scholarly journals A novel role for Myosin-Va in mitochondrial fission

2019 ◽  
Author(s):  
Jackeline S Araujo ◽  
Rui M P Silva-Junior ◽  
Tong Zhang ◽  
Cara R Schiavon ◽  
Qian Chu ◽  
...  
Keyword(s):  
Molecular Motors ◽  
Molecular Motor ◽  
Mitochondrial Fission ◽  
Regulatory Protein ◽  
Melanoma Cells ◽  
Cellular Respiration ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Myosin Va ◽  
The Warburg Effect

ABSTRACTIn cancer cells metabolic changes and mitochondrial morphology are coupled. It is known that the cytoskeleton and molecular motors are directly involved in regulating mitochondrial morphology. Here we show that myosin-Va, an actin-based molecular motor, is required for the malignant properties of melanoma cells and localizes to mitochondria in these cells. Knockdown of myosin-Va increases cellular respiration rates and ROS production and decreases glucose uptake and lactate secretion. In addition, knockdown of myosin-Va results in reduced mitochondrial fission and correspondingly elongated mitochondria. We show that myosin-Va interacts with the mitochondrial outer membrane protein Spire1C, an actin-regulatory protein implicated in mitochondrial fission, and that Spire1C recruits myosin-Va to mitochondria. Finally, we show that during mitochondrial fission myosin-Va localization to mitochondria increases, and that myosin-Va localizes to mitochondrial fission sites immediately adjacent to Drp1 punctae. We conclude that myosin-Va facilitates mitochondrial fission. These data implicate myosin-Va as a target for the Warburg effect in melanoma cells.

scholarly journals Elephant seal muscle cells adapt to sustained glucocorticoid exposure by shifting their metabolic phenotype

2021 ◽  
Author(s):  
Julia Maria Torres-Velarde ◽  
Sree Rohit Raj Kolora ◽  
Jane I. Khudyakov ◽  
Daniel E. Crocker ◽  
Peter H. Sudmant ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Survival ◽  
Food Deprivation ◽  
Mitochondrial Fission ◽  
Elephant Seal ◽  
Metabolic Phenotype ◽  
Cellular Respiration ◽  
Mitochondrial Morphology ◽  
Cellular Mechanisms ◽  
Elephant Seals

AbstractElephant seals experience natural periods of prolonged food deprivation while breeding, molting, and undergoing postnatal development. Prolonged food deprivation in elephant seals increases circulating glucocorticoids without inducing muscle atrophy, but the cellular mechanisms that allow elephant seals to cope with such conditions remain elusive. We generated a cellular model and conducted transcriptomic, metabolic, and morphological analyses to study how seal cells adapt to sustained glucocorticoid exposure. Seal muscle progenitor cells differentiate into contractile myotubes with a distinctive morphology, gene expression profile, and metabolic phenotype. Exposure to dexamethasone at three ascending concentrations for 48h modulated the expression of 6 clusters of genes related to structural constituents of muscle and pathways associated with energy metabolism and cell survival. Knockdown of the glucocorticoid receptor (GR) and downstream expression analyses corroborated that GR mediates the observed effects. Dexamethasone also decreased cellular respiration, shifted the metabolic phenotype towards glycolysis, and induced mitochondrial fission and dissociation of mitochondria-ER interactions without decreasing cell viability. Knockdown of DDIT4, a GR target involved in the dissociation of mitochondria-ER membranes, recovered respiration and modulated antioxidant gene expression. These results show that adaptation to sustained glucocorticoid exposure in elephant seal myotubes involves a metabolic shift toward glycolysis, which is supported by alterations in mitochondrial morphology and a reduction in mitochondria-ER interactions, resulting in decreased respiration without compromising cell survival.

Abstract 393: MCL-1 Promotes Survival and Influences Mitochondrial Dynamics in Cardiac Myocytes

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Alexandra G Moyzis ◽  
Robert L Thomas ◽  
Jennifer Kuo ◽  
Åsa B Gustafsson
Keyword(s):  
Cell Death ◽  
Cardiac Myocytes ◽  
Apoptotic Cell ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Apoptotic Cell Death ◽  
Mitochondrial Fusion ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Rapid Degradation

The BCL-2 family proteins are important regulators of mitochondrial structure and integrity. MCL-1 is an anti-apoptotic BCL-2 protein that is highly expressed in the myocardium compared to the other anti-apoptotic proteins BCL-2 and BCL-X L. Recently, we reported that MCL-1 is essential for myocardial homeostasis. Cardiac-specific deletion of MCL-1 in mice led to rapid mitochondrial dysfunction, hypertrophy, and lethal cardiomyopathy. Surprisingly, MCL-1 deficient myocytes did not undergo apoptotic cell death. Instead, the cells displayed signs of mitochondrial deterioration and necrotic cell death, suggesting that MCL-1 has an additional role in maintaining mitochondrial function in cardiac myocytes. Similarly, deletion of MCL-1 in fibroblasts caused rapid mitochondrial fragmentation followed by cell death at 72 hours. Interestingly, the MCL-1 deficient fibroblasts retained cytochrome c in the mitochondria , confirming that the cells were not undergoing apoptotic cell death. We have also identified that MCL-1 localizes to the mitochondrial outer membrane (OM) and the matrix in the myocardium and that the two forms respond differently to stress. MCL-1 OM was rapidly degraded after myocardial infarction or fasting, whereas MCL-1 Matrix levels were maintained. Similarly, starvation of MEFs resulted in rapid degradation of MCL-1 OM , whereas MCL-1 Matrix showed delayed degradation. Treatment with the mitochondrial uncoupler FCCP led to rapid degradation of both forms. This suggests that the susceptibility to degradation is dependent on its localization and the nature of the stress. Our data also suggests that these two forms perform distinct functions in regulating mitochondrial morphology and survival. Overexpression of MCL-1 Matrix promoted mitochondrial fusion in fibroblasts under baseline conditions and protected cells against FCCP-mediated mitochondrial fission and clearance by autophagosomes. Thus, our data suggest that MCL-1 exists in two separate locations where it performs different functions. MCL-1 Matrix promotes mitochondrial fusion, which protects cells against excessive mitochondrial clearance during unfavorable conditions.

scholarly journals The Dynamin-Related Gtpase, Mgm1p, Is an Intermembrane Space Protein Required for Maintenance of Fusion Competent Mitochondria

2000 ◽  
Vol 151 (2) ◽  
pp. 341-352 ◽  
Author(s):  
Edith D. Wong ◽  
Jennifer A. Wagner ◽  
Steven W. Gorsich ◽  
J. Michael McCaffery ◽  
Janet M. Shaw ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Fission ◽  
Mitochondrial Fusion ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Temperature Sensitive ◽  
Intermembrane Space ◽  
Direct Role ◽  
Membrane Fission ◽  
Mitochondrial Intermembrane Space

Mutations in the dynamin-related GTPase, Mgm1p, have been shown to cause mitochondrial aggregation and mitochondrial DNA loss in Saccharomyces cerevisiae cells, but Mgm1p's exact role in mitochondrial maintenance is unclear. To study the primary function of MGM1, we characterized new temperature sensitive MGM1 alleles. Examination of mitochondrial morphology in mgm1 cells indicates that fragmentation of mitochondrial reticuli is the primary phenotype associated with loss of MGM1 function, with secondary aggregation of mitochondrial fragments. This mgm1 phenotype is identical to that observed in cells with a conditional mutation in FZO1, which encodes a transmembrane GTPase required for mitochondrial fusion, raising the possibility that Mgm1p is also required for fusion. Consistent with this idea, mitochondrial fusion is blocked in mgm1 cells during mating, and deletion of DNM1, which encodes a dynamin-related GTPase required for mitochondrial fission, blocks mitochondrial fragmentation in mgm1 cells. However, in contrast to fzo1 cells, deletion of DNM1 in mgm1 cells restores mitochondrial fusion during mating. This last observation indicates that despite the phenotypic similarities observed between mgm1 and fzo1 cells, MGM1 does not play a direct role in mitochondrial fusion. Although Mgm1p was recently reported to localize to the mitochondrial outer membrane, our studies indicate that Mgm1p is localized to the mitochondrial intermembrane space. Based on our localization data and Mgm1p's structural homology to dynamin, we postulate that it functions in inner membrane remodeling events. In this context, the observed mgm1 phenotypes suggest that inner and outer membrane fission is coupled and that loss of MGM1 function may stimulate Dnm1p-dependent outer membrane fission, resulting in the formation of mitochondrial fragments that are structurally incompetent for fusion.

Theoretical Prediction of Run Speed Distribution for a Molecular Motor

2008 ◽  
Author(s):  
Sam Walcott ◽  
Neil M. Kad
Keyword(s):  
Molecular Motors ◽  
Molecular Motor ◽  
Realistic Model ◽  
Variable Step Size ◽  
Step Size ◽  
Run Length ◽  
Speed Distribution ◽  
Myosin Va ◽  
Cell Transforming ◽  
Run Speed

Processive molecular motors are large proteins that “walk” along filaments in a cell, transforming chemical energy into mechanical work. These microscopic motors behave, at least qualitatively, like macroscopic walking machines. The dynamics and stability of macroscopic walkers are understood by analysis of “stride functions” (Poincare´ maps from one step to the next). We show that molecular motors have linear, probabilistic stride functions. Using these functions, we derive expressions for three measurable distributions: step period, run length and average run speed. The former two distributions are well known, the latter is new. We validate our calculation with simulations of a realistic model for Myosin Va (a molecular motor). The parameters of the run speed distribution specify both the run-length and step period distributions. As step-period distributions are difficult to measure under physiologically relevant conditions, this technique provides new information. Finally, we discuss the effects of variable step size and experimental error.

scholarly journals Elephant seal muscle cells adapt to sustained glucocorticoid exposure by shifting their metabolic phenotype

2021 ◽  
Author(s):  
Julia María Torres-Velarde ◽  
Sree Rohit Raj Kolora ◽  
Jane I Khudyakov ◽  
Daniel E. Crocker ◽  
Peter H Sudmant ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Survival ◽  
Food Deprivation ◽  
Mitochondrial Fission ◽  
Elephant Seal ◽  
Metabolic Phenotype ◽  
Cellular Respiration ◽  
Mitochondrial Morphology ◽  
Cellular Mechanisms ◽  
Elephant Seals

Elephant seals experience natural periods of prolonged food deprivation while breeding, molting, and undergoing postnatal development. Prolonged food deprivation in elephant seals increases circulating glucocorticoids without inducing muscle atrophy, but the cellular mechanisms that allow elephant seals to cope with such conditions remain elusive. We generated a cellular model and conducted transcriptomic, metabolic, and morphological analyses to study how seal cells adapt to sustained glucocorticoid exposure. Seal muscle progenitor cells differentiate into contractile myotubes with a distinctive morphology, gene expression profile, and metabolic phenotype. Exposure to dexamethasone at three ascending concentrations for 48h modulated the expression of 6 clusters of genes related to structural constituents of muscle and pathways associated with energy metabolism and cell survival. Knockdown of the glucocorticoid receptor (GR) and downstream expression analyses corroborated that GR mediates the observed effects. Dexamethasone also decreased cellular respiration, shifted the metabolic phenotype towards glycolysis, and induced mitochondrial fission and dissociation of mitochondria-ER interactions without decreasing cell viability. Knockdown of DDIT4, a GR target involved in the dissociation of mitochondria-ER membranes, recovered respiration and modulated antioxidant gene expression. These results show that adaptation to sustained glucocorticoid exposure in elephant seal myotubes involves a metabolic shift toward glycolysis, which is supported by alterations in mitochondrial morphology and a reduction in mitochondria-ER interactions, resulting in decreased respiration without compromising cell survival.

scholarly journals Myosin Va binding to neurofilaments is essential for correct myosin Va distribution and transport and neurofilament density

2002 ◽  
Vol 159 (2) ◽  
pp. 279-290 ◽  
Author(s):  
Mala V. Rao ◽  
Linda J. Engle ◽  
Panaiyur S. Mohan ◽  
Aidong Yuan ◽  
Dike Qiu ◽  
...  
Keyword(s):  
Normal Distribution ◽  
Axonal Transport ◽  
Immunoelectron Microscopy ◽  
Molecular Motors ◽  
Peripheral Nerves ◽  
Molecular Motor ◽  
Neurofilament Proteins ◽  
Myosin Va ◽  
Slow Transport

The identification of molecular motors that modulate the neuronal cytoskeleton has been elusive. Here, we show that a molecular motor protein, myosin Va, is present in high proportions in the cytoskeleton of mouse CNS and peripheral nerves. Immunoelectron microscopy, coimmunoprecipitation, and blot overlay analyses demonstrate that myosin Va in axons associates with neurofilaments, and that the NF-L subunit is its major ligand. A physiological association is indicated by observations that the level of myosin Va is reduced in axons of NF-L–null mice lacking neurofilaments and increased in mice overexpressing NF-L, but unchanged in NF-H–null mice. In vivo pulse-labeled myosin Va advances along axons at slow transport rates overlapping with those of neurofilament proteins and actin, both of which coimmunoprecipitate with myosin Va. Eliminating neurofilaments from mice selectively accelerates myosin Va translocation and redistributes myosin Va to the actin-rich subaxolemma and membranous organelles. Finally, peripheral axons of dilute-lethal mice, lacking functional myosin Va, display selectively increased neurofilament number and levels of neurofilament proteins without altering axon caliber. These results identify myosin Va as a neurofilament-associated protein, and show that this association is essential to establish the normal distribution, axonal transport, and content of myosin Va, and the proper numbers of neurofilaments in axons.

scholarly journals Emr1 regulates the number of foci of the endoplasmic reticulum-mitochondria encounter structure complex

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Faiz Rasul ◽  
Fan Zheng ◽  
Fenfen Dong ◽  
Jiajia He ◽  
Ling Liu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Mitochondrial Fission ◽  
Regulatory Protein ◽  
Mitochondrial Morphology ◽  
Lipid Transfer ◽  
Core Component ◽  
Dynamic Regulation ◽  
Mtdna Inheritance ◽  
Mutant Cells ◽  
Mitochondrial Membrane Protein

AbstractThe endoplasmic reticulum-mitochondria encounter structure (ERMES) complex creates contact sites between the endoplasmic reticulum and mitochondria, playing crucial roles in interorganelle communication, mitochondrial fission, mtDNA inheritance, lipid transfer, and autophagy. The mechanism regulating the number of ERMES foci within the cell remains unclear. Here, we demonstrate that the mitochondrial membrane protein Emr1 contributes to regulating the number of ERMES foci. We show that the absence of Emr1 significantly decreases the number of ERMES foci. Moreover, we find that Emr1 interacts with the ERMES core component Mdm12 and colocalizes with Mdm12 on mitochondria. Similar to ERMES mutant cells, cells lacking Emr1 display defective mitochondrial morphology and impaired mitochondrial segregation, which can be rescued by an artificial tether capable of linking the endoplasmic reticulum and mitochondria. We further demonstrate that the cytoplasmic region of Emr1 is required for regulating the number of ERMES foci. This work thus reveals a crucial regulatory protein necessary for ERMES functions and provides mechanistic insights into understanding the dynamic regulation of endoplasmic reticulum-mitochondria communication.

scholarly journals Gag3p, an Outer Membrane Protein Required for Fission of Mitochondrial Tubules

2000 ◽  
Vol 151 (2) ◽  
pp. 333-340 ◽  
Author(s):  
Peter Fekkes ◽  
Kelly A. Shepard ◽  
Michael P. Yaffe
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Fission ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Gene Products ◽  
Mitochondrial Fragmentation ◽  
Gene Encoding ◽  
Peripheral Protein ◽  
And Function ◽  
Two Hybrid

Mitochondrial morphology and function depend on MGM1, a Saccharomyces cerevisiae gene encoding a dynamin-like protein of the mitochondrial outer membrane. Here, we show that mitochondrial fragmentation and mitochondrial genome loss caused by lesions in MGM1 are suppressed by three novel mutations, gag1, gag2, and gag3 (for glycerol-adapted growth). Cells with any of the gag mutations displayed aberrant mitochondrial morphology characterized by elongated, unbranched tubes and highly fenestrated structures. Additionally, each of the gag mutations prevented mitochondrial fragmentation caused by loss of the mitochondrial fusion factor, Fzo1p, or by treatment of cells with sodium azide. The gag1 mutation mapped to DNM1 that encodes a dynamin-related protein required for mitochondrial fission. GAG3 encodes a novel WD40-repeat protein previously found to interact with Dnm1p in a two-hybrid assay. Gag3p was localized to mitochondria where it was found to associate as a peripheral protein on the cytosolic face of the outer membrane. This association requires neither the DNM1 nor GAG2 gene products. However, the localization of Dnm1p to the mitochondrial outer membrane is substantially reduced by the gag2 mutation, but unaffected by loss of Gag3p. These results indicate that Gag3p plays a distinct role on the mitochondrial surface to mediate the fission of mitochondrial tubules.

scholarly journals A uvs-5 Strain Is Deficient for a Mitofusin Gene Homologue, fzo1 , Involved in Maintenance of Long Life Span in Neurospora crassa

2012 ◽  
Vol 12 (2) ◽  
pp. 233-243 ◽  
Author(s):  
Kiminori Kurashima ◽  
Michael Chae ◽  
Hirokazu Inoue ◽  
Shin Hatakeyama ◽  
Shuuitsu Tanaka
Keyword(s):  
Life Span ◽  
Neurospora Crassa ◽  
Mitochondrial Fission ◽  
Single Amino Acid ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Wild Type ◽  
Content Type ◽  
Long Life ◽  
Mutant Phenotypes

ABSTRACT Mitochondria are highly dynamic organelles that continuously fuse and divide. To maintain mitochondria, cells establish an equilibrium of fusion and fission events, which are mediated by dynamin-like GTPases. We previously showed that an mus-10 strain, a mutagen-sensitive strain of the filamentous fungus Neurospora crassa , is defective in an F-box protein that is essential for the maintenance of mitochondrial DNA (mtDNA), long life span, and mitochondrial morphology. Similarly, a uvs-5 mutant accumulates deletions within its mtDNA, has a shortened life span, and harbors fragmented mitochondria, the latter of which is indicative of an imbalance between mitochondrial fission and fusion. Since the uvs-5 mutation maps very close to the locus of fzo1 , encoding a mitofusin homologue thought to mediate mitochondrial outer membrane fusion, we determined the sequence of the fzo1 gene in the uvs-5 mutant. A single amino acid substitution (Q368R) was found in the GTPase domain of the FZO1 protein. Expression of wild-type FZO1 in the uvs-5 strain rescued the mutant phenotypes, while expression of a mutant FZO1 protein did not. Moreover, when knock-in of the Q368R mutation was performed on a wild-type strain, the resulting mutant displayed phenotypes identical to those of the uvs-5 mutant. Therefore, we concluded that the previously unidentified uvs-5 gene is fzo1 . Furthermore, we used immunoprecipitation analysis to show that the FZO1 protein interacts with MUS-10, which suggests that these two proteins may function together to maintain mitochondrial morphology.

scholarly journals A model of processive walking and slipping of kinesin-8 molecular motors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ping Xie
Keyword(s):  
Single Molecule ◽  
Molecular Motors ◽  
External Load ◽  
Molecular Motor ◽  
Velocity Versus ◽  
Stick Slip ◽  
Load Dependence ◽  
Chemomechanical Coupling ◽  
Similarities And Differences ◽  
Stick Slip Motion

AbstractKinesin-8 molecular motor can move with superprocessivity on microtubules towards the plus end by hydrolyzing ATP molecules, depolymerizing microtubules. The available single molecule data for yeast kinesin-8 (Kip3) motor showed that its superprocessive movement is frequently interrupted by brief stick–slip motion. Here, a model is presented for the chemomechanical coupling of the kinesin-8 motor. On the basis of the model, the dynamics of Kip3 motor is studied analytically. The analytical results reproduce quantitatively the available single molecule data on velocity without including the slip and that with including the slip versus external load at saturating ATP as well as slipping velocity versus external load at saturating ADP and no ATP. Predicted results on load dependence of stepping ratio at saturating ATP and load dependence of velocity at non-saturating ATP are provided. Similarities and differences between dynamics of kinesin-8 and that of kinesin-1 are discussed.

Sign in / Sign up

Export Citation Format

Share Document