bims-mikwok 2023-11-19 papers

Cell Death Dis. 2023 11 11. 14(11): 735

Integration of FUNDC1-associated mitochondrial protein import and mitochondrial quality control contributes to TDP-43 degradation.

Jinfa Ma, Lei Liu, Lu Song, Jianghong Liu, Lingyao Yang, Quan Chen, Jane Y Wu, Li Zhu.

Though TDP-43 protein can be translocated into mitochondria and causes mitochondrial damage in TDP-43 proteinopathy, little is known about how TDP-43 is imported into mitochondria. In addition, whether mitochondrial damage is caused by mitochondrial mislocalization of TDP-43 or a side effect of mitochondria-mediated TDP-43 degradation remains to be investigated. Here, our bioinformatical analyses reveal that mitophagy receptor gene FUNDC1 is co-expressed with TDP-43, and both TDP-43 and FUNDC1 expression is correlated with genes associated with mitochondrial protein import pathway in brain samples of patients diagnosed with TDP-43 proteinopathy. FUNDC1 promotes mitochondrial translocation of TDP-43 possibly by promoting TDP-43-TOM70 and DNAJA2-TOM70 interactions, which is independent of the LC3 interacting region of FUNDC1 in cellular experiments. In the transgenic fly model of TDP-43 proteinopathy, overexpressing FUNDC1 enhances TDP-43 induced mitochondrial damage, whereas down-regulating FUNDC1 reverses TDP-43 induced mitochondrial damage. FUNDC1 regulates mitochondria-mediated TDP-43 degradation not only by regulating mitochondrial TDP-43 import, but also by increasing LONP1 level and by activating mitophagy, which plays important roles in cytosolic TDP-43 clearance. Together, this study not only uncovers the mechanism of mitochondrial TDP-43 import, but also unravels the active role played by mitochondria in regulating TDP-43 homeostasis.

DOI: https://doi.org/10.1038/s41419-023-06261-6

Int J Mol Sci. 2023 Oct 31. pii: 15788. [Epub ahead of print]24(21):

Therapeutic Effects of Mesenchymal Stromal Cells Require Mitochondrial Transfer and Quality Control.

Avinash Naraiah Mukkala, Mirjana Jerkic, Zahra Khan, Katalin Szaszi, Andras Kapus, Ori Rotstein.

Due to their beneficial effects in an array of diseases, Mesenchymal Stromal Cells (MSCs) have been the focus of intense preclinical research and clinical implementation for decades. MSCs have multilineage differentiation capacity, support hematopoiesis, secrete pro-regenerative factors and exert immunoregulatory functions promoting homeostasis and the resolution of injury/inflammation. The main effects of MSCs include modulation of immune cells (macrophages, neutrophils, and lymphocytes), secretion of antimicrobial peptides, and transfer of mitochondria (Mt) to injured cells. These actions can be enhanced by priming (i.e., licensing) MSCs prior to exposure to deleterious microenvironments. Preclinical evidence suggests that MSCs can exert therapeutic effects in a variety of pathological states, including cardiac, respiratory, hepatic, renal, and neurological diseases. One of the key emerging beneficial actions of MSCs is the improvement of mitochondrial functions in the injured tissues by enhancing mitochondrial quality control (MQC). Recent advances in the understanding of cellular MQC, including mitochondrial biogenesis, mitophagy, fission, and fusion, helped uncover how MSCs enhance these processes. Specifically, MSCs have been suggested to regulate peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α)-dependent biogenesis, Parkin-dependent mitophagy, and Mitofusins (Mfn1/2) or Dynamin Related Protein-1 (Drp1)-mediated fission/fusion. In addition, previous studies also verified mitochondrial transfer from MSCs through tunneling nanotubes and via microvesicular transport. Combined, these effects improve mitochondrial functions, thereby contributing to the resolution of injury and inflammation. Thus, uncovering how MSCs affect MQC opens new therapeutic avenues for organ injury, and the transplantation of MSC-derived mitochondria to injured tissues might represent an attractive new therapeutic approach.

Keywords: cell treatment; injury resolution; microvesicles; mitochondria; mitochondrial transfer

DOI: https://doi.org/10.3390/ijms242115788

Food Chem Toxicol. 2023 Nov 13. pii: S0278-6915(23)00592-6. [Epub ahead of print] 114190

Study of ATF4/CHOP axis-mediated mitochondrial unfolded protein response in neuronal apoptosis induced by methylmercury.

Si Xu, Haihui Liu, Chen Wang, Yu Deng, Bin Xu, Tianyao Yang, Wei Liu.

Methylmercury (MeHg) is a widely distributed environmental pollutant that can easily cross the blood-brain barrier and accumulate in the brain, thereby damaging the central nervous system. Studies have shown that MeHg-induced mitochondrial damage and apoptosis play a crucial role in its neurotoxic effects. Mitochondrial unfolded protein response (UPRmt) is indispensable to maintain mitochondrial protein homeostasis and ensure mitochondrial function, and the ATF4/CHOP axis is one of the signaling pathways to activate UPRmt. In this study, the role of the ATF4/CHOP axis-mediated UPRmt in the neurotoxicity of MeHg has been investigated by C57BL/6 mice and the HT22 cell line. We discovered that mice exposed to MeHg had abnormal neurobehavioral patterns. The pathological section showed a significant decrease in the number of neurons. MeHg also resulted in a reduction in mtDNA copy number and mitochondrial membrane potential (MMP). Additionally, the ATF4/CHOP axis and UPRmt were found to be significantly activated. Subsequently, we used siRNA to knock down ATF4 or CHOP and observed that the expression of UPRmt-related proteins and the apoptosis rate were significantly reduced. Our research showed that exposure to MeHg can over-activate the UPRmt through the ATF4/CHOP axis, leading to mitochondrial damage and ultimately inducing neuronal apoptosis.

Keywords: ATF4; Apoptosis; CHOP; Methylmercury; Neurotoxicity; UPR(mt)

DOI: https://doi.org/10.1016/j.fct.2023.114190

PNAS Nexus. 2023 Nov;2(11): pgad336

Aberrant mitochondrial dynamics contributes to diaphragmatic weakness induced by mechanical ventilation.

Haikel Dridi, Marc Yehya, Robert Barsotti, Yang Liu, Steven Reiken, Lan Azria, Qi Yuan, Laith Bahlouli, Rajesh Kumar Soni, Andrew R Marks, Alain Lacampagne, Stefan Matecki.

In critical care patients, the ""temporary inactivity of the diaphragm caused by mechanical ventilation (MV) triggers a series of events leading to diaphragmatic dysfunction and atrophy, commonly known as ventilator-induced diaphragm dysfunction (VIDD). While mitochondrial dysfunction related to oxidative stress is recognized as a crucial factor in VIDD, the exact molecular mechanism remains poorly understood. In this study, we observe that 6 h of MV triggers aberrant mitochondrial dynamics, resulting in a reduction in mitochondrial size and interaction, associated with increased expression of dynamin-related protein 1 (DRP1). This effect can be prevented by P110, a molecule that inhibits the recruitment of DRP1 to the mitochondrial membrane. Furthermore, isolated mitochondria from the diaphragms of ventilated patients exhibited increased production of reactive oxygen species (ROS). These mitochondrial changes were associated with the rapid oxidation of type 1 ryanodine receptor (RyR1) and a decrease in the stabilizing subunit calstabin 1. Subsequently, we observed that the sarcoplasmic reticulum (SR) in the ventilated diaphragms showed increased calcium leakage and reduced contractile function. Importantly, the mitochondrial fission inhibitor P110 effectively prevented all of these alterations. Taken together, the results of our study illustrate that MV leads, in the diaphragm, to both mitochondrial fragmentation and dysfunction, linked to the up-/down-regulation of 320 proteins, as assessed through global comprehensive quantitative proteomics analysis, primarily associated with mitochondrial function. These outcomes underscore the significance of developing compounds aimed at modulating the balance between mitochondrial fission and fusion as potential interventions to mitigate VIDD in human patients.

Keywords: FIS1 inhibitor; calcium homeostasis; dynamin-related protein 1; mitochondrial fission

DOI: https://doi.org/10.1093/pnasnexus/pgad336

Mol Cell Endocrinol. 2023 Nov 11. pii: S0303-7207(23)00260-5. [Epub ahead of print] 112109

Activation of mitophagy improves cognitive dysfunction in diabetic mice with recurrent non-severe hypoglycemia.

Kejun Wu, Cuihua Huang, Wenrong Zheng, Yubin Wu, Qintao Huang, Menghua Lin, Ruonan Gao, Liqin Qi, Guanlian He, Xiaoying Liu, Xiaohong Liu, Linxi Wang, Zhou Chen, Libin Liu.

Recurrent non-severe hypoglycemia (RH) in patients with diabetes might be associated with cognitive impairment. Previously, we found that mitochondrial dysfunction plays an important role in this pathological process; however, the mechanism remains unclear. The objective of this study was to determine the molecular mechanisms of mitochondrial damage associated with RH in diabetes mellitus (DM). We found that RH is associated with reduced hippocampal mitophagy in diabetic mice, mainly manifested by reduced autophagosome formation and impaired recognition of impaired mitochondria, mediated by the PINK1/Parkin pathway. The same impaired mitophagy initiation was observed in an in vitro high-glucose cultured astrocyte model with recurrent low-glucose interventions. Promoting autophagosome formation and activating PINK1/Parkin-mediated mitophagy protected mitochondrial function and cognitive function in mice. The results showed that impaired mitophagy is involved in the occurrence of mitochondrial dysfunction, mediating the neurological impairment associated with recurrent low glucose under high glucose conditions.

Keywords: Astrocyte; Cognitive impairment; Diabetes; Mitophagy; Recurrent non-severe hypoglycemia

DOI: https://doi.org/10.1016/j.mce.2023.112109