bims-mikwok 2023-02-05 papers

Issue of 2023‒02‒05
five papers selected by
Avinash N. Mukkala
University of Toronto

Sci Signal. 2023 Jan 31. 16(770): eabo4457

Deciphering functional roles and interplay between Beclin1 and Beclin2 in autophagosome formation and mitophagy.

Justin M Quiles, Rita H Najor, Eileen Gonzalez, Monica Jeung, Wenjing Liang, Sarah M Burbach, Erika A Zumaya, Rachel Y Diao, Mark A Lampert, Åsa B Gustafsson.

The degradation of macromolecules and organelles by the process of autophagy is critical for cellular homeostasis and is often compromised during aging and disease. Beclin1 and Beclin2 are implicated in autophagy induction, and these homologs share a high degree of amino acid sequence similarity but have divergent N-terminal regions. Here, we investigated the functions of the Beclin homologs in regulating autophagy and mitophagy, a specialized form of autophagy that targets mitochondria. Both Beclin homologs contributed to autophagosome formation, but a mechanism of autophagosome formation independent of either Beclin homolog occurred in response to starvation or mitochondrial damage. Mitophagy was compromised only in Beclin1-deficient HeLa cells and mouse embryonic fibroblasts because of defective autophagosomal engulfment of mitochondria, and the function of Beclin1 in mitophagy required the phosphorylation of the conserved Ser15 residue by the kinase Ulk1. Mitochondria-ER-associated membranes (MAMs) are important sites of autophagosome formation during mitophagy, and Beclin1, but not Beclin2 or a Beclin1 mutant that could not be phosphorylated at Ser15, localized to MAMs during mitophagy. Our findings establish a regulatory role for Beclin1 in selective mitophagy by initiating autophagosome formation adjacent to mitochondria, a function facilitated by Ulk1-mediated phosphorylation of Ser15 in its distinct N-terminal region.

DOI: https://doi.org/10.1126/scisignal.abo4457

Autophagy. 2023 Feb 01. 1-3

Metabolic function of autophagy is essential for cell survival.

Lucia Sedlackova, Tetsushi Kataura, Sovan Sarkar, Viktor I Korolchuk.

Age-related human pathologies present with a multitude of molecular and metabolic phenotypes, which individually or synergistically contribute to tissue degeneration. However, current lack of understanding of the interdependence of these molecular pathologies limits the potential range of existing therapeutic intervention strategies. In our study, we set out to understand the chain of molecular events, which underlie the loss of cellular viability in macroautophagy/autophagy deficiency associated with aging and age-related disease. We discover a novel axis linking autophagy, a cellular waste disposal pathway, and a metabolite, nicotinamide adenine dinucleotide (NAD). The axis connects multiple organelles, molecules and stress response pathways mediating cellular demise when autophagy becomes dysfunctional. By elucidating the steps on the path from efficient mitochondrial recycling to NAD maintenance and ultimately cell viability, we highlight targets potentially receptive to therapeutic interventions in a range of genetic and age-related diseases associated with autophagy dysfunction.Abbreviations: IMM: inner mitochondrial membrane; NAD: nicotinamide dinucleotide; OXPHOS: oxidative phosphorylation; PARP: poly(ADP-ribose) polymerase; ROS: reactive oxygen species.

Keywords: Aging; DNA damage; NAD; PARP; ROS; autophagy; mitochondria; mitophagy; sirtuins

DOI: https://doi.org/10.1080/15548627.2023.2165753

Animal Model Exp Med. 2023 Feb 03.

Mitochondrial transplantation ameliorates hippocampal damage following status epilepticus.

Xiaoxia Jia, Qinghua Wang, Jianlun Ji, Wenchun Lu, Zhidong Liu, Hao Tian, Lin Guo, Yun Wang.

BACKGROUND: Hippocampal damage caused by status epilepticus (SE) can bring about cognitive decline and emotional disorders, which are common clinical comorbidities in patients with epilepsy. It is therefore imperative to develop a novel therapeutic strategy for protecting hippocampal damage after SE. Mitochondrial dysfunction is one of contributing factors in epilepsy. Given the therapeutic benefits of mitochondrial replenishment by exogenous mitochondria, we hypothesized that transplantation of mitochondria would be capable of ameliorating hippocampal damage following SE.METHODS: Pilocarpine was used to induced SE in mice. SE-generated cognitive decline and emotional disorders were determined using novel object recognition, the tail suspension test, and the open field test. SE-induced hippocampal pathology was assessed by quantifying loss of neurons and activation of microglia and astrocytes. The metabolites underlying mitochondrial transplantation were determined using metabonomics.
RESULTS: The results showed that peripheral administration of isolated mitochondria could improve cognitive deficits and depressive and anxiety-like behaviors. Exogenous mitochondria blunted the production of reactive oxygen species, proliferation of microglia and astrocytes, and loss of neurons in the hippocampus. The metabonomic profiles showed that mitochondrial transplantation altered multiple metabolic pathways such as sphingolipid signaling pathway and carbon metabolism. Among potential affected metabolites, mitochondrial transplantation decreased levels of sphingolipid (d18:1/18:0) and methylmalonic acid, and elevated levels of D-fructose-1,6-bisphosphate.
CONCLUSION: To the best of our knowledge, these findings provide the first direct experimental evidence that artificial mitochondrial transplantation is capable of ameliorating hippocampal damage following SE. These new findings support mitochondrial transplantation as a promising therapeutic strategy for epilepsy-associated psychiatric and cognitive disorders.

Keywords: cognitive deficit; emotional disorders; hippocampal damage; mitochondrial transplantation; status epilepticus

DOI: https://doi.org/10.1002/ame2.12310

Antioxid Redox Signal. 2023 Feb 03.

T cell Nrf2/Keap1 gene editing using CRISPR/Cas9 and experimental kidney ischemia-reperfusion injury.

Johanna Thea Kurzhagen, Sanjeev Noel, Kyungho Lee, Mohanraj Sadasivam, Sepideh Gharaie, Aparna Ankireddy, Sul A Lee, Andrea Newman-Rivera, Jing Gong, Lois J Arend, Abdel R A Hamad, Sekhar P Reddy, Hamid Rabb.

AIMS: T cells play pathophysiologic roles in kidney ischemia reperfusion injury (IRI) and the Nrf2/Keap1 pathway regulates T cell responses. We hypothesized that CRISPR/Cas9 mediated Keap1-knock out (KO) augments Nrf2 antioxidant potential of CD4+ T cells and that Keap1-KO CD4+ T cell immunotherapy protects from kidney IRI.RESULTS: CD4+ T cell Keap1-KO resulted in significant increase of Nrf2 target genes Nqo1, Hmox1, Gclc and Gclm. Keap1-KO cells displayed no signs of exhaustion and had significantly lower levels of IL2 and IL6 in normoxic conditions, but increased IFNγ in hypoxic conditions in vitro. In vivo, adoptive transfer of Keap1-KO CD4+ T cells prior to IRI improved kidney function in T cell deficient nu/nu mice compared to mice receiving unedited control CD4+ T cells. Keap1-KO CD4+ T cells isolated from recipient kidneys 24h post ischemia reperfusion (IR) were less activated compared to unedited CD4+ T cells, isolated from control kidneys.
INNOVATION: Editing Nrf2/Keap1 pathway in murine T cells using CRISPR/Cas9 is an innovative and promising immunotherapy approach for kidney IRI and possibly other solid organ IRI.
CONCLUSION: CRISPR/Cas9 mediated Keap1-KO increased Nrf2 regulated antioxidant gene expression in murine CD4+ T cells, modified responses to in vitro hypoxia and in vivo kidney IRI. Gene editing targeting the Nrf2/Keap1 pathway in T cells is a promising approach for immune-mediated kidney diseases.

DOI: https://doi.org/10.1089/ars.2022.0058

J Clin Invest. 2023 Feb 01. pii: e162940. [Epub ahead of print]133(3):

Neutrophil CEACAM1 determines susceptibility to NETosis by regulating the S1PR2/S1PR3 axis in liver transplantation.

Hirofumi Hirao, Hidenobu Kojima, Kenneth J Dery, Kojiro Nakamura, Kentaro Kadono, Yuan Zhai, Douglas G Farmer, Fady M Kaldas, Jerzy W Kupiec-Weglinski.

Neutrophils, the largest innate immune cell population in humans, are the primary proinflammatory sentinel in the ischemia-reperfusion injury (IRI) mechanism in orthotopic liver transplantation (OLT). Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, CC1, or CD66a) is essential in neutrophil activation and serves as a checkpoint regulator of innate immune-driven IRI cascade in OLT. Although CC1 alternative splicing generates two functionally distinct short and long cytoplasmic isoforms, their role in neutrophil activation remains unknown. Here, we undertook molecular and functional studies to interrogate the significance of neutrophil CC1 signaling in mouse and human OLT recipients. In the experimental arm, we employed a mouse OLT model to document that ablation of recipient-derived neutrophil CC1-long (CC1-L) isotype aggravated hepatic IRI by promoting neutrophil extracellular traps (NETs). Notably, by regulating the S1P-S1PR2/S1PR3 axis, neutrophil CC1-L determined susceptibility to NET formation via autophagy signaling. In the clinical arm, liver grafts from 55 transplant patients selectively enriched for neutrophil CC1-L showed relative resistance to ischemia-reperfusion (IR) stress/tissue damage, improved hepatocellular function, and clinical outcomes. In conclusion, despite neutrophils being considered a principal villain in peritransplant tissue injury, their CC1-L isoform may serve as a regulator of IR stress resistance/NETosis in human and mouse OLT recipients.

Keywords: Hypoxia; Neutrophils; Organ transplantation; Transplantation

DOI: https://doi.org/10.1172/JCI162940