Endoplasmic reticulum (ER) stress represents a critical pathophysiological condition that plays a central role in the development of various human diseases, including protein misfolding diseases. While the small molecule Vx-445 (Elexacaftor) exhibits robust cellular bioactivity, its cryptic intracellular targets and off-label mechanisms of action remain poorly defined. This study investigates the cytoprotective efficacy and molecular targets of Vx-445 in Thapsigargin-induced ER stress in a neuronal cell model. Integrating biochemical assays, gene expression proteomics, and label-free functional proteomics, we demonstrate that Vx-445 significantly mitigates oxidative stress by reducing intracellular levels of reactive oxygen species, restores calcium homeostasis to baseline levels, and prevents apoptosis by inhibiting cytochrome c release. These phenotypic modifications correlated with changes in proteomic expression and were validated by Drug Affinity Responsive Target Stability (DARTS) analysis to map restored cellular pathways and identify potential protein interaction partners. Together, these findings uncover alternative molecular targets for Vx-445, providing a mechanistic basis for drug repurposing strategies in endoplasmic reticulum stress-related diseases.

Protein misfolding diseases are characterized by structurally abnormal proteins that lose their functionality, resulting in cellular and tissue dysfunction. Neurodegenerative diseases, including Parkinson’s disease, Alzheimer’s disease and Huntington’s disease, share a common etiopathogenesis characterize by the accumulation of misfolded proteins. These proteins autonomously aggregate within neuronal cells, triggering inflammation and cell death. The accumulation of misfolded proteins triggers endoplasmic reticulum (ER) stress, leading to alter Ca2+ homeostasis. This prolonged stress condition induces the cleavage of procaspase 4 which is resident in ER and activates NF-kB pathway activation, leading to inflammatory responses and cell death. In this study, the efficacy of the drug Vx-445 (Elexacaftor), used in the pharmacological treatment of cystic fibrosis, was assessed in human adenocarcinomic basal alveolar epithelial (A549) and neuronal (SH-SY5Y) cell lines, where ER stress was induced by Thapsigargin. The aim was to assess whether the corrector was able to reduce ER stress by restoring cellular homeostasis and, probably, the proper folding of misfolded proteins and reducing the inflammatory response triggered by these events. Therefore, protein levels of IkBα, p-STAT 3 and COXII were analyzed by flow cytofluorimetry, while Ca2+ content was measured by spectrofluorimetry. The results obtained suggest a significant effect of Vx-445 in restoring cellular homeostasis, leading to reduced expression of inflammation-related proteins, such as IL-6, tested by ELISA. Although preliminary, these results encourage further studies to explore the potential repurpose of Vx-445 as a therapeutic candidate for conditions involving ER stress and chronic inflammatory diseases associated with protein misfolding, beyond its current use in cystic fibrosis.

The field of neurodegenerative diseases represents one of the most challenging and fascinating areas of modern cellular and molecular biology [...]

Most neurodegenerative diseases share a common etiopathogenesis, the accumulation of protein aggregates. An imbalance in homeostasis brought on by the buildup of misfolded proteins within the endoplasmic reticulum (ER) results in ER stress in the cell. Three distinct proteins found in the ER membrane—IRE1α, PERK, and ATF6—control the unfolded protein response (UPR), a signal transduction pathway that is triggered to restore normal physiological conditions. Buildup of misfolded proteins in ER lumen leads to a shunting of GRP78/BiP, thus triggering the UPR. PERK autophosphorylation leads to activation of ATF4, the transcription factor; finally, ATF6 activates the UPR’s target genes, including GRP78/Bip. Accordingly, the UPR is a cellular reaction to an ER stress state that, if left unchecked for an extended period, results in apoptosis and irreversible damage. The identification of caspase 4, which is in the ER and is selectively activated by apoptotic stimuli caused by reticular stress, further demonstrated the connection between reticular stress and programed cell death. Moreover, oxidative stress and ER stress are linked. Oxidative stress is brought on by elevated quantities of radical oxygen species, both mitochondrial and cytosolic, that are not under the enzymatic regulation of superoxide dismutases, whose levels fall with increasing stress. Here, we evaluated the activity of Vx-809 (Lumacaftor), a drug used in cystic fibrosis, in SH-SY5Y neuronal cells, in which an ER stress condition was induced by Thapsigargin, to verify whether the drug could improve protein folding, suggesting its possible therapeutic use in proteinopathies, such as neurodegenerative diseases (NDs). Our data show that Vx-809 is involved in the significant reduction in protein produced under ER stress, particularly in the levels of Bip, ATF4, and ATF6 by Western blotting analysis, the reduction in ROS in the cytosol and mitochondria, and the reduction in the activation of the apoptotic pathway, measured by flow cytofluorimetry analysis and in restoring calcium homeostasis.

Correct protein folding is the basis of cellular well-being; thus, accumulation of misfolded proteins within the endoplasmic reticulum (ER) leads to an imbalance of homeostasis that causes stress to the ER. Various studies have shown that protein misfolding is a significant factor in the etiology of many human diseases, including cancer, diabetes, and cystic fibrosis. Misfolded protein accumulation in the ER triggers a sophisticated signal transduction pathway, the unfolded protein response (UPR), which is controlled by three proteins, resident in ER: IRE1α, PERK, and ATF6. Briefly, when ER stress is irreversible, IRE1α induces the activation of pro-inflammatory proteins; PERK phosphorylates eIF2α which induces ATF4 transcription, while ATF6 activates genes encoding ER chaperones. Reticular stress causes an alteration of the calcium homeostasis, which is released from the ER and taken up by the mitochondria, leading to an increase in the oxygen radical species production, and consequently, to oxidative stress. Accumulation of intracellular calcium, in combination with lethal ROS levels, has been associated with an increase of pro-inflammatory protein expression and the initiation of the inflammatory process. Lumacaftor (Vx-809) is a common corrector used in cystic fibrosis treatment which enhances the folding of mutated F508del-CFTR, one of the most prevalent impaired proteins underlying the disease, promoting a higher localization of the mutant protein on the cell membrane. Here, we demonstrate that this drug reduces the ER stress and, consequently, the inflammation that is caused by such events. Thus, this molecule is a promising drug to treat several pathologies that present an etiopathogenesis due to the accumulation of protein aggregates that lead to chronic reticular stress.

Seven new terpenoids, namely, guaiane (1-4), eudesmane (5), and bisabolane (6) sesquiterpenoids and a furanone (7), were isolated from the aerial parts of Ammoides atlantica, a herbaceous plant growing in Algeria, together with eight known compounds. All metabolites were characterized by their 1D and 2D NMR and HRESIMS data. A combined DFT/NMR method was applied to study the relative configurations of 1-4, 6, and 7. All compounds, except 2, were assayed against MCF-7, A375, A549, HaCaT, and Jurkat cell lines. Compounds 8, 10, and 11 induced a dose-dependent reduction in cell viability with different potency on almost all cell lines used. The most active compounds, 8 and 10, were studied to assess their potential apoptotic effects and cell cycle inhibition.

Despite the progressions in COVID-19 understanding, the optimization of patient-specific therapies remains a challenge. Statins, the most widely prescribed lipid-lowering drugs, received considerable attention due to their pleiotropic effects, encompassing lipid metabolism control and immunomodulatory and anti-thrombotic effects. In COVID-19 patients, statins improve clinical outcomes, reducing Intensive Care Unit admission, the onset of ARDS, and in-hospital death. However, the safety of statins in COVID-19 patients has been debated, mainly for statins’ ability to induce the expression of the ACE2 receptor, the main entry route of SARS-CoV-2. Unfortunately, the dynamic of statins’ mechanism in COVID-19 disease and prevention remains elusive. Using different in vitro models expressing different levels of ACE2 receptor, we investigated the role of lipophilic and hydrophilic statins on ACE2 receptor expression and subcellular localization. We demonstrated that the statin-mediated increase of ACE2 receptor expression does not necessarily coincide with its localization in lipid rafts domains, particularly after treatments with the lipophilic atorvastatin that disrupt lipid rafts’ integrity. Through a proteomic array, we analyzed the cytokine patterns demonstrating that statins inhibit the release of cytokines and factors involved in mild to severe COVID-19 cases. The results obtained provide additional information to dissect the mechanism underlying the protective effects of statin use in COVID-19.

Cystic fibrosis is a monogenic, autosomal, recessive disease characterized by an alteration of chloride transport caused by mutations in the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) gene. The loss of Phe residue in position 508 (ΔF508-CFTR) causes an incorrect folding of the protein causing its degradation and electrolyte imbalance. CF patients are extremely predisposed to the development of a chronic inflammatory process of the bronchopulmonary system. When the cells of a tissue are damaged, the immune cells are activated and trigger the production of free radicals, provoking an inflammatory process. In addition to routine therapies, today drugs called correctors are available for mutations such as ΔF508-CFTR as well as for others less frequent ones. These active molecules are supposed to facilitate the maturation of the mutant CFTR protein, allowing it to reach the apical membrane of the epithelial cell. Matrine induces ΔF508-CFTR release from the endoplasmic reticulum to cell cytosol and its localization on the cell membrane. We now have evidence that Matrine and Lumacaftor not only restore the transport of mutant CFTR protein, but probably also counteract the inflammatory process by improving the course of the disease.

Cutaneous melanoma, the most aggressive form of skin cancer, is characterized by activating BRAF mutations. Despite the initial success of selective BRAF inhibitors, only few patients exhibited complete responses, whereas many showed disease progression. Melanoma is one of the few types of cancer in which p53 is not frequently mutated, but p53 inactivation can be indirectly achieved by a stable activation of MDM2 induced by a deletion in CDKN2A (Cyclin Dependent Kinase Inhibitor 2A) locus, encoding for p16INK4A and p14ARF, two tumor suppressor genes. In this study, we tested the efficacy of the previously synthesized tetra-substituted pyrrole derivatives, 8 g, 8 h and 8i, in melanoma cell lines, and we compared the effects of the most active of these, the 8i compound, with that exerted by Nutlin 3, a well-known inhibitor of p53-MDM2 interaction. The obtained results showed that 8i potentiates the inhibitory effect of Nutlin 3 and the combined use of 8i and Nutlin 3 triggers apoptosis and significantly impairs melanoma viability. Finally, the 8i compound reduces p53-MDM2 interaction and induces p53-HSP90 complex formation, suggesting that the observed raise in p53 transcriptional activity could be mediated by HSP90. Because the main feature of melanoma is the resistance to most chemotherapeutics, our studies suggest that the 8i tetra-substituted pyrrole derivative, restoring p53 functions and its transcriptional activities, may have potential application, at least as adjuvant, in the treatment of human melanoma.

Interleukin (IL)-6 has been detected in serum and ascites from patients affected by epithelial ovarian cancers, and also in some human ovarian cancer cell lines. To investigate the role of IL-6 in ovarian lesions, we first measured its levels in serum samples of 24 healthy donors and in 17 and 9 patients affected by ovarian carcinomas and ovarian benign cysts respectively. IL 6 levels were significantly higher than healthy donors in serum samples from ovarian cancer patients, but not in benign ovarian cysts. We then investigated the mechanism of IL-6 production in two cell lines obtained from the same patient with high grade serous ovarian carcinoma before (PEA1) and after (PEA2) development of cisplatinum resistance. The levels of intracellular IL-6, analysed by western blotting, did not relevantly differ in the two cell lines, and they did not change after the cell treatment with an AKT inhibitor. Although the interleukin was present in supernatants from both cell lines, its concentration in the supernatant of chemoresistant cells was significantly higher than chemosensitive cells. Interestingly, exposure to the AKT inhibitor resulted in a reduced IL-6 release in PEA1, but not in PEA2 cells. These results let infer different mechanisms of IL-6 release in chemoresistant and chemosensitive cell lines, and contribute new insights in ovarian cancer biology that suggest more in depth studies about the role of AKT in IL-6 release and in development of chemoresistance.

Phenethyl isothiocyanate (PEITC), a cruciferous vegetable-derived compound, is a versatile cancer chemopreventive agent that displays the ability to inhibit tumor growth during initiation, promotion, and progression phases in several animal models of carcinogenesis. In this report, we dissect the cellular events induced by noncytotoxic concentrations of PEITC in human umbilical vein endothelial cells (HUVECs). In the early phase, PEITC treatment elicited cells' morphological changes that comprise reduction in cell volume and modification of actin organization concomitantly with a rapid activation of the PI3K/Akt pathway. Downstream to PI3K, PEITC also induces the activity of Rac1 and activation of c-Jun N-terminal kinase (JNK), well-known regulators of actin cytoskeleton dynamics. Interestingly, PEITC modifications of the actin cytoskeleton were abrogated by pretreatment with JNK inhibitor, SP600125. JNK signaling led also to the activation of the c-Jun transcription factor, which is involved in the upregulation of several genes; among them is the BAG3 protein. This protein, a member of the BAG family of heat shock protein (Hsp) 70 cochaperones, is able to sustain survival in different tumor cell lines and neoangiogenesis by directly regulating the endothelial cell cycle. Furthermore, BAG3 is involved in maintaining actin folding. Our findings indicate that BAG3 protein expression is induced in endothelial cells upon exposure to a noncytotoxic concentration of PEITC and its expression is requested for the recovery of normal cell size and morphology after the stressful stimuli. This assigns an additional role for BAG3 protein in the endothelial cells after a stress event.

We read with great interest the article by Zhang et al 1 showing that CD8+ cell infiltration in pancreatic tumours can be enhanced by depletion of myeloid cells (CD11b+ macrophages and myeloid-derived suppressor cells) and that the depletion of CD11b+ cells resulted in decreased PD-L1 expression on cancer cells thus impairing the triggering of the inhibitory receptor PD-1 on T cells.1 Recruitment and activation of CD8+ lymphocytes in tumours are suppressed by mechanisms only partially understood and rescuing CD8+ cell infiltrate in tumours is one of the objectives of immunotherapies.1 2 Tumour-associated macrophages (TAMs) play a crucial role in the relation between tumour cells and their environment.3 Here, we confirm the interplay between macrophages and CD8+ cells in pancreatic cancer and identify a potential way to exploit this enhancing effect of anti-PD-1 treatment. Indeed, we show that reduction of macrophage infiltrate, through treatment with an anti-Bcl-2-Associated athanoGene 3 (BAG3) antibody,4 results in increased number of CD8+ cells in pancreatic tumours in a murine model. BAG3 is a co-chaperone of …

BAG3 is a multifunctional protein that can bind to heat shock proteins (Hsp) 70 through its BAG domain and to other partners through its WW domain, proline-rich (PXXP) repeat and IPV (Ile-Pro-Val) motifs. Its intracellular expression can be induced by stressful stimuli, while is constitutive in skeletal muscle, cardiac myocytes and several tumour types. BAG3 can modulate the levels, localisation or activity of its partner proteins, thereby regulating major cell pathways and functions, including apoptosis, autophagy, mechanotransduction, cytoskeleton organisation, motility. A secreted form of BAG3 has been identified in studies on pancreatic ductal adenocarcinoma (PDAC). Secreted BAG3 can bind to a specific receptor, IFITM2, expressed on macrophages, and induce the release of factors that sustain tumour growth and the metastatic process. BAG3 neutralisation therefore appears to constitute a novel potential strategy in the therapy of PDAC and, possibly, other tumours.

Citral, 3,7-dimethyl-2,6-octadienal, is a key component of the essential oils extracted from several lemon-scented herbal plants. It has been demonstrated to be an effective antifungal agent and in recent years, to have antiproliferative effect in certain tumor cell lines: thus citral could be a potential anticancer drug. In this study, we investigated the effect of citral on the proliferation of pancreatic cell tumor lines (MIA PaCa-2 cells) and human B-lymphoma (DeFew cells). To analyze which part of the molecule is pivotal for the activity, we also studied the effect of several citral related compounds, in particular focusing on some chemical aspects of the terpenic scaffold. The in vitro studies revealed the significant cytotoxic activity of some of the tested compounds.

Background Bcl2-associated athanogene 3 (BAG-3) is a co-chaperone protein that interacts with the ATPase domain on heat-shock protein 70. BAG-3 is involved is several biologic processes including apoptosis, cytoskeleton organization and autophagy and, therefore, it has been extensively investigated in the field of tumorigenesis (1). In particular, BAG-3 expression is constitutive in human primary tumors including leukemias and lymphomas and it is induced in different normal cell types, including leukocytes, by a variety of stimuli. BAG-3 is able to induce and maintain cell proliferation, resistance to therapy and cell motility, namely metastatization. On this basis, a role of BAG-3 in chronic inflammatory diseases may be postulated, but data on this topic are not available. Objectives The purpose of our study was to investigate the expression of BAG-3 in primary Sjogren9s syndrome (pSS) and the relationship with clinical and serological features. Methods BAG-3 concentration was assessed in the serum of 103 patients with pSS according to the 2002 American-European classification criteria and in 40 sex and age matched healthy donors (HD). Clinical and serological records were collected and statistical analysis was performed with SPSS 21.0. Results Twenty-six pSS patients were positive for BAG-3 (BAG-3+), with serum levels ranging from 32.1 to 950 pg/ml. When setting the cut-off value according to the highest value found in HD (300 pg/ml), we identified 13 pSS patients displaying a peculiar clinical serological phenotype. In detail, in this subgroup of pSS patients the prevalence of purpura, low C4, both anti-Ro and anti-La autontibodies, rheumatoid factor and lymphoma was higher, when compared to pSS patients with BAG-3 levels <300 pg/ml or BAG-3- (all p<0.05). Furthermore, they displayed less frequently sicca symptoms such as xerostomia and xerophtalmia (both p<0.05). Binary logistic regression analysis revealed that pSS patients with BAG-3 levels >300 pg/ml had on odds ratio (OR) of 12 (95% CI 1.9–86, p=0.009) for lymphoma and this association was independent of the presence of purpura, a well know marker of lymphoma in pSS. When including low complement, another feature associated with lymphoma, in the multivariable analysis, both low C4 and BAG-3 levels >300 pg/ml resulted independently associated to lymphoma (OR=24 and 12.4 respectively). Conclusions Our study assessed for the first time serum BAG-3 levels in a large cohort of pSS patients. The results showed that the highest levels of BAG-3 identify a peculiar clinical and serological pSS phenotype, as consequence of a B-cell hyperactivity. Since it is known that BAG-3 is an anti-apoptotic protein playing a pivotal role in cell survival, and that B-cell hyperactivity in pSS is the consequence of coordinated and integrated actions of several stimuli and appropriate cytokines, our results may suggest that BAG-3 overexpression is involved in B-cell proliferation and activity, as well as in oligoclonal and monoclonal expansion in pSS. References Rosati A et al. Cell Death Dis 2011;2:e141. Disclosure of Interest None declared

Abstract Interactions between cancer cells and stromal cells are critically involved in tumor formation, progression and development of metastasis. Here we report for the first time that human pancreatic adenocarcinoma (PDAC) cells secrete BAG3 that binds and activates macrophages, inducing their activation and the secretion of pancreatic cancer- supporting factors. We also identify IFITM-2 as a BAG3 receptor, by its co-precipitation with BAG3 from macrophage cell membrane and by impairment of BAG3- induced activation in IFITM-2- silenced macrophages. Finally we show the importance of this pathway in vivo since in nu/nu mice carrying orthotopic xenografts of human PDAC (MIA PaCa-2) cells, BAG3 sequestration by an anti-BAG3 antibody results in reduced tumor growth and prevents metastastasis formation. In conclusion we have identified a novel paracrine loop involved in PDAC growth and metastatic spreading and shown that its pharmacological blockage with an anti-BAG3 antibody has therapeutic potential. Citation Format: Alessandra Rosati, Anna Basile, Raffaella D'Auria, Morena d'Avenia, Margot De Marco, Antonia Falco, Michelina Festa, Luana Guerriero, Vittoria Iorio, Maria Pascale, Renato Franco, Claudio Arra, Antonio Barbieri, Domenica Rea, Giulio Menichini, Michael Hahne, Marteen Bijlsma, Daniela Barcaroli, David A. Tuveson, Jelena Todoric, Michael Karin, Vincenzo De Laurenzi, Maria Caterina Turco. PDAC cells release BAG3 that activates a paracrine loop with stromal macrophages. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2393. doi:10.1158/1538-7445.AM2015-2393

The incidence and death rate of pancreatic ductal adenocarcinoma (PDAC) have increased in recent years, therefore the identification of novel targets for treatment is extremely important. Interactions between cancer and stromal cells are critically involved in tumour formation and development of metastasis. Here we report that PDAC cells secrete BAG3, which binds and activates macrophages, inducing their activation and the secretion of PDAC supporting factors. We also identify IFITM-2 as a BAG3 receptor and show that it signals through PI3K and the p38 MAPK pathways. Finally, we show that the use of an anti-BAG3 antibody results in reduced tumour growth and prevents metastasis formation in three different mouse models. In conclusion, we identify a paracrine loop involved in PDAC growth and metastatic spreading, and show that an anti-BAG3 antibody has therapeutic potential.

BAG3, member the HSP70 co-chaperones family, has been shown to play a relevant role in the survival, growth and invasiveness of different tumor types. In this study, we investigate the expression of BAG3 in 66 specimens from different lung tumors and the role of this protein in small cell lung cancer (SCLC) tumor growth. Normal lung tissue did not express BAG3 while we detected the expression of BAG3 by immunohistochemistry in all the 13 squamous cell carcinomas, 13 adenocarcinomas and 4 large cell carcinomas. Furthermore, we detected BAG3 expression in 22 of the 36 SCLCs analyzed. The role on SCLC cell survival was determined by down-regulating BAG3 levels in two human SCLC cell lines, i.e. H69 and H446, in vitro and measuring cisplatin induced apoptosis. Indeed down-regulation of BAG3 determines increased cell death and sensitizes cells to cisplatin treatment. The effect of BAG3 down-regulation on tumor growth was also investigated in an in vivo xenograft model by treating mice with an adenovirus expressing a specific bag3 siRNA. Treatment with bag3 siRNA-Ad significantly reduced tumor growth and improved animal survival. In conclusion we show that a subset of SCLCs over express BAG3 that exerts an anti-apoptotic effect resulting in resistance to chemotherapy.

Dear Editor, Bcl-2-associated athanogene 3 (BAG3) protein belongs to the family of co-chaperones that interact with the ATPase domain of the heat shock protein HSP70 through the BAG domain (amino acids 110–124). BAG3 contains also a WW domain, a proline-rich repeat (PXXP) and two conserved Ile-Pro-Val motifs that mediate binding to other proteins.1 bag3 gene is constitutively expressed in a few normal cell types, including myocytes, and in several primary tumors, while its expression is inducible by stressors in other cell types. Many evidence indicate that BAG3 has a role in sustaining cell survival, through mechanisms that, depending on the cell context, rely on the ability of BAG3 to modulate levels or localization of apoptosis-regulating proteins, such as IKKγ, Bax or BRAF, in either an Hsp70-dependent or -independent fashion.1, 2, 3 BAG3 is expressed during cardiomyoblast differentiation and sustains myogenin expression. In cardiomyocytes, BAG3 protein localizes at the Z-disc and interacts with the actin capping protein, CapZβ1, stabilizing myofibril structure; BAG3 mutations can impair the Z-disc assembly and increase the sensitivity to stress-induced apoptosis. Mutations in bag3 gene have been associated with some forms of myofibrillar myopathy and dilated cardiomyopathy.4, 5, 6, 7 Interestingly, we detected BAG3 protein in supernatants of the rat cardiomyocyte cell line H9c2 and adult Human Cardiac Myocytes (HCMa) after 16 h of serum deprivation (Figure 1a). We then verified that BAG3 was present in extracellular vesicles isolated through a differential centrifugation procedure (Supplementary Figure S1A). To investigate the possibility that BAG3 could be released in vivo and become detectable in sera in conditions in which the heart is undergoing chronic stress, we analyzed sera from two patients affected by chronic heart failure (CHF). By western blot analysis, we detected a band recognized by anti-BAG3 antibody at the expected molecular weight in sera from patients but not from healthy donors (Figure 1b). We excised the band from a replica gel and subjected it to mass spectrometry, unmistakably identifying BAG3 (Supplementary Figure S1B). Furthermore, we found that sera from CHF patients recognized BAG3 protein in western blotting, using an anti-human IgG as secondary antibody (Supplementary Figure S1C). This result indicated the presence of anti-BAG3 antibodies in CHF patients' sera. To confirm this finding, we developed an ELISA test using recombinant BAG3 to coat plates and anti-human IgG to reveal and analyzed sera from 52 CHF patients (EF<45%), compared with sera from 84 healthy donors. As shown in Figure 1c (and in Supplementary Figure S1D), we detected significantly higher values of anti-BAG3 antibodies in patients' compared with controls' sera. These data suggest that upon cardiac stress cardiomyocytes release BAG3 and this in turn results in production of auto-antibodies. There is no correlation with NYHA scores and antibody levels at this stage but screening of a larger number of patients in the future might be necessary to reveal potential correlations. Figure 1 (a) Detection of BAG3 protein in supernatants from cultured cardiomyocytes. Human (HCMa) and rat (H9c2) cardiomyocytes, at 80% confluence, were incubated with or without 10% FBS for 16 h at 37 °C in a 5% ... These results describe for the first time an extracellular BAG3 (eBAG3) released by stressed cardiomyocytes. As BAG3 lacks the consensus signal required for secretion via ER–Golgi pathway, it is likely to be released by the non-classical secretory pathway.8 eBAG3 release by stressed cardiomyocytes appears to result in production of auto-antibodies that could potentially be used as a biomarker for CHF patients, in combination with other already established markers. The presence of anti-BAG3 antibodies in CHF patients' sera indicates that released BAG3 can activate the immune system, and might therefore exert positive or negative functional effects on cardiac function, depending on the context. Future studies are required to clarify the biological roles of BAG3 and anti-BAG3 antibodies in CHF, and the utility of anti-BAG3 antibodies as a tool contributing to the study of the disease.