bims-mikwok 2023-12-03 papers

bims-mikwok

Biomed News

on Mitochondrial quality control

Issue of 2023–12–03
seventeen papers selected by
Gavin McStay, Liverpool John Moores University

Review title: Mechanisms of mitochondrial reorganization.
Mitochondrial quality control in health and cardiovascular diseases.
Restoring the infected powerhouse: Mitochondrial quality control in sepsis.
Protocol for evaluating mitochondrial morphology changes in response to CCCP-induced stress through open-source image processing software.
Metabolic control of mitophagy.
Basal activity of PINK1 and PRKN in cell models and rodent brain.
Biased placement of Mitochondria fission facilitates asymmetric inheritance of protein aggregates during yeast cell division.
Mitochondrial E3 ligase MARCH5 is a safeguard against DNA-PKcs-mediated immune signaling in mitochondria-damaged cells.
In vitro anticancer effect of azithromycin targeting hypoxic lung cancer cells via the inhibition of mitophagy.
BNIP3 as a new tool to promote healthy brain aging.
Histone deacetylase inhibitor pracinostat suppresses colorectal cancer by inducing CDK5-Drp1 signaling-mediated peripheral mitofission.
CARM1 drives mitophagy and autophagy flux during fasting-induced skeletal muscle atrophy.
Mitochondrial protein BNIP3 regulates Chikungunya virus replication in the early stages of infection.
Regular exercise attenuates alcoholic myopathy in zebrafish by modulating mitochondrial homeostasis.
Palmitic acid activates NLRP3 inflammasome through NF-κB and AMPK-mitophagy-ROS pathways to induce IL-1β production in large yellow croaker (Larimichthys crocea).
Effects of phosphorylation on Drp1 activation by its receptors, actin, and cardiolipin.
Melittin kills A549 cells by targeting mitochondria and blocking mitophagy flux.

J Biochem. 2023 Nov 28. pii: mvad098. [Epub ahead of print]

Review title: Mechanisms of mitochondrial reorganization.

Tatsuro Maruyama, Yutaro Hama, Nobuo N Noda.

  The cytoplasm of eukaryotes is dynamically zoned by membrane-bound and membraneless organelles. Cytoplasmic zoning allows various biochemical reactions to take place at the right time and place. Mitochondrion is a membrane-bound organelle that provides a zone for intracellular energy production and metabolism of lipids and iron. A key feature of mitochondria is their high dynamics: mitochondria constantly undergo fusion and fission, and excess or damaged mitochondria are selectively eliminated by mitophagy. Therefore, mitochondria are appropriate model systems to understand dynamic cytoplasmic zoning by membrane organelles. In this review, we summarize the molecular mechanisms of mitochondrial fusion and fission as well as mitophagy unveiled through studies using yeast and mammalian models.

Keywords:  cytoplasmic zoning; mitochondria; mitochondrial fission; mitochondrial fusion; mitophagy

DOI:  https://doi.org/10.1093/jb/mvad098
Front Cell Dev Biol. 2023 ;11 1290046

Mitochondrial quality control in health and cardiovascular diseases.

Asli E Atici, Timothy R Crother, Magali Noval Rivas.

  Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.

Keywords:  ROS; cardiovascular disease; mitobiogenesis; mitochondria; mitochondrial dynamics; mitophagy

DOI:  https://doi.org/10.3389/fcell.2023.1290046
Redox Biol. 2023 Nov 23. pii: S2213-2317(23)00369-5. [Epub ahead of print]68 102968

Restoring the infected powerhouse: Mitochondrial quality control in sepsis.

F M Lira Chavez, L P Gartzke, F E van Beuningen, S E Wink, R H Henning, G Krenning, H R Bouma.

  Sepsis is a dysregulated host response to an infection, characterized by organ failure. The pathophysiology is complex and incompletely understood, but mitochondria appear to play a key role in the cascade of events that culminate in multiple organ failure and potentially death. In shaping immune responses, mitochondria fulfil dual roles: they not only supply energy and metabolic intermediates crucial for immune cell activation and function but also influence inflammatory and cell death pathways. Importantly, mitochondrial dysfunction has a dual impact, compromising both immune system efficiency and the metabolic stability of end organs. Dysfunctional mitochondria contribute to the development of a hyperinflammatory state and loss of cellular homeostasis, resulting in poor clinical outcomes. Already in early sepsis, signs of mitochondrial dysfunction are apparent and consequently, strategies to optimize mitochondrial function in sepsis should not only prevent the occurrence of mitochondrial dysfunction, but also cover the repair of the sustained mitochondrial damage. Here, we discuss mitochondrial quality control (mtQC) in the pathogenesis of sepsis and exemplify how mtQC could serve as therapeutic target to overcome mitochondrial dysfunction. Hence, replacing or repairing dysfunctional mitochondria may contribute to the recovery of organ function in sepsis. Mitochondrial biogenesis is a process that results in the formation of new mitochondria and is critical for maintaining a pool of healthy mitochondria. However, exacerbated biogenesis during early sepsis can result in accumulation of structurally aberrant mitochondria that fail to restore bioenergetics, produce excess reactive oxygen species (ROS) and exacerbate the disease course. Conversely, enhancing mitophagy can protect against organ damage by limiting the release of mitochondrial-derived damage-associated molecules (DAMPs). Furthermore, promoting mitophagy may facilitate the growth of healthy mitochondria by blocking the replication of damaged mitochondria and allow for post sepsis organ recovery through enabling mitophagy-coupled biogenesis. The remaining healthy mitochondria may provide an undamaged scaffold to reproduce functional mitochondria. However, the kinetics of mtQC in sepsis, specifically mitophagy, and the optimal timing for intervention remain poorly understood. This review emphasizes the importance of integrating mitophagy induction with mtQC mechanisms to prevent undesired effects associated with solely the induction of mitochondrial biogenesis.

Keywords:  Mitochondrial biogenesis; Mitochondrial dynamics; Mitochondrial quality control; Mitophagy; Sepsis

DOI:  https://doi.org/10.1016/j.redox.2023.102968
STAR Protoc. 2023 Nov 29. pii: S2666-1667(23)00712-8. [Epub ahead of print]4(4): 102745

Protocol for evaluating mitochondrial morphology changes in response to CCCP-induced stress through open-source image processing software.

Sudeshna Nag, Kaitlin Szederkenyi, Christopher M Yip, G Angus McQuibban.

  Mitochondrial morphology is an indicator of cellular health and function; however, its quantification and categorization into different subclasses is a complicated process. Here, we present a protocol for mitochondrial morphology quantification in the presence and absence of carbonyl cyanide m-chlorophenyl hydrazone stress. We describe steps for the preparation of cells for immunofluorescence microscopy, staining, and morphology quantification. The quantification protocol generates an aspect ratio that helps to categorize mitochondria into two clear subclasses. For complete details on the use and execution of this protocol, please refer to Nag et al.1.

Keywords:  Cell Biology; Cell culture; Metabolism; Microscopy; Molecular/Chemical Probes

DOI:  https://doi.org/10.1016/j.xpro.2023.102745
Eur J Clin Invest. 2023 Dec 01. e14138

Metabolic control of mitophagy.

Andreas Zimmermann, Frank Madeo, Abhinav Diwan, Junichi Sadoshima, Simon Sedej, Guido Kroemer, Mahmoud Abdellatif.

  Mitochondrial dysfunction is a major hallmark of ageing and related chronic disorders. Controlled removal of damaged mitochondria by the autophagic machinery, a process known as mitophagy, is vital for mitochondrial homeostasis and cell survival. The central role of mitochondria in cellular metabolism places mitochondrial removal at the interface of key metabolic pathways affecting the biosynthesis or catabolism of acetyl-coenzyme A, nicotinamide adenine dinucleotide, polyamines, as well as fatty acids and amino acids. Molecular switches that integrate the metabolic status of the cell, like AMP-dependent protein kinase, protein kinase A, mechanistic target of rapamycin and sirtuins, have also emerged as important regulators of mitophagy. In this review, we discuss how metabolic regulation intersects with mitophagy. We place special emphasis on the metabolic regulatory circuits that may be therapeutically targeted to delay ageing and mitochondria-associated chronic diseases. Moreover, we identify outstanding knowledge gaps, such as the ill-defined distinction between basal and damage-induced mitophagy, which must be resolved to boost progress in this area.

Keywords:  AMPK; NAD; acetyl-CoA; ageing; ageing-related disease; metabolism; mitophagy; spermidine

DOI:  https://doi.org/10.1111/eci.14138
Autophagy. 2023 Dec 02. 1-12

Basal activity of PINK1 and PRKN in cell models and rodent brain.

Jens O Watzlawik, Fabienne C Fiesel, Gabriella Fiorino, Bernardo A Bustillos, Zahra Baninameh, Briana N Markham, Xu Hou, Caleb S Hayes, Jenny M Bredenberg, Nicholas W Kurchaba, Dominika Fričová, Joanna Siuda, Zbigniew K Wszolek, Sachiko Noda, Shigeto Sato, Nobutaka Hattori, Asheeta A Prasad, Deniz Kirik, Howard S Fox, Kelly L Stauch, Matthew S Goldberg, Wolfdieter Springer.

  The ubiquitin kinase-ligase pair PINK1-PRKN recognizes and transiently labels damaged mitochondria with ubiquitin phosphorylated at Ser65 (p-S65-Ub) to mediate their selective degradation (mitophagy). Complete loss of PINK1 or PRKN function unequivocally leads to early-onset Parkinson disease, but it is debated whether impairments in mitophagy contribute to disease later in life. While the pathway has been extensively studied in cell culture upon acute and massive mitochondrial stress, basal levels of activation under endogenous conditions and especially in vivo in the brain remain undetermined. Using rodent samples, patient-derived cells, and isogenic neurons, we here identified age-dependent, brain region-, and cell type-specific effects and determined expression levels and extent of basal and maximal activation of PINK1 and PRKN. Our work highlights the importance of defining critical risk and therapeutically relevant levels of PINK1-PRKN signaling which will further improve diagnosis and prognosis and will lead to better stratification of patients for future clinical trials.

Keywords:  Mitophagy; PINK1; PRKN; Parkinson disease; parkin; ubiquitin

DOI:  https://doi.org/10.1080/15548627.2023.2286414
PLoS Comput Biol. 2023 Nov 27. 19(11): e1011588

Biased placement of Mitochondria fission facilitates asymmetric inheritance of protein aggregates during yeast cell division.

Gordon Sun, Christine Hwang, Tony Jung, Jian Liu, Rong Li.

Mitochondria are essential and dynamic eukaryotic organelles that must be inherited during cell division. In yeast, mitochondria are inherited asymmetrically based on quality, which is thought to be vital for maintaining a rejuvenated cell population; however, the mechanisms underlying mitochondrial remodeling and segregation during this process are not understood. We used high spatiotemporal imaging to quantify the key aspects of mitochondrial dynamics, including motility, fission, and fusion characteristics, upon aggregation of misfolded proteins in the mitochondrial matrix. Using these measured parameters, we developed an agent-based stochastic model of dynamics of mitochondrial inheritance. Our model predicts that biased mitochondrial fission near the protein aggregates facilitates the clustering of protein aggregates in the mitochondrial matrix, and this process underlies asymmetric mitochondria inheritance. These predictions are supported by live-cell imaging experiments where mitochondrial fission was perturbed. Our findings therefore uncover an unexpected role of mitochondrial dynamics in asymmetric mitochondrial inheritance.

DOI: https://doi.org/10.1371/journal.pcbi.1011588
Cell Death Dis. 2023 Dec 01. 14(12): 788

Mitochondrial E3 ligase MARCH5 is a safeguard against DNA-PKcs-mediated immune signaling in mitochondria-damaged cells.

June Heo, Yeon-Ji Park, Yonghyeon Kim, Ho-Soo Lee, Jeongah Kim, Soon-Hwan Kwon, Myeong-Gyun Kang, Hyun-Woo Rhee, Woong Sun, Jae-Ho Lee, Hyeseong Cho.

Mitochondrial dysfunction is important in various chronic degenerative disorders, and aberrant immune responses elicited by cytoplasmic mitochondrial DNA (mtDNA) may be related. Here, we developed mtDNA-targeted MTERF1-FokI and TFAM-FokI endonuclease systems to induce mitochondrial DNA double-strand breaks (mtDSBs). In these cells, the mtDNA copy number was significantly reduced upon mtDSB induction. Interestingly, in cGAS knockout cells, synthesis of interferon β1 and interferon-stimulated gene was increased upon mtDSB induction. We found that mtDSBs activated DNA-PKcs and HSPA8 in a VDAC1-dependent manner. Importantly, the mitochondrial E3 ligase MARCH5 bound active DNA-PKcs in cells with mtDSBs and reduced the type І interferon response through the degradation of DNA-PKcs. Likewise, mitochondrial damage caused by LPS treatment in RAW264.7 macrophage cells increased phospho-HSPA8 levels and the synthesis of mIFNB1 mRNA in a DNA-PKcs-dependent manner. Accordingly, in March5 knockout macrophages, phospho-HSPA8 levels and the synthesis of mIFNB1 mRNA were prolonged after LPS stimulation. Together, cytoplasmic mtDNA elicits a cellular immune response through DNA-PKcs, and mitochondrial MARCH5 may be a safeguard to prevent persistent inflammatory reactions.

DOI: https://doi.org/10.1038/s41419-023-06315-9
Oncol Lett. 2024 Jan;27(1): 12

In vitro anticancer effect of azithromycin targeting hypoxic lung cancer cells via the inhibition of mitophagy.

Kazutoshi Toriyama, Takashi Okuma, Shinji Abe, Hiroyuki Nakamura, Kazutetsu Aoshiba.

  Solid tumors are predisposed to hypoxia, which induces tumor progression, and causes resistance to treatment. Hypoxic tumor cells exploit auto- and mitophagy to facilitate metabolism and mitochondrial renewal. Azithromycin (AZM), a widely used macrolide, inhibits autophagy in cancer cells. The aim of the present study was to determine whether AZM targeted hypoxic cancer cells by inhibiting mitophagy. Lung cancer cell lines (A549, H1299 and NCI-H441) were cultured for up to 72 h under normoxic (20% O2) or hypoxic (0.3% O2) conditions in the presence or absence of AZM (≤25 µM), and the cell survival, autophagy flux and mitophagy flux were evaluated. AZM treatment reduced cell survival under hypoxic conditions, caused mitolysosome dysfunction with raised lysosomal pH and impaired the efficient removal of hypoxia-damaged mitochondria, eventually inducing apoptosis in the cancer cells. The cytotoxic effect of AZM under hypoxic conditions was abolished in mitochondria-deficient A549 cells (ρ° cells). The present study demonstrated that AZM reduced lung cancer cell survival under hypoxic conditions by interfering with the efficient removal of damaged mitochondria through mitophagy inhibition. Thus, AZM may be considered as a promising anticancer drug that targets the mitochondrial vulnerability of hypoxic lung cancer cells.

Keywords:  AZM; TME; autophagy; hypoxia; mitophagy

DOI:  https://doi.org/10.3892/ol.2023.14146
Aging Cell. 2023 Nov 29. e14042

BNIP3 as a new tool to promote healthy brain aging.

Kit Neikirk, Andrea G Marshall, Monica M Santisteban, Antentor Hinton.

  The article "Neuronal induction of BNIP3-mediated mitophagy slows systemic aging in Drosophila" reveals BCL2-interacting protein 3 as a therapeutic target to counteract brain aging and prolong overall organismal health with age. In this spotlight, we consider the roles of BNIP3, a mitochondrial outer membrane protein, in the adult nervous system, including its induction of mitophagy and prevention of dysfunctional mitochondria in the aged brain. Implications for other tissue types to reduce the burden of aging are further considered.

Keywords:  BNIP3; age-related pathology; aging; mitochondria; neuronal

DOI:  https://doi.org/10.1111/acel.14042
J Pharm Anal. 2023 Oct;13(10): 1168-1182

Histone deacetylase inhibitor pracinostat suppresses colorectal cancer by inducing CDK5-Drp1 signaling-mediated peripheral mitofission.

Xiao-Ling Liang, Lan Ouyang, Nan-Nan Yu, Zheng-Hua Sun, Zi-Kang Gui, Yu-Long Niu, Qing-Yu He, Jing Zhang, Yang Wang.

  Divisions at the periphery and midzone of mitochondria are two fission signatures that determine the fate of mitochondria and cells. Pharmacological induction of excessively asymmetric mitofission-associated cell death (MFAD) by switching the scission position from the mitochondrial midzone to the periphery represents a promising strategy for anticancer therapy. By screening a series of pan-inhibitors, we identified pracinostat, a pan-histone deacetylase (HDAC) inhibitor, as a novel MFAD inducer, that exhibited a significant anticancer effect on colorectal cancer (CRC) in vivo and in vitro. Pracinostat increased the expression of cyclin-dependent kinase 5 (CDK5) and induced its acetylation at residue lysine 33, accelerating the formation of complex CDK5/CDK5 regulatory subunit 1 and dynamin-related protein 1 (Drp1)-mediated mitochondrial peripheral fission. CRC cells with high level of CDK5 (CDK5-high) displayed midzone mitochondrial division that was associated with oncogenic phenotype, but treatment with pracinostat led to a lethal increase in the already-elevated level of CDK5 in the CRC cells. Mechanistically, pracinostat switched the scission position from the mitochondrial midzone to the periphery by improving the binding of Drp1 from mitochondrial fission factor (MFF) to mitochondrial fission 1 protein (FIS1). Thus, our results revealed the anticancer mechanism of HDACi pracinostat in CRC via activating CDK5-Drp1 signaling to cause selective MFAD of those CDK5-high tumor cells, which implicates a new paradigm to develop potential therapeutic strategies for CRC treatment.

Keywords:  Acetylation; CDK5; Drp1; HDAC inhibitor; Mitochondrial fission; Pracinostat

DOI:  https://doi.org/10.1016/j.jpha.2023.06.005
Autophagy. 2023 Nov 29.

CARM1 drives mitophagy and autophagy flux during fasting-induced skeletal muscle atrophy.

Derek W Stouth, Tiffany L vanLieshout, Andrew I Mikhail, Sean Y Ng, Rozhin Raziee, Brittany A Edgett, Goutham Vasam, Erin K Webb, Kevin S Gilotra, Matthew Markou, Hannah C Pineda, Brianna G Bettencourt-Mora, Haleema Noor, Zachary Moll, Megan E Bittner, Brendon J Gurd, Keir J Menzies, Vladimir Ljubicic.

  CARM1 (coactivator associated arginine methyltransferase 1) has recently emerged as a powerful regulator of skeletal muscle biology. However, the molecular mechanisms by which the methyltransferase remodels muscle remain to be fully understood. In this study, carm1 skeletal muscle-specific knockout (mKO) mice exhibited lower muscle mass with dysregulated macroautophagic/autophagic and atrophic signaling, including depressed AMP-activated protein kinase (AMPK) site-specific phosphorylation of ULK1 (unc-51 like autophagy activating kinase 1; Ser555) and FOXO3 (forkhead box O3; Ser588), as well as MTOR (mechanistic target of rapamycin kinase)-induced inhibition of ULK1 (Ser757), along with AKT/protein kinase B site-specific suppression of FOXO1 (Ser256) and FOXO3 (Ser253). In addition to lower mitophagy and autophagy flux in skeletal muscle, carm1 mKO led to increased mitochondrial PRKN/parkin accumulation, which suggests that CARM1 is required for basal mitochondrial turnover and autophagic clearance. carm1 deletion also elicited PPARGC1A (PPARG coactivator 1 alpha) activity and a slower, more oxidative muscle phenotype. As such, these carm1 mKO-evoked adaptations disrupted mitophagy and autophagy induction during food deprivation and collectively served to mitigate fasting-induced muscle atrophy. Furthermore, at the threshold of muscle atrophy during food deprivation experiments in humans, skeletal muscle CARM1 activity decreased similarly to our observations in mice, and was accompanied by site-specific activation of ULK1 (Ser757), highlighting the translational impact of the methyltransferase in human skeletal muscle. Taken together, our results indicate that CARM1 governs mitophagic, autophagic, and atrophic processes fundamental to the maintenance and remodeling of muscle mass. Targeting the enzyme may provide new therapeutic approaches for mitigating skeletal muscle atrophy.

Keywords:  Atrophy; autophagy; coactivator-associated arginine methyltransferase 1; fasting; mitophagy; skeletal muscle

DOI:  https://doi.org/10.1080/15548627.2023.2288528
PLoS Negl Trop Dis. 2023 Nov 27. 17(11): e0010751

Mitochondrial protein BNIP3 regulates Chikungunya virus replication in the early stages of infection.

Liliana Echavarria-Consuegra, Nilima Dinesh Kumar, Marleen van der Laan, Mario Mauthe, Denise Van de Pol, Fulvio Reggiori, Jolanda M Smit.

Chikungunya virus (CHIKV) is a human pathogen causing outbreaks of febrile illness for which vaccines and specific treatments remain unavailable. Autophagy-related (ATG) proteins and autophagy receptors are a set of host factors that participate in autophagy, but have also shown to function in other unrelated cellular pathways. Although autophagy is reported to both inhibit and enhance CHIKV replication, the specific role of individual ATG proteins remains largely unknown. Here, a siRNA screen was performed to evaluate the importance of the ATG proteome and autophagy receptors in controlling CHIKV infection. We observed that 7 out of 50 ATG proteins impact the replication of CHIKV. Among those, depletion of the mitochondrial protein and autophagy receptor BCL2 Interacting Protein 3 (BNIP3) increased CHIKV infection. Interestingly, BNIP3 controls CHIKV independently of autophagy and cell death. Detailed analysis of the CHIKV viral cycle revealed that BNIP3 interferes with the early stages of infection. Moreover, the antiviral role of BNIP3 was found conserved across two distinct CHIKV genotypes and the closely related Semliki Forest virus. Altogether, this study describes a novel and previously unknown function of the mitochondrial protein BNIP3 in the control of the early stages of the alphavirus viral cycle.

DOI: https://doi.org/10.1371/journal.pntd.0010751
PLoS One. 2023 ;18(11): e0294700

Regular exercise attenuates alcoholic myopathy in zebrafish by modulating mitochondrial homeostasis.

Wei Wen, Cheng Guo, Zhanglin Chen, Dong Yang, Danting Zhu, Quwen Jing, Lan Zheng, Chenchen Sun, Changfa Tang.

Alcoholic myopathy is caused by chronic consumption of alcohol (ethanol) and is characterized by weakness and atrophy of skeletal muscle. Regular exercise is one of the important ways to prevent or alleviate skeletal muscle myopathy. However, the beneficial effects and the exact mechanisms underlying regular exercise on alcohol myopathy remain unclear. In this study, a model of alcoholic myopathy was established using zebrafish soaked in 0.5% ethanol. Additionally, these zebrafish were intervened to swim for 8 weeks at an exercise intensity of 30% of the absolute critical swimming speed (Ucrit), aiming to explore the beneficial effects and underlying mechanisms of regular exercise on alcoholic myopathy. This study found that regular exercise inhibited protein degradation, improved locomotion ability, and increased muscle fiber cross-sectional area (CSA) in ethanol-treated zebrafish. In addition, regular exercise increases the functional activity of mitochondrial respiratory chain (MRC) complexes and upregulates the expression levels of MRC complexes. Regular exercise can also improve oxidative stress and mitochondrial dynamics in zebrafish skeletal muscle induced by ethanol. Additionally, regular exercise can activate mitochondrial biogenesis and inhibit mitochondrial unfolded protein response (UPRmt). Together, our results suggest regular exercise is an effective intervention strategy to improve mitochondrial homeostasis to attenuate alcoholic myopathy.

DOI: https://doi.org/10.1371/journal.pone.0294700
Biochim Biophys Acta Mol Cell Biol Lipids. 2023 Nov 27. pii: S1388-1981(23)00152-X. [Epub ahead of print] 159428

Palmitic acid activates NLRP3 inflammasome through NF-κB and AMPK-mitophagy-ROS pathways to induce IL-1β production in large yellow croaker (Larimichthys crocea).

Xueshan Li, Kangsen Mai, Qinghui Ai.

  Studies on marine fish showed that vegetable oils substituted for excessive fish oil increased interleukin-1β (IL-1β) production. However, whether the nucleotide-binding oligomerization domain, leucine-rich repeat-containing family, pyrin domain-containing-3 (NLRP3) inflammasome has a substantial role in fatty acid-induced IL-1β production in fish remains unclear. The associated specific mechanism is also unknown. In this study, nlrp3, caspase-1 and apoptosis-associated speck-like protein containing a CARD (asc) were successfully cloned, and NLRP3 inflammasome consisted of NLRP3, caspase-1 and ASC in large yellow croaker. Primary hepatocytes of fish incubated with palmitic acid (PA) exhibited the highest expression of pro-inflammatory genes (il-1β and tnfα) and NLRP3 inflammasome related genes (nlrp3, caspase-1 and asc), caspase-1 activity and IL-1β production among different treatments. Furthermore, PA-induced NLRP3 inflammasome activation was confirmed to require two signals: the first signal was that PA promoted the NF-κB (P65) protein into the nucleus, and NF-κB increased NLRP3 promoter activity and nlrp3 transcription. The second signal was that PA inhibited AMPK phosphorylation and decreased mitophagy by inhibiting the expression of PINK and parkin proteins, thereby damaging the mitochondria that could not be effectively cleared. Mitochondrial damage generated excessive amounts of reactive oxygen species, which activated the NLRP3 inflammasome and then induced caspase-1 activity and IL-1β production. Therefore, excessive dietary PA activated NLRP3 inflammasome through NF-κB and AMPK-mitophagy-ROS pathways to induce IL-1β production, thereby leading to inflammation in fish.

Keywords:  IL-1β; Inflammatory response; Large yellow croaker; NLRP3 inflammasome; Palmitic acid

DOI:  https://doi.org/10.1016/j.bbalip.2023.159428
Mol Biol Cell. 2023 Nov 29. mbcE23110427

Effects of phosphorylation on Drp1 activation by its receptors, actin, and cardiolipin.

Ao Liu, Anna L Hatch, Henry N Higgs.

Drp1 is a dynamin family GTPase required for mitochondrial and peroxisomal division. Oligomerization increases Drp1 GTPase activity through interactions between neighboring GTPase domains. In cells, Drp1 is regulated by several factors including Drp1 receptors, actin filaments, cardiolipin, and phosphorylation at two sites: S579 and S600. Commonly, phosphorylation of S579 is considered activating, while S600 phosphorylation is considered inhibiting. However, direct effects of phosphorylation on Drp1 GTPase activity have not been investigated in detail. Here, we compare effects of S579 and S600 phosphorylation on purified Drp1, using phospho-mimetic mutants and in vitro phosphorylation. Both phospho-mimetic mutants are shifted toward smaller oligomers. Both phospho-mimetic mutations maintain basal GTPase activity, but eliminate GTPase stimulation by actin and decrease GTPase stimulation by cardiolipin, Mff, and MiD49. Phosphorylation of S579 by Erk2 produces similar effects. When mixed with wildtype Drp1, both S579D and S600D phospho-mimetic mutants reduce the actin-stimulated GTPase activity of Drp1-WT. Conversely, a Drp1 mutant (K38A) lacking GTPase activity stimulates Drp1-WT GTPase activity under both basal and actin-stimulated conditions. These results suggest that the effect of S579 phosphorylation is not to activate Drp1 directly. In addition, our results suggest that nearest neighbor interactions within the Drp1 oligomer affect catalytic activity.

DOI: https://doi.org/10.1091/mbc.E23-11-0427
Redox Rep. 2023 Dec;28(1): 2284517

Melittin kills A549 cells by targeting mitochondria and blocking mitophagy flux.

Xuan Li, Zheng Li, Yu-Qi Meng, Hui Qiao, Ke-Rong Zhai, Zhen-Qing Li, Shi-Lin Wei, Bin Li.

  Melittin, a naturally occurring polypeptide found in bee venom, has been recognized for its potential anti-tumor effects, particularly in the context of lung cancer. Our previous study focused on its impact on human lung adenocarcinoma cells A549, revealing that melittin induces intracellular reactive oxygen species (ROS) burst and oxidative damage, resulting in cell death. Considering the significant role of mitochondria in maintaining intracellular redox levels and ROS, we further examined the involvement of mitochondrial damage in melittin-induced apoptosis in lung cancer cells. Our findings demonstrated that melittin caused changes in mitochondrial membrane potential (MMP), triggered mitochondrial ROS burst (Figure 1), and activated the mitochondria-related apoptosis pathway Bax/Bcl-2 by directly targeting mitochondria in A549 cells (Figure 2). Further, we infected A549 cells using a lentivirus that can express melittin-Myc and confirmed that melittin can directly target binding to mitochondria, causing the biological effects described above (Figure 2). Notably, melittin induced mitochondrial damage while inhibiting autophagy, resulting in abnormal degradation of damaged mitochondria (Figure 5). To summarize, our study unveils that melittin targets mitochondria, causing mitochondrial damage, and inhibits the autophagy-lysosomal degradation pathway. This process triggers mitoROS burst and ultimately activates the mitochondria-associated Bax/Bcl-2 apoptotic signaling pathways in A549 cells.

Keywords:  A549 cells; Melittin; ROS; apoptosis; autophagy; mitochondria damage; mitophagy; mitophagy flux

DOI:  https://doi.org/10.1080/13510002.2023.2284517