
Huyen T. Bui ◽  
Mary A. Karren ◽  
Debjani Bhar ◽  
Janet M. Shaw
Keyword(s):  
Mitochondrial Membrane ◽  
Mitochondrial Fission ◽  
Adaptor Proteins ◽  
Structural Features ◽  
Outer Mitochondrial Membrane ◽  
Membrane Recruitment ◽  
Suppressor Mutations ◽  
Guanosine Triphosphatase ◽  
Related Proteins ◽  
Binding Interfaces

To initiate mitochondrial fission, dynamin-related proteins (DRPs) must bind specific adaptors on the outer mitochondrial membrane. The structural features underlying this interaction are poorly understood. Using yeast as a model, we show that the Insert B domain of the Dnm1 guanosine triphosphatase (a DRP) contains a novel motif required for association with the mitochondrial adaptor Mdv1. Mutation of this conserved motif specifically disrupted Dnm1–Mdv1 interactions, blocking Dnm1 recruitment and mitochondrial fission. Suppressor mutations in Mdv1 that restored Dnm1–Mdv1 interactions and fission identified potential protein-binding interfaces on the Mdv1 β-propeller domain. These results define the first known function for Insert B in DRP–adaptor interactions. Based on the variability of Insert B sequences and adaptor proteins, we propose that Insert B domains and mitochondrial adaptors have coevolved to meet the unique requirements for mitochondrial fission of different organisms.

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