Mitochondrial abnormalities contribute to muscle weakness in a Dnajb6 deficient zebrafish model.

Mutations in DNAJB6 are a well-established cause of limb girdle muscular dystrophy type D1 (LGMD D1). Patients with LGMD D1 develop progressive muscle weakness with histology showing fibre damage, autophagic vacuoles, and aggregates. Whilst there are many reports of LGMD D1 patients, the role of DNAJB6 in the muscle is still unclear. In this study, we developed a loss of function zebrafish model in order to investigate the role of Dnajb6. Using a double dnajb6a and dnajb6b mutant model, we show that loss of Dnajb6 leads to a late onset muscle weakness. Interestingly, we find that adult fish lacking Dnajb6 do not have autophagy or myofibril defects, however, they do show mitochondrial changes and damage. This study demonstrates that loss of Dnajb6 causes mitochondrial defects and suggests that this contributes to muscle weakness in LGMD D1. These findings expand our knowledge of the role of Dnajb6 in the muscle and provides a model to screen novel therapies for LGMD D1.

DNAJB6 is expressed in neurons and oligodendrocytes of the human brain.

DNAJB6 is a suppressor of α-synuclein aggregation in vivo and in vitro. DNAJB6 is strongly expressed in the brain, and its overall protein expression is altered in neurodegenerative conditions such as Parkinson's Disease (PD) and Multiple System Atrophy (MSA). These two diseases are characterized by accumulation of aggregated α-synuclein in neurons and oligodendrocytes, respectively. To further explore this, we employed post-mortem normal human brain material to investigate the regional and cell type specific protein expression of DNAJB6. We found that the DNAJB6 protein is ubiquitously expressed across various regions of the brain. Notably, we demonstrate for the first time that DNAJB6 is present in nearly half (41%-53%) of the oligodendrocyte population and in the majority (68%-80%) of neurons. However, DNAJB6 was only sparsely present in other cell types such as astrocytes and microglia. Given that α-synuclein aggregation in oligodendrocytes is a hallmark of MSA, we investigated DNAJB6 presence in MSA brains compared to control brains. We found no significant difference in the percentage of oligodendrocytes where DNAJB6 was present in MSA brains relative to control brains. In conclusion, our results reveal an expression of the DNAJB6 protein across various regions of the human brain, and that DNAJB6 is almost exclusively present in neurons and oligodendrocytes. Since prior studies have shown that PD and MSA brains have altered levels of DNAJB6 relative to control brains, DNAJB6 may be an interesting target for drug development.

Human milk exosome-derived circDNAJB6 improves bronchopulmonary dysplasia model by promoting DNAJB6 gene transcription.

To verify the protective effect of circDNAJB6 on Bronchopulmonary dysplasia (BPD) cell and animal models and to explore the possible mechanism of its protective effect. The function of circDNAJB6 was investigated at the cell and animal levels. Nuclear and Cytoplasmic RNA extraction kits and fluorescence in situ hybridization (FISH) were used to explore the distribution of circDNAJB6 in cells, and the potential mechanism of circDNAJB6 was verified by q-PCR, luciferase assays and rescue experiments.CircDNAJB6 is abundant in breast milk exosomes. Overexpression of circDNAJB6 can ameliorate damage in BPD models caused by hyperoxia exposure in vivo and in vitro. Mechanistically, circDNAJB6 can target the downstream DNAJB6 gene and promote the transcription of DNAJB6, exertive a protective effect on the experimental BPD model. Our results showed that circDNAJB6 alleviated damage and inhibited the proliferation of alveolar epithelial cells in the BPD model by promoting transcription of parent gene DNAJB6. Human milk exosome-derived circDNAJB6 provides new directions for preventing and treating BPD.

The HSP40 family chaperone isoform DNAJB6b prevents neuronal cells from tau aggregation.

BACKGROUND: Alzheimer's disease (AD) is the most common neurodegenerative disorder with clinical presentations of progressive cognitive and memory deterioration. The pathologic hallmarks of AD include tau neurofibrillary tangles and amyloid plaque depositions in the hippocampus and associated neocortex. The neuronal aggregated tau observed in AD cells suggests that the protein folding problem is a major cause of AD. J-domain-containing proteins (JDPs) are the largest family of cochaperones, which play a vital role in specifying and directing HSP70 chaperone functions. JDPs bind substrates and deliver them to HSP70. The association of JDP and HSP70 opens the substrate-binding domain of HSP70 to help the loading of the clients. However, in the initial HSP70 cycle, which JDP delivers tau to the HSP70 system in neuronal cells remains unclear. RESULTS: We screened the requirement of a diverse panel of JDPs for preventing tau aggregation in the human neuroblastoma cell line SH-SY5Y by a filter retardation method. Interestingly, knockdown of DNAJB6, one of the JDPs, displayed tau aggregation and overexpression of DNAJB6b, one of the isoforms generated from the DNAJB6 gene by alternative splicing, reduced tau aggregation. Further, the tau bimolecular fluorescence complementation assay confirmed the DNAJB6b-dependent tau clearance. The co-immunoprecipitation and the proximity ligation assay demonstrated the protein-protein interaction between tau and the chaperone-cochaperone complex. The J-domain of DNAJB6b was critical for preventing tau aggregation. Moreover, reduced DNAJB6 expression and increased tau aggregation were detected in an age-dependent manner in immunohistochemical analysis of the hippocampus tissues of a mouse model of tau pathology. CONCLUSIONS: In summary, downregulation of DNAJB6b increases the insoluble form of tau, while overexpression of DNAJB6b reduces tau aggregation. Moreover, DNAJB6b associates with tau. Therefore, this study reveals that DNAJB6b is a direct sensor for its client tau in the HSP70 folding system in neuronal cells, thus helping to prevent AD.

MUC1 promotes lymph node metastasis in esophageal squamous cell carcinoma by downregulating DNAJB6 expression.

BACKGROUND: Aberrant expression of MUC1 correlates with the progression of esophageal squamous cell carcinoma (ESCC), this study aimed to explore the effect of targeting MUC1 by Go-203 on malignant behavior of ESCC and the underlying mechanism. METHODS AND RESULTS: IHC was used to examine the expression of MUC1 and DNAJB6 in ESCC samples. qRT-PCR and western blotting were used to examine the expression of MUC1 and DNAJB6 in ESCC cell lines. CCK8, wound healing, and transwell assays were used to determine the effect of regulating MUC1/DNAJB6 on the proliferation, migration, and invasion of ESCC cells. The effect of overexpressing/targeting MUC1 on the activation of the AKT/HSF-1 pathway was determined by western blotting. A negative correlation was confirmed between the expression of DNAJB6 and MUC1 in ESCC tissue samples by IHC, and high expression of MUC1 and low expression of DNAJB6 correlated with lymph node metastasis in ESCC patients. Overexpressing MUC1 downregulated the expression of DNAJB6, promoted ESCC proliferation, invasion, migration and activated the AKT pathway, while targeting MUC1 suppressed proliferation, invasion, migration, and the AKT pathway and up-regulated DNAJB6 expression in vitro. Moreover, MUC1 increased the phosphorylation of HSF-1 via the AKT pathway, and inhibiting AKT-HSF-1 increased the expression of DNAJB6 in vitro. CONCLUSIONS: This study indicated that MUC1 could promote tumorigenesis and metastasis in ESCC by downregulating DNAJB6 expression through AKT-HSF-1 pathway.

miR-632 Induces DNAJB6 Inhibition Stimulating Endothelial-to-Mesenchymal Transition and Fibrosis in Marfan Syndrome Aortopathy.

Marfan syndrome (MFS) is a connective tissue disorder caused by FBN1 gene mutations leading to TGF-ß signaling hyperactivation, vascular wall weakness, and thoracic aortic aneurysms (TAAs). The pathogenetic mechanisms are not completely understood and patients undergo early vascular surgery to prevent TAA ruptures. We previously reported miR-632 upregulation in MFS TAA tissues compared with non-genetic TAA tissues. DNAJB6 is a gene target of miR-632 in cancer and plays a critical role in blocking epithelial-to-mesenchymal transition by inhibiting the Wnt/ß catenin pathway. TGF-ß signaling also activates Wnt/ß catenin signaling and induces endothelial-to-mesenchymal transition (End-Mt) and fibrosis. We documented that miR-632 upregulation correlated with DNAJB6 expression in both the endothelium and the tunica media of MFS TAA (p < 0.01). Wnt/ß catenin signaling, End-Mt, and fibrosis markers were also upregulated in MFS TAA tissues (p < 0.05, p < 0.01 and p < 0.001). Moreover, miR-632 overexpression inhibited DNAJB6, inducing Wnt/ß catenin signaling, as well as End-Mt and fibrosis exacerbation (p < 0.05 and p < 0.01). TGF-ß1 treatment also determined miR-632 upregulation (p < 0.01 and p < 0.001), with the consequent activation of the aforementioned processes. Our study provides new insights about the pathogenetic mechanisms in MFS aortopathy. Moreover, the high disease specificity of miR-632 and DNAJB6 suggests new potential prognostic factors and/or therapeutic targets in the progression of MFS aortopathy.

DNAJB6 suppresses alpha-synuclein induced pathology in an animal model of Parkinson's disease.

BACKGROUND: α-synuclein (α-syn) aggregation can lead to degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) as invariably observed in patients with Parkinson's Disease (PD). The co-chaperone DNAJB6 has previously been found to be expressed at higher levels in PD patients than in control subjects and was also found in Lewy bodies. Our previous experiments showed that knock out of DNAJB6 induced α-syn aggregation in cellular level. However, effects of overexpression of DNAJB6 against α-syn aggregation remains to be investigated. METHODS: We used a α-syn CFP/YFP HEK293 FRET cell line to investigate the effects of overexpression of DNAJB6 in cellular level. α-syn aggregation was induced by transfection α-syn preformed fibrils (PPF), then was measured FRET analysis. We proceeded to investigate if DNAJB6b can impair α-syn aggregation and toxicity in an animal model and used adeno associated vira (AAV6) designed to overexpress of human wt α-syn, GFP-DNAJB6 or GFP in rats. These vectors were injected into the SNpc of the rats, unilaterally. Rats injected with vira to express α-syn along with GFP in the SNpc where compared to rats expressing α-syn and GFP-DNAJB6. We evaluated motor functions, dopaminergic cell death, and axonal degeneration in striatum. RESULTS: We show that DNAJB6 prevent α-syn aggregation induced by α-syn PFF's, in a cell culture model. In addition, we observed α-syn overexpression caused dopaminergic cell death and that this was strongly reduced by co-expression of DNAJB6b. The lesion caused by α-syn overexpression resulted in behavior deficits, which increased over time as seen in stepping test, which was rescued by co-expression of DNAJB6b. CONCLUSION: We here demonstrate for the first time that DNAJB6 is a strong suppressor of α-syn aggregation in cells and in animals and that this results in a suppression of dopaminergic cell death and PD related motor deficits in an animal model of PD.

DnaJB6 is a RanGTP-regulated protein required for microtubule organization during mitosis.

Bipolar spindle organization is essential for the faithful segregation of chromosomes during cell division. This organization relies on the collective activities of motor proteins. The minus-end-directed dynein motor complex generates spindle inward forces and plays a major role in spindle pole focusing. The dynactin complex regulates many dynein functions, increasing its processivity and force production. Here, we show that DnaJB6 is a novel RanGTP-regulated protein. It interacts with the dynactin subunit p150Glued (also known as DCTN1) in a RanGTP-dependent manner specifically in M-phase, and promotes spindle pole focusing and dynein force generation. Our data suggest a novel mechanism by which RanGTP regulates dynein activity during M-phase.

Long non-coding RNA Hsp4 alleviates lipopolysaccharide-induced apoptosis of lung epithelial cells via miRNA-466m-3p/DNAjb6 axis.

Acute lung injury (ALI), as a life-threatening syndrome, is mainly characterized with diffuse alveolar injury, excessive pulmonary inflammation, edema and apoptosis of lung epithelial cells. This study investigated the effects of LncRNA Hsp4 (Hsp4, ENSMUST00000175718) on lipopolysaccharide (LPS)-induced apoptosis of MLE-12 cells. In our research, we found that LPS treatment remarkably induced apoptosis of MLE-12 cells and decreased the expression of Hsp4. Overexpression of Hsp4 significantly reversed LPS-induced cell apoptosis through inhibiting mTOR signaling, while suppression of Hsp4 presented opposite effects. Further results showed that Hsp4 positively regulated the expression of miR-466m-3p. Knockdown of miR-466m-3p reversed LPS-induced cell apoptosis via increasing the levels of DNAjb6 which was confirmed to be the target gene of miR-466m-3p. This finding will be helpful for further understanding the critical roles of Hsp4 in ALI and may provide potential targets for ALI diagnosis and treatment.

DNAJB6 Promotes Ferroptosis in Esophageal Squamous Cell Carcinoma.

BACKGROUND: DnaJ/Hsp40 homolog, subfamily B, member 6 (DNAJB6) is significantly down-regulated in esophageal squamous cell carcinoma (ESCC), while its complicated molecular mechanisms are still unknown. AIMS: To investigate the relationship between DNAJB6 and ESCC. METHODS: The expression of DNAJB6 was detected in ESCC patient by Western blot and immunohistochemistry. To overexpress DNAJB6a by lentivirus infection, colony-forming, CCK-8, transwell, mouse xenograft assays were utilized to verify the proliferous, invasive, and migratory role of DNAJB6a in ESCC cells. The MDA and GSH assays determine whether DNAJB6a participates in cell redox reaction. The variation of AKT and GPX4 was detected by Western blot. RESULTS: The correlation between DNAJB6 level and lymph node metastasis in ESCC patient was negative. Overexpressing DNAJB6a shows tumor-suppressive effects in vitro and in vivo. In addition, DNAJB6a overexpression was accompanied together with a remarkable reduction in the protein levels of GPX4 and phosphorylated AKT (p-AKT). CONCLUSION: DNAJB6 plays an important anti-oncogenic role in ESCC evolvement via ferroptosis.

CircPLEKHM3 acts as a tumor suppressor through regulation of the miR-9/BRCA1/DNAJB6/KLF4/AKT1 axis in ovarian cancer.

BACKGROUND: Emerging evidence has shown that circular RNAs (circRNAs) play essential roles in cancer biology and are potential biomarkers and targets for cancer therapy. However, the expression and function of circRNAs in ovarian carcinogenesis and its progression remain elusive. METHODS: RNA sequencing was performed to reveal circRNA expression profiles in ovarian cancerous and normal tissues. Single-molecule RNA in-situ hybridization was used to quantify circPLEKHM3 expression in tumor tissues. Cell-based in-vitro and in-vivo assays were subsequently conducted to support the clinical findings. RESULTS: CircPLEKHM3 was identified as one of the most significantly down-regulated circRNAs in ovarian cancer tissues compared with normal tissues. Its expression was further decreased in peritoneal metastatic ovarian carcinomas compared to primary ovarian carcinomas. Patients with lower circPLEKHM3 tend to have a worse prognosis. Functionally, circPLEKHM3 overexpression inhibited cell growth, migration and epithelial-mesenchymal transition, whereas its knockdown exerted an opposite role. Further analyses showed that circPLEKHM3 sponged miR-9 to regulate the endogenous expression of BRCA1, DNAJB6 and KLF4, and consequently inactivate AKT1 signaling. In addition, AKT inhibitor MK-2206 could block the tumor-promoting effect of circPLEKHM3 depletion, and potentiate Taxol-induced growth inhibition of ovarian cancer cells. CONCLUSIONS: Our findings demonstrated that circPLEKHM3 functions as a tumor suppressor in ovarian cancer cells by targeting the miR-9/BRCA1/DNAJB6/KLF4/AKT1 axis and may be used as a prognostic indicator and therapeutic target in ovarian cancer patients. The new strategy for treating ovarian cancer by a combination therapy of Taxol with MK-2206 is worth further investigation, especially in ovarian cancer patients with loss of circPLEKHM3 expression.

Astrocytic expression of the chaperone DNAJB6 results in non-cell autonomous protection in Huntington's disease.

Several neurodegenerative diseases like Huntington's, a polyglutamine (PolyQ) disease, are initiated by protein aggregation in neurons. Furthermore, these diseases are also associated with a multitude of responses in non-neuronal cells in the brain, in particular glial cells, like astrocytes. These non-neuronal responses have repeatedly been suggested to play a disease-modulating role, but how these may be exploited to delay the progression of neurodegeneration has remained unclear. Interestingly, one of the molecular changes that astrocytes undergo includes the upregulation of certain Heat Shock Proteins (HSPs) that are classically considered to maintain protein homeostasis, thus resulting in cell autonomous protection. Previously, we discovered DNAJB6, a member of the human DNAJ family, as potent cell autonomous suppressor of PolyQ aggregation and related neurodegeneration. Using cell type specific expression systems in D. melanogaster, we show that exclusive expression of DNAJB6 in astrocytes (that do not express PolyQ protein) can delay neurodegeneration and expands lifespan when the PolyQ protein is exclusively expressed in neurons (that do not co-express DNAJB6 themselves). This provides direct evidence for a non-cell autonomous protective role of astrocytes in PolyQ diseases.

Hsp40 Protein DNAJB6 Interacts with Viral NS3 and Inhibits the Replication of the Japanese Encephalitis Virus.

The Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus prevalent in east and southeast Asia, the Western Pacific, and northern Australia. Since viruses are obligatory intracellular pathogens, the dynamic processes of viral entry, replication, and assembly are dependent on numerous host-pathogen interactions. Efforts to identify JEV-interacting host factors are ongoing because their identification and characterization remain incomplete. Three enzymatic activities of flavivirus non-structural protein 3 (NS3), including serine protease, RNA helicase, and triphosphatase, play major roles in the flaviviruses lifecycle. To identify cellular factors that interact with NS3, we screened a human brain cDNA library using a yeast two-hybrid assay, and identified eight proteins that putatively interact with NS3: COPS5, FBLN5, PPP2CB, CRBN, DNAJB6, UBE2N, ZNF350, and GPR137B. We demonstrated that the DnaJ heat shock protein family (Hsp40) member B6 (DNAJB6) colocalizes and interacts with NS3, and has a negative regulatory function in JEV replication. We also show that loss of DNAJB6 function results in significantly increased viral replication, but does not affect viral binding or internalization. Moreover, the time-course of DNAJB6 disruption during JEV infection varies in a viral load-dependent manner, suggesting that JEV targets this host chaperone protein for viral benefit. Deciphering the modes of NS3-interacting host proteins functions in virion production will shed light on JEV pathogenic mechanisms and may also reveal new avenues for antiviral therapeutics.

Human J-protein DnaJB6b Cures a Subset of Saccharomyces cerevisiae Prions and Selectively Blocks Assembly of Structurally Related Amyloids.

Human chaperone DnaJB6, an Hsp70 co-chaperone whose defects cause myopathies, protects cells from polyglutamine toxicity and prevents purified polyglutamine and Aß peptides from forming amyloid. Yeast prions [URE3] and [PSI(+)] propagate as amyloid forms of Ure2 and Sup35 proteins, respectively. Here we find DnaJB6-protected yeast cells from polyglutamine toxicity and cured yeast of both [URE3] prions and weak variants of [PSI(+)] prions but not strong [PSI(+)] prions. Weak and strong variants of [PSI(+)] differ only in the structural conformation of their amyloid cores. In line with its anti-prion effects, DnaJB6 prevented purified Sup35NM from forming amyloids at 37 °C, which produce predominantly weak [PSI(+)] variants when used to infect yeast, but not at 4 °C, which produces mostly strong [PSI(+)] variants. Thus, structurally distinct amyloids composed of the same protein were differentially sensitive to the anti-amyloid activity of DnaJB6 both in vitro and in vivo. These findings have important implications for strategies using DnaJB6 as a target for therapy in amyloid disorders.

A novel DNAJB6 mutation causes dominantly inherited distal-onset myopathy and compromises DNAJB6 function.

BACKGROUND: Mutations in the DNAJB6 gene have been identified as a rare cause of dominantly inherited limb-girdle muscular dystrophy or distal-onset myopathy. MATERIALS AND METHODS: Exome sequencing was performed to investigate a Taiwanese family with a dominantly inherited distal-onset myopathy. Functional effects of the causal mutation were investigated in vitro. RESULTS: Exome sequencing of the two affected individuals in this family identified a heterozygous mutation, c.287C>T (p.Pro96Leu) in the DNAJB6 gene, which co-segregated with the myopathy within all 12 family members. Notably, this mutation is novel and localizes within the glycine and phenylalanine-rich (G/F) domain and alters an amino acid residue previously reported with a different mutation. Furthermore, immunofluorescence analyses and filter trap assay demonstrated that the c.287C>T (p.Pro96Leu) mutation possessed a dominant negative effect on the anti-aggregation function of DNAJB6 protein. CONCLUSION: This study expands the molecular spectrum of DNAJB6 mutations and also emphasizes the pathogenic role of DNAJB6 dysfunction in distal-onset myopathy.

Overexpression of DNAJB6 promotes colorectal cancer cell invasion through an IQGAP1/ERK-dependent signaling pathway.

DNAJB6 is a member of the heat shock protein 40 (Hsp40) family. We here investigated the clinical correlation and biological role of DNAJB6 overexpression in colorectal cancer (CRC). The expression of DNAJB6 protein was examined in 200 cases of colorectal adenocarcinomas by immunohistochemistry (IHC) technology. Gene transfection and RNA interference were performed to determine the effect of DNAJB6 expression on the invasion of CRC cells and to explore the underlying molecular mechanisms in vitro and in vivo. Overexpression of DNAJB6 was found in 39% (78/200) of the CRC tissues, especially in tumors at pT4 as compared with at pT1-3 (P = 0.02). A Kaplan-Meier survival analysis revealed a correlation between DNAJB6 expression and overall survival (OS) times (P = 0.003). Multivariate analysis confirmed that DNAJB6 overexpression was an independent prognostic factor for CRC (P = 0.002). RNA interference-mediated silencing of the DNAJB6 gene inhibited the invasion of CRC cells in vitro were accompanied by a significant reduction in the protein levels of IQ-domain GTPase-activating protein 1 (IQGAP1) and phosphorylated ERK (pERK). An in vivo assay showed that inhibition of DNAJB6 expression decreased the lung metastases of CRC cells. IHC analysis of serial sections showed that there was a positive correlation between DNAJB6 and IQGAP1 expression in primary CRC tissues (P = 0.013). The data suggest that DNAJB6 plays an important oncogenic role in CRC cell invasion by up-regulating IQGAP1 and activating the ERK signaling pathway and that DNAJB6 may be used as a prognostic marker for CRC.

DNAJB6 myopathy: a vacuolar myopathy with childhood onset.

INTRODUCTION: DNAJB6 mutations cause an autosomal dominant myopathy that can manifest as limb-girdle muscular dystrophy (LGMD1D/1E) or distal-predominant myopathy. In the majority of patients this myopathy manifests in adulthood and shows vacuolar changes on muscle biopsy. METHODS: Clinical, electrophysiological, pathological, and molecular findings are reported. RESULTS: We report a 56-year-old woman, who, like 3 other family members, became symptomatic in childhood with slowly progressive limb-girdle muscle weakness, normal serum creatine kinase (CK) values, and myopathic electromyographic findings. Muscle biopsy showed vacuolar changes and congophilic inclusions, and molecular analysis revealed a pathogenic mutation in the DNAJB6 gene. Differences and similarities with previously described cases are assessed. CONCLUSIONS: Childhood-onset of DNAJB6 myopathy is more frequent than previously believed; congophilic inclusions may be present in the muscle of these patients.

Abnormally High Expression of DNAJB6 Accelerates Malignant Progression of Lung Adenocarcinoma.

DNAJB6, a major member of the DNAJ/HSP40 family, plays an important role in tumor development. We explored the effect of DNAJB6 expression on the prognosis of patients and its biological role in lung adenocarcinoma (LUAD). mRNA and clinical data were obtained from The Cancer Genome Atlas (TCGA). Enriched pathways were determined by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. A nomogram incorporating DNAJB6 and three clinical features was constructed to predict the survival rate. DNAJB6 expression and function in LUAD were explored using immunohistochemistry, Western blotting, proliferation, cell cycle analysis, RNA sequencing, and xenograft tumor assays. DNAJB6 mRNA levels were elevated in the LUAD-TCGA dataset. DNAJB6 protein levels were higher in LUAD tumor tissues than in normal tissues. A high DNAJB6 level was an independent risk factor for poor prognosis in patients with LUAD. The proportion of tumor-infiltrating immune cells significantly differed between high and low DNAJB6 expression. DNAJB6 was associated with cell cycle pathways; therefore, its knockdown induced G2/M cell cycle arrest and inhibited LUAD cell proliferation. This is the first report of the DNAJB6 requirement for LUAD cell proliferation and its potentially crucial role in LUAD prognosis.

DNAJB8 oligomerization is mediated by an aromatic-rich motif that is dispensable for substrate activity.

J-domain protein (JDP) molecular chaperones have emerged as central players that maintain a healthy proteome. The diverse members of the JDP family function as monomers/dimers and a small subset assemble into micron-sized oligomers. The oligomeric JDP members have eluded structural characterization due to their low-complexity, intrinsically disordered middle domains. This in turn, obscures the biological significance of these larger oligomers in protein folding processes. Here, we identified a short, aromatic motif within DNAJB8 that drives self-assembly through π-π stacking and determined its X-ray structure. We show that mutations in the motif disrupt DNAJB8 oligomerization in vitro and in cells. DNAJB8 variants that are unable to assemble bind to misfolded tau seeds more specifically and retain capacity to reduce protein aggregation in vitro and in cells. We propose a new model for DNAJB8 function in which the sequences in the low-complexity domains play distinct roles in assembly and substrate activity.

Intrinsic Disorder in the Host Proteins Entrapped in Rabies Virus Particles.

A proteomics analysis of purified rabies virus (RABV) revealed 47 entrapped host proteins within the viral particles. Out of these, 11 proteins were highly disordered. Our study was particularly focused on five of the RABV-entrapped mouse proteins with the highest levels of disorder: Neuromodulin, Chmp4b, DnaJB6, Vps37B, and Wasl. We extensively utilized bioinformatics tools, such as FuzDrop, D2P2, UniProt, RIDAO, STRING, AlphaFold, and ELM, for a comprehensive analysis of the intrinsic disorder propensity of these proteins. Our analysis suggested that these disordered host proteins might play a significant role in facilitating the rabies virus pathogenicity, immune system evasion, and the development of antiviral drug resistance. Our study highlighted the complex interaction of the virus with its host, with a focus on how the intrinsic disorder can play a crucial role in virus pathogenic processes, and suggested that these intrinsically disordered proteins (IDPs) and disorder-related host interactions can also be a potential target for therapeutic strategies.