Search Results (566)

Endosymbiosis is a necessary process in eukaryotic evolution, yet the steps leading to full integration remain poorly understood. Trypanosomatids provide a comparative framework to study this transition through two independent systems representing distinct levels of integration. Strigomonadinae comprises a subfamily derived from a single ancestral acquisition, which maintains a single cytosolic bacterium closely synchronized with the host cell cycle. In contrast, Novymonas esmeraldas harbors multiple bacteria within symbiontophorous vacuoles, presenting a more limited coordination of division. The generation of aposymbiotic strains enables direct functional assessment of endosymbiont contributions to host biology. Comparative analyses reveal strong metabolic interdependence, with the endosymbiont supplying essential amino acids, heme, vitamins, and purines, while relying on the host for key metabolic resources including non-essential amino acids, cofactors, energy metabolism, and lipid biosynthesis. Beyond metabolism, the endosymbiont impacts protein homeostasis and cellular regulation, modulating proteolytic pathways such as GP63, cysteine peptidases, and the ubiquitin–proteasome system, as well as host networks involving kinetoplast-associated proteins (KAPs). Host-encoded endosymbiont-targeted proteins (ETPs) further mediate endosymbiont positioning, organization, and coordinated maintenance and division. Here, we critically synthesize current knowledge on mEHTs using a comparative framework based on interconnected dimensions of host–endosymbiont integration. Full article

Among primary central nervous system malignancies in adults, malignant glioma ranks first in incidence, with glioblastoma (GBM) standing as its most aggressive phenotype. This malignancy remains a devastating disease with limited therapeutic options, largely owing to the intricate network of dysregulated signaling pathways. SUMOylation, a post-translational modification that governs thousands of substrate proteins, is markedly hyperactivated in GBM and represents a rational but underexploited target. Here, we found that honokiol (HNK), a natural biphenolic compound extracted from the traditional Chinese medicine Magnolia species, suppressed SUMOylation in glioma cells, with a more prominent reduction in SUMO1-conjugated species than in SUMO2/3-conjugated species. Through a combination of label-free proteomic screening and functional biological assays, we pinpointed YAP1, a core Hippo pathway effector and established oncogenic driver in glioma cells, as a critical downstream target. Furthermore, our research indicated that inhibition of SUMOylation by HNK was associated with reduced levels of YAP1, resulting in glioma cell growth inhibition. Mechanistically, HNK induced YAP1 ubiquitin–proteasome degradation by disrupting SUMO1-YAP1 conjugation, leading to the subsequent blockade of YAP1 signaling. Collectively, our findings unveiled a previously unrecognized mechanism linking pharmacological deSUMOylation to YAP1 destabilization and emphasized the SUMO–YAP1 interface as a therapeutically actionable vulnerability. Overall, this work provides a strong rationale for developing HNK or its optimized derivatives as a first-in-class therapeutic strategy that addresses the network-level complexity of GBM. Full article

Lymphoid malignancies comprise a diverse group of hematologic cancers characterized by extensive genetic, epigenetic, and microenvironmental heterogeneity. Despite substantial advances in targeted therapies and immunotherapeutic approaches, disease relapse and therapeutic resistance remain major clinical challenges. Increasing evidence suggests that malignant lymphoid cells are highly dependent on protein homeostasis (proteostasis) networks to cope with the elevated proteotoxic stress imposed by oncogenic signaling, rapid proliferation, immunoglobulin synthesis, and microenvironmental stressors. This dependence, often referred to as proteostasis addiction, represents a critical vulnerability that can be therapeutically exploited. Proteostasis is maintained through an integrated network that regulates protein synthesis, folding, quality control, and degradation. In lymphoid malignancies, dysregulation of these pathways drives adaptive responses involving molecular chaperones, the unfolded protein response (UPR), the ubiquitin–proteasome system (UPS), and autophagy–lysosome pathways. These mechanisms collectively enable tumor cells to survive conditions that would otherwise induce proteotoxic collapse and cell death. Notably, the clinical success of proteasome inhibitors in plasma cell neoplasms has provided proof of concept that targeting proteostasis can yield meaningful therapeutic benefit. In this review, we discuss the major sources of proteotoxic stress in lymphoid malignancies and summarize the molecular mechanisms that sustain proteostasis addiction. We further examine current and emerging therapeutic strategies aimed at disrupting proteostasis networks, including proteasome inhibitors, UPR-targeted agents, chaperone-directed therapies, and novel targeted protein degradation technologies. Finally, we highlight the contribution of proteostasis remodeling to therapeutic resistance and discuss future opportunities for biomarker development and precision medicine. A deeper understanding of proteostasis dependencies may facilitate the identification of novel therapeutic vulnerabilities and improve outcomes for patients with lymphoid malignancies. Full article

Stem cell-derived extracellular vesicles (EVs) hold therapeutic potential for hypoxia-associated injury, yet the molecular mechanisms underlying their protective effects remain incompletely defined. Herein, we performed comparative proteomic profiling of extracellular vesicles (EVs) secreted by human placenta-derived perivascular stem cells (hPPSCs) and human umbilical cord mesenchymal stem cells (hUCMSCs). We found that hPPSCs-EVs are enriched in proteasome-related proteins. Enzymatic activity assays further confirmed that proteasome activity in hPPSCs-EVs was significantly higher than that in hUCMSCs-EVs. Additionally, we observed that hPPSCs-EVs were efficiently endocytosed by human umbilical vein endothelial cells (hUVECs), leading to marked downregulation of hypoxia-inducible factor 1-alpha (HIF-1α) and intracellular ubiquitinated proteins. Importantly, this HIF-1α degradation persisted even when the host ubiquitin–proteasome system was blocked, indicating that hPPSCs-EVs can function independently of the host proteasomal pathway. These results reveal that hPPSCs-EVs deliver functional proteasomes to endothelial cells, thereby compensating for impaired protein degradation and protecting cells under hypoxic stress. Collectively, our findings provide evidence for an intercellular transfer of proteolytic capacity via stem cell-derived EVs, a mechanism that preserves endothelial proteostasis and highlights the therapeutic potential of proteasome-rich EVs for hypoxia-associated diseases. Full article

Repeat expansion cerebellar ataxias comprise a genetically and mechanistically heterogeneous group of neurodegenerative disorders unified by the pathological expansion of short tandem repeats (STRs) beyond a disease-causing threshold. Depending on their genomic localization, these expansions can lead to toxic protein gain-of-function, as in polyglutamine (polyQ) cerebellar ataxias, or to RNA-mediated toxicity and repeat-associated non-AUG (RAN) translation, for which recent evidence supports a major pathogenic role in non-coding spinocerebellar ataxias (SCAs). Despite these distinct upstream mechanisms, disruption of neuronal homeostasis occurs through converging pathogenic processes, including proteostasis impairment, transcriptional dysregulation, and mitochondrial dysfunction, leading to progressive neuronal loss. Importantly, impaired autophagy has been consistently reported across multiple repeat expansion ataxias, including both dominant SCAs and recessive conditions, such as Friedreich’s ataxia, suggesting that impairment of this pathway may represent a shared downstream event in disease progression. Indeed, in polyQ cerebella ataxias, the accumulation of misfolded and aggregation-prone proteins places a substantial burden on cellular quality control systems, particularly the ubiquitin-proteasome system and autophagy. Similarly, in non-coding SCAs, toxic RNA species and RAN-derived peptides might interfere with protein clearance mechanisms and contribute to cellular stress. In this review, we will discuss the evidence supporting autophagy impairment as a convergent pathogenic pathway in repeat expansion cerebellar ataxias. Full article

The intracellular iron levels are tightly controlled by the coordinated action of specialized proteins that regulate iron uptake, storage, and export pathways in response to iron availability. For example, Ferroportin serves as the sole mammalian iron exporter; whereas ferritin acts as the primary intracellular iron storage complex. Although both Ferroportin and ferritin are reported to be primarily degraded through lysosomal pathways, it is possible that these proteins can also be regulated through the proteasomal pathway, which may provide a more rapid mechanism to modulate intracellular iron availability. Here, we identify MDM2 as a previously unrecognized regulator of cellular iron homeostasis. We found that MDM2 is required to maintain intracellular labile iron. Mechanistically, we found that MDM2 interacts with and promotes the degradation of both Ferroportin and ferritin heavy chain. Consequently, MDM2 exerts a critical role in modulating cellular iron retention by simultaneously suppressing iron storage and iron export pathways. These findings expand the biological functions of MDM2 beyond its established role as a p53 E3 ubiquitin ligase, revealing a previously unappreciated link between MDM2 signaling and iron metabolism. Full article

Background/Objectives: Cancer resistance, pathway redundancy, and compensatory signaling challenge traditional therapies. Dual target strategies address this by engaging two disease-relevant proteins within a single molecule. This review compares classical dual inhibitors with dual proteolysis-targeting chimeras (dual PROTACs) to evaluate the therapeutic advantages of degradation over occupancy. Methods: We examine oncology target pairs featuring documented examples of both dual inhibitors and dual PROTACs. The biological rationale for co-targeting is analyzed alongside a comparative assessment of their chemical frameworks, focusing heavily on the synthetic strategies, length, and structure of linkers required for dual PROTAC ternary complex formation. Results: While dual inhibitors rely on active-site occupancy, dual PROTACs leverage the ubiquitin–proteasome system for catalytic target elimination. Transitioning from dual inhibition to dual degradation in most cases (>85%) enhances antitumor efficacy, extends duration of action, and overcomes resistance mutations. Optimizing linker design remains the critical factor in balancing the simultaneous degradation kinetics of two distinct proteins. Conclusions: Dual PROTACs provide distinct advantages over traditional inhibitors by completely destroying target proteins rather than merely blocking them. This comparison offers a practical entry point and actionable synthetic strategies for medicinal chemists designing multi-target protein degraders. Full article

Backgrounds: Early-life nutritional excess increases the risk of depressive-like phenotypes in offspring, yet the underlying mechanisms remain unclear. This study investigated whether perinatal and adolescent high-fat diet (HFD) exposure is associated with depressive-like behaviors through disruption of the autophagy–GABARAP pathway in hypothalamic neurons. Methods: A mouse model of HFD exposure during both periods was established. Depressive-like behaviors, hypothalamic autophagic flux, and GABARAP–GABA_AR co-localization were assessed. Primary hypothalamic neuronal cultures were treated with rapamycin. RNA sequencing and co-immunoprecipitation were performed to identify transcriptional changes and protein–protein interactions. Results: HFD exposure induced metabolic disturbances and depressive-like behaviors, suppressed autophagic flux (p62 and LC3-II accumulation), increased GABARAP–GABA_AR co-localization, and reduced GABA_AR protein abundance with elevated hypothalamic neuronal activity. Rapamycin reversed these alterations in primary neurons. RNA sequencing identified 87 differentially expressed genes (e.g., upregulated Plin4, Txnip; downregulated Npas4, Avp), while GABA receptor subunits and core autophagy genes remained unchanged at the transcriptional level. Enrichment analyses linked differentially expressed genes to mitophagy, oxidative phosphorylation, and the ubiquitin–proteasome system, with downregulated neuronal pathways. Co-immunoprecipitation confirmed direct GABARAP–GABA_AR interaction. Conclusions: Impaired autophagic flux correlates with reduced GABA_AR protein levels and increased hypothalamic neuronal activity, suggesting a link between autophagy–GABARAP dysregulation and depressive-like behaviors. The autophagy–GABARAP axis, together with transcriptomic reprogramming, may represent a key link between early-life nutritional excess and offspring depressive-like phenotypes, warranting further investigation as an intervention target. Full article

The aim of this study was to examine the hepatoprotective activity of multicomponent mixtures of natural origin in the BALB/C mouse model (n = 59), with acute direct toxic liver injury (DTLI) induced by the administration of streptozotocin (STZ) (100 mg/kg) in combination with a high-fat and high-fructose diet (HFFD). The hepatoprotective activity of activated hydrolytic lignin (Bp-Cx-1), methanolic fraction of Bp-Cx-1 (Bp-Cx-M) and isoflavones from kudzu Pueraria lobata roots (IFL) were evaluated on molecular level using mass spectrometry (MS)-based omics technologies. Untargeted label-free DIA quantitation resulted in 7214 protein groups identification (FDR 1%) after filtering across 40 liver tissue extracts. All treatment groups were closer to the control samples on the liver proteomic landscape compared to the untreated DTLI group, with the best results shown for the Bp-Cx-M and IFL groups. In order to identify differences between specific groups, we applied the post hoc Dunn’s test and used Hedges’ g as the effect size metric, revealing 64 proteins that tended to return to their normal level after treatment. In-depth proteomic liver tissue analysis enabled us not only to reveal the main pathways such as inflammation and oxidative stress, which are in a good agreement with DTLI and non-alcoholic liver disease pathophysiology, but also to evaluate hepatoprotective activity of multicomponent mixtures of natural origin containing polyphenols and mostly associated with protein metabolism (e.g., PSMD7, HCFC1) and deubiquitination pathways (e.g., UCHL3). It is worth noting that the Bp-Cx-1 isolated methanol fraction (Bp-Cx-M) demonstrated a pronounced increased hepatoprotective activity compared to the parent material due to the enrichment with active components such as polyphenols. Consistent with the proteomic findings of restored ubiquitin–proteasome function, assessment by comet assay revealed that treatments with Bp-Cx-M and IFL significantly reduced DNA damage by 50% compared to the untreated DTLI group. The developed MS-based multi-omics approach may be implemented for the robust and high-throughput screening method during assessment of new hepatoprotective agents of synthetic or natural origin. Full article

Skeletal muscle dysfunction (SMD) is a critical extrapulmonary comorbidity in chronic obstructive pulmonary disease (COPD), contributing to exercise intolerance, poor quality of life, and increased mortality. Building upon and extending the disuse model, this review synthesizes evidence establishing COPD-induced SMD as a distinct myopathy with intrinsic disease drivers. Its pathophysiology is driven by a self-reinforcing network: mitochondrial energetic crisis featuring bioenergetic failure and dysregulated dynamics, chronic oxidative stress and inflammation fueling catabolic drive via ubiquitin–proteasome system activation, and epigenetic dysregulation through alterations in key histone deacetylases (HDACs) and microRNA expression, which collectively orchestrate a pro-atrophic phenotype. We further explore how these molecular insights are translating into novel diagnostic tools, including circulating biomarkers like myomiRs and C-terminal agrin fragment, and imaging techniques such as shear wave elastography. Although exercise training remains the cornerstone of management, its limited efficacy underscores the need for adjunctive and targeted therapies. We discuss promising strategies from pharmacological and nutritional support to emerging agents targeting specific pathways, including the IL-36 receptor, lipoprotein-associated phospholipase A2, aryl hydrocarbon receptor, and mitsugumin 53. Effective management of COPD-related SMD will hinge on a precision medicine framework, leveraging biomarker-guided stratification to deploy personalized combinatorial interventions aimed at preserving muscle mass and function. Full article

Neurodegenerative diseases are characterized by the accumulation of misfolded and aggregation-prone proteins, reflecting a failure of proteostasis. The ubiquitin–proteasome system (UPS), a major pathway for selective intracellular protein degradation, is essential for maintaining neuronal protein homeostasis. Proteasome dysfunction has been implicated in several major neurodegenerative disorders, including Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington’s disease (HD), although its extent and mechanisms vary across disease contexts. In this review, we examine current evidence for proteasome dysfunction in neurodegeneration and discuss how disease-associated proteins impair proteasome function through direct inhibition, defective substrate processing, and sequestration into protein aggregates. We also address the contribution of oxidative stress, neuroinflammation, and aging to proteasome dysregulation. Finally, we highlight emerging therapeutic strategies aimed at restoring proteasome function, including pharmacological activation, modulation of proteasome assembly and stability, and targeted protein degradation approaches. Understanding the context-dependent nature of proteasome dysfunction will be important for developing effective proteostasis-based therapies. Full article

Background: The glucocorticoid receptor NR3C1 exhibits antiepileptic properties, but the mechanisms governing its stability during epileptogenesis remain elusive. This study investigated whether the E3 ubiquitin ligase TRIM8 regulates neuronal hyperexcitability and epileptic activity by modulating NR3C1. Methods: We established an in vivo epilepsy model via intrahippocampal kainic acid (KA) injection and an in vitro epileptiform model using Mg²⁺-free artificial cerebrospinal fluid in primary hippocampal neurons. The roles of TRIM8 and NR3C1 were assessed using in vivo and in vitro gain- and loss-of-function approaches, alongside co-immunoprecipitation, Western blotting, immunofluorescence and whole-cell patch-clamp recording. Results: TRIM8 is significantly upregulated in hippocampal and temporal lobe neurons in epileptic mice. TRIM8 was markedly upregulated in the hippocampal neurons of epileptic mice, inversely correlating with NR3C1 levels. Mechanistically, TRIM8 interacted with NR3C1, promoting its polyubiquitination and proteasomal degradation. This TRIM8-mediated NR3C1 reduction enhanced the phosphorylation of AMPA receptor (AMPAR) subunits GluR1 (Ser831) and GluR2 (Ser880) without affecting total receptor expression. In vitro, TRIM8 overexpression exacerbated calcium dysregulation, neuronal injury, and AMPAR phosphorylation; crucially, concurrent NR3C1 overexpression rescued these effects. In vivo, knockdown of TRIM8 significantly reduced seizure frequency, prolonged the latency to the first Stage III seizure, shortened average seizure duration, and decreased total seizure burden in KA-induced epileptic mice. Electrophysiologically, TRIM8 overexpression significantly increased the frequency of spontaneous action potentials and amplitudes of spontaneous excitatory postsynaptic currents under Mg²⁺-free conditions. Furthermore, in vivo knockdown of TRIM8 attenuated KA-induced seizure severity, restored NR3C1 protein stability, and suppressed aberrant AMPAR phosphorylation in the hippocampus. Triple immunofluorescence staining showed that KA-induced epilepsy increased TRIM8 but decreased NR3C1 immunoreactivity in NeuN⁺ hippocampal neurons, and TRIM8 knockdown reversed these changes. Conclusions: TRIM8 acts as a critical driver of epileptiform activity by targeting NR3C1 for degradation, thereby disinhibiting AMPAR phosphorylation and enhancing network hyperexcitability. The TRIM8-NR3C1-AMPAR axis emerges as a previously unrecognized molecular pathway in epileptogenesis, highlighting its potential as a promising therapeutic target for epilepsy. Full article

Global warming poses serious threats to plant reproduction and agricultural productivity by affecting the timing of flowering, a critical developmental transition. Although transcriptional regulation of flowering pathways has been extensively studied, posttranslational and protein-level regulatory mechanisms are gaining increasing attention as important thermosensory switches enabling rapid and reversible responses to temperature fluctuations. These mechanisms include temperature-dependent protein degradation, ubiquitination, liquid–liquid phase separation of intrinsically disordered proteins, protein sequestration, and dynamic protein–protein interactions. This review summarizes current understanding of posttranslational flowering time regulation under high-temperature conditions, focusing on the major interconnected thermosensory modules, such as the temperature-dependent proteostasis of floral repressors and the emergence of temperature-responsive liquid–liquid phase separation (LLPS) of intrinsically disordered proteins (IDPs). Recent discoveries indicate that temperature-responsive flowering relies not only on transcriptional networks but also on dynamic protein-level regulatory mechanisms, including ubiquitination, proteasomal degradation, and liquid–liquid phase separation. However, the fact that these mechanisms have not been validated in crop species leaves their translational potential an open question. Full article

Hepatocellular carcinoma is challenging to detect at an early stage, and its severity increases over time. Recently, the incidence of hepatocellular carcinoma has increased, partly due to lifestyle-related factors such as excessive alcohol intake, sedentary behavior, and diets high in fat, which contribute to the growing prevalence of fatty liver and hepatitis. Various therapeutic strategies are being explored for hepatocellular carcinoma, among which therapies targeting deubiquitinating enzymes (DUBs) have attracted growing attention. Ubiquitination acts as a crucial modulator in the regulation of intracellular signaling across many diseases. E3 ligase recognizes the target protein and transfers ubiquitin, received from the E2 enzyme, to the lysine residues of the substrate, thereby conferring specificity to the ubiquitination process. Once a ubiquitin chain is attached to a target protein by an E3 ligase, the protein is directed to the ubiquitin–proteasome system (UPS) for degradation. In this process, the 26S proteasome complex recognizes the ubiquitin chain and degrades the target protein, thereby serving as a major mechanism for maintaining protein homeostasis. Through this pathway, cells regulate signal transduction, eliminate abnormal proteins, and perform various essential functions. On the other hand, deubiquitinating enzymes (DUBs) recognize the ubiquitin chains on target proteins and remove them by hydrolyzing the isopeptide bonds of ubiquitin, thereby enabling the target proteins to evade degradation by the proteasome system. Furthermore, deubiquitinating enzymes independently remove ubiquitin from proteins and can serve as central regulators in signaling pathways related to hepatocellular carcinoma. Full article

Viral myocarditis (VMC), predominantly driven by Coxsackievirus B3 (CVB3) infection and the resultant excessive immune response, lacks effective treatments and specific antiviral drugs in clinical practice. Chlorogenic acid (CGA) has been proven to have significant antiviral and anti-inflammatory properties. This study evaluated the potential and mechanism of action of CGA against CVB3-induced viral myocarditis. Our research results showed that CGA significantly alleviated myocardial tissue damage in vivo. This protective effect was accompanied by effective inhibition of myocardial inflammatory responses and viral replication. Further in vitro experiments confirmed that CGA significantly inhibited the replication of CVB3 in a dose-dependent manner, and its inhibitory effect mainly targeted the replication stage of the viral life cycle. Mechanistically, CGA treatment correlates with reduced ZBP1 expression and accelerated ZBP1 degradation involving the ubiquitin–proteasome pathway, accompanied by suppressed activation of PANoptosis markers. These findings suggest that CGA alleviates CVB3-induced myocarditis through concerted antiviral and anti-inflammatory effects, with ZBP1-mediated PANoptosis as a potential contributing mechanism. Full article