bims-nenemi 2023-07-02 papers

bims-nenemi

Biomed News

on Neuroinflammation, neurodegeneration and mitochondria

Issue of 2023–07–02
seven papers selected by
Marco Tigano, Thomas Jefferson University

Single-cell multi-omics of mitochondrial DNA disorders reveals dynamics of purifying selection across human immune cells.
The unfolded protein response of the endoplasmic reticulum supports mitochondrial biogenesis by buffering non-imported proteins.
Ultrasound-responsive low-dose doxorubicin liposomes trigger mitochondrial DNA release and activate cGAS-STING-mediated antitumour immunity.
Acarbose suppresses symptoms of mitochondrial disease in a mouse model of Leigh syndrome.
Single-cell multiomic analyses sheds light on mitochondrial mutational selection.
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.
Aurora kinase A/AURKA functionally interacts with the mitochondrial ATP synthase to regulate energy metabolism and cell death.

Nat Genet. 2023 Jun 29.

Single-cell multi-omics of mitochondrial DNA disorders reveals dynamics of purifying selection across human immune cells.

Caleb A Lareau, Sonia M Dubois, Frank A Buquicchio, Yu-Hsin Hsieh, Kopal Garg, Pauline Kautz, Lena Nitsch, Samantha D Praktiknjo, Patrick Maschmeyer, Jeffrey M Verboon, Jacob C Gutierrez, Yajie Yin, Evgenij Fiskin, Wendy Luo, Eleni P Mimitou, Christoph Muus, Rhea Malhotra, Sumit Parikh, Mark D Fleming, Lena Oevermann, Johannes Schulte, Cornelia Eckert, Anshul Kundaje, Peter Smibert, Santosha A Vardhana, Ansuman T Satpathy, Aviv Regev, Vijay G Sankaran, Suneet Agarwal, Leif S Ludwig.

Pathogenic mutations in mitochondrial DNA (mtDNA) compromise cellular metabolism, contributing to cellular heterogeneity and disease. Diverse mutations are associated with diverse clinical phenotypes, suggesting distinct organ- and cell-type-specific metabolic vulnerabilities. Here we establish a multi-omics approach to quantify deletions in mtDNA alongside cell state features in single cells derived from six patients across the phenotypic spectrum of single large-scale mtDNA deletions (SLSMDs). By profiling 206,663 cells, we reveal the dynamics of pathogenic mtDNA deletion heteroplasmy consistent with purifying selection and distinct metabolic vulnerabilities across T-cell states in vivo and validate these observations in vitro. By extending analyses to hematopoietic and erythroid progenitors, we reveal mtDNA dynamics and cell-type-specific gene regulatory adaptations, demonstrating the context-dependence of perturbing mitochondrial genomic integrity. Collectively, we report pathogenic mtDNA heteroplasmy dynamics of individual blood and immune cells across lineages, demonstrating the power of single-cell multi-omics for revealing fundamental properties of mitochondrial genetics.

DOI: https://doi.org/10.1038/s41588-023-01433-8
Mol Biol Cell. 2023 Jun 28. mbcE23050205

The unfolded protein response of the endoplasmic reticulum supports mitochondrial biogenesis by buffering non-imported proteins.

Katharina Knöringer, Carina Groh, Lena Krämer, Kevin C Stein, Katja G Hansen, Jannik Zimmermann, Bruce Morgan, Johannes M Herrmann, Judith Frydman, Felix Boos.

Almost all mitochondrial proteins are synthesized in the cytosol and subsequently targeted to mitochondria. The accumulation of non-imported precursor proteins occurring upon mitochondrial dysfunction can challenge cellular protein homeostasis. Here we show that blocking protein translocation into mitochondria results in the accumulation of mitochondrial membrane proteins at the endoplasmic reticulum, thereby triggering the unfolded protein response (UPRER). Moreover, we find that mitochondrial membrane proteins are also routed to the ER under physiological conditions. The level of ER-resident mitochondrial precursors is enhanced by import defects as well as metabolic stimuli that increase the expression of mitochondrial proteins. Under such conditions, the UPRER is crucial to maintain protein homeostasis and cellular fitness. We propose the ER serves as a physiological buffer zone for those mitochondrial precursors that cannot be immediately imported into mitochondria while engaging the UPRER to adjust the ER proteostasis capacity to the extent of precursor accumulation.

DOI: https://doi.org/10.1091/mbc.E23-05-0205
Nat Commun. 2023 Jun 30. 14(1): 3877

Ultrasound-responsive low-dose doxorubicin liposomes trigger mitochondrial DNA release and activate cGAS-STING-mediated antitumour immunity.

Chaoyu Wang, Ruoshi Zhang, Jia He, Lvshan Yu, Xinyan Li, Junxia Zhang, Sai Li, Conggang Zhang, Jonathan C Kagan, Jeffrey M Karp, Rui Kuai.

DNA derived from chemotherapeutics-killed tumor cells is one of the most important damage-associated molecular patterns that can activate the cGAS-STING (cyclic GMP-AMP synthase-stimulator of interferon genes) pathway in antigen-presenting cells (APCs) and promote antitumor immunity. However, conventional chemotherapy displays limited tumor cell killing and ineffective transfer of stable tumor DNA to APCs. Here we show that liposomes loaded with an optimized ratio of indocyanine green and doxorubicin, denoted as LID, efficiently generate reactive oxygen species upon exposure to ultrasound. LID plus ultrasound enhance the nuclear delivery of doxorubicin, induce tumor mitochondrial DNA oxidation, and promote oxidized tumor mitochondrial DNA transfer to APCs for effective activation of cGAS-STING signaling. Depleting tumor mitochondrial DNA or knocking out STING in APCs compromises the activation of APCs. Furthermore, systemic injection of LID plus ultrasound over the tumor lead to targeted cytotoxicity and STING activation, eliciting potent antitumor T cell immunity, which upon the combination with immune checkpoint blockade leads to regression of bilateral MC38, CT26, and orthotopic 4T1 tumors in female mice. Our study sheds light on the importance of oxidized tumor mitochondrial DNA in STING-mediated antitumor immunity and may inspire the development of more effective strategies for cancer immunotherapy.

DOI: https://doi.org/10.1038/s41467-023-39607-x
Nat Metab. 2023 06;5(6): 955-967

Acarbose suppresses symptoms of mitochondrial disease in a mouse model of Leigh syndrome.

Alessandro Bitto, Anthony S Grillo, Takashi K Ito, Ian B Stanaway, Bao M G Nguyen, Kejun Ying, Herman Tung, Kaleb Smith, Ngoc Tran, Gunnar Velikanje, Silvan R Urfer, Jessica M Snyder, Jacob Barton, Ayush Sharma, Ernst-Bernhard Kayser, Lu Wang, Daniel L Smith, J Will Thompson, Laura DuBois, William DePaolo, Matt Kaeberlein.

Mitochondrial diseases represent a spectrum of disorders caused by impaired mitochondrial function, ranging in severity from mortality during infancy to progressive adult-onset disease. Mitochondrial dysfunction is also recognized as a molecular hallmark of the biological ageing process. Rapamycin, a drug that increases lifespan and health during normative ageing, also increases survival and reduces neurological symptoms in a mouse model of the severe mitochondrial disease Leigh syndrome. The Ndufs4 knockout (Ndufs4-/-) mouse lacks the complex I subunit NDUFS4 and shows rapid onset and progression of neurodegeneration mimicking patients with Leigh syndrome. Here we show that another drug that extends lifespan and delays normative ageing in mice, acarbose, also suppresses symptoms of disease and improves survival of Ndufs4-/- mice. Unlike rapamycin, acarbose rescues disease phenotypes independently of inhibition of the mechanistic target of rapamycin. Furthermore, rapamycin and acarbose have additive effects in delaying neurological symptoms and increasing maximum lifespan in Ndufs4-/- mice. We find that acarbose remodels the intestinal microbiome and alters the production of short-chain fatty acids. Supplementation with tributyrin, a source of butyric acid, recapitulates some effects of acarbose on lifespan and disease progression, while depletion of the endogenous microbiome in Ndufs4-/- mice appears to fully recapitulate the effects of acarbose on healthspan and lifespan in these animals. To our knowledge, this study provides the first evidence that alteration of the gut microbiome plays a significant role in severe mitochondrial disease and provides further support for the model that biological ageing and severe mitochondrial disorders share underlying common mechanisms.

DOI: https://doi.org/10.1038/s42255-023-00815-w
Nat Genet. 2023 Jun 29.

Single-cell multiomic analyses sheds light on mitochondrial mutational selection.

Sarah J Pickett, Gavin Hudson, Laura C Greaves.

DOI: https://doi.org/10.1038/s41588-023-01436-5
Biomedicines. 2023 May 30. pii: 1585. [Epub ahead of print]11(6):

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.

Panagiotis Keramidas, Eleni Papachristou, Rigini M Papi, Aglaia Mantsou, Theodora Choli-Papadopoulou.

  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 ORF3a 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, ATF4, CHOP, GADD34), has been clearly demonstrated. Furthermore, the overexpression of BAX and BH3-only pro-apoptotic protein PUMA, the upregulation of Bcl-2 family genes (BAX, BAK, BID, BAD), 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 NFκB, 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 ORF3a 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.

Keywords:  ER stress; GSK2606414; ORF3a; PERK; SARS-CoV-2; apoptosis; cytokine storm; inflammation; pyroptosis

DOI:  https://doi.org/10.3390/biomedicines11061585
Cell Death Discov. 2023 Jun 29. 9(1): 203

Aurora kinase A/AURKA functionally interacts with the mitochondrial ATP synthase to regulate energy metabolism and cell death.

Rakesh Kumar Sharma, Abderrahman Chafik, Giulia Bertolin.

Cancer cells often hijack metabolic pathways to obtain the energy required to sustain their proliferation. Understanding the molecular mechanisms underlying cancer cell metabolism is key to fine-tune the metabolic preference of specific tumors, and potentially offer new therapeutic strategies. Here, we show that the pharmacological inhibition of mitochondrial Complex V delays the cell cycle by arresting breast cancer cell models in the G0/G1 phase. Under these conditions, the abundance of the multifunctional protein Aurora kinase A/AURKA is specifically lowered. We then demonstrate that AURKA functionally interacts with the mitochondrial Complex V core subunits ATP5F1A and ATP5F1B. Altering the AURKA/ATP5F1A/ATP5F1B nexus is sufficient to trigger G0/G1 arrest, and this is accompanied by decreased glycolysis and mitochondrial respiration rates. Last, we discover that the roles of the AURKA/ATP5F1A/ATP5F1B nexus depend on the specific metabolic propensity of triple-negative breast cancer cell lines, where they correlate with cell fate. On one hand, the nexus induces G0/G1 arrest in cells relying on oxidative phosphorylation as the main source of energy. On the other hand, it allows to bypass cell cycle arrest and it triggers cell death in cells with a glycolytic metabolism. Altogether, we provide evidence that AURKA and mitochondrial Complex V subunits cooperate to maintain cell metabolism in breast cancer cells. Our work paves the way to novel anti-cancer therapies targeting the AURKA/ATP5F1A/ATP5F1B nexus to lower cancer cell metabolism and proliferation.

DOI: https://doi.org/10.1038/s41420-023-01501-2