Biology subjects

Baron, K. R.

Publications and source records attributed to Baron, K. R..

4 recordsLinked to original sources

bioRxiv2023

Pharmacologic Activation of an Integrated Stress Response Kinase Promotes Mitochondrial Remodeling

The integrated stress response (ISR) comprises the eIF2 kinases PERK, GCN2, HRI, and PKR, which induce translational and transcriptional signaling in response to diverse insults. Deficiencies in PERK signaling lead to mitochondrial dysfunction and contribute to the pathogenesis of numerous diseases. We define the potential for pharmacologic activation of compensatory eIF2 kinases to rescue ISR signaling and promote mitochondrial adaptation in PERK-deficient cells. We show that the HRI activator BtdCPU and GCN2 activator halofuginone promote ISR signaling and rescue ER stress sensitivity in PERK-deficient cells. However, BtdCPU induces mitochondrial depolarization, leading to mitochondrial fragmentation and activation of the OMA1-DELE1-HRI signaling axis. In contrast, halofuginone promotes mitochondrial elongation and adaptive mitochondrial respiration, mimicking regulation induced by PERK. This shows halofuginone can compensate for deficiencies in PERK signaling and promote adaptive mitochondrial remodeling, highlighting the potential for pharmacologic ISR activation to mitigate mitochondrial dysfunction and motivating the pursuit of highly-selective ISR activators.

cell biology↗

bioRxiv2022

DELE1 oligomerization promotes integrated stress response activation

Mitochondria are dynamic organelles that must continually adapt and respond to cellular stress. Recent studies demonstrated that mitochondrial stress can be relayed from mitochondria to the cytosol by the release of a C-terminal proteolytic fragment of DELE1 that binds to the eIF2 kinase HRI to initiate integrate stress response (ISR) signaling. Here, we report the cryo-electron microscopy structure of the active, C-terminal cleavage product of human DELE1 at[~] 3.8 A{degrees} resolution. Our structure reveals that DELE1 assembles into a high-order oligomer that is observed both in vitro and in mammalian cells. Structurally, the oligomer consists of eight DELE1 monomers that assemble with D4 symmetry via two sets of distinct hydrophobic inter-subunit interactions. We identified the key residues involved in DELE1 oligomerization, and confirmed their role in stabilizing the octamer in vitro and in cells using mutagenesis. Further, we show that assembly impaired DELE1 mutants are compromised in their ability to induce ISR activation in cell culture models. Together, our findings provide molecular insights into the activity of DELE1 and how it signals to promote ISR activity following mitochondrial insult.

molecular biology↗

bioRxiv2022

PERK Signaling Promotes Mitochondrial Elongation By Remodeling Membrane Phosphatidic Acid

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 also promotes adaptive remodeling of mitochondrial membrane phosphatidic acid (PA) to induce protective mitochondrial elongation during 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. Together, these processes lead to the accumulation of PA on the outer mitochondrial membrane where it induces 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 functions to adapt organellar shape in response to ER stress.

cell biology↗

bioRxiv2021

Metabolically Activated Proteostasis Regulators Protect Against Glutamate Toxicity by Activating NRF2

The extracellular accumulation of glutamate is a pathologic hallmark of numerous neurodegenerative diseases including ischemic stroke and Alzheimers disease. At high extracellular concentrations, glutamate causes neuronal damage by promoting oxidative stress which can lead to cellular death. This has led to significant interest in developing pharmacologic approaches to mitigate the oxidative toxicity caused by high levels of glutamate. Here, we show that the small molecule proteostasis regulator AA147 protects against glutamate-induced cell death in a neuronal-derived cell culture model by reducing intracellular levels of reactive oxygen species. While originally developed as an activator of the ATF6 arm of the unfolded protein response, we show AA147-dependent protection against glutamate toxicity is primarily mediated through activation of the NRF2-regulated oxidative stress response. We demonstrate that AA147 activates NRF2 through a mechanism involving metabolic activation to a reactive electrophile and covalent modification of KEAP1 - a mechanism analogous to that involved in AA147-dependent activation of ATF6. These results define the potential for AA147 to protect against glutamate induced oxidative toxicity and highlight the potential for metabolically-activated proteostasis regulators like AA147 to activate both protective ATF6 and NRF2 stress-responsive signaling pathways to mitigate oxidative damage associated with diverse neurologic diseases.

biochemistry↗