BAG3 induces α-SMA expression in human fibroblasts and its over-expression correlates with poorer survival in fibrotic cancer patients

BAG3 localizes to mitochondria in cardiac fibroblasts and regulates mitophagy

The co-chaperone Bcl2-associated athanogene 3 (BAG3) is a central node in protein quality control in the heart. In humans and animal models, decreased BAG3 expression is associated with cardiac dysfunction and dilated cardiomyopathy. Although previous studies focused on BAG3 in cardiomyocytes, cardiac fibroblasts are also critical drivers of pathologic remodeling. Yet, the role of BAG3 in cardiac fibroblasts is almost completely unexplored. Here, we show that BAG3 is expressed in primary rat neonatal cardiac fibroblasts and preferentially localizes to mitochondria. Knockdown of BAG3 reduces mitophagy and enhances fibroblast activation, which is associated with fibrotic remodeling. Heat shock protein 70 (Hsp70) is a critical binding partner for BAG3 and inhibiting this interaction in fibroblasts using the drug JG-98 decreased autophagy, decreased mitofusin-2 expression, and disrupted mitochondrial morphology. Together, these data indicate that BAG3 is expressed in cardiac fibroblasts, where it facilitates mitophagy and promotes fibroblast quiescence. This suggests that depressed BAG3 levels in heart failure may exacerbate fibrotic pathology, thus contributing to myocardial dysfunction through sarcomere-independent pathways.NEW & NOTEWORTHY We report BAG3's localization to mitochondria and its role in mitophagy for the first time in primary ventricular cardiac fibroblasts. We have also collected the first evidence showing that loss of BAG3 increases cardiac fibroblast activation into myofibroblasts, which are major drivers of cardiac fibrosis and pathological remodeling during heart disease.

Remodeling the tumor microenvironment to overcome treatment resistance in HPV-negative head and neck cancer

Despite intensive efforts and refined techniques, overall survival in HPV-negative head and neck cancer remains poor. Robust immune priming is required to elicit a strong and durable antitumor immune response in immunologically cold and excluded tumors like HPV-negative head and neck cancer. This review highlights how the tumor microenvironment could be affected by different immune and stromal cell types, weighs the need to integrate metabolic regulation of the tumor microenvironment into cancer treatment strategies and summarizes the emerging clinical applicability of personalized immunotherapeutic strategies in HPV-negative head and neck cancer.

Unraveling the mystery: How bad is BAG3 in hematological malignancies?

BAG3, also known as BIS and CAIR-1, interacts with Hsp70 via its BAG domain and with other molecules through its WW domain, PXXP repeats and IPV motifs. BAG3 can participate in major cellular pathways including apoptosis, autophagy, cytoskeleton structure, and motility by regulating the expression, location, and activity of its chaperone proteins. As a multifunctional protein, BAG3 is highly expressed in skeletal muscle, cardiomyocytes and multiple tumors, and its intracellular expression can be stimulated by stress. The functions and mechanisms of BAG3 in hematological malignancies have recently been a topic of interest. BAG3 has been confirmed to be involved in the development and chemoresistance of hematological malignancies and to act as a prognostic indicator. Modulation of BAG3 and its corresponding proteins has thus emerged as a promising therapeutic and experimental target. In this review, we consider the characteristics of BAG3 in hematological malignancies as a reference for further clinical and fundamental investigations.

Hepatocyte-specific deletion of Bis causes senescence in the liver without deteriorating hepatic function

Bcl-2-interacting cell death suppressor (BIS), also called as BAG3, regulates numerous physiological processes, such as apoptosis, protein quality control, and senescence. Whole-body Bis-knockout (KO) mice exhibit early lethality following cardiac and skeletal muscle dysfunction. The first attempt to generate organ-specific knockout mice resulted in constitutive or inducible heart-specific Bis-knockout mice, which exhibited cardiac dilation and underwent premature death. Here, we generated hepatocyte-specific Bis-knockout (Bis-HKO) mice and found no abnormalities in metabolic function and survival. However, depletion of HSPB8 and accumulation of p62 indicated impaired autophagy in Bis-HKO livers. Interestingly, the number of peroxisomes wrapped by phagophore membranes increased as evidenced by transmission electron microscopy analysis, indicating defects in the progression of pexophagy. In addition, increased dihydroethidine intensities and histone H3 K9me3-positive nuclei indicated increased oxidative stress and senescence induction in Bis-HKO livers. Mechanistically, p27 was upregulated in Bis-HKO livers. In SNU368 hepatocellular carcinoma cells, BIS depletion led to p27 upregulation, and increase in histone H3 K9me3 levels and senescence-associated β-galactosidase staining; therefore, reproducing the in vivo senescence phenotype. Despite the observation of no metabolic abnormalities, BIS depletion led to defective autophagy, increased oxidative stress, and senescence in Bis-HKO livers. Collectively, our results suggest a role for BIS in maintaining liver regeneration potential under pathological conditions.

Biophysics involved in the process of tumor immune escape

Much of the current research into immune escape from cancer is focused on molecular and cellular biology, an area of biophysics that is easily overlooked. A large number of immune drugs entering the clinic are not effective for all patients. Apart from the molecular heterogeneity of tumors, the biggest reason for this may be that knowledge of biophysics has not been considered, and therefore an exploration of biophysics may help to address this challenge. To help researchers better investigate the relationship between tumor immune escape and biophysics, this paper provides a brief overview on recent advances and challenges of the biophysical factors and strategies by which tumors acquire immune escape and a comprehensive analysis of the relevant forces acting on tumor cells during immune escape. These include tumor and stromal stiffness, fluid interstitial pressure, shear stress, and viscoelasticity. In addition, advances in biophysics cannot be made without the development of detection tools, and this paper also provides a comprehensive summary of the important detection tools available at this stage in the field of biophysics.