Armadillo Repeat Research Articles

Diversity and structural-functional insights of alpha-solenoid proteins.

Alpha-solenoids are a significant and diverse subset of structured tandem repeat proteins (STRPs) that are important in various domains of life. This review examines their structural and functional diversity and highlights their role in critical cellular processes such as signaling, apoptosis, and transcriptional regulation. Alpha-solenoids can be classified into three geometric folds: low curvature, high curvature, and corkscrew, as well as eight subfolds: ankyrin repeats; Huntingtin, elongation factor 3, protein phosphatase 2A, and target of rapamycin; armadillo repeats; tetratricopeptide repeats; pentatricopeptide repeats; Pumilio repeats; transcription activator-like; and Sel-1 and Sel-1-like repeats. These subfolds represent distinct protein families with unique structural properties and functions, highlighting the versatility of alpha-solenoids. The review also discusses their association with disease, highlighting their potential as therapeutic targets and their role in protein design. Advances in state-of-the-art structure prediction methods provide new opportunities and challenges in the functional characterization and classification of this kind of fold, emphasizing the need for continued development of methods for their identification and proper data curation and deposition in the main databases.

Kadukkai maathirai (Indian herbal drug) prevents hepatocellular cancer progression by enhancing GSTM1 expression and modulating β catenin transcription: in-silico and in-vivo study

Background Hepatocellular carcinoma (HCC) is an aggressive malignancy with poor clinical outcomes. Hence cost-effective drugs with fewer side effects as a standard supportive therapy might yield substantial advantages in efficacy and safety. Kadukkai maathirai (KM) is being used as a supplement in hepatocellular carcinoma. We evaluated whether KM has any preventive action on cancer progression in diethyl nitrosamine (DEN) - induced HCC in rats. Methods DEN was injected to produce HCC in rats, which was confirmed after 16 weeks. All the rats were orally administered KM for 4 weeks. Hepatoprotective potential (serum AST, ALT, ALP, Bilirubin) and anticancer efficacy (body weight, nodule count, tumor progression by histopathology, expression of GSTM1 by Liquid chromatography-mass spectrometry (LC-MS), and In-silico analysis of phytoconstituents against β catenin and LRP analysis were evaluated. Results KM prevented cancer progression against DEN-induced HCC by an increase in GSTM1, a phase II detoxifying enzyme. It significantly reversed altered nodule count, relative liver weight, body weight, and histopathological features of HCC. In silico analysis of phytoconstituents of KM showed that they modulate the intracellular transcription process by inhibiting the armadillo repeat region of β catenin. Conclusions Our results elucidate the potential of KM as a supplement in HCC by reducing nodule count, protecting the liver from further damage, GSTM1 expression, and inhibiting armadillo repeat region of β catenin.

Transcriptome-wide Identification of Nine Tandem Repeat Protein Families in Roselle (Hibiscus sabdariffa L.).

Plants are rich in tandem repeats-containing proteins. It is postulated that the occurrence of tandem repeat gene families facilitates the adaptation and survival of plants in adverse environmental conditions. This study intended to identify the tandem repeats in the transcriptome of a high potential tropical horticultural plant, roselle (Hibiscus sabdariffa L.). A total of 92,974 annotated de novo assembled transcripts were analysed using in silico approach, and 6,541 transcripts that encoded proteins containing tandem repeats with length of 20-60 amino acid residues were identified. Domain analysis revealed a total of nine tandem repeat protein families in the transcriptome of roselle, which are the Ankyrin repeats (ANK), Armadillo repeats (ARM), elongation factor-hand domain repeats (EF-hand), Huntingtin, elongation factor 3, protein phosphatase 2A, yeast kinase TOR1 repeats (HEAT), Kelch repeats (Kelch), leucine rich repeats (LRR), pentatricopeptide repeats (PPR), tetratricopeptide repeats (TPR) and WD40 repeats (WD40). Functional annotation analysis further matched 6,236 transcripts to 1,045 known proteins that contained tandem repeats including proteins implicated in plant development, protein-protein interaction, immunity and abiotic stress responses. The findings provide new insights into the occurrence of tandem repeats in the transcriptome and lay the foundation to elucidate the functional associations between tandem peptide repeats (TRs) and proteins in roselle and facilitate the identification of novel biotic and abiotic response related tandem repeats genes that may be useful in breeding improved varieties.

Candidate proteins interacting with cytoskeleton in cells from the basal airway epithelium in vitro.

Introduction: The cytoskeleton consists of actin, microtubules, septins, and intermediate filaments and, in most cells, is anchored to an extracellular matrix. Each cell has a unique arrangement of this network and readjusts it from time to time. To investigate the regulation of these reorganizations, we identified interactors from extracts of four cultured lines representing basal cells from the airway epithelium. Methods: After immunoprecipitation with an antibody against keratin 17, samples were processed by liquid chromatography and tandem mass spectrometry. Samples not undergoing antibody-mediated capture were processed in parallel. Results: The main keratins of basal cells, namely, Krt14 (type I) and Krt5 (type II), constituted 67% of the total keratin recovered. Several other intermediate filament proteins, nestin, lamin-B1, and prelamin A/C, were present but not enriched upon immunoprecipitation. Although the class of armadillo-repeat proteins was represented by beta-catenin1 and plakoglobin, other desmosome plaque constituents were absent. Large cytolinkers were represented by the spectraplakin, microtubule-actin cross-linking factor (Macf1), which was enriched by immunoprecipitation, and the plakin, plectin, which was not enriched. Subunits of actin filaments and microtubules, along with numerous proteins associated with them, were recovered in both immunoprecipitated samples and those lacking the capture step. Coefficients of determination were computed based on abundance. The actin-associated proteins, alpha-spectrin and brain-specific angiogenesis inhibitor (Baiaip2l), were modestly correlated with keratin abundance but highly correlated with one another and with the keratin-binding protein, annexin A2. This interaction network resembled the pedestal formed by pathogenic Escherichia coli. Microtubule-associated proteins, dynamin 1-like protein and cytoplasmic dynein 1 heavy chain (Dync1h1), were enriched by immunoprecipitation, suggesting association with keratins, whereas kinesin-1 heavy chain and microtubule-associated protein retinitis pigmentosa 1 (EB1), were not enriched. Dync1h1 abundance was negatively correlated with that of all the septins, suggesting resemblance to a known antagonistic septin-dynein 1 relationship on microtubules. Conclusion: The cell lines showed remarkable uniformity with respect to the candidates interacting with cytoskeleton. The alpha-spectrin-Baiap2l network may link actin filaments to keratin precursor particles. A smaller interaction network centered on Dync1h1 was negatively correlated with all spectrin-Baiap2l constituents, suggesting that it and its binding partners are excluded from the pedestal-like domain.

PUB40 attenuates Phytophthora capsici resistance by destabilizing the MEK2-SIPK/WIPK cascade in Nicotiana benthamiana

The mitogen-activated protein kinase (MAPK) cascade MEK2-SIPK/WIPK is essential for immunity in Solanaceae plants. This cascade is tightly controlled to prevent harmful hyperactivation. However, the E3 ubiquitin ligases utilized by plants to reduce MEK2- SIPK/WIPK protein levels remain largely elusive. Here, we confirmed the essential role of Nicotiana benthamiana MEK2-SIPK/WIPK in resistance to the oomycete pathogen Phytophthora capsici. Using tobacco rattle virus (TRV)-based gene silencing, we screened prevalent plant U-box protein (PUB)-type E3 ligases with Armadillo (ARM) repeats to characterize those involved in Phytophthora resistance and MEK2-SIPK/WIPK degradation. We found that pub40 knockdown mutants exhibited significantly enhanced resistance to P. capsici. NbPUB40 was under ubiquitination and proteasomal degradation in planta, with two conserved sites (Cys28 and Val41) in the U-box domain being essential for its activity. NbPUB40 was shown to interact with the whole MEK2-SIPK/WIPK cascade and promote their degradation, the ubiquitination levels of which were also notably reduced in the pub40 mutant. Our results reveal a mechanism in which a PUB E3 ubiquitin ligase negatively regulates plant P. capsici resistance by destabilizing the MEK2-SIPK/WIPK cascade.

Modular binder technology by NGS-aided, high-resolution selection in yeast of designed armadillo modules

Establishing modular binders as diagnostic detection agents represents a cost- and time-efficient alternative to the commonly used binders that are generated one molecule at a time. In contrast to these conventional approaches, a modular binder can be designed in silico from individual modules to, in principle, recognize any desired linear epitope without going through a selection and hit-validation process, given a set of preexisting, amino acid-specific modules. Designed armadillo repeat proteins (dArmRP) have been developed as modular binder scaffolds, and we report here the generation of highly specific dArmRP modules by yeast surface display selection, performed on a rationally designed dArmRP library. A selection strategy was developed to distinguish the binding difference resulting from a single amino acid mutation in the target peptide. Our reverse-competitor strategy introduced here employs the designated target as a competitor to increase the sensitivity when separating specific from cross-reactive binders that show similar affinities for the target peptide. With this switch in selection focus from affinity to specificity, we found that the enrichment during this specificity sort is indicative of the desired phenotype, regardless of the binder abundance. Hence, deep sequencing of the selection pools allows retrieval of phenotypic hits with only 0.1% abundance in the selectivity sort pool from the next-generation sequencing data alone. In a proof-of-principle study, a binder was created by replacing all corresponding wild-type modules with a newly selected module, yielding a binder with very high affinity for the designated target that has been successfully validated as a detection agent in western blot analysis.

Structure of the E3 ligase CRL2-ZYG11B with substrates reveals the molecular basis for N-degron recognition and ubiquitination.

ZYG11B is a substrate specificity factor for Cullin-RING ubiquitin ligase (CRL2) involved in many biological processes, including Gly/N-degron pathways. Yet how the binding of ZYG11B with CRL2 is coupled to substrate recognition and ubiquitination is unknown. We present the Cryo-EM structures of the CRL2-ZYG11B holoenzyme alone and in complex with a Gly/N-peptide from the inflammasome-forming pathogen sensor NLRP1. The structures indicate ZYG11B folds into a Leucine-Rich Repeat followed by two armadillo repeat domains that promote assembly with CRL2 and recognition of NLRP1 Gly/N-degron. ZYG11B promotes activation of the NLRP1 inflammasome through recognition and subsequent ubiquitination of the NLRP1 Gly/N-degron revealed by viral protease cleavage. Our structural and functional data indicate that blocking ZYG11B recognition of the NLRP1 Gly/N-degron inhibits NLRP1 inflammasome activation by a viral protease. Overall, we show how the CRL2-ZYG11B E3 ligase complex recognizes Gly/N-degron substrates, including those that are involved in viral protease-mediated activation of the NLRP1 inflammasome.

Clinical characteristics and pathophysiological properties of newly discovered LRRK2 variants associated with Parkinson's disease

Leucine-rich repeat kinase 2 (LRRK2) is the most common gene responsible for familial Parkinson's disease (PD). The gene product of LRRK2 contains multiple protein domains, including armadillo repeat, ankyrin repeat, leucine-rich repeat (LRR), Ras-of-complex (ROC), C-terminal of ROC (COR), kinase, and WD40 domains. In this study, we performed genetic screening of LRRK2 in our PD cohort, detecting sixteen LRRK2 rare variants. Among them, we selected seven variants that are likely to be familial and characterized them in terms of LRRK2 protein function, along with clinical information and one pathological analysis. The seven variants were S1120P and N1221K in the LRR domain; I1339M, S1403R, and V1447M in the ROC domain; and I1658F and D1873H in the COR domain. The kinase activity of the LRRK2 variants N1221K, S1403R, V1447M, and I1658F toward Rab10, a well-known phosphorylation substrate, was higher than that of wild-type LRRK2. LRRK2 D1873H showed enhanced self-association activity, whereas LRRK2 S1403R and D1873H showed reduced microtubule-binding activity. Pathological analysis of a patient with the LRRK2 V1447M variant was also performed, which revealed Lewy pathology in the brainstem. No functional alterations in terms of kinase activity, self-association activity, and microtubule-binding activity were detected in LRRK2 S1120P and I1339M variants. However, the patient with PD carrying LRRK2 S1120P variant also had a heterozygous Glucosylceramidase beta 1 (GBA1) L444P variant. In conclusion, we characterized seven LRRK2 variants potentially associated with PD. Five of the seven variants in different LRRK2 domains exhibited altered properties in kinase activity, self-association, and microtubule-binding activity, suggesting that each domain variant may contribute to disease progression in different ways.

Kadukkai maathirai (Indian herbal drug) prevents hepatocellular cancer progression by enhancing GSTM1 expression and modulating β catenin transcription: in-silico and in-vivo study

Background Hepatocellular carcinoma (HCC) is an aggressive malignancy with poor clinical outcomes. Hence cost-effective drugs with fewer side effects as a standard supportive therapy might yield substantial advantages in efficacy and safety. Kadukkai maathirai (KM) is being used as a supplement in hepatocellular carcinoma. We evaluated whether KM has any preventive action on cancer progression in diethyl nitrosamine (DEN) - induced HCC in rats. Methods DEN was injected to produce HCC in rats, which was confirmed after 16 weeks. All the rats were orally administered KM for 4 weeks. Hepatoprotective potential (serum AST, ALT, ALP, Bilirubin) and anticancer efficacy (body weight, nodule count, tumor progression by histopathology, expression of GSTM1 by Liquid chromatography-mass spectrometry (LC-MS), and In-silico analysis of phytoconstituents against β catenin and LRP analysis were evaluated. Results KM prevented cancer progression against DEN-induced HCC by an increase in GSTM1, a phase II detoxifying enzyme. It significantly reversed altered nodule count, relative liver weight, body weight, and histopathological features of HCC. In silico analysis of phytoconstituents of KM showed that they modulate the intracellular transcription process by inhibiting the armadillo repeat region of β catenin. Conclusions Our results elucidate the potential of KM as a supplement in HCC by reducing nodule count, protecting the liver from further damage, GSTM1 expression, and inhibiting armadillo repeat region of β catenin.

The unconventional resistance protein PTR recognizes the Magnaporthe oryzae effector AVR-Pita in an allele-specific manner.

Blast disease caused by the fungus Magnaporthe oryzae is one of the most devastating rice diseases. Disease resistance genes such as Pi-ta or Pi-ta2 are critical in protecting rice production from blast. Published work reports that Pi-ta codes for a nucleotide-binding and leucine-rich repeat domain protein (NLR) that recognizes the fungal protease-like effector AVR-Pita by direct binding. However, this model was challenged by the recent discovery that Pi-ta2 resistance, which also relies on AVR-Pita detection, is conferred by the unconventional resistance gene Ptr, which codes for a membrane protein with a cytoplasmic armadillo repeat domain. Here, using NLR Pi-ta and Ptr RNAi knockdown and CRISPR/Cas9 knockout mutant rice lines, we found that AVR-Pita recognition relies solely on Ptr and that the NLR Pi-ta has no role in it, indicating that it is not the Pi-ta resistance gene. Different alleles of Ptr confer different recognition specificities. The A allele of Ptr (PtrA) detects all natural sequence variants of the effector and confers Pi-ta2 resistance, while the B allele of Ptr (PtrB) recognizes a restricted set of AVR-Pita alleles and, thereby, confers Pi-ta resistance. Analysis of the natural diversity in AVR-Pita and of mutant and transgenic strains identified one specific polymorphism in the effector sequence that controls escape from PtrB-mediated resistance. Taken together, our work establishes that the M. oryzae effector AVR-Pita is detected in an allele-specific manner by the unconventional rice resistance protein Ptr and that the NLR Pi-ta has no function in Pi-ta resistance and the recognition of AVR-Pita.

Unveiling the Binding between the Armadillo-Repeat Domain of Plakophilin 1 and the Intrinsically Disordered Transcriptional Repressor RYBP.

Plakophilin 1 (PKP1), a member of the p120ctn subfamily of the armadillo (ARM)-repeat-containing proteins, is an important structural component of cell-cell adhesion scaffolds although it can also be ubiquitously found in the cytoplasm and the nucleus. RYBP (RING 1A and YY1 binding protein) is a multifunctional intrinsically disordered protein (IDP) best described as a transcriptional regulator. Both proteins are involved in the development and metastasis of several types of tumors. We studied the binding of the armadillo domain of PKP1 (ARM-PKP1) with RYBP by using in cellulo methods, namely immunofluorescence (IF) and proximity ligation assay (PLA), and in vitro biophysical techniques, namely fluorescence, far-ultraviolet (far-UV) circular dichroism (CD), and isothermal titration calorimetry (ITC). We also characterized the binding of the two proteins by using in silico experiments. Our results showed that there was binding in tumor and non-tumoral cell lines. Binding in vitro between the two proteins was also monitored and found to occur with a dissociation constant in the low micromolar range (~10 μM). Finally, in silico experiments provided additional information on the possible structure of the binding complex, especially on the binding ARM-PKP1 hot-spot. Our findings suggest that RYBP might be a rescuer of the high expression of PKP1 in tumors, where it could decrease the epithelial-mesenchymal transition in some cancer cells.

In silico evaluation of anti-colorectal cancer inhibitors by Resveratrol derivatives targeting Armadillo repeats domain of APC: molecular docking and molecular dynamics simulation.

Colorectal cancer is the second leading cause of cancer-related deaths. In 2018, there were an estimated 1.8 million cases, and this number is expected to increase to 2.2 million by 2030. Despite its prevalence, the current therapeutic option has a lot of side effects and limitations. Therefore, this study was designed to employ a computational approach for the identification of anti-cancer inhibitors against colorectal cancer using Resveratrol derivatives. Initially, the pass prediction spectrum of 50 derivatives was conducted and selected top seven compounds based on the maximum pass prediction score. After that, a comprehensive analysis, including Lipinski Rule, pharmacokinetics, ADMET profile study, molecular orbitals analysis, molecular docking, molecular dynamic simulations, and MM-PBSA binding free energy calculations. The reported binding affinity ranges of Resveratrol derivatives from molecular docking were -6.1 kcal/mol to -7.9 kcal/mol against the targeted receptor of human armadillo repeats domain of adenomatous polyposis coli (APC) (PDB ID: 3NMW). Specifically, our findings reported that two compounds [(03) Resveratrol 3-beta-mono-D-glucoside, and (29) Resveratrol 3-Glucoside] displayed the highest level of effectiveness compared to all other derivatives (-7.7 kcal/mol and -7.9 kcal/mol), and favorable drug-likeness, and exceptional safety profiles. Importantly, almost all the molecules were reported as free from toxic effects. Subsequently, molecular dynamic simulations conducted over 100ns confirmed the stability of the top two ligand-protein complexes. These findings suggest that Resveratrol derivatives may be effective drug candidate to manage the colorectal cancer. However, further experimental research, such as in vitro/in vivo studies, is essential to validate these computational findings and confirm their practical value.

Familial bilateral macronodular adrenal hyperplasia due to a novel ARMC 5 germline mutation: Clinical status and possible association with other neoplasms

Introduction/ObjectivesMutations in the ARMC5 (armadillo repeat containing 5, OMIM 615549) gene, a putative tumor suppressor gene, have recently been identified as a common cause of sporadic and familial bilateral macronodular adrenal hyperplasia (BMAH). Familial BMAH is thought to be caused by two mutations, one germline and the other somatic, as suggested by the 2-hit theory. The objective is to describe a new mutation and develop its clinical characteristics and implications. Methods, Results and ConclusionsWe present an affected family with 11 members carrying a novel mutation of the ARMC5 gene (NM_001288767.1): c.2162T>C p. (Leu721Pro). Two of the carriers developed clinical Cushing's syndrome (CS), two mild autonomous cortisol secretion (MACS) and one presented with autonomous cortisol secretion (ACS). Four patients developed other tumors, three of whom died from this cause. It is not known whether these tumors could be related to the described mutation.

A systematic analysis of ARM genes revealed that GhARM144 regulates the resistance against Verticillium dahliae via interaction with GhOSM34.

Proteins of the armadillo repeat gene family play important roles in plant pathogen response. Here, 169 armadillo (ARM) genes were identified in upland cotton (Gossypium hirsutum). Phylogenetic analysis grouped these into 11 subfamilies, with conserved protein structures within each subfamily. The results signify that the expansion of the gene family occurred via whole genome duplication and dispersed duplication. Expression profiling and network analysis suggest that GhARM144 may regulate cotton resistance to Verticillium dahliae. GhARM144 was upregulated in roots by V. dahliae infection or salicylic acid treatment. This upregulation indicates a negative regulatory role of GhARM144' in the cotton immune responses, potentially by manipulating salicylic acid biosynthesis. Protein interaction studies found that GhARM144 associates with an osmotin-like protein, GhOSM34, at the plasma membrane. Silencing GhOSM34 reduced the resistance to V. dahliae, suggesting it may play a positive regulatory role. The results demonstrate that GhARM144 modulates cotton immunity through interaction with GhOSM34 and salicylic acid signalling. Further study of these proteins may yield insights into disease resistance mechanisms in cotton and other plants.

Identification of CTNNB1 in the lined seahorse, Hippocampus erectus, and its function in innate immunity and cell proliferation

Abstractβ‐Catenin (CTNNB) is a core downstream mediator in the Wnt/β‐catenin signaling pathway, which plays a role in immune regulation and cell differentiation. In the present study, two CTNNB genes were identified by genomic analysis of Hippocampus erectus and named He‐CTNNB1 and He‐CTNNB2. He‐CTNNB1 was more conserved than He‐CTNNB2. The full length of He‐CTNNB1 was 2369 bp, including an open reading frame of 2275 bp that encoded 737 amino acids containing 12 armadillo repeats. Phylogenetic analysis revealed that He‐CTNNB1 clusters had homologs in other bony fishes. Tissue distribution analysis showed the highest mRNA expression of He‐CTNNB1 in the ovary, liver, and kidney of the lined seahorse under normal physiological conditions. The transcription level of He‐CTNNB1 was significantly increased in the liver and kidney in response to LPS, poly I:C, and Edwardsiella tarda challenge (p < 0.05). In vitro overexpression of He‐CTNNB1 significantly upregulated the expression of key genes of the canonical Wnt/β‐catenin signaling pathway, such as axin2, cMyc, and cyclinD (p < 0.05), which increased cell proliferation during the wound‐healing process. Taken together, our results suggest that He‐CTNNB1 is essential for cell proliferation and the innate immune response in H. erectus.

Familial bilateral macronodular adrenal hyperplasia due to a novel ARMC 5 germline mutation: Clinical status and possible association with other neoplasms

Introduction/ObjectivesMutations in the ARMC5 (armadillo repeat containing 5, OMIM 615549) gene, a putative tumor suppressor gene, have recently been identified as a common cause of sporadic and familial bilateral macronodular adrenal hyperplasia (BMAH). Familial BMAH is thought to be caused by two mutations, one germline and the other somatic, as suggested by the 2-hit theory. The objective is to describe a new mutation and develop its clinical characteristics and implications. Methods, Results and ConclusionsWe present an affected family with 11 members carrying a novel mutation of the ARMC5 gene (NM_001288767.1): c.2162T>C p. (Leu721Pro). Two of the carriers developed clinical Cushing's syndrome (CS), two mild autonomous cortisol secretion (MACS) and one presented with autonomous cortisol secretion (ACS). Four patients developed other tumors, three of whom died from this cause. It is not known whether these tumors could be related to the described mutation.

Plant U-box E3 ligases PUB20 and PUB21 negatively regulate pattern-triggered immunity in Arabidopsis.

Plant U-box E3 ligases PUB20 and PUB21 are flg22-triggered signaling components and negatively regulate immune responses. Plant U-box proteins (PUBs) constitute a class of E3 ligases that are associated with various stress responses. Among the class IV PUBs featuring C-terminal Armadillo (ARM) repeats, PUB20 and PUB21 are closely related homologs. Here, we show that both PUB20 and PUB21 negatively regulate innate immunity in plants. Loss of PUB20 and PUB21 function leads to enhanced resistance to surface inoculation with the virulent bacterium Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). However, the resistance levels remain unaffected after infiltration inoculation, suggesting that PUB20 and PUB21 primarily function during the early defense stages. The enhanced resistance to Pst DC3000 in PUB mutant plants (pub20-1, pub21-1, and pub20-1/pub21-1) correlates with extensive flg22-triggered reactive oxygen production, strong MPK3 activation, and enhanced transcriptional activation of early immune response genes. Additionally, PUB mutant plants (except pub21-1) exhibit constitutive stomatal closure after Pst DC3000 inoculation, implying the significant role of PUB20 in stomatal immunity. Comparative analyses of flg22 responses between PUB mutants and wild-type plants reveals that the robust activation of the pattern-induced immune responses may enhance resistance against Pst DC3000. Notably, the hypersensitivity responses triggered by RPM1/avrRpm1 and RPS2/avrRpt2 are independent of PUB20 and PUB21. These results suggest that PUB20 and PUB21 knockout mutations affect bacterial invasion, likely during the early stages, acting as negative regulators of plant immunity.

Exploring the Impact of the β-Catenin Mutations in Hepatocellular Carcinoma: An In-Depth Review.

Liver cancer, primarily hepatocellular carcinoma, represents a major global health issue with significant clinical, economic, and psychological impacts. Its incidence continues to rise, driven by risk factors such as hepatitis B and C infections, nonalcoholic steatohepatitis, and various environmental influences. The Wnt/β-Catenin signaling pathway, frequently dysregulated in HCC, emerges as a promising therapeutic target. Critical genetic alterations, particularly in the CTNNB1 gene, involve mutations at key phosphorylation sites on β-catenin's N-terminal domain (S33, S37, T41, and S45) and in armadillo repeat domains (K335I and N387K). These mutations impede β-catenin degradation, enhancing its oncogenic potential. In addition to genetic alterations, molecular and epigenetic mechanisms, including DNA methylation, histone modifications, and noncoding RNAs, further influence β-catenin signaling and tumor progression. However, β-catenin activation alone is insufficient for hepatocarcinogenesis; additional genetic "hits" are required for tumor initiation. Mutations or alterations in genes such as Ras, c-Met, NRF2, and LKB1, when combined with β-catenin activation, significantly contribute to HCC development and progression. Understanding these cooperative mutations provides crucial insights into the disease and reveals potential therapeutic strategies. The complex interplay between genetic variations and the tumor microenvironment, coupled with novel therapeutic approaches targeting the Wnt/β-Catenin pathway, offers promise for improved treatment of HCC. Despite advances, translating preclinical findings into clinical practice remains a challenge. Future research should focus on elucidating how specific β-catenin mutations and additional genetic alterations contribute to HCC pathogenesis, leveraging genetically clengineered mouse models to explore distinct signaling impacts, and identifying downstream targets. Relevant clinical trials will be essential for advancing personalized therapies and enhancing patient outcomes. This review provides a comprehensive analysis of β-Catenin signaling in HCC, highlighting its role in pathogenesis, diagnosis, and therapeutic targeting, and identifies key research directions to improve understanding and clinical outcomes.

DGARM/C10orf76/ARMH3 for Ceramide Transfer Zone at the Endoplasmic Reticulum-Distal Golgi Contacts.

Phosphatidylinositol 4-monophosphate (PtdIns(4)P) is one of the key membrane components which mark the membrane contact sites. In the mammalian Golgi complex, PtdIns(4)P is produced at various subregions via specific mechanisms for each site. Particularly, PtdIns(4)P pools generated at the distal Golgi regions are pivotal for the determination of membrane contacts between the endoplasmic reticulum (ER) and Golgi, at which inter-organelle lipid transport takes place. In this short review, we will focus on C10orf76 (or ARMH3), which we propose to rename as DGARM after a distal Golgi armadillo repeat protein, for its function in generating a PtdIns(4)P pool crucial for ER-to-distal Golgi ceramide transport. We further discuss from the viewpoint of the evolutionary conservation of DGARM.

Unexpected dynamics in femtomolar complexes of binding proteins with peptides

Ultra-tight binding is usually observed for proteins associating with rigidified molecules. Previously, we demonstrated that femtomolar binders derived from the Armadillo repeat proteins (ArmRPs) can be designed to interact very tightly with fully flexible peptides. Here we show for ArmRPs with four and seven sequence-identical internal repeats that the peptide-ArmRP complexes display conformational dynamics. These dynamics stem from transient breakages of individual protein-residue contacts that are unrelated to overall unbinding. The labile contacts involve electrostatic interactions. We speculate that these dynamics allow attaining very high binding affinities, since they reduce entropic losses. Importantly, only NMR techniques can pick up these local events by directly detecting conformational exchange processes without complications from changes in solvent entropy. Furthermore, we demonstrate that the interaction surface of the repeat protein regularizes upon peptide binding to become more compatible with the peptide geometry. These results provide novel design principles for ultra-tight binders.