The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Paola Pizzo - One of the best experts on this subject based on the ideXlab platform.
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Mitofusin 2 from functions to disease
Cell Death and Disease, 2018Co-Authors: Riccardo Filadi, Paola Pizzo, Diana PendinAbstract:Mitochondria are highly dynamic organelles whose functions are essential for cell viability. Within the cell, the mitochondrial network is continuously remodeled through the balance between fusion and fission events. Moreover, it dynamically contacts other organelles, particularly the endoplasmic reticulum, with which it enterprises an important functional relationship able to modulate several cellular pathways. Being mitochondria key bioenergetics organelles, they have to be transported to all the specific high-energy demanding sites within the cell and, when damaged, they have to be efficiently removed. Among other proteins, Mitofusin 2 represents a key player in all these mitochondrial activities (fusion, trafficking, turnover, contacts with other organelles), the balance of which results in the appropriate mitochondrial shape, function, and distribution within the cell. Here we review the structural and functional properties of Mitofusin 2, highlighting its crucial role in several cell pathways, as well as in the pathogenesis of neurodegenerative diseases, metabolic disorders, cardiomyopathies, and cancer.
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highlighting the endoplasmic reticulum mitochondria connection focus on Mitofusin 2
Pharmacological Research, 2018Co-Authors: Riccardo Filadi, Elisa Greotti, Paola PizzoAbstract:Abstract The endoplasmic reticulum (ER) and the mitochondrial network are two highly interconnected cellular structures. By proteinaceous tethers, specialized membrane domains of the ER are tightly associated with the outer membrane of mitochondria, allowing the assembly of signaling platforms where different cell functions take place or are modulated, such as lipid biosynthesis, Ca2+ homeostasis, inflammation, autophagy and apoptosis. The ER-mitochondria coupling is highly dynamic and contacts between the two organelles can be modified in their number, extension and thickness by different stimuli. Importantly, several pathological conditions, such as cancer, neurodegenerative diseases and metabolic syndromes show alterations in this feature, underlining the key role of ER-mitochondria crosstalk in cell physiology. In this contribution, we will focus on one of the major modulator of ER-mitochondria apposition, Mitofusin 2, discussing the structure of the protein and its debated role on organelles tethering. Moreover, we will critically describe different techniques commonly used to investigate this crucial issue, highlighting their advantages, drawbacks and limits.
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on the role of Mitofusin 2 in endoplasmic reticulum mitochondria tethering
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Riccardo Filadi, Elisa Greotti, Gabriele Turacchio, Alberto Luini, Paola Pizzo, Tullio PozzanAbstract:The recent paper by Naon et al. (1) claims that their new data “definitively” prove the role of Mitofusin 2 (Mfn2) as an endoplasmic reticulum (ER)–mitochondria tether, supporting their original proposal (2) and arguing against evidence presented by ourselves and others (3⇓⇓–6) suggesting that Mfn2 is a negative regulator of tethering. A careful reading of the paper highlights that Naon et al.’s (1) claims are not supported by the data presented. Below are some pivotal examples. First, the key parameter (number of ER–mitochondria contacts) that both we and others (3, 4) found doubled in Mfn2 −/− cells is simply not addressed. Second, the ER–mitochondria distance was determined by electron microscopy to be 2 nm larger in Mfn2 −/− cells, compared with wild-type; using the … [↵][1]1To whom correspondence may be addressed. Email: tullio.pozzan{at}unipd.it or paola.pizzo{at}unipd.it. [1]: #xref-corresp-1-1
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presenilin 2 modulates endoplasmic reticulum mitochondria coupling by tuning the antagonistic effect of Mitofusin 2
Cell Reports, 2016Co-Authors: Riccardo Filadi, Elisa Greotti, Gabriele Turacchio, Alberto Luini, Tullio Pozzan, Paola PizzoAbstract:Summary Communication between organelles plays key roles in cell biology. In particular, physical and functional coupling of the endoplasmic reticulum (ER) and mitochondria is crucial for regulation of various physiological and pathophysiological processes. Here, we demonstrate that Presenilin 2 (PS2), mutations in which underlie familial Alzheimer's disease (FAD), promotes ER-mitochondria coupling only in the presence of Mitofusin 2 (Mfn2). PS2 is not necessary for the antagonistic effect of Mfn2 on organelle coupling, although its abundance can tune it. The two proteins physically interact, whereas their homologues Mfn1 and PS1 are dispensable for this interplay. Moreover, PS2 mutants associated with FAD are more effective than the wild-type form in modulating ER-mitochondria tethering because their binding to Mfn2 in mitochondria-associated membranes is favored. We propose a revised model for ER-mitochondria interaction to account for these findings and discuss possible implications for FAD pathogenesis.
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Mitofusin 2 knockdown increases er mitochondria contact and decreases amyloid β peptide production
Journal of Cellular and Molecular Medicine, 2016Co-Authors: Nuno Santos Leal, Riccardo Filadi, Paola Pizzo, Bernadette Schreiner, Catarina Moreira Pinho, Birgitta Wiehager, Helena Karlstrom, Maria AnkarcronaAbstract:Mitochondria are physically and biochemically in contact with other organelles including the endoplasmic reticulum (ER). Such contacts are formed between mitochondria-associated ER membranes (MAM), specialized subregions of ER, and the outer mitochondrial membrane (OMM). We have previously shown increased expression of MAM-associated proteins and enhanced ER to mitochondria Ca(2+) transfer from ER to mitochondria in Alzheimer's disease (AD) and amyloid β-peptide (Aβ)-related neuronal models. Here, we report that siRNA knockdown of Mitofusin-2 (Mfn2), a protein that is involved in the tethering of ER and mitochondria, leads to increased contact between the two organelles. Cells depleted in Mfn2 showed increased Ca(2+) transfer from ER to mitchondria and longer stretches of ER forming contacts with OMM. Interestingly, increased contact resulted in decreased concentrations of intra- and extracellular Aβ40 and Aβ42 . Analysis of γ-secretase protein expression, maturation and activity revealed that the low Aβ concentrations were a result of impaired γ-secretase complex function. Amyloid-β precursor protein (APP), β-site APP-cleaving enzyme 1 and neprilysin expression as well as neprilysin activity were not affected by Mfn2 siRNA treatment. In summary, our data shows that modulation of ER-mitochondria contact affects γ-secretase activity and Aβ generation. Increased ER-mitochondria contact results in lower γ-secretase activity suggesting a new mechanism by which Aβ generation can be controlled.
Ruiping Xiao - One of the best experts on this subject based on the ideXlab platform.
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central role of Mitofusin 2 in autophagosome lysosome fusion in cardiomyocytes
Journal of Biological Chemistry, 2012Co-Authors: Ting Zhao, Heping Cheng, Xiaohu Huang, Liang Han, Xianhua Wang, Hongqiang Cheng, Yungang Zhao, Quan Chen, Ju Chen, Ruiping XiaoAbstract:Abstract In the heart, autophagy has been implicated in cardioprotection and ischemia-reperfusion tolerance, and the dysregulation of autophagy is associated with the development of heart failure. Mitochondrial dynamic proteins are profoundly involved in autophagic processes, especially the initiation and formation of autophagosomes, but it is not clear whether they play any role in cardiac autophagy. We previously reported that Mitofusin 2 (MFN2), a mitochondrial outer membrane protein, serves as a major determinant of cardiomyocyte apoptosis mediated by oxidative stress. Here, we reveal a novel and essential role of MFN2 in mediating cardiac autophagy. We found that specific deletion of MFN2 in cardiomyocytes caused extensive accumulation of autophagosomes. In particular, the fusion of autophagosomes with lysosomes, a critical step in autophagic degradation, was markedly retarded without altering the formation of autophagosomes and lysosomes in response to ischemia-reperfusion stress. Importantly, MFN2 co-immunoprecipitated with RAB7 in the heart, and starvation further increased it. Knockdown of MFN2 by shRNA prevented, whereas re-expression of MFN2 restored, the autophagosome-lysosome fusion in neonatal cardiomyocytes. Hearts from cardiac-specific MFN2 knock-out mice had abnormal mitochondrial and cellular metabolism and were vulnerable to ischemia-reperfusion challenge. Our study defined a novel and essential role of MFN2 in the cardiac autophagic process by mediating the maturation of autophagy at the phase of autophagosome-lysosome fusion; deficiency of MFN2 caused multiple molecular and functional defects that undermined cardiac reserve and gradually led to cardiac vulnerability and dysfunction.
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Mitofusin 2 triggers vascular smooth muscle cell apoptosis via mitochondrial death pathway
Circulation Research, 2007Co-Authors: Xiaomei Guo, Kuang-hueih Chen, Jian Tang, Yanhong Guo, Hua Liao, Ruiping XiaoAbstract:Previous studies have shown that Mitofusin 2 (Mfn-2) (or hyperplasia suppressor gene [HSG]) inhibits vascular smooth muscle cell (VSMC) proliferation. Here, we demonstrate that Mfn-2 is a primary determinant of VSMC apoptosis. First, oxidative stress with H2O2, inhibition of protein kinase C with staurosporine, activation of protein kinase A with forskolin, and serum deprivation concurrently elevate Mfn-2 expression and induce VSMC apoptosis. Second, overexpression of Mfn-2 also triggers apoptosis of VSMCs in culture and in balloon-injured rat carotid arteries, thus contributing to Mfn-2-mediated prevention of neointima formation after angioplasty. Third, Mfn-2 silencing protects VSMCs against H2O2 or Mfn-2 overexpression-induced apoptosis, indicating that upregulation of Mfn-2 is necessary and sufficient for oxidative stress-mediated VSMC apoptosis. The Mfn-2 proapoptotic effect is independent of its role in mitochondrial fusion but mainly mediated by inhibition of Akt signaling and the resultant activation of the mitochondrial apoptotic pathway, as manifested by decreased Akt phosphorylation, increased mitochondrial Bax/Bcl-2 ratio, cytochrome c release, and activation of caspases-9 and caspase-3. Furthermore, Mfn-2-induced apoptosis was blocked by overexpression of an active phosphoinositide 3-kinase mutant or Bcl-xL or inhibition of caspase-9 but not caspases-8. Thus, in addition to its antiproliferative effects, Mfn-2 constitutes a primary determinant of VSMC apoptosis.
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Mitofusin 2 is a major determinant of oxidative stress mediated heart muscle cell apoptosis
Journal of Biological Chemistry, 2007Co-Authors: Tao Shen, Kuang-hueih Chen, Ming Zheng, Chunlei Chen, Jian Tang, Wanrui Zhang, Heping Cheng, Ruiping XiaoAbstract:Abstract An inexorable loss of terminally differentiated heart muscle cells is a crucial causal factor for heart failure. Here, we have provided several lines of evidence to demonstrate that Mitofusin-2 (Mfn-2; also called hyperplasia suppressor gene), a member of the Mitofusin family, is a major determinant of oxidative stress-mediated cardiomyocyte apoptosis. First, oxidative stress with H2O2 led to concurrent increases in Mfn-2 expression and apoptosis in cultured neonatal rat cardiomyocytes. Second, overexpression of Mfn-2 to a level similar to that induced by H2O2 was sufficient to trigger myocyte apoptosis, which is associated with profound inhibition of Akt activation without altering ERK1/2 signaling. Third, Mfn-2 silencing inhibited oxidative stress-induced apoptosis in H9C2 cells, a cardiac muscle cell line. Furthermore, Mfn-2-induced myocyte apoptosis was abrogated by inhibition of caspase-9 (but not caspase-8) and by overexpression of Bcl-xL or enhanced activation of phosphatidylinositol 3-kinase-Akt, suggesting that inhibition of Akt signaling and activation of the mitochondrial death pathway are essentially involved in Mfn-2-induced heart muscle cell apoptosis. These results indicate that increased cardiac Mfn-2 expression is both necessary and sufficient for oxidative stress-induced heart muscle cell apoptosis, suggesting that Mfn-2 deregulation may be a crucial pathogenic element and a potential therapeutic target for heart failure.
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Mitofusin 2 is a major determinant of oxidative stress mediated heart muscle cell apoptosis
Journal of Biological Chemistry, 2007Co-Authors: Tao Shen, Kuang-hueih Chen, Ming Zheng, Chunlei Chen, Jian Tang, Wanrui Zhang, Heping Cheng, Ruiping Xiao, Chunmei CaoAbstract:An inexorable loss of terminally differentiated heart muscle cells is a crucial causal factor for heart failure. Here, we have provided several lines of evidence to demonstrate that Mitofusin-2 (Mfn-2; also called hyperplasia suppressor gene), a member of the Mitofusin family, is a major determinant of oxidative stress-mediated cardiomyocyte apoptosis. First, oxidative stress with H2O2 led to concurrent increases in Mfn-2 expression and apoptosis in cultured neonatal rat cardiomyocytes. Second, overexpression of Mfn-2 to a level similar to that induced by H2O2 was sufficient to trigger myocyte apoptosis, which is associated with profound inhibition of Akt activation without altering ERK1/2 signaling. Third, Mfn-2 silencing inhibited oxidative stress-induced apoptosis in H9C2 cells, a cardiac muscle cell line. Furthermore, Mfn-2-induced myocyte apoptosis was abrogated by inhibition of caspase-9 (but not caspase-8) and by overexpression of Bcl-xL or enhanced activation of phosphatidylinositol 3-kinase-Akt, suggesting that inhibition of Akt signaling and activation of the mitochondrial death pathway are essentially involved in Mfn-2-induced heart muscle cell apoptosis. These results indicate that increased cardiac Mfn-2 expression is both necessary and sufficient for oxidative stress-induced heart muscle cell apoptosis, suggesting that Mfn-2 deregulation may be a crucial pathogenic element and a potential therapeutic target for heart failure.
Xiaomei Guo - One of the best experts on this subject based on the ideXlab platform.
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Mitofusin 2 mediated tethering of mitochondria and endoplasmic reticulum promotes cell cycle arrest of vascular smooth muscle cells in g0 g1 phase
Acta Biochimica et Biophysica Sinica, 2015Co-Authors: Yang Guan, Xiaomei GuoAbstract:Mitofusin-2 (Mfn-2) is a hyperplasia suppressor. Changes in Mfn-2 expression are thought to reflect mitochondrial remodeling during cell proliferation. However, it is unclear how the participation of Mfn-2 in mitochondrial remodeling prevents cellular proliferation. Here we show that arresting vascular smooth muscle cells (VSMCs) in the G0/G1 phase by serum starvation up-regulates Mfn-2 expression and causes mitochondria to assemble into a tubular network and to attach to the endoplasmic reticulum (ER). In the S phase, short rod-shaped mitochondrial structures that were dissociated from the ER were observed. Levels of glucose, ATP, l-amino acid, and NADP(+) did not vary throughout the cell cycle. However, NAD(+) level was lower and NADH level was higher in the G0/G1 phase than in the S phase. Mitochondrial membrane potential was lower in the S phase than in the G0/G1 phase. Infecting VSMCs with an adenovirus encoding full-length Mfn-2 increased NADH level and reduced NAD(+) level, while infecting the cells with an adenovirus that silences the p21(ras) signature motif produced opposite effects. These results suggest that Mfn-2 up-regulation causes mitochondrial fusion into tubular networks and attachment to the ER, which in turn halts proliferation of VSMCs.
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mutation of the protein kinase a phosphorylation site influences the anti proliferative activity of Mitofusin 2
Atherosclerosis, 2010Co-Authors: Wei Zhou, Kuang-hueih Chen, Hua Liao, Wenjing Cao, Jingwei Zeng, Li Zhao, Xiaomei GuoAbstract:Abstract Objective Mitofusin 2 (Mfn2) is an important suppressor of vascular smooth muscle cell (VSMC) proliferation. It contains a protein kinase A (PKA) phosphorylation site at serine 442 (S442) and can be phosphorylated by PKA. This study examined the role of phosphorylating specific sites on the regulation of Mfn2 protein activity in vitro and in vivo . Methods and results We introduced two mutations at S442 in rat Mfn2, and investigated their effects using cultured rat VSMCs and the balloon injury model. Our results indicated that, in VSMCs, Mfn2 expression and mitochondrial morphology are affected by adenoviral-mediated overexpression of the two Mfn2 mutant proteins in the same way as the wild-type Mfn2 protein. Specifically, overexpression of the protein harboring the phospho-deficient mutation Mfn2-S442A (serine replaced by alanine at residue 442) increased the inhibitory effects of Mfn2 on proliferation of VSMCs in culture, and neointimal hyperplasia and restenosis in the rat carotid artery balloon injury model at days 14 after injury. On the other hand, the phospho-mimetic mutation Mfn2-S442D (serine replaced by aspartic acid at residue 442) led to loss of growth suppressor activity. Conclusions These results suggest that this specific PKA phosphorylation site plays a key role in Mfn2-mediated suppression of VSMC growth, which is independent of its effects on modulation of mitochondrial morphology.
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Mitofusin 2 triggers vascular smooth muscle cell apoptosis via mitochondrial death pathway
Circulation Research, 2007Co-Authors: Xiaomei Guo, Kuang-hueih Chen, Jian Tang, Yanhong Guo, Hua Liao, Ruiping XiaoAbstract:Previous studies have shown that Mitofusin 2 (Mfn-2) (or hyperplasia suppressor gene [HSG]) inhibits vascular smooth muscle cell (VSMC) proliferation. Here, we demonstrate that Mfn-2 is a primary determinant of VSMC apoptosis. First, oxidative stress with H2O2, inhibition of protein kinase C with staurosporine, activation of protein kinase A with forskolin, and serum deprivation concurrently elevate Mfn-2 expression and induce VSMC apoptosis. Second, overexpression of Mfn-2 also triggers apoptosis of VSMCs in culture and in balloon-injured rat carotid arteries, thus contributing to Mfn-2-mediated prevention of neointima formation after angioplasty. Third, Mfn-2 silencing protects VSMCs against H2O2 or Mfn-2 overexpression-induced apoptosis, indicating that upregulation of Mfn-2 is necessary and sufficient for oxidative stress-mediated VSMC apoptosis. The Mfn-2 proapoptotic effect is independent of its role in mitochondrial fusion but mainly mediated by inhibition of Akt signaling and the resultant activation of the mitochondrial apoptotic pathway, as manifested by decreased Akt phosphorylation, increased mitochondrial Bax/Bcl-2 ratio, cytochrome c release, and activation of caspases-9 and caspase-3. Furthermore, Mfn-2-induced apoptosis was blocked by overexpression of an active phosphoinositide 3-kinase mutant or Bcl-xL or inhibition of caspase-9 but not caspases-8. Thus, in addition to its antiproliferative effects, Mfn-2 constitutes a primary determinant of VSMC apoptosis.
Jian Tang - One of the best experts on this subject based on the ideXlab platform.
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Mitofusin 2 triggers vascular smooth muscle cell apoptosis via mitochondrial death pathway
Circulation Research, 2007Co-Authors: Xiaomei Guo, Kuang-hueih Chen, Jian Tang, Yanhong Guo, Hua Liao, Ruiping XiaoAbstract:Previous studies have shown that Mitofusin 2 (Mfn-2) (or hyperplasia suppressor gene [HSG]) inhibits vascular smooth muscle cell (VSMC) proliferation. Here, we demonstrate that Mfn-2 is a primary determinant of VSMC apoptosis. First, oxidative stress with H2O2, inhibition of protein kinase C with staurosporine, activation of protein kinase A with forskolin, and serum deprivation concurrently elevate Mfn-2 expression and induce VSMC apoptosis. Second, overexpression of Mfn-2 also triggers apoptosis of VSMCs in culture and in balloon-injured rat carotid arteries, thus contributing to Mfn-2-mediated prevention of neointima formation after angioplasty. Third, Mfn-2 silencing protects VSMCs against H2O2 or Mfn-2 overexpression-induced apoptosis, indicating that upregulation of Mfn-2 is necessary and sufficient for oxidative stress-mediated VSMC apoptosis. The Mfn-2 proapoptotic effect is independent of its role in mitochondrial fusion but mainly mediated by inhibition of Akt signaling and the resultant activation of the mitochondrial apoptotic pathway, as manifested by decreased Akt phosphorylation, increased mitochondrial Bax/Bcl-2 ratio, cytochrome c release, and activation of caspases-9 and caspase-3. Furthermore, Mfn-2-induced apoptosis was blocked by overexpression of an active phosphoinositide 3-kinase mutant or Bcl-xL or inhibition of caspase-9 but not caspases-8. Thus, in addition to its antiproliferative effects, Mfn-2 constitutes a primary determinant of VSMC apoptosis.
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overexpression of Mitofusin 2 inhibited oxidized low density lipoprotein induced vascular smooth muscle cell proliferation and reduced atherosclerotic lesion formation in rabbit
Biochemical and Biophysical Research Communications, 2007Co-Authors: Yanhong Guo, Kuang-hueih Chen, Wei Gao, Li Chen, Guisong Wang, Jian TangAbstract:Abstract Our previous studies have implies that Mitofusin 2 (Mfn2), which was progressively reduced in arteries from ApoE−/− mice during the development of atherosclerosis, may take part in pathogenesis of atherosclerosis. In this study, we found that overexpression of Mfn2 inhibited oxidized low-density lipoprotein or serum induced vascular smooth muscle cell proliferation by down-regulation of Akt and ERK phosphorylation. Then we investigated the in vivo role of Mfn2 on the development of atherosclerosis in rabbits using adenovirus expressing Mitofusin 2 gene (AdMfn2). By morphometric analysis we found overexpression of Mfn2 inhibited atherosclerotic lesion formation and intima/media ratio by 66.7% and 74.6%, respectively, compared with control group. These results suggest that local Mfn2 treatment suppresses the development of atherosclerosis in vivo in part by attenuating the smooth muscle cell proliferation induced by lipid deposition and vascular injury.
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Mitofusin 2 is a major determinant of oxidative stress mediated heart muscle cell apoptosis
Journal of Biological Chemistry, 2007Co-Authors: Tao Shen, Kuang-hueih Chen, Ming Zheng, Chunlei Chen, Jian Tang, Wanrui Zhang, Heping Cheng, Ruiping XiaoAbstract:Abstract An inexorable loss of terminally differentiated heart muscle cells is a crucial causal factor for heart failure. Here, we have provided several lines of evidence to demonstrate that Mitofusin-2 (Mfn-2; also called hyperplasia suppressor gene), a member of the Mitofusin family, is a major determinant of oxidative stress-mediated cardiomyocyte apoptosis. First, oxidative stress with H2O2 led to concurrent increases in Mfn-2 expression and apoptosis in cultured neonatal rat cardiomyocytes. Second, overexpression of Mfn-2 to a level similar to that induced by H2O2 was sufficient to trigger myocyte apoptosis, which is associated with profound inhibition of Akt activation without altering ERK1/2 signaling. Third, Mfn-2 silencing inhibited oxidative stress-induced apoptosis in H9C2 cells, a cardiac muscle cell line. Furthermore, Mfn-2-induced myocyte apoptosis was abrogated by inhibition of caspase-9 (but not caspase-8) and by overexpression of Bcl-xL or enhanced activation of phosphatidylinositol 3-kinase-Akt, suggesting that inhibition of Akt signaling and activation of the mitochondrial death pathway are essentially involved in Mfn-2-induced heart muscle cell apoptosis. These results indicate that increased cardiac Mfn-2 expression is both necessary and sufficient for oxidative stress-induced heart muscle cell apoptosis, suggesting that Mfn-2 deregulation may be a crucial pathogenic element and a potential therapeutic target for heart failure.
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Mitofusin 2 is a major determinant of oxidative stress mediated heart muscle cell apoptosis
Journal of Biological Chemistry, 2007Co-Authors: Tao Shen, Kuang-hueih Chen, Ming Zheng, Chunlei Chen, Jian Tang, Wanrui Zhang, Heping Cheng, Ruiping Xiao, Chunmei CaoAbstract:An inexorable loss of terminally differentiated heart muscle cells is a crucial causal factor for heart failure. Here, we have provided several lines of evidence to demonstrate that Mitofusin-2 (Mfn-2; also called hyperplasia suppressor gene), a member of the Mitofusin family, is a major determinant of oxidative stress-mediated cardiomyocyte apoptosis. First, oxidative stress with H2O2 led to concurrent increases in Mfn-2 expression and apoptosis in cultured neonatal rat cardiomyocytes. Second, overexpression of Mfn-2 to a level similar to that induced by H2O2 was sufficient to trigger myocyte apoptosis, which is associated with profound inhibition of Akt activation without altering ERK1/2 signaling. Third, Mfn-2 silencing inhibited oxidative stress-induced apoptosis in H9C2 cells, a cardiac muscle cell line. Furthermore, Mfn-2-induced myocyte apoptosis was abrogated by inhibition of caspase-9 (but not caspase-8) and by overexpression of Bcl-xL or enhanced activation of phosphatidylinositol 3-kinase-Akt, suggesting that inhibition of Akt signaling and activation of the mitochondrial death pathway are essentially involved in Mfn-2-induced heart muscle cell apoptosis. These results indicate that increased cardiac Mfn-2 expression is both necessary and sufficient for oxidative stress-induced heart muscle cell apoptosis, suggesting that Mfn-2 deregulation may be a crucial pathogenic element and a potential therapeutic target for heart failure.
Riccardo Filadi - One of the best experts on this subject based on the ideXlab platform.
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Mitofusin 2 from functions to disease
Cell Death and Disease, 2018Co-Authors: Riccardo Filadi, Paola Pizzo, Diana PendinAbstract:Mitochondria are highly dynamic organelles whose functions are essential for cell viability. Within the cell, the mitochondrial network is continuously remodeled through the balance between fusion and fission events. Moreover, it dynamically contacts other organelles, particularly the endoplasmic reticulum, with which it enterprises an important functional relationship able to modulate several cellular pathways. Being mitochondria key bioenergetics organelles, they have to be transported to all the specific high-energy demanding sites within the cell and, when damaged, they have to be efficiently removed. Among other proteins, Mitofusin 2 represents a key player in all these mitochondrial activities (fusion, trafficking, turnover, contacts with other organelles), the balance of which results in the appropriate mitochondrial shape, function, and distribution within the cell. Here we review the structural and functional properties of Mitofusin 2, highlighting its crucial role in several cell pathways, as well as in the pathogenesis of neurodegenerative diseases, metabolic disorders, cardiomyopathies, and cancer.
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highlighting the endoplasmic reticulum mitochondria connection focus on Mitofusin 2
Pharmacological Research, 2018Co-Authors: Riccardo Filadi, Elisa Greotti, Paola PizzoAbstract:Abstract The endoplasmic reticulum (ER) and the mitochondrial network are two highly interconnected cellular structures. By proteinaceous tethers, specialized membrane domains of the ER are tightly associated with the outer membrane of mitochondria, allowing the assembly of signaling platforms where different cell functions take place or are modulated, such as lipid biosynthesis, Ca2+ homeostasis, inflammation, autophagy and apoptosis. The ER-mitochondria coupling is highly dynamic and contacts between the two organelles can be modified in their number, extension and thickness by different stimuli. Importantly, several pathological conditions, such as cancer, neurodegenerative diseases and metabolic syndromes show alterations in this feature, underlining the key role of ER-mitochondria crosstalk in cell physiology. In this contribution, we will focus on one of the major modulator of ER-mitochondria apposition, Mitofusin 2, discussing the structure of the protein and its debated role on organelles tethering. Moreover, we will critically describe different techniques commonly used to investigate this crucial issue, highlighting their advantages, drawbacks and limits.
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on the role of Mitofusin 2 in endoplasmic reticulum mitochondria tethering
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Riccardo Filadi, Elisa Greotti, Gabriele Turacchio, Alberto Luini, Paola Pizzo, Tullio PozzanAbstract:The recent paper by Naon et al. (1) claims that their new data “definitively” prove the role of Mitofusin 2 (Mfn2) as an endoplasmic reticulum (ER)–mitochondria tether, supporting their original proposal (2) and arguing against evidence presented by ourselves and others (3⇓⇓–6) suggesting that Mfn2 is a negative regulator of tethering. A careful reading of the paper highlights that Naon et al.’s (1) claims are not supported by the data presented. Below are some pivotal examples. First, the key parameter (number of ER–mitochondria contacts) that both we and others (3, 4) found doubled in Mfn2 −/− cells is simply not addressed. Second, the ER–mitochondria distance was determined by electron microscopy to be 2 nm larger in Mfn2 −/− cells, compared with wild-type; using the … [↵][1]1To whom correspondence may be addressed. Email: tullio.pozzan{at}unipd.it or paola.pizzo{at}unipd.it. [1]: #xref-corresp-1-1
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presenilin 2 modulates endoplasmic reticulum mitochondria coupling by tuning the antagonistic effect of Mitofusin 2
Cell Reports, 2016Co-Authors: Riccardo Filadi, Elisa Greotti, Gabriele Turacchio, Alberto Luini, Tullio Pozzan, Paola PizzoAbstract:Summary Communication between organelles plays key roles in cell biology. In particular, physical and functional coupling of the endoplasmic reticulum (ER) and mitochondria is crucial for regulation of various physiological and pathophysiological processes. Here, we demonstrate that Presenilin 2 (PS2), mutations in which underlie familial Alzheimer's disease (FAD), promotes ER-mitochondria coupling only in the presence of Mitofusin 2 (Mfn2). PS2 is not necessary for the antagonistic effect of Mfn2 on organelle coupling, although its abundance can tune it. The two proteins physically interact, whereas their homologues Mfn1 and PS1 are dispensable for this interplay. Moreover, PS2 mutants associated with FAD are more effective than the wild-type form in modulating ER-mitochondria tethering because their binding to Mfn2 in mitochondria-associated membranes is favored. We propose a revised model for ER-mitochondria interaction to account for these findings and discuss possible implications for FAD pathogenesis.
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Mitofusin 2 knockdown increases er mitochondria contact and decreases amyloid β peptide production
Journal of Cellular and Molecular Medicine, 2016Co-Authors: Nuno Santos Leal, Riccardo Filadi, Paola Pizzo, Bernadette Schreiner, Catarina Moreira Pinho, Birgitta Wiehager, Helena Karlstrom, Maria AnkarcronaAbstract:Mitochondria are physically and biochemically in contact with other organelles including the endoplasmic reticulum (ER). Such contacts are formed between mitochondria-associated ER membranes (MAM), specialized subregions of ER, and the outer mitochondrial membrane (OMM). We have previously shown increased expression of MAM-associated proteins and enhanced ER to mitochondria Ca(2+) transfer from ER to mitochondria in Alzheimer's disease (AD) and amyloid β-peptide (Aβ)-related neuronal models. Here, we report that siRNA knockdown of Mitofusin-2 (Mfn2), a protein that is involved in the tethering of ER and mitochondria, leads to increased contact between the two organelles. Cells depleted in Mfn2 showed increased Ca(2+) transfer from ER to mitchondria and longer stretches of ER forming contacts with OMM. Interestingly, increased contact resulted in decreased concentrations of intra- and extracellular Aβ40 and Aβ42 . Analysis of γ-secretase protein expression, maturation and activity revealed that the low Aβ concentrations were a result of impaired γ-secretase complex function. Amyloid-β precursor protein (APP), β-site APP-cleaving enzyme 1 and neprilysin expression as well as neprilysin activity were not affected by Mfn2 siRNA treatment. In summary, our data shows that modulation of ER-mitochondria contact affects γ-secretase activity and Aβ generation. Increased ER-mitochondria contact results in lower γ-secretase activity suggesting a new mechanism by which Aβ generation can be controlled.