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 Fzo1, a Protein Involved in Mitochondrial Fusion, Inhibits Apoptosis

2004 ◽  
Vol 279 (50) ◽  
pp. 52726-52734 ◽  
Author(s):  
Rie Sugioka ◽  
Shigeomi Shimizu ◽  
Yoshihide Tsujimoto
Keyword(s):  
Cell Death ◽  
Conformational Changes ◽  
Apoptotic Cell ◽  
Mitochondrial Fission ◽  
Apoptotic Cell Death ◽  
Mitochondrial Fusion ◽  
Mitochondrial Morphology ◽  
Human Homolog ◽  
Mitochondrial Fragmentation ◽  
Apoptotic Death

Mitochondrial morphology and physiology are regulated by the processes of fusion and fission. Some forms of apoptosis are reported to be associated with mitochondrial fragmentation. We showed that overexpression of Fzo1A/B (rat) proteins involved in mitochondrial fusion, or silencing of Dnm1 (rat)/Drp1 (human) (a mitochondrial fission protein), increased elongated mitochondria in healthy cells. After apoptotic stimulation, these interventions inhibited mitochondrial fragmentation and cell death, suggesting that a process involved in mitochondrial fusion/fission might play a role in the regulation of apoptosis. Consistently, silencing of Fzo1A/B or Mfn1/2 (a human homolog of Fzo1A/B) led to an increase of shorter mitochondria and enhanced apoptotic death. Overexpression of Fzo1 inhibited cytochromecrelease and activation of Bax/Bak, as assessed from conformational changes and oligomerization. Silencing of Mfn or Drp1 caused an increase or decrease of mitochondrial sensitivity to apoptotic stimulation, respectively. These results indicate that some of the proteins involved in mitochondrial fusion/fission modulate apoptotic cell death at the mitochondrial level.

scholarly journals Inhibition of Drp1 Sensitizes Cancer Cells to Cisplatin-Induced Apoptosis through Transcriptional Inhibition of c-FLIP Expression

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5793
Author(s):  
Seon Min Woo ◽  
Kyoung-jin Min ◽  
Taeg Kyu Kwon
Keyword(s):  
Cell Death ◽  
Cancer Cells ◽  
Apoptotic Cell ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Combined Treatment ◽  
Ectopic Expression ◽  
Specific Inhibitor ◽  
Apoptotic Cell Death ◽  
Induced Apoptosis

Mitochondrial fragmentation occurs during the apoptosis. Dynamin-related protein 1 (Drp1) acts as an important component in mitochondrial fission machinery and can regulate various biological processes including apoptosis, cell cycle, and proliferation. The present study demonstrates that dysfunction of mitochondrial dynamics plays a pivotal role in cisplatin-induced apoptosis. Inhibiting the mitochondrial fission with the specific inhibitor (Mdivi-1) did not affect apoptotic cell death in low concentrations (<10 μM). Interestingly, mdivi-1 enhanced cisplatin-induced apoptosis in cancer cells, but not in normal cells. Particularly in the presence of mdivi-1, several human cancer cell lines, including renal carcinoma cell line Caki-1, became vulnerable to cisplatin by demonstrating the traits of caspase 3-dependent apoptosis. Combined treatment induced downregulation of c-FLIP expression transcriptionally, and ectopic expression of c-FLIP attenuated combined treatment-induced apoptotic cell death with mdivi-1 plus cisplatin. Collectively, our data provide evidence that mdivi-1 might be a cisplatin sensitizer.

scholarly journals Mitochondrial fusion regulates proliferation and differentiation in the type II neuroblast lineage in Drosophila

2021 ◽  
Author(s):  
Dnyanesh Dubal ◽  
Prachiti Moghe ◽  
Bhavin Uttekar ◽  
Richa Rikhy
Keyword(s):  
Notch Signaling ◽  
Mitochondrial Dynamics ◽  
Stem Cell Differentiation ◽  
Mitochondrial Fusion ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Activity ◽  
Mitochondrial Morphology ◽  
Type Ii ◽  
Mitochondrial Fragmentation ◽  
Proliferation And Differentiation

Optimal mitochondrial function determined by mitochondrial dynamics, morphology and activity is coupled to stem cell differentiation and organism development. However, the mechanisms of interaction of signaling pathways with mitochondrial morphology and activity are not completely understood. We assessed the role of mitochondrial fusion and fission in differentiation of neural stem cells called neuroblasts (NB) in the Drosophila brain. Depletion of mitochondrial inner membrane fusion protein Opa1 and mitochondrial outer membrane protein Marf in the Drosophila type II neuroblast lineage led to mitochondrial fragmentation and loss of activity. Opa1 and Marf depletion did not affect the numbers and polarity of type II neuroblasts but led to a decrease in proliferation and differentiation of cells in the lineage. On the contrary, loss of mitochondrial fission protein Drp1 led to mitochondrial fusion but did not show defects in proliferation and differentiation. Depletion of Drp1 along with Opa1 or Marf also led to mitochondrial fusion and suppressed fragmentation, loss of mitochondrial activity, proliferation and differentiation in the type II NB lineage. We found that Notch signaling depletion via the canonical pathway showed mitochondrial fragmentation and loss of differentiation similar to Opa1 mutants. An increase in Notch signaling required mitochondrial fusion for NB proliferation. Further, Drp1 mutants in combination with Notch depletion showed mitochondrial fusion and drove differentiation in the lineage suggesting that fused mitochondria can influence Notch signaling driven differentiation in the type II NB lineage. Our results implicate a crosstalk between Notch signalling, mitochondrial activity and mitochondrial fusion as an essential step in type II NB differentiation.

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.

Abstract 375: MCL-1 Regulates Mitochondrial Dynamics and Mitophagy

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Alexandra G Moyzis ◽  
Leonardo Leon ◽  
Robert L Thomas ◽  
Åsa B Gustafsson
Keyword(s):  
Cell Death ◽  
Apoptotic Cell ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Myeloid Cell ◽  
Serum Starvation ◽  
Necrotic Cell ◽  
Efficient Removal ◽  
Family Protein ◽  
Specific Deletion

The anti-apoptotic BCL-2 family protein Myeloid Cell Leukemia-1 (MCL-1) is essential for maintaining mitochondrial integrity and cardiac function in the adult heart. Recently, we reported that cardiac-specific deletion of MCL-1 in mice leads to rapid mitochondrial dysfunction, hypertrophy, and lethal cardiomyopathy. Surprisingly, MCL-1 ablation does not result in apoptotic cell death, but rather cells show signs of mitochondrial deterioration and necrotic cell death. This suggests that in addition to its anti-apoptotic role, MCL-1 has unidentified roles in maintaining mitochondrial function in cardiac myocytes. MCL-1 exists in two distinct locations in myocytes: one form is localized to the outer mitochondrial membrane (MCL-1 OM ) and a shorter cleaved form exists in the mitochondrial matrix (MCL-1 Matrix ). Interestingly, overexpression of MCL-1 WT or MCL-1 OM , but not MCL-1 Matrix , leads to translocation of Drp1 to mitochondria, which correlates with fission and perinuclear aggregation of mitochondria. We also found that Drp1 co-immunoprecipitates with MCL-1 in heart lysates and that MCL-1-deficient hearts lack mitochondrial Drp1. Additionally, the interaction between Drp1 and MCL-1 and mitochondrial fission increase in response to serum starvation in neonatal myocytes. This suggests that MCL-1 OM recruits Drp1 to mitochondria to induce fission. Since there is a strong link between mitochondrial fission and degradation, we examined the effect of MCL-1 on mitophagy. Parkin is an E3 ubiquitin ligase that plays an important role in mitophagy. MEFs, which lack detectable Parkin, do not efficiently clear their depolarized mitochondria in response to FCCP treatment. However, overexpression of Parkin or MCL-1 increased the efficiency of mitophagy in MEFs in response to FCCP treatment. MCL-1-mediated mitophagy is abrogated in autophagy-deficient Atg5 -/- MEFs, confirming that the clearance occurs via enhanced autophagy. Thus, our data suggest that MCL-1 OM has dual actions in coordinating Drp1-mediated fission and mitophagy, which allows for more efficient removal of damaged mitochondria.

Abstract 151: MCL-1 Promotes Mitochondrial Fusion and Survival in Cardiac Myocytes

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Robert L Thomas ◽  
Jennifer Kuo ◽  
Åsa B Gustafsson
Keyword(s):  
Cardiac Myocytes ◽  
Mitochondrial Fission ◽  
Myeloid Cell ◽  
Mitochondrial Fusion ◽  
Cellular Stress Response ◽  
Border Zone ◽  
Mitochondrial Outer Membrane ◽  
Chaperone Protein ◽  
The Stability ◽  
Specific Deletion

Myeloid cell leukemia-1 (MCL-1) is an anti-apoptotic BCL-2 protein that is highly expressed in myocardium, but little is known about its function in myocytes. Recently, we reported that MCL-1 is essential for myocardial homeostasis and autophagy. Cardiac-specific deletion of MCL-1 in mice led to rapid mitochondrial dysfunction, hypertrophy, and lethal cardiomyopathy. Despite extensive mitochondrial damage, MCL-1 deficient hearts failed to activate mitochondrial autophagy. Parkin, an E3 ubiquitin ligase, normally translocates to damaged mitochondria to promote mitochondrial autophagy, but loss of MCL-1 resulted in cytosolic accumulation of Parkin. However, we found no evidence that MCL-1 functions as a mitochondrial Parkin receptor or substrate. Instead, loss of MCL-1 reduced mitochondrial accumulation of PINK1, which is involved in Parkin recruitment. Additionally, we identified mitochondrial outer membrane (OM) and matrix isoforms of MCL-1 in mouse hearts and found that the two forms respond differently to ischemic injury. Four hours after myocardial infarction, MCL-1 OM levels were reduced by 40% in border zone tissue. After 24 hours, MCL-1 OM levels returned to baseline. Meanwhile, MCL-1 Matrix levels were preserved at four hours, and increased significantly compared to control 24 hours after infarction. These changes correlated with increased expression of HSP70, a chaperone protein that stabilizes MCL-1 and participates in import of mitochondrial proteins. Overexpression of MCL-1 Matrix promoted mitochondrial fusion in fibroblasts under baseline conditions and protected cells against FCCP-mediated mitochondrial fission. While 94.1% (1269 of 1349) of control cells exhibited fragmented mitochondria after two hours of FCCP treatment, mitochondria were only fragmented in 41.3% (391 of 947) of cells overexpressing MCL-1 Matrix . These data suggest MCL-1 isoforms play different roles in the cellular stress response. MCL-1 OM protects against apoptosis, whereas MCL-1 Matrix protects mitochondria by promoting fusion. In addition, upregulation of HSP70 may preserve mitochondrial function and cell viability in damaged cardiac myocytes by increasing the stability and mitochondrial import of MCL-1.

scholarly journals Ganglioside-induced differentiation associated protein 1 is a regulator of the mitochondrial network

2005 ◽  
Vol 170 (7) ◽  
pp. 1067-1078 ◽  
Author(s):  
Axel Niemann ◽  
Marcel Ruegg ◽  
Veronica La Padula ◽  
Angelo Schenone ◽  
Ueli Suter
Keyword(s):  
Mitochondrial Dynamics ◽  
Point Mutations ◽  
Mitochondrial Fusion ◽  
Proper Function ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Activity ◽  
Mitochondrial Morphology ◽  
Mitochondrial Network ◽  
Induced Differentiation ◽  
Mixed Features

Mutations in GDAP1 lead to severe forms of the peripheral motor and sensory neuropathy, Charcot-Marie-Tooth disease (CMT), which is characterized by heterogeneous phenotypes, including pronounced axonal damage and demyelination. We show that neurons and Schwann cells express ganglioside-induced differentiation associated protein 1 (GDAP1), which suggest that both cell types may contribute to the mixed features of the disease. GDAP1 is located in the mitochondrial outer membrane and regulates the mitochondrial network. Overexpression of GDAP1 induces fragmentation of mitochondria without inducing apoptosis, affecting overall mitochondrial activity, or interfering with mitochondrial fusion. The mitochondrial fusion proteins, mitofusin 1 and 2 and Drp1(K38A), can counterbalance the GDAP1-dependent fission. GDAP1-specific knockdown by RNA interference results in a tubular mitochondrial morphology. GDAP1 truncations that are found in patients who have CMT are not targeted to mitochondria and have lost mitochondrial fragmentation activity. The latter activity also is reduced strongly for disease-associated GDAP1 point mutations. Our data indicate that an exquisitely tight control of mitochondrial dynamics, regulated by GDAP1, is crucial for the proper function of myelinated peripheral nerves.

scholarly journals Bcl-xL increases mitochondrial fission, fusion, and biomass in neurons

2009 ◽  
Vol 184 (5) ◽  
pp. 707-719 ◽  
Author(s):  
Sarah B. Berman ◽  
Ying-bei Chen ◽  
Bing Qi ◽  
J. Michael McCaffery ◽  
Edmund B. Rucker ◽  
...  
Keyword(s):  
Cell Death ◽  
Apoptotic Cell ◽  
Mitochondrial Fission ◽  
Cell Types ◽  
Synaptic Activity ◽  
Mitochondrial Morphology ◽  
Cultured Neurons ◽  
Neuronal Dysfunction ◽  
Neuronal Processes ◽  
Organelle Morphology

Mitochondrial fission and fusion are linked to synaptic activity in healthy neurons and are implicated in the regulation of apoptotic cell death in many cell types. We developed fluorescence microscopy and computational strategies to directly measure mitochondrial fission and fusion frequencies and their effects on mitochondrial morphology in cultured neurons. We found that the rate of fission exceeds the rate of fusion in healthy neuronal processes, and, therefore, the fission/fusion ratio alone is insufficient to explain mitochondrial morphology at steady state. This imbalance between fission and fusion is compensated by growth of mitochondrial organelles. Bcl-xL increases the rates of both fusion and fission, but more important for explaining the longer organelle morphology induced by Bcl-xL is its ability to increase mitochondrial biomass. Deficits in these Bcl-xL–dependent mechanisms may be critical in neuronal dysfunction during the earliest phases of neurodegeneration, long before commitment to cell death.

Manganese induces mitochondrial dynamics impairment and apoptotic cell death: A study in human Gli36 cells

2013 ◽  
Vol 554 ◽  
pp. 76-81 ◽  
Author(s):  
Agustina Alaimo ◽  
Roxana M. Gorojod ◽  
Esteban A. Miglietta ◽  
Alejandro Villarreal ◽  
Alberto J. Ramos ◽  
...  
Keyword(s):  
Cell Death ◽  
Apoptotic Cell ◽  
Mitochondrial Dynamics ◽  
Apoptotic Cell Death
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