Biology subjects

Rosarda, J. D.

Publications and source records attributed to Rosarda, J. D..

5 recordsLinked to original sources

bioRxiv2023

Pharmacologic Targeting of PDIA1 Inhibits NLRP3 Inflammasome Assembly and Activation

The NLRP3 inflammasome is a cytosolic protein complex that regulates innate immune signaling in response to diverse pathogenic insults through the proteolytic processing and secretion of pro-inflammatory cytokines such as IL-1{beta}. Hyperactivation of NLRP3 inflammasome signaling is implicated in the onset and pathogenesis of numerous diseases, motivating the discovery of new strategies to suppress NLRP3 inflammasome activity. We sought to define the potential for the proteostasis regulator AA147 to inhibit the assembly and activation of the NLRP3 inflammasome. AA147 is a pro-drug that is metabolically converted to a reactive metabolite at the endoplasmic reticulum (ER) membrane to covalently modify ER-localized proteins such as protein disulfide isomerases (PDIs). We show that AA147 inhibits NLRP3 inflammasome activity in monocytes and monocyte-derived macrophages through a mechanism involving impaired assembly of the active inflammasome complex. This inhibition is mediated through AA147-dependent covalent modification of PDIA1. Genetic depletion or treatment with other highly selective PDIA1 inhibitors similarly blocks NLRP3 inflammasome assembly and activation. Our results identify PDIA1 as a potential therapeutic target to mitigate NLRP3 inflammasome-mediated pro-inflammatory signaling implicated in etiologically diverse diseases.

cell biology↗

bioRxiv2023

Covalent targeting as a common mechanism for inhibiting NLRP3 inflammasome assembly.

The NLRP3 inflammasome is a cytosolic protein complex important for the regulation and secretion of inflammatory cytokines including IL-1{beta} and IL-18. Aberrant overactivation of NLRP3 is implicated in numerous inflammatory disorders. However, the activation and regulation of NLRP3 inflammasome signaling remains poorly understood, limiting our ability to develop pharmacologic approaches to target this important inflammatory complex. Here, we developed and implemented a high-throughput screen to identify compounds that inhibit inflammasome assembly and activity. From this screen we identify and profile inflammasome inhibition of 20 new covalent compounds across 9 different chemical scaffolds, as well as many known inflammasome covalent inhibitors. Intriguingly, our results indicate that NLRP3 possesses numerous reactive cysteines on multiple domains whose covalent targeting blocks activation of this inflammatory complex. Specifically, focusing on compound VLX1570, which possesses multiple electrophilic moieties, we demonstrate that this compound allows covalent, intermolecular crosslinking of NLRP3 cysteines to inhibit inflammasome assembly. Our results, along with the recent identification of numerous covalent molecules that inhibit NLRP3 inflammasome activation, suggests that NLRP3 serves as a cellular electrophile sensor important for coordinating inflammatory signaling in response to redox stress. Further, our results support the potential for covalent cysteine modification of NLRP3 for regulating inflammasome activation and activity.

biochemistry↗

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

Imbalanced Unfolded Protein Response Signaling Contributes to 1-Deoxysphingolipid Retinal Toxicity

1-Deoxysphingolipids (1-dSLs) are atypical cytotoxic sphingolipids formed through the substitution of alanine for serine in de novo sphingolipid biosynthesis. Accumulation of 1-dSLs has been linked to diseases of the eye such as diabetic retinopathy and Macular Telangiectasia Type 2 (MacTel). However, the molecular mechanisms by which 1-dSLs induce toxicity in retinal cells remains poorly understood. Here, we integrate bulk and single-nucleus RNA-sequencing to define the biological pathways that contribute to toxicity caused by the 1-dSL species, 1-deoxysphinganine (1-dSA), in human retinal organoids. Our results demonstrate that 1-dSA preferentially and differentially activates signaling arms of the unfolded protein response (UPR) in photoreceptor cells and Muller glia within retinal organoids. Using a combination of pharmacologic inhibitors and activators, we define the roles for individual arms of the UPR in 1-dSL-mediated toxicity. We show that sustained PERK signaling through the integrated stress response (ISR) promotes 1-dSL-induced apoptosis in photoreceptors. In contrast, deficiencies in signaling through the ATF6 arm of the UPR contribute to photoreceptor toxicity. These results indicate that imbalanced signaling between the pro-apoptotic PERK/ISR and protective ATF6 arms of the UPR contributes to 1-dSL-induced photoreceptor toxicity. Further, our results identify new opportunities to intervene in 1-dSL linked diseases through targeting different signaling arms of the UPR.

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↗