Search Results (281)

The life-threatening disease pertussis, also known as whooping cough, is caused by a complex interplay of several virulence factors produced by the bacterium Bordetella (B.) pertussis. These include the AB-type protein toxin pertussis toxin (PT), the main causative agent of pertussis. After infection with B. pertussis, PT is released and binds to its human target cells, which internalize PT. The enzyme subunit of PT is then taken up into the cytosol, where it catalyzes the ADP-ribosylation of the α-subunit of inhibitory GTP-binding proteins from the Gαi type. This ultimately leads to the development of the characteristic clinical symptoms associated with pertussis. Pertussis is a vaccine-preventable but highly infectious respiratory disease, and especially younger children are prone to develop severe pertussis. Despite the vaccination, over the past few years, increasing case numbers have been reported globally. Moreover, treatment options are strongly limited to antibiotics and symptomatic treatment. Therefore, novel therapies against toxin-mediated diseases are urgently required, while AB-type toxins such as PT are promising pharmacological targets to combat these associated diseases. To identify novel pharmacological inhibitors for AB-type toxins, huge potential lies within the human proteome/peptidome. Endogenous protein or peptide inhibitors for bacterial toxins might have evolved as part of the innate immunity and are awaited to be discovered. The scientific community is committed to identify potential candidates through targeted screening or explorative hypothesis-driven approaches. This review summarizes the recent efforts in the identification and characterization of the human body’s own proteins and peptides that inhibit PT. PT-inhibiting peptides were found by unbiased screening of peptide libraries from human hemofiltrate or hypothesis-driven evaluation, and PT-neutralizing mechanisms were discovered in cell-based approaches. The identification of endogenous peptides and proteins, e.g., defensins and α₁-antitrypsin, as potent inhibitors of PT paves the way towards the development of novel therapeutic options against pertussis. Full article

Pertussis toxin (PTx) is a major virulence factor of Bordetella pertussis and an AB5-type exotoxin that disrupts host signaling. Its enzymatic A subunit ADP-ribosylates the α-subunit of inhibitory G proteins (Gα_i), preventing them from mediating receptor-induced inhibition of adenylyl cyclase (AC). This leads to unrestrained cAMP accumulation in host cells, a canonical mechanism underlying many pertussis disease manifestations. PTx works in concert with the bacterium’s adenylate cyclase toxin (ACT) to subvert immune defenses and establish infection. Interestingly, PTx exerts both cAMP-dependent and cAMP-independent effects. In addition to the well-known cAMP-mediated pathway, PTx’s B oligomer can engage host cell surface receptors to trigger signaling cascades independent of the A subunit’s catalytic activity. Such B oligomer-mediated pathways modulate cellular responses in the absence of ADP-ribosylation. This review provides a comprehensive analysis of PTx’s dual functionality, distinguishing its G_i protein-dependent elevation of cAMP from the noncanonical activities of the B oligomer. It also highlights how disruption of constitutive G_i signaling and the interplay between PTx and ACT shape host–pathogen interaction in pertussis pathogenesis. Full article

Therapeutic resistance remains a major obstacle to durable cancer control, with functional reprogramming of the DNA damage response (DDR) network playing a central role. The poly(ADP-ribose) polymerase (PARP) family, particularly PARP1 and PARP2, is crucial for maintaining genomic integrity. By exploiting synthetic lethality, PARP inhibitors (PARPi) selectively target tumors with homologous recombination deficiency (HRD) and are integral to precision therapy in ovarian, breast, and prostate cancers. However, over 40% of patients with BRCA1/2 alterations develop resistance, and patient eligibility remains limited by the low prevalence of HRD mutations. In this review, we summarize the molecular mechanisms of PARPi action, resistance pathways, and emerging combination strategies. PARPi resistance arises through HR restoration (e.g., BRCA1/2 reversion mutations), replication fork protection, RAD51-mediated strand invasion, and metabolic reprogramming. Combination therapies, integrating PARPi with histone deacetylase inhibitors, cyclin-dependent kinase inhibitors, immune checkpoint blockade, or radiation, enhance efficacy by converging on DNA repair pathways and the tumor immune microenvironment. A deeper understanding of coordinated DDR regulation and rationally designed combination regimens will be essential for overcoming PARPi resistance and advancing adaptive, precision-based therapeutic strategies. Full article

Poly(ADP-ribose) polymerases (PARPs) regulate genome maintenance through NAD⁺-dependent ADP-ribosylation, yet PARP function in fungi remains poorly defined. Here, we reconstituted the activity of the Magnaporthe oryzae PARP1 homolog (MoPARP1) in Saccharomyces cerevisiae, a genetically tractable organism that lacks endogenous PARP enzymes. Upon galactose induction, expression of MoPARP1 reduced yeast growth, whereas a catalytically inactive mutant showed no defect, indicating that the growth phenotype depends on PARP catalytic activity. Consistent with this requirement, PARylation was detected in MoPARP1-expressing yeast cells but not in the catalytic mutant. In a multidrug transporter-deficient background, the PARP inhibitor 3-aminobenzamide and the clinically used PARP inhibitor olaparib rescued the growth of MoPARP1-expressing strains, establishing a framework for inhibitor testing in vivo. Finally, MoPARP1-GFP localized to the nucleus independent of catalytic activity, supporting correct targeting in this heterologous system. Together, these findings establish yeast as a platform to dissect fungal PARP biology and evaluate chemical inhibition. Full article

Tankyrases (TNKS1 and TNKS2) are multifunctional enzymes of the poly(ADP-ribose) polymerase (PARP) family that regulate cellular homeostasis by catalyzing poly(ADP-ribosyl)ation and stabilizing protein–protein interactions through their ankyrin repeat clusters. By engaging with diverse sets of proteins, TNKSs act as central hubs that coordinate signaling and metabolic pathways. In this review, we discuss how TNKS –protein interactions underpin their roles across multiple biological pathways, including Wnt/β-catenin, YAP and SRC signaling, mTORC1 signaling, DNA damage repair (via PARP crosstalk and recruitment of repair factors), telomere maintenance, cell-cycle regulation, glucose metabolism, cytoskeleton rearrangement, autophagy, proteasomal degradation, and apoptosis. We highlight the structural basis of these interactions, emphasizing ankyrin repeat domain recognition motifs and the consequences of TNKS-mediated PARylation on protein stability and localization. By integrating findings from oncology, virology, and metabolism, we illustrate how TNKS functions as a nodal regulator linking genome stability, signaling fidelity, and metabolic control. The interplay between TNKS and these varied pathways is essential for the well-being of the organism, with its dysregulation having severe biological and clinical consequences, which are discussed here. Finally, we consider therapeutic implications of disrupting TNKS–protein interactions, with particular attention paid to selective small-molecule inhibitors and their translational potential in cancer, viral infections, and degenerative diseases. Full article

ADP-ribosylation of nucleic acids is a modification found in both eukaryotes and bacteria, where it contributes to genome maintenance but can also serve as a toxic mechanism used by bacterial toxins to disrupt essential cellular processes. This modification is catalysed by ADP-ribosyltransferases and can be reversed by antagonistic ADP-ribosylgylcohydrolase enzymes. To date, ADP-ribosylation of nucleic acid bases has been described only for adenosine, guanosine, and thymidine. Here we report the ADP-ribosylation of cytidine, catalysed by members of the pierisin family of bacterial toxins—ScARP (SCO5461) and Scabin. We also show that ADP-ribosylation of cytidine is reversible through removal by certain NADAR family proteins, including NADAR proteins from the bacterium Streptomyces coelicolor (SCO5665) and the sponge Amphimedon queenslandica, as well as YbiA-type NADAR proteins. The conservation of cytidine de-ADP-ribosylating activity of NADAR proteins across phylogenetically distant species suggests that this modification may have important physiological significance. Full article

Proteoglycans are macromolecules consisting of a core protein and one or more glycosaminoglycan side chains. Proteoglycans synthesized by vascular endothelial cells modulate various functions such as anticoagulant activity and vascular permeability. We previously reported that some heavy metals interfere with proteoglycan expression, and that organic–inorganic hybrid molecules, such as metal complexes and organometallic compounds, serve as useful tools to analyze proteoglycan synthesis mechanisms. However, the effects of metal compounds lacking electrophilicity on proteoglycan synthesis remain unclear. Au₂₅(SG)₁₈, a nanoscale gold cluster consisting of a metal core protected by gold–glutathione complexes, exhibits extremely low intramolecular polarity. In this study, we investigated the effect of Au₂₅(SG)₁₈ on proteoglycan synthesis in vascular endothelial cells. Au₂₅(SG)₁₈ accumulated significantly in vascular endothelial cells at low cell density and suppressed the expression of perlecan, a major heparan sulfate proteoglycan in cells, by inactivating ADP-ribosylation factor 6 (Arf6). Additionally, Au₂₅(SG)₁₈ reduced the expression of biglycan, a small dermatan sulfate proteoglycan, in vascular endothelial cells at low cell density; however, the underlying mechanisms remain unclear. Overall, our findings suggest that organic–inorganic hybrid molecules regulate the activity of Arf6-mediated protein transport to the extracellular space and that perlecan is regulated through this mechanism, highlighting the importance of Arf6-mediated extracellular transport for maintaining vascular homeostasis. Full article

ADP-ribosylation factor (Arf) proteins are small GTPases that regulate intracellular membrane trafficking and actin remodeling through tightly controlled cycles of GTP binding and hydrolysis. Arf1, a central coordinator of Golgi and endosomal transport, and Arf6, which regulates plasma membranes and endosomal dynamics, have both been implicated in late stages of the HIV-1 life cycle. However, the mechanisms by which these GTPases support viral assembly and release remain incompletely defined. Here, we provide direct evidence that both Arf1 and Arf6 are required for efficient trafficking of the HIV-1 Gag polyprotein, assembly, and virion production. Perturbation of Arf1 function using either GTP-locked (Q71L) or GDP-locked (T31N) mutants significantly reduced virus release, impaired Gag association with membrane compartments, and prevented its accumulation at the plasma membrane. Manipulation of Arf1 cycling through the GTPase-activating protein AGAP1 further demonstrated that dynamic transitions between GTP- and GDP-bound states are essential for productive Gag trafficking. Similarly, expression of a constitutively active Arf6 mutant (Q67L) misrouted Gag to intracellular membranes and markedly suppressed virion release. Importantly, disruption of Arf1 or Arf6 activity did not affect the expression, surface levels, or intracellular distribution of the host restriction factor BST-2. Together, these findings identify Arf1- and Arf6-mediated trafficking pathways as critical host determinants of HIV-1 assembly and release and establish that their functions operate independently of BST-2 antagonism. Full article

The poly(ADP-ribose) polymerase (PARP) family constitutes a major group of proteins and enzymes essential for the maintenance of cellular homeostasis under physiological conditions and plays a pivotal role in the onset and progression of multiple pathological states. Members of the PARP family are classified into distinct subgroups based on their subcellular localization, structural organization, and ADP-ribosyltransferase activity. To date, the majority of studies have focused on DNA-dependent PARPs, owing to their well-established involvement in DNA repair mechanisms, cell cycle regulation, and diverse human pathologies. Nevertheless, over the past decade, a smaller subset of PARPs—limited in both abundance and enzymatic activity—has emerged as a critical regulator of numerous cellular processes, including embryonic development and disease progression. Within this subset, mono(ADP-ribosyl) transferases (MARTs) have gained growing attention as potential therapeutic targets in cancer, cardiovascular disorders, and neurodegenerative diseases. The ADP-ribose (ADPr) cycle, which comprises both branched poly(ADP-ribose) (PAR) polymers and mono-ADP-ribose moieties present either in free form or covalently bound to cellular substrates, is tightly regulated to ensure cellular homeostasis. This regulation relies on a finely tuned balance between ADP-ribosylation, DePARylation, and the subsequent recycling of mono-ADP-ribose. In this review, we provide a comprehensive overview of the biological roles of mono-ADP-ribosylation (MARylation) and DePARylation, with particular emphasis on their contribution to cancer-related processes. In addition, we discuss emerging evidence supporting their translational relevance and therapeutic potential. In conclusion, MARylation and DePARylation represent two increasingly recognized regulatory pathways whose expanding clinical significance highlights the need for deeper mechanistic understanding and further exploration in both basic and translational research. Full article

Triple-negative breast cancer (TNBC) is an aggressive subtype characterized by a lack of targetable receptors, leading to limited treatment options and a critical need for novel therapeutic strategies. This study aimed to evaluate the potential of azelastine, a clinically approved H1-antihistamine, for drug repositioning against TNBC and to elucidate its underlying HRH1-independent mechanism of action. Cell viability assays (CCK-8) were performed on TNBC cell lines (MDA-MB-231 and BT-549) following treatment with azelastine and its major metabolite, desmethyl azelastine. After observing ambiguous clinical associations between HRH1 expression and patient prognosis, HRH1 dependency was assessed through histamine stimulation and HRH1 knockdown (siRNA). Subsequently, the role of ADP-ribosylation factor 1 (ARF1), found to be overexpressed in TNBC and linked to poor prognosis, was investigated using ARF1 knockdown (siRNA), co-treatment with the Golgi-specific brefeldin A-resistance guanine nucleotide exchange factor 1 (GBF1) inhibitor golgicide A (GCA), and co-treatment with the Drp1 inhibitor M-divi 1. Azelastine and desmethyl azelastine potently reduced MDA-MB-231 cell viability in a dose- and time-dependent manner, achieving cell survivals of 61.3 ± 6.1% (30 µM) and 34.9 ± 3.7% (50 µM) for azelastine, and 52.4 ± 12.5% (30 µM) for desmethyl azelastine, respectively, after 72 h, with an IC₅₀ of 35.93 µM determined for azelastine in MDA-MB-231 cells. Additionally, azelastine significantly reduced the viability of BT-549 cells. Bioinformatic analysis of clinical datasets revealed HRH1 downregulation in tumors and, functionally, neither histamine stimulation nor HRH1 knockdown mediated azelastine cytotoxicity in cell culture. Importantly, ARF1 expression was significantly upregulated in TNBC and associated with poor prognosis. Co-treatment with GCA, preventing ARF1 activation, restored viability to near-control levels, supporting dependence on the GBF1–ARF1 activation axis of azelastine, whereas the Dynamic-related protein 1 (Drp1) inhibitor M-divi 1 not only partially rescued CCK-8-based cell viability but also normalized azelastine-induced loss of MitoTracker™ Red CMXRos signal and partially preserved (4′,6-diamidino-2-phenylindole) DAPI-based cell density, indicating Drp1-dependent mitochondrial dysfunction. Furthermore, azelastine selectively reduced p-ERK phosphorylation in the cell signaling pathway. Azelastine exerts potent anticancer effects in TNBC cells via an HRH1-independent, ARF1-dependent mechanism that attenuates the Extracellular signal-regulated kinase (ERK)–Drp1 axis, and induces Drp1-dependent mitochondrial dysfunction, independent of its canonical HRH1 receptor function. This ARF1-dependent mechanism provides strong scientific rationale for the drug repositioning of azelastine as an effective therapeutic agent for ARF1-driven TNBC. Full article

Peripheral blood serves both as a source of effector immune cells that migrate to exocrine glands and as a reflection of the immunological changes occurring in patients with Sjögren’s disease (SjD). These changes may be linked to the clinical state of these patients. We analyzed total cell counts in the peripheral blood, as well as frequencies of individual leukocyte subpopulations, membrane expression levels of CD38 and CD157, and serum concentrations of soluble sCD38 and sCD157 in SjD patients (n = 40) and age-matched healthy controls (n = 20). Hierarchical clustering based on the cell count of leukocyte subpopulations was employed to identify distinct patient subgroups. Associations between these clusters and clinical parameters were subsequently evaluated. Key findings included a reduction in lymphocyte counts and their subpopulations, alongside increased CD38 expression on CD38⁺ B cells (p = 0.047) and, unexpectedly, on monocytes (p = 0.014) when comparing patients and controls. The involvement of innate immunity was further supported by the differential expression of CD157 across patient samples. Patients with low cell counts exhibited reduced CD157 expression on monocytes and granulocytes (p < 0.02), tested positive for anti-Ro antibodies, and reported severe fatigue. Our findings suggest that innate immune cells, such as monocytes and granulocytes in peripheral blood, are also likely to contribute to the manifestation and progression of SjD. The differential expression of CD157 may reflect distinct immunopathological states and warrants further investigation, as its precise role in exocrine gland involvement and extra-glandular manifestations lies beyond the scope of this study. Full article

Sclerotinia sclerotiorum, a soil-borne phytopathogenic fungus with a broad host range, often leads to severe disease and significant economic losses in agricultural production. The guanine exchange factor EFA6 of ADP-ribosylation factor 6 (ARF6) has been extensively studied in animals, but its function in fungi is seldom reported. Here, reverse genetics methods were employed to explore the effects of SsEFA6 in the process of pathogenicity of S. sclerotiorum. Knockout of SsEFA6 hindered appressoria formation and sclerotia production. However, it did not affect the secretion of oxalic acid, the sensitivity to cell wall inhibitors, or hyperosmotic stress. Nevertheless, SsEFA6 deletion did result in a significant decrease in mutant virulence, indicative of its indispensability in virulence. Therefore, SsEFA6 plays an essential role in appressoria formation, sclerotia production, and fungal virulence in S. sclerotiorum. Full article

Cancer remains one of the most pressing health challenges of the 21st century, with rising global incidence underscoring the need for innovative therapeutic strategies. Despite significant advances in biotechnology, curative outcomes remain limited, prompting interest in integrative approaches. Ayurveda, the traditional Indian system of medicine, suggests a holistic therapeutic framework that is now gaining molecular validation in oncology. In this review, the literature was systematically collected and analyzed from major databases, including PubMed, Scopus, and Web of Science, encompassing studies across ethnopharmacology, biochemistry, and cancer biology. The analysis focused on Ayurvedic phytochemicals that modulate ADP-ribosylation (ADPr), a dynamic post-translational modification central to DNA repair, chromatin organization, and cellular stress responses, with particular emphasis on poly (ADP-ribose) polymerase (PARP)-mediated pathways and their oncological relevance. We have also explored the role of p53, a key stress-response regulator intricately linked to ADPr dynamics, which acts as a downstream effector integrating these molecular events with cell fate decisions. Evidence indicates that several Ayurvedic compounds, including curcumin, resveratrol, and withaferin A, influence PARP–p53 signaling networks, thereby modulating DNA repair fidelity, apoptosis, and tumor adaptation. The review further addresses challenges related to the poor solubility of these phytochemicals and highlights recent advances in Phyto-nanomedicine-based delivery systems that enhance their stability and therapeutic efficacy. Overall, the synthesis of Ayurvedic pharmacology with molecular oncology reveals mechanistic insights that may inform the rational development of novel, mechanism-driven cancer therapeutics. Full article

Poly(ADP-ribose)polymerase 1 (PARP1) is an enzyme that interacts with chromatin during DNA repair and transcription processes; the molecular mechanisms of these processes remain to be determined. Previously, we have shown that PARP1 can bind to and reorganize nucleosomes using two modes of interaction with a mono-nucleosome, which are realized through PARP1 binding to the ends of linker DNA and to the nucleosome core. Here, it is shown that the latter mode of binding induces the reorganization of nucleosome structure and is more stable under the conditions of poly(ADP-ribosyl)ation (PARylation). The initial nucleosome structure is fully recovered after the dissociation of autoPARylated PARP1. The competition between PARP1 and linker histone H1.0 for binding to a nucleosome is mediated by the PARP1-H1.0 interaction and is affected by the length of linker DNA fragments. Longer linkers stabilize H1.0-nucleosome complexes, while shorter linkers facilitate displacement of H1.0 from the chromatosome by PARP1. PARylation removes both H1.0 and PARP1 from the complexes with nucleosomes. The data suggest that the H1.0 displacement from chromatin by PARP1 that is likely modulated by the density of nucleosomes might reduce chromatin compaction and facilitate access of PARP1-dependent DNA repair and transcription factors to nucleosome and inter-nucleosomal DNA. Full article

Intrinsically disordered regions (IDRs) are present in nearly all proteins, often accounting for more than 40% of their amino acid sequence. Unlike structured domains, IDRs lack sequence or structural conservation across species while maintaining conserved biological functions. Here, we discovered that the previously uncharacterized disordered tail region of Poly(ADP-ribose) glycohydrolase (PARG) controls its localization and activity. Despite its structural divergence, this domain supports conserved regulatory functions across species. Deletion of the disordered tail results in cytoplasmic mislocalization, aberrant accumulation in the nucleolus, impaired chromatin association, and reduced enzymatic activity. Mass spectrometry analysis reveals that this disordered region mediates interactions with nuclear transport factors, post-translational modification enzymes, and chromatin-associated complexes. Together, these results demonstrate that the disordered tail region of PARG acts as a regulatory hub that integrates multiple layers of control to ensure proper subcellular localization and chromatin function. Full article