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Nature Oct 2023Senescent cells drive age-related tissue dysfunction partially through the induction of a chronic senescence-associated secretory phenotype (SASP). Mitochondria are...
Senescent cells drive age-related tissue dysfunction partially through the induction of a chronic senescence-associated secretory phenotype (SASP). Mitochondria are major regulators of the SASP; however, the underlying mechanisms have not been elucidated. Mitochondria are often essential for apoptosis, a cell fate distinct from cellular senescence. During apoptosis, widespread mitochondrial outer membrane permeabilization (MOMP) commits a cell to die. Here we find that MOMP occurring in a subset of mitochondria is a feature of cellular senescence. This process, called minority MOMP (miMOMP), requires BAX and BAK macropores enabling the release of mitochondrial DNA (mtDNA) into the cytosol. Cytosolic mtDNA in turn activates the cGAS-STING pathway, a major regulator of the SASP. We find that inhibition of MOMP in vivo decreases inflammatory markers and improves healthspan in aged mice. Our results reveal that apoptosis and senescence are regulated by similar mitochondria-dependent mechanisms and that sublethal mitochondrial apoptotic stress is a major driver of the SASP. We provide proof-of-concept that inhibition of miMOMP-induced inflammation may be a therapeutic route to improve healthspan.
Topics: Animals; Mice; Apoptosis; Cellular Senescence; Cytosol; DNA, Mitochondrial; Mitochondria; Mitochondrial Transmembrane Permeability-Driven Necrosis; Proof of Concept Study; Inflammation; Phenotype; Longevity; Healthy Aging
PubMed: 37821702
DOI: 10.1038/s41586-023-06621-4 -
Science Advances May 2023Degradation of defective mitochondria is an essential process to maintain cellular homeostasis and it is strictly regulated by the ubiquitin-proteasome system (UPS) and...
Degradation of defective mitochondria is an essential process to maintain cellular homeostasis and it is strictly regulated by the ubiquitin-proteasome system (UPS) and lysosomal activities. Here, using genome-wide CRISPR and small interference RNA screens, we identified a critical contribution of the lysosomal system in controlling aberrant induction of apoptosis following mitochondrial damage. After treatment with mitochondrial toxins, activation of the PINK1-Parkin axis triggered a BAX- and BAK-independent process of cytochrome c release from mitochondria followed by APAF1 and caspase 9-dependent apoptosis. This phenomenon was mediated by UPS-dependent outer mitochondrial membrane (OMM) degradation and was reversed using proteasome inhibitors. We found that the subsequent recruitment of the autophagy machinery to the OMM protected cells from apoptosis, mediating the lysosomal degradation of dysfunctional mitochondria. Our results underscore a major role of the autophagy machinery in counteracting aberrant noncanonical apoptosis and identified autophagy receptors as key elements in the regulation of this process.
Topics: Mitophagy; bcl-2-Associated X Protein; Apoptosis; Autophagy; Mitochondria; Ubiquitin
PubMed: 37224250
DOI: 10.1126/sciadv.adg8156 -
Thrombosis Research Nov 2023In a healthy individual, the lifespan of most platelets is tightly regulated by intrinsic, or mitochondrial, apoptosis. This is a special form of programmed cell death... (Review)
Review
In a healthy individual, the lifespan of most platelets is tightly regulated by intrinsic, or mitochondrial, apoptosis. This is a special form of programmed cell death governed by the BCL-2 family of proteins, where the prosurvival protein BCL-X maintains platelet viability by restraining the prodeath proteins BAK and BAX. Restriction of platelet lifespan by activation of BAK and BAX mediated intrinsic apoptosis is essential to maintain a functional, haemostatically reactive platelet population. This review focuses on the molecular regulation of intrinsic apoptosis in platelets, reviews conditions linked to enhanced platelet death, discusses ex vivo storage of platelets and describes caveats associated with the assessment of platelet apoptosis.
Topics: Humans; bcl-2-Associated X Protein; Blood Platelets; Apoptosis; bcl-X Protein
PubMed: 36739256
DOI: 10.1016/j.thromres.2022.11.024 -
Cell Death & Disease Jul 2023Small molecule direct BAK activators can potentially be used for the development of anti-cancer drugs or as tools to study BAK activation. The thrombopoietin receptor...
Small molecule direct BAK activators can potentially be used for the development of anti-cancer drugs or as tools to study BAK activation. The thrombopoietin receptor agonist eltrombopag (Eltro) inhibits BAX activation and BAX-mediated apoptosis. Here we report that, in contrast to its function as a BAX inhibitor, Eltro directly binds BAK but induces its activation in vitro. Moreover, Eltro induces or sensitizes BAK-dependent cell death in mouse embryonic fibroblasts (MEFs) and Jurkat cells. Chemical shift perturbation analysis by NMR indicates that Eltro binds to the BAK α4/α6/α7 groove to initiate BAK activation. Further molecular docking by HADDOCK suggests that several BAK residues, including R156, F157, and H164, play an important role in the interaction with Eltro. The introduction of an R156E mutation in the BAK α4/α6/α7 groove not only decreases Eltro binding and Eltro-induced BAK activation in vitro but also diminishes Eltro-induced apoptosis. Thus, our data suggest that Eltro directly induces BAK activation and BAK-dependent apoptosis, providing a starting point for the future development of more potent and selective direct BAK activators.
Topics: Animals; Mice; Molecular Docking Simulation; bcl-2-Associated X Protein; Fibroblasts; Apoptosis
PubMed: 37393297
DOI: 10.1038/s41419-023-05918-6 -
The Journal of Clinical Investigation Jul 2023Targeted therapies such as venetoclax (VEN) (Bcl-2 inhibitor) have revolutionized the treatment of chronic lymphocytic leukemia (CLL). We previously reported that...
Targeted therapies such as venetoclax (VEN) (Bcl-2 inhibitor) have revolutionized the treatment of chronic lymphocytic leukemia (CLL). We previously reported that persister CLL cells in treated patients overexpress multiple antiapoptotic proteins and display resistance to proapoptotic agents. Here, we demonstrated that multidrug-resistant CLL cells in vivo exhibited apoptosis restriction at a pre-mitochondrial level due to insufficient activation of the Bax and Bak (Bax/Bak) proteins. Co-immunoprecipitation analyses with selective BH domain antagonists revealed that the pleiotropic proapoptotic protein (Bim) was prevented from activating Bax/Bak by "switching" interactions to other upregulated antiapoptotic proteins (Mcl-1, Bcl-xL, Bcl-2). Hence, treatments that bypass Bax/Bak restriction are required to deplete these resistant cells in patients. Protein phosphatase 2A (PP2A) contributes to oncogenesis and treatment resistance. We observed that small-molecule activator of PP2A (SMAP) induced cytotoxicity in multiple cancer cell lines and CLL samples, including multidrug-resistant leukemia and lymphoma cells. The SMAP (DT-061) activated apoptosis in multidrug-resistant CLL cells through induction of mitochondrial permeability transition pores, independent of Bax/Bak. DT-061 inhibited the growth of wild-type and Bax/Bak double-knockout, multidrug-resistant CLL cells in a xenograft mouse model. Collectively, we discovered multidrug-resistant CLL cells in patients and validated a pharmacologically tractable pathway to deplete this reservoir.
Topics: Humans; Animals; Mice; bcl-2-Associated X Protein; Leukemia, Lymphocytic, Chronic, B-Cell; Protein Phosphatase 2; Myeloid Cell Leukemia Sequence 1 Protein; Proto-Oncogene Proteins c-bcl-2; Apoptosis; Apoptosis Regulatory Proteins; Drug Resistance, Multiple
PubMed: 37166997
DOI: 10.1172/JCI155938 -
Cell Death & Disease Jul 2023BH3 mimetics, targeting the Bcl-2 family anti-apoptotic proteins, represent a promising therapeutic opportunity in cancers. ABT-199, the first specific Bcl-2 inhibitor,...
BH3 mimetics, targeting the Bcl-2 family anti-apoptotic proteins, represent a promising therapeutic opportunity in cancers. ABT-199, the first specific Bcl-2 inhibitor, was approved by FDA for the treatment of several hematological malignancies. We have recently discovered IS21, a novel pan BH3 mimetic with preclinical antitumor activity in several tumor types. Here, we evaluated the efficacy of IS21 and other BH3 mimetics, both as single agents and combined with the currently used antineoplastic agents in T-cell acute lymphoblastic leukemia, ovarian cancer, and melanoma. IS21 was found to be active in T-cell acute lymphoblastic leukemia, melanoma, lung, pancreatic, and ovarian cancer cell lines. Bcl-xL and Mcl-1 protein levels predicted IS21 sensitivity in melanoma and ovarian cancer, respectively. Exploring IS21 mechanism of action, we found that IS21 activity depends on the presence of BAX and BAK proteins: complexes between Bcl-2 and Bcl-xL proteins and their main binding partners were reduced after IS21 treatment. In combination experiments, BH3 mimetics sensitized leukemia cells to chemotherapy, ovarian cancer cells and melanoma models to PARP and MAPK inhibitors, respectively. We showed that this enhancing effect was related to the potentiation of the apoptotic pathway, both in hematologic and solid tumors. In conclusion, our data suggest the use of inhibitors of anti-apoptotic proteins as a therapeutic strategy to enhance the efficacy of anticancer treatment.
Topics: Humans; Female; Apoptosis; Proto-Oncogene Proteins c-bcl-2; Myeloid Cell Leukemia Sequence 1 Protein; Antineoplastic Agents; bcl-X Protein; Apoptosis Regulatory Proteins; bcl-2 Homologous Antagonist-Killer Protein; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Melanoma; Ovarian Neoplasms; Cell Line, Tumor
PubMed: 37460459
DOI: 10.1038/s41419-023-05963-1 -
Journal of Translational Medicine Jul 2023Preeclampsia is a common pregnancy complication characterized by high blood pressure and damage to organs. Abnormal placenta and vascular function can lead to...
BACKGROUND
Preeclampsia is a common pregnancy complication characterized by high blood pressure and damage to organs. Abnormal placenta and vascular function can lead to preeclampsia. Accumulating evidence has suggested a potential link between circular RNAs (circRNAs) and preeclampsia. As a placenta and endothelial-expressed circRNA, hsa_circ_0002348, may be promising to be the novel molecular target for preeclampsia. However, the function and mechanism of hsa_circ_0002348 in preeclampsia has not been elucidated.
MATERIALS AND METHODS
An overlap analysis of two circRNA profiles from placenta and endothelial cells was used to identify a functionally unknown circRNA, hsa_circ_0002348. Quantitative real-time PCR (qRT-PCR) and in situ hybridization (ISH) were used to detect its expression in the trophoblast cells and placental tissues. The mouse model of lipopolysaccharide (LPS)-induced preeclampsia was established to determine the in vivo role of hsa_circ_0002348. RNA immunoprecipitation (RIP), Luciferase reporter assay, qRT-PCR, western blot, gain- and loss-of-function and rescue experiments were conducted to uncover the role of hsa_circ_0002348 and its interaction with miR-126-3p and BAK1 in regulating trophoblast proliferation and apoptosis. Fluorescence in situ hybridization (FISH) and Immunohistochemistry (IHC) were performed to examine the expression of miR-126-3p and BAK1 in mice and human placentas, respectively.
RESULTS
Hsa_circ_0002348 was significantly increased in the preeclampsia placentas, and positively correlated with the severity of preeclampsia patients' clinical manifestations. Its overexpression exacerbated preeclampsia-like features in the mouse model of LPS-induced preeclampsia. Functionally, hsa_circ_0002348 was found to inhibit trophoblast proliferation and promote trophoblast apoptosis. Mechanistically, hsa_circ_0002348, as an endogenous miR-126-3p sponge, upregulated the expression of BAK1. Additionally, both hsa_circ_0002348 knockdown and miR-126-3p overexpression enhanced the mammalian target of rapamycin (mTOR) and ERK1/2 signaling pathway.
CONCLUSIONS
Hsa_circ_0002348 might be a novel regulator of trophoblast proliferation and apoptosis through miR-126-3p/BAK1 axis in preeclampsia, which may serve as a potential target for detecting and treating preeclampsia.
Topics: Animals; Female; Humans; Mice; Pregnancy; Apoptosis; bcl-2 Homologous Antagonist-Killer Protein; Cell Proliferation; Disease Models, Animal; Endothelial Cells; In Situ Hybridization, Fluorescence; Lipopolysaccharides; Mammals; MicroRNAs; Placenta; Pre-Eclampsia; RNA, Circular; Trophoblasts
PubMed: 37507742
DOI: 10.1186/s12967-023-04240-1 -
Proceedings of the National Academy of... Aug 2023Cataract is a leading ocular disease causing global blindness. The mechanism of cataractogenesis has not been well defined. Here, we demonstrate that the heat shock...
Cataract is a leading ocular disease causing global blindness. The mechanism of cataractogenesis has not been well defined. Here, we demonstrate that the heat shock protein 90β (HSP90β) plays a fundamental role in suppressing cataractogenesis. HSP90β is the most dominant HSP in normal lens, and its constitutive high level of expression is largely derived from regulation by Sp1 family transcription factors. More importantly, HSP90β is significantly down-regulated in human cataract patients and in aging mouse lenses, whereas HSP90β silencing in zebrafish causes cataractogenesis, which can only be rescued by itself but not other HSP90 genes. Mechanistically, HSP90β can directly interact with CHMP4B, a newly-found client protein involved in control of cytokinesis. HSP90β silencing causes upregulation of CHMP4B and another client protein, the tumor suppressor p53. CHMP4B upregulation or overexpression induces excessive division of lens epithelial cells without proper differentiation. As a result, these cells were triggered to undergo apoptosis due to activation of the p53/Bak-Bim pathway, leading to cataractogenesis and microphthalmia. Silence of both HSP90β and CHMP4B restored normal phenotype of zebrafish eye. Together, our results reveal that HSP90β is a critical inhibitor of cataractogenesis through negative regulation of CHMP4B and the p53-Bak/Bim pathway.
Topics: Animals; Humans; Mice; Aging; Cataract; Endosomal Sorting Complexes Required for Transport; HSP90 Heat-Shock Proteins; Multivesicular Bodies; Tumor Suppressor Protein p53; Zebrafish
PubMed: 37487085
DOI: 10.1073/pnas.2221522120 -
Biomedicines May 2023SARS-CoV-2 ORF3a accessory protein was found to be involved in virus release, immunomodulation and exhibited a pro-apoptotic character. In order to unravel a potential...
Inhibition of PERK Kinase, an Orchestrator of the Unfolded Protein Response (UPR), Significantly Reduces Apoptosis and Inflammation of Lung Epithelial Cells Triggered by SARS-CoV-2 ORF3a Protein.
SARS-CoV-2 ORF3a accessory protein was found to be involved in virus release, immunomodulation and exhibited a pro-apoptotic character. In order to unravel a potential ORF3a-induced apoptotic and inflammatory death mechanism, lung epithelial cells (A549) were transfected with in vitro synthesized mRNA. The protein's dynamic involvement as "stress factor" for the endoplasmic reticulum, causing the activation of PERK kinase and other UPR-involved proteins and therefore the upregulation of their signaling pathway executioners (ATF6, XBP-1s, PERK, phospho eIF2a, , CHOP, ), has been clearly demonstrated. Furthermore, the overexpression of BAX and BH3-only pro-apoptotic protein PUMA, the upregulation of Bcl-2 family genes (), the reduced expression of Bcl-2 in mRNA and protein levels, and lastly, the cleavage of PARP-1 and caspase family members (caspase-3,-8 and -9) indicate that ORF3a displays its apoptotic character through the mitochondrial pathway of apoptosis. Moreover, the upregulation of , phosphorylation of p65 and IκΒα and the elevated expression of pro-inflammatory cytokines (IL-1b, IL-6, IL-8 and IL-18) in transfected cells with mRNA indicate that this protein causes the inflammatory response through NFκB activation and therefore triggers lung injury. An intriguing finding of our study is that upon treatment of the ORF3a-transfected cells with GSK2606414, a selective PERK inhibitor, both complications (apoptosis and inflammatory response) were neutralized, and cell survival was favored, whereas treatment of transfected cells with z-VAD (a pan-caspase inhibitor) despite inhibiting cell death, could not ameliorate the inflammatory response of transfected A549 cells. Given the above, we point out that PERK kinase is a "master tactician" and its activation constitutes the main stimulus for the emergence of ORF3a apoptotic and inflammatory nature and therefore could serve as potential target for developing novel therapeutic approaches against COVID-19.
PubMed: 37371681
DOI: 10.3390/biomedicines11061585