This content will become publicly available on October 8, 2025
- Award ID(s):
- 2327631
- PAR ID:
- 10552252
- Publisher / Repository:
- Biochemical Society Transactions
- Date Published:
- Journal Name:
- Biochemical Society Transactions
- ISSN:
- 0300-5127
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
null (Ed.)Selective autolysosomal degradation of damaged mitochondria, also called mitophagy, is an indispensable process for maintaining integrity and homeostasis of mitochondria. One well-established mechanism mediating selective removal of mitochondria under relatively mild mitochondria-depolarizing stress is PINK1-Parkin-mediated or ubiquitin-dependent mitophagy. However, additional mechanisms such as LC3-mediated or ubiquitin-independent mitophagy induction by heavy environmental stress exist and remain poorly understood. The present study unravels a novel role of stress-inducible protein Sestrin2 in degradation of mitochondria damaged by transition metal stress. By utilizing proteomic methods and studies in cell culture and rodent models, we identify autophagy kinase ULK1-mediated phosphorylation sites of Sestrin2 and demonstrate Sestrin2 association with mitochondria adaptor proteins in HEK293 cells. We show that Ser-73 and Ser-254 residues of Sestrin2 are phosphorylated by ULK1, and a pool of Sestrin2 is strongly associated with mitochondrial ATP5A in response to Cu-induced oxidative stress. Subsequently, this interaction promotes association with LC3-coated autolysosomes to induce degradation of mitochondria damaged by Cu-induced ROS. Treatment of cells with antioxidants or a Cu chelator significantly reduces Sestrin2 association with mitochondria. These results highlight the ULK1-Sestrin2 pathway as a novel stress-sensing mechanism that can rapidly induce autophagic degradation of mitochondria under severe heavy metal stress.more » « less
-
Abstract Mitochondrial DNA (mtDNA) is indispensable for mitochondrial function and is maintained by DNA repair, turnover, mitochondrial dynamics and mitophagy, along with the inherent redundancy of mtDNA. Base excision repair (BER) is a major DNA repair mechanism in mammalian mitochondria. Mitochondrial BER enzymes are implicated in mtDNA-mediated immune response and inflammation. mtDNA is organized into mitochondrial nucleoids by mitochondrial transcription factor A (TFAM). The regulation of DNA repair activities by TFAM-DNA interactions remains understudied. Here, we demonstrate the modulation of DNA repair enzymes by TFAM concentrations, DNA sequences and DNA modifications. Unlike previously reported inhibitory effects, we observed that human uracil-DNA glycosylase 1 (UNG1) and AP endonuclease I (APE1) have optimal activities at specific TFAM/DNA molar ratios. High TFAM/DNA ratios inhibited other enzymes, OGG1 and AAG. In addition, TFAM reduces the accumulation of certain repair intermediates. Molecular dynamics simulations and DNA-binding experiments demonstrate that the presence of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) in certain sequence motifs enhances TFAM-DNA binding, partially explaining the inhibition of OGG1 activity. Bioinformatic analysis of published 8-oxodG, dU, and TFAM-footprint maps reveals a correlation between 8-oxodG and TFAM locations in mtDNA. Collectively, these results highlight the complex regulation of mtDNA repair by DNA sequence, TFAM concentrations, lesions and repair enzymes.
-
Beard, D (Ed.)Neurons rely on localized mitochondria to fulfill spatially heterogeneous metabolic demands. Mitochondrial aging occurs on timescales shorter than the neuronal lifespan, necessitating transport of fresh material from the soma. Maintaining an optimal distribution of healthy mitochondria requires an interplay between a stationary pool localized to sites of high metabolic demand and a motile pool capable of delivering new material. Interchange between these pools can occur via transient fusion / fission events or by halting and restarting entire mitochondria. Our quantitative model of neuronal mitostasis identifies key parameters that govern steady-state mitochondrial health at discrete locations. Very infrequent exchange between stationary and motile pools optimizes this system. Exchange via transient fusion allows for robust maintenance, which can be further improved by selective recycling through mitophagy. These results provide a framework for quantifying how perturbations in organelle transport and interactions affect mitochondrial homeostasis in neurons, a key aspect underlying many neurodegenerative disorders.more » « less
-
Mitochondrial population maintenance in neurons is essential for neuron function and survival. Contact sites between mitochondria and the endoplasmic reticulum (ER) are poised to regulate mitochondrial homeostasis in neurons. These contact sites can facilitate transfer of calcium and lipids between the organelles and have been shown to regulate aspects of mitochondrial dynamics. Vesicle-associated membrane protein-associated protein B (VapB) is an ER membrane protein present at a subset of ER–mitochondrial contact sites. A proline-to-serine mutation in VapB at amino acid 56 (P56S) correlates with susceptibility to amyotrophic lateral sclerosis (ALS) type 8. Given the relationship between failed mitochondrial health and neurodegenerative disease, we investigated the function of VapB in mitochondrial population maintenance. We demonstrated that transgenic expression of VapBP56Sin zebrafish larvae (sex undetermined) increased mitochondrial biogenesis, causing increased mitochondrial population size in the axon terminal. Expression of wild-type VapB did not alter biogenesis but, instead, increased mitophagy in the axon terminal. Using genetic manipulations to independently increase mitochondrial biogenesis, we show that biogenesis is normally balanced by mitophagy to maintain a constant mitochondrial population size. VapBP56Stransgenics fail to increase mitophagy to compensate for the increase in mitochondrial biogenesis, suggesting an impaired mitophagic response. Finally, using a synthetic ER–mitochondrial tether, we show that VapB's function in mitochondrial turnover is likely independent of ER–mitochondrial tethering by contact sites. Our findings demonstrate that VapB can control mitochondrial turnover in the axon terminal, and this function is altered by the P56S ALS-linked mutation.
-
Abstract Endoplasmic reticulum (ER) stress and mitochondrial dysfunction are linked in the onset and pathogenesis of numerous diseases. This has led to considerable interest in defining the mechanisms responsible for regulating mitochondria during ER stress. The PERK signaling arm of the unfolded protein response (UPR) has emerged as a prominent ER stress‐responsive signaling pathway that regulates diverse aspects of mitochondrial biology. Here, we show that PERK activity promotes adaptive remodeling of mitochondrial membrane phosphatidic acid (PA) to induce protective mitochondrial elongation during acute ER stress. We find that PERK activity is required for ER stress‐dependent increases in both cellular PA and YME1L‐dependent degradation of the intramitochondrial PA transporter PRELID1. These two processes lead to the accumulation of PA on the outer mitochondrial membrane where it can induce mitochondrial elongation by inhibiting mitochondrial fission. Our results establish a new role for PERK in the adaptive remodeling of mitochondrial phospholipids and demonstrate that PERK‐dependent PA regulation adapts organellar shape in response to ER stress.