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Yoshimi Hiraumi

Other affiliations: Cedars-Sinai Medical Center
Bio: Yoshimi Hiraumi is an academic researcher from Kyoto University. The author has contributed to research in topics: Autophagy & Apoptosis. The author has an hindex of 10, co-authored 11 publications receiving 524 citations. Previous affiliations of Yoshimi Hiraumi include Cedars-Sinai Medical Center.

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Journal ArticleDOI
TL;DR: Respirometry reveals that the constituents of these newly established mitochondrial networks are better primed for OXPHOS and are more tightly coupled than those in myoblasts, which highlights the integral role of autophagy and mitophagy in myogenic differentiation.
Abstract: Myogenesis is a crucial process governing skeletal muscle development and homeostasis. Differentiation of primitive myoblasts into mature myotubes requires a metabolic switch to support the increased energetic demand of contractile muscle. Skeletal myoblasts specifically shift from a highly glycolytic state to relying predominantly on oxidative phosphorylation (OXPHOS) upon differentiation. We have found that this phenomenon requires dramatic remodeling of the mitochondrial network involving both mitochondrial clearance and biogenesis. During early myogenic differentiation, autophagy is robustly upregulated and this coincides with DNM1L/DRP1 (dynamin 1-like)-mediated fragmentation and subsequent removal of mitochondria via SQSTM1 (sequestosome 1)-mediated mitophagy. Mitochondria are then repopulated via PPARGC1A/PGC-1α (peroxisome proliferator-activated receptor gamma, coactivator 1 alpha)-mediated biogenesis. Mitochondrial fusion protein OPA1 (optic atrophy 1 [autosomal dominant]) is then briskly upregulated, resulting in the reformation of mitochondrial networks. The final product is a myotube replete with new mitochondria. Respirometry reveals that the constituents of these newly established mitochondrial networks are better primed for OXPHOS and are more tightly coupled than those in myoblasts. Additionally, we have found that suppressing autophagy with various inhibitors during differentiation interferes with myogenic differentiation. Together these data highlight the integral role of autophagy and mitophagy in myogenic differentiation.

257 citations

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TL;DR: It is shown that the histone deacetylase (HDAC) inhibitor FK228 (depsipeptide) has an antitumor effect on MRT cells both in vitro and in vivo.
Abstract: Malignant rhabdoid tumors (MRT) exhibit a very poor prognosis because of their resistance to chemotherapeutic agents and new therapies are needed for the treatment of this cancer Here, we show that the histone deacetylase (HDAC) inhibitor FK228 (depsipeptide) has an antitumor effect on MRT cells both in vitro and in vivo FK228 is a unique cyclic peptide and is among the most potent inhibitors of both Class I and Class II HDACs FK228 inhibited proliferation and induced apoptosis in all MRT cell lines tested Preincubation with the pancaspase inhibitor zVAD-fmk did not completely rescue FK228-induced cell death, although it did inhibit apoptosis Transmission electron microscopy (TEM) showed that FK228 could stimulate MRT cells to undergo apoptosis, necrosis or autophagy FK228 converted unconjugated microtubule-associated protein light chain 3 (LC3-I) to conjugated light chain 3 (LC3-II) and induced localization of LC3 to autophagosomes Apoptosis inducing factor (AIF), which plays a role in caspase-independent cell death, translocated to the nucleus in response to FK228 treatment Moreover, small interfering RNA (siRNA) targeting of AIF prevented the morphological changes associated with autophagy and redistribution of LC3 to autophagosomes Disrupting autophagy with chloroquine treatment enhanced FK228-induced cell death In vivo, FK228 caused a reduction in tumor size and induced autophagy in tumor tissues Using immunoelectron microscopy, we confirmed AIF translocation into the nucleus of FK228-induced autophagic cells in vivo Thus, FK228 is a novel candidate for an antitumor agent for MRT cells

79 citations

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TL;DR: It is demonstrated that INNO-406, a second-generation Bcr-Abl TK inhibitor, induces programmed cell death (PCD) in chronic myelogenous leukemia (CML) cell lines through both caspase-mediated and casp enzyme-independent pathways.
Abstract: Bcr-Abl tyrosine kinase (TK) inhibitors are promising therapeutic agents for Bcr-Abl-positive (Bcr-Abl(+)) leukemias. Although they are known to promote caspase-mediated apoptosis, it remains unclear whether caspase-independent cell death-inducing mechanisms are also triggered. Here we demonstrated that INNO-406, a second-generation Bcr-Abl TK inhibitor, induces programmed cell death (PCD) in chronic myelogenous leukemia (CML) cell lines through both caspase-mediated and caspase-independent pathways. The latter pathways include caspase-independent apoptosis (CIA) and necrosis-like cell death (CIND), and the cell lines varied regarding which mechanism was elicited upon INNO-406 treatment. We also observed that the propensity toward CIA or CIND in cells was strongly associated with cellular dependency on apoptosome-mediated caspase activity. Cells that undergo CIND have a high apoptosome activity potential whereas cells that undergo CIA tend to have a lower potential. Moreover, we found that INNO-406 promotes autophagy. When autophagy was inhibited with chloroquine or gene knockdown of beclin1 by shRNA, INNO-406-induced cell death was enhanced, which indicates that the autophagic response of the tumor cells is protective. These findings suggest new insights into the biology and therapy of Bcr-Abl(+) leukemias.

64 citations

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TL;DR: In this paper, the authors compared mGS, embryonic stem (ES), and embryonic germ (EG) cells with regard to their ability to differentiate into mesodermal cells, namely, cardiomyocytes and endothelial cells.
Abstract: Multipotent germline stem (mGS) cells have been established from neonatal mouse testes. Here, we compared mGS, embryonic stem (ES), and embryonic germ (EG) cells with regard to their ability to differentiate into mesodermal cells, namely, cardiomyocytes and endothelial cells. The in situ morphological appearances of undifferentiated mGS, ES, and EG cells were similar, and 4 days after being induced to differentiate, approximately 30%-40% of each cell type differentiated into Flk1(+) cells. The sorted Flk1(+) cells differentiated efficiently into cardiomyocytes and endothelial cells. By day 10 after differentiation induction, the three cell types generated equal number of endothelial colonies. However, by day 13 after differentiation induction, the Flk1(+) mGS cells generated more contractile colonies than did the Flk1(+) ES cells, whereas the Flk1(+) EG cells generated equivalent numbers as the Flk1(+) mGS cells. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis of differentiation markers such as Rex1, FGF-5, GATA-4, Brachyury, and Flk1 revealed that mGS cells expressed these markers more slowly during days 0-4 after differentiation induction than did ES cells, but that this mGS cell pattern was similar to that of the EG cells. RT-PCR analysis also revealed that the three differentiation cell types expressed various cardiac markers. Moreover, immunohistochemical analysis revealed that the contractile colonies derived from Flk1(+) mGS cells express mature cardiac cell-specific markers. In conclusion, mGS cells are phenotypically similar to ES and EG cells and have a similar potential to differentiate into cardiomyocytes and endothelial cells. Disclosure of potential conflicts of interest is found at the end of this article.

47 citations

Journal ArticleDOI
TL;DR: EK-8 treatment can prevent and cure murine DCM, so SOD/catalase mimetic treatment is proposed as a potential therapy for DCM.
Abstract: Background: Mice lacking manganese-superoxide dismutase (Mn-SOD) activity exhibit the typical pathology of dilated cardiomyopathy (DCM). In the present study, presymptomatic and symptomatic mutant mice were treated with the SOD/catalase mimetic, EUK-8. Methods and Results: Presymptomatic heart/muscle-specific Mn-SOD-deficient mice (H/M-Sod2-/-) were treated with EUK-8 (30 mg · kg-1 · day-1) for 4 weeks, and then cardiac function and the reactive oxygen species (ROS) production in their heart mitochondria were assessed. EUK-8 treatment suppressed the progression of cardiac dysfunction and diminished ROS production and oxidative damage. Furthermore, EUK-8 treatment effectively reversed the cardiac dilatation and dysfunction observed in symptomatic H/M-Sod2-/- mice. Interestingly, EUK-8 treatment repaired a molecular defect in connexin43. Conclusions: EUK-8 treatment can prevent and cure murine DCM, so SOD/catalase mimetic treatment is proposed as a potential therapy for DCM. (Circ J 2009; 73: 2125-2134)

40 citations


Cited by
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Journal ArticleDOI
TL;DR: The current knowledge on the key genes composing the autophagy machinery in eukaryotes from yeast to mammalian cells and the signaling pathways that sense the status of different types of stress and induce autophagic for cell survival and homeostasis are presented.
Abstract: Autophagy is a process of self-degradation of cellular components in which double-membrane autophagosomes sequester organelles or portions of cytosol and fuse with lysosomes or vacuoles for breakdown by resident hydrolases. Autophagy is upregulated in response to extra- or intracellular stress and signals such as starvation, growth factor deprivation, ER stress, and pathogen infection. Defective autophagy plays a significant role in human pathologies, including cancer, neurodegeneration, and infectious diseases. We present our current knowledge on the key genes composing the autophagy machinery in eukaryotes from yeast to mammalian cells and the signaling pathways that sense the status of different types of stress and induce autophagy for cell survival and homeostasis. We also review the recent advances on the molecular mechanisms that regulate the autophagy machinery at various levels, from transcriptional activation to post-translational protein modification.

3,249 citations

Journal ArticleDOI
TL;DR: The current understanding of the core components of the autophagy machinery and the functional relevance of autophile within the tumor microenvironment is described and how this knowledge has informed preclinical investigations combining the autophile inhibitor hydroxychloroquine (HCQ) with chemotherapy, targeted therapy, and immunotherapy is outlined.
Abstract: Autophagy is an evolutionarily conserved, intracellular self-defense mechanism in which organelles and proteins are sequestered into autophagic vesicles that are subsequently degraded through fusion with lysosomes. Cells, thereby, prevent the toxic accumulation of damaged or unnecessary components, but also recycle these components to sustain metabolic homoeostasis. Heightened autophagy is a mechanism of resistance for cancer cells faced with metabolic and therapeutic stress, revealing opportunities for exploitation as a therapeutic target in cancer. We summarize recent developments in the field of autophagy and cancer and build upon the results presented at the Cancer Therapy Evaluation Program (CTEP) Early Drug Development meeting in March 2010. Herein, we describe our current understanding of the core components of the autophagy machinery and the functional relevance of autophagy within the tumor microenvironment, and we outline how this knowledge has informed preclinical investigations combining the autophagy inhibitor hydroxychloroquine (HCQ) with chemotherapy, targeted therapy, and immunotherapy. Finally, we describe ongoing clinical trials involving HCQ as a first generation autophagy inhibitor, as well as strategies for the development of novel, more potent, and specific inhibitors of autophagy.

814 citations

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TL;DR: The development of new compounds and the re-evaluation of compounds originally designed for other targets as transport inhibitors of ATP-dependent drug efflux pumps are summarized.

573 citations

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TL;DR: An overview of the cardiac metabolic network is provided and alterations observed in cardiac pathologies as well as strategies used as metabolic therapies in heart failure are highlighted.
Abstract: The network for cardiac fuel metabolism contains intricate sets of interacting pathways that result in both ATP-producing and non-ATP-producing end points for each class of energy substrates. The most salient feature of the network is the metabolic flexibility demonstrated in response to various stimuli, including developmental changes and nutritional status. The heart is also capable of remodeling the metabolic pathways in chronic pathophysiological conditions, which results in modulations of myocardial energetics and contractile function. In a quest to understand the complexity of the cardiac metabolic network, pharmacological and genetic tools have been engaged to manipulate cardiac metabolism in a variety of research models. In concert, a host of therapeutic interventions have been tested clinically to target substrate preference, insulin sensitivity, and mitochondrial function. In addition, the contribution of cellular metabolism to growth, survival, and other signaling pathways through the production of metabolic intermediates has been increasingly noted. In this review, we provide an overview of the cardiac metabolic network and highlight alterations observed in cardiac pathologies as well as strategies used as metabolic therapies in heart failure. Lastly, the ability of metabolic derivatives to intersect growth and survival are also discussed.

554 citations

Journal ArticleDOI
TL;DR: In this article, insights into the mechanisms of mitochondrial dysfunction in heart failure are presented, along with an overview of emerging treatments with the potential to improve the function of the failing heart by targeting mitochondria.
Abstract: Heart failure is a pressing worldwide public-health problem with millions of patients having worsening heart failure. Despite all the available therapies, the condition carries a very poor prognosis. Existing therapies provide symptomatic and clinical benefit, but do not fully address molecular abnormalities that occur in cardiomyocytes. This shortcoming is particularly important given that most patients with heart failure have viable dysfunctional myocardium, in which an improvement or normalization of function might be possible. Although the pathophysiology of heart failure is complex, mitochondrial dysfunction seems to be an important target for therapy to improve cardiac function directly. Mitochondrial abnormalities include impaired mitochondrial electron transport chain activity, increased formation of reactive oxygen species, shifted metabolic substrate utilization, aberrant mitochondrial dynamics, and altered ion homeostasis. In this Consensus Statement, insights into the mechanisms of mitochondrial dysfunction in heart failure are presented, along with an overview of emerging treatments with the potential to improve the function of the failing heart by targeting mitochondria.

462 citations