Inhibition of Macroautophagy Triggers Apoptosis

ABSTRACT Mammalian cells were observed to die under conditions in which nutrients were depleted and, simultaneously, macroautophagy was inhibited either genetically (by a small interfering RNA targeting Atg5, Atg6/Beclin 1-1, Atg10, or Atg12) or pharmacologically (by 3-methyladenine, hydroxychloroquine, bafilomycin A1, or monensin). Cell death occurred through apoptosis (type 1 cell death), since it was reduced by stabilization of mitochondrial membranes (with Bcl-2 or vMIA, a cytomegalovirus-derived gene) or by caspase inhibition. Under conditions in which the fusion between lysosomes and autophagosomes was inhibited, the formation of autophagic vacuoles was enhanced at a preapoptotic stage, as indicated by accumulation of LC3-II protein, ultrastructural studies, and an increase in the acidic vacuolar compartment. Cells exhibiting a morphology reminiscent of (autophagic) type 2 cell death, however, recovered, and only cells with a disrupted mitochondrial transmembrane potential were beyond the point of no return and inexorably died even under optimal culture conditions. All together, these data indicate that autophagy may be cytoprotective, at least under conditions of nutrient depletion, and point to an important cross talk between type 1 and type 2 cell death pathways.

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Caspase-cleaved HPK1 induces CD95L-independent activation-induced cell death in T and B lymphocytes

Blood ◽

10.1182/blood-2007-01-071167 ◽

2007 ◽

Vol 110 (12) ◽

pp. 3968-3977 ◽

Cited By ~ 29

Author(s):

Dirk Brenner ◽

Alexander Golks ◽

Mareike Becker ◽

Wolfgang Müller ◽

Christian R. Frey ◽

...

Keyword(s):

T Cells ◽

Cell Death ◽

Cell Fate ◽

B Lymphocytes ◽

T And B Lymphocytes ◽

Cell Death Pathways ◽

Activation Induced Cell Death ◽

Cell Death Pathway ◽

Dependent Cell ◽

Interfering Rna

Abstract Life and death of peripheral lymphocytes is strictly controlled to maintain physiologic levels of T and B cells. Activation-induced cell death (AICD) is one mechanism to delete superfluous lymphocytes by restimulation of their immunoreceptors and it depends partially on the CD95/CD95L system. Recently, we have shown that hematopoietic progenitor kinase 1 (HPK1) determines T-cell fate. While full-length HPK1 is essential for NF-κB activation in T cells, the C-terminal fragment of HPK1, HPK1-C, suppresses NF-κB and sensitizes toward AICD by a yet undefined cell death pathway. Here we show that upon IL-2–driven expansion of primary T cells, HPK1 is converted to HPK1-C by a caspase-3 activity below the threshold of apoptosis induction. HPK1-C se-lectively blocks induction of NF-κB–dependent antiapoptotic Bcl-2 family members but not of the proapoptotic Bcl-2 family member Bim. Interestingly, T and B lymphocytes from HPK1-C transgenic mice undergo AICD independently of the CD95/CD95L system but involving caspase-9. Knock down of HPK1/HPK1-C or Bim by small interfering RNA shows that CD95L-dependent and HPK1/HPK1-C–dependent cell death pathways complement each other in AICD of primary T cells. Our results define HPK1-C as a suppressor of antiapoptotic Bcl-2 proteins and provide a molecular basis for our understanding of CD95L-independent AICD of lymphocytes.

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Mitochondrial morphology and distribution in mammalian cells

Biological Chemistry ◽

10.1515/bc.2006.193 ◽

2006 ◽

Vol 387 (12) ◽

pp. 1551-1558 ◽

Cited By ~ 80

Author(s):

Ann E. Frazier ◽

Clement Kiu ◽

Diana Stojanovski ◽

Nicholas J. Hoogenraad ◽

Michael T. Ryan

Keyword(s):

Cell Death ◽

Neurological Disorders ◽

Mammalian Cells ◽

Morphological Changes ◽

Mitochondrial Fission ◽

Gene Mutations ◽

Current Understanding ◽

Mitochondrial Morphology ◽

Cell Death Pathways ◽

Mitochondrial Distribution

Abstract It is now appreciated that mitochondria form tubular networks that adapt to the requirements of the cell by undergoing changes in their shape through fission and fusion. Proper mitochondrial distribution also appears to be required for ATP delivery and calcium regulation, and, in some cases, for cell development. While we now realise the great importance of mitochondria for the cell, we are only beginning to work out how these organelles undergo the drastic morphological changes that are essential for cellular function. Of the few known components involved in shaping mitochondria, some have been found to be essential to life and their gene mutations are linked to neurological disorders, while others appear to be recruited in the activation of cell death pathways. Here we review our current understanding of the functions of the main players involved in mitochondrial fission, fusion and distribution in mammalian cells.

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Alternative Cell Death Pathways and Cell Metabolism

International Journal of Cell Biology ◽

10.1155/2013/463637 ◽

2013 ◽

Vol 2013 ◽

pp. 1-4 ◽

Cited By ~ 12

Author(s):

Simone Fulda

Keyword(s):

Cell Death ◽

Metabolic Pathways ◽

Mammalian Cells ◽

Cell Metabolism ◽

Environmental Cues ◽

Cell Death Pathways ◽

Mitochondrial Signaling ◽

Transduction Mechanisms ◽

Cell Death Signaling ◽

Critical Components

While necroptosis has for long been viewed as an accidental mode of cell death triggered by physical or chemical damage, it has become clear over the last years that necroptosis can also represent a programmed form of cell death in mammalian cells. Key discoveries in the field of cell death research, including the identification of critical components of the necroptotic machinery, led to a revised concept of cell death signaling programs. Several regulatory check and balances are in place in order to ensure that necroptosis is tightly controlled according to environmental cues and cellular needs. This network of regulatory mechanisms includes metabolic pathways, especially those linked to mitochondrial signaling events. A better understanding of these signal transduction mechanisms will likely contribute to open new avenues to exploit our knowledge on the regulation of necroptosis signaling for therapeutic application in the treatment of human diseases.

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An interaction between type 1 and type 2 programmed cell death and clonogenic survival

Medical Hypotheses ◽

10.1016/s0306-9877(03)00236-6 ◽

2003 ◽

Vol 61 (5-6) ◽

pp. 583-585 ◽

Cited By ~ 1

Author(s):

K.M Anderson ◽

P Bonomi ◽

Y Hu ◽

J.E Harris

Keyword(s):

Cell Death ◽

Programmed Cell Death ◽

Clonogenic Survival

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CRH Acts on CRH-R1 and -R2 to Differentially Modulate the Expression of Large-Conductance Calcium-Activated Potassium Channels in Human Pregnant Myometrium

Endocrinology ◽

10.1210/en.2011-0262 ◽

2011 ◽

Vol 152 (11) ◽

pp. 4406-4417 ◽

Cited By ~ 10

Author(s):

Chen Xu ◽

Lu Gao ◽

Xingji You ◽

Ling Dai ◽

Yuan Li ◽

...

Keyword(s):

Potassium Channels ◽

Receptor Type ◽

Uterine Contractility ◽

Myometrial Cells ◽

Calcium Activated Potassium Channels ◽

Spontaneous Contractions ◽

Crh Receptor Type 1 ◽

Interfering Rna

CRH has been implicated to play a key role in the control of human pregnancy and parturition. Large-conductance potassium channels (BKCa) play a pivotal role in the modulation of uterine contractility during pregnancy. The objectives of the present study were to investigate the effect of CRH on BKCa expression in human pregnant myometrial cells. Myometrial tissues were collected at cesarean section from pregnant women not-in-labor (TNL) or in-labor (TL) at term, and myocytes were isolated and cultured. CRH was identified in human pregnant myometrium and mainly expressed in myometrial myocytes. Cultured myometrial cells were able to secrete CRH. In TNL myometrial cells, CRH treatment increased the expression of BKCa α- and β-subunits. CRH receptor type 1 (CRH-R1) antagonist, antalarmin, decreased whereas CRH receptor type 2 (CRH-R2) antagonist, astressin2b, increased the expression of BKCa. CRH-R2 small interfering RNA (siRNA) caused an increase, but CRH-R1 siRNA resulted in a decrease, in BKCa expression. In contrast to TNL cells, CRH exhibited an opposite effect on BKCa expression in TL myometrial cells, i.e. decreased BKCa expression. Antalarmin enhanced but astressin2b reduced BKCa expression. CRH-R2 siRNA decreased whereas CRH-R1 siRNA increased BKCa expression. 1,3-Dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one significantly inhibited the frequency of spontaneous contractions of myometrial strips, and this effect was significantly decreased in TL strips compared with TNL ones. Our data suggest that CRH-R1 and CRH-R2 show differential regulation of BKCa expression. These effects mediated by CRH-R1 and CRH-R2 are changed after the onset of labor. This leads us to suggest that CRH may fine-tune myometrial contractility by modulating the expression of BKCa during pregnancy and labor.

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Small interfering RNA targeting bovine papillomavirus type 1 E2 induces apoptosis in equine sarcoid transformed fibroblasts

Virus Research ◽

10.1016/j.virusres.2009.06.019 ◽

2009 ◽

Vol 145 (1) ◽

pp. 162-165 ◽

Cited By ~ 10

Author(s):

Philipe A.M. Gobeil ◽

ZhengQiang Yuan ◽

Elizabeth A. Gault ◽

Iain M. Morgan ◽

M. Saveria Campo ◽

...

Keyword(s):

Small Interfering Rna ◽

Bovine Papillomavirus ◽

Equine Sarcoid ◽

Transformed Fibroblasts ◽

Rna Targeting ◽

Interfering Rna

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Mechanisms of Pancreatic -Cell Death in Type 1 and Type 2 Diabetes: Many Differences, Few Similarities

Diabetes ◽

10.2337/diabetes.54.suppl_2.s97 ◽

2005 ◽

Vol 54 (Supplement 2) ◽

pp. S97-S107 ◽

Cited By ~ 912

Author(s):

M. Cnop ◽

N. Welsh ◽

J.-C. Jonas ◽

A. Jorns ◽

S. Lenzen ◽

...

Keyword(s):

Type 2 Diabetes ◽

Cell Death ◽

Pancreatic Cell

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A novel dynein-type AAA+ protein with peroxisomal targeting signal type 2

The Journal of Biochemistry ◽

10.1093/jb/mvaa018 ◽

2020 ◽

Vol 167 (5) ◽

pp. 429-432

Author(s):

Tsuneo Imanaka ◽

Kosuke Kawaguchi

Keyword(s):

Mammalian Cells ◽

Ring Structure ◽

Family Protein ◽

Peroxisomal Targeting ◽

Signal Type ◽

Targeting Signal ◽

Aaa Protein ◽

Peroxisomal Targeting Signal

Abstract Peroxisomal matrix proteins are imported into peroxisomes in a process mediated by peroxisomal targeting signal (PTS) type 1 and 2. The PTS2 proteins are imported into peroxisomes after binding with Pex7p. Niwa et al. (A newly isolated Pex7-binding, atypical PTS2 protein P7BP2 is a novel dynein-type AAA+ protein. J Biochem 2018;164:437–447) identified a novel Pex7p-binding protein in CHO cells and characterized the subcellular distribution and molecular properties of the human homologue, ‘P7BP2’. Interestingly, P7BP2 possesses PTS2 at the NH2 terminal and six putative AAA+ domains. Another group has suggested that the protein also possesses mitochondrial targeting signal at the NH2 terminal. In fact, the P7BP2 expressed in mammalian cells is targeted to both peroxisomes and mitochondria. The purified protein from Sf9 cells is a monomer and has a disc-like ring structure, suggesting that P7BP2 is a novel dynein-type AAA+ family protein. The protein expressed in insect cells exhibits ATPase activity. P7BP2 localizes to peroxisomes and mitochondria, and has a common function related to dynein-type ATPases in both organelles.

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High Levels of miR-7-5p Potentiate Crizotinib-Induced Cytokilling and Autophagic Flux by Targeting RAF1 in NPM-ALK Positive Lymphoma Cells

Cancers ◽

10.3390/cancers12102951 ◽

2020 ◽

Vol 12 (10) ◽

pp. 2951 ◽

Cited By ~ 1

Author(s):

Domenico Sorrentino ◽

Julie Frentzel ◽

Géraldine Mitou ◽

Rafael B. Blasco ◽

Avédis Torossian ◽

...

Keyword(s):

Cell Death ◽

Kinase Inhibitor ◽

Combined Therapy ◽

Large Cell ◽

Autophagic Flux ◽

Lymphoma Cells ◽

Anaplastic Lymphoma ◽

Rna Targeting ◽

Alk Positive ◽

Interfering Rna

Anaplastic lymphoma kinase positive anaplastic large cell lymphomas (ALK+ ALCL) are an aggressive pediatric disease. The therapeutic options comprise chemotherapy, which is efficient in approximately 70% of patients, and targeted therapies, such as crizotinib (an ALK tyrosine kinase inhibitor (TKI)), used in refractory/relapsed cases. Research efforts have also converged toward the development of combined therapies to improve treatment. In this context, we studied whether autophagy could be modulated to improve crizotinib therapy. Autophagy is a vesicular recycling pathway, known to be associated with either cell survival or cell death depending on the cancer and therapy. We previously demonstrated that crizotinib induced cytoprotective autophagy in ALK+ lymphoma cells and that its further intensification was associated with cell death. In line with these results, we show here that combined ALK and Rapidly Accelerated Fibrosarcoma 1 (RAF1) inhibition, using pharmacological (vemurafenib) or molecular (small interfering RNA targeting RAF1 (siRAF1) or microRNA-7-5p (miR-7-5p) mimics) strategies, also triggered autophagy and potentiated the toxicity of TKI. Mechanistically, we found that this combined therapy resulted in the decrease of the inhibitory phosphorylation on Unc-51-like kinase-1 (ULK1) (a key protein in autophagy initiation), which may account for the enforced autophagy and cytokilling effect. Altogether, our results support the development of ALK and RAF1 combined inhibition as a new therapeutic approach in ALK+ ALCL.

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Islet Amyloid Polypeptide: Structure, Function, and Pathophysiology

Journal of Diabetes Research ◽

10.1155/2016/2798269 ◽

2016 ◽

Vol 2016 ◽

pp. 1-18 ◽

Cited By ~ 86

Author(s):

Rehana Akter ◽

Ping Cao ◽

Harris Noor ◽

Zachary Ridgway ◽

Ling-Hsien Tu ◽

...

Keyword(s):

Type 2 Diabetes ◽

Cell Death ◽

Type 1 Diabetes ◽

Islet Amyloid Polypeptide ◽

Amyloid Formation ◽

Islet Amyloid

The hormone islet amyloid polypeptide (IAPP, or amylin) plays a role in glucose homeostasis but aggregates to form islet amyloid in type-2 diabetes. Islet amyloid formation contributes toβ-cell dysfunction and death in the disease and to the failure of islet transplants. Recent work suggests a role for IAPP aggregation in cardiovascular complications of type-2 diabetes and hints at a possible role in type-1 diabetes. The mechanisms of IAPP amyloid formationin vivoorin vitroare not understood and the mechanisms of IAPP inducedβ-cell death are not fully defined. Activation of the inflammasome, defects in autophagy, ER stress, generation of reactive oxygen species, membrane disruption, and receptor mediated mechanisms have all been proposed to play a role. Open questions in the field include the relative importance of the various mechanisms ofβ-cell death, the relevance of reductionist biophysical studies to the situationin vivo, the molecular mechanism of amyloid formationin vitroandin vivo, the factors which trigger amyloid formation in type-2 diabetes, the potential role of IAPP in type-1 diabetes, the development of clinically relevant inhibitors of islet amyloidosis toxicity, and the design of soluble, bioactive variants of IAPP for use as adjuncts to insulin therapy.

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