HSPB6 Deficiency Promotes the Development of Aortic Dissection and Rupture

To better understand the pathogenesis of acute type A aortic dissection, high-sensitivity liquid chromatography-tandem mass spectrometry/mass spectrometry (LC-MS/MS)-based proteomics and phosphoproteomics approaches were used to identify differential proteins. Heat shock protein family B (small) member 6 (HSPB6) in aortic dissection was significantly reduced in human and mouse aortic dissection samples by real-time PCR, western blotting, and immunohistochemical staining techniques. Using an HSPB6-knockout mouse, we investigated the potential role of HSPB6 in β-aminopropionitrile monofumarate-induced aortic dissection. We found increased mortality and increased probability of ascending aortic dissection after HSPB6 knockout compared with wild-type mice. Mechanistically, our data suggest that HSPB6 deletion promoted vascular smooth muscle cell apoptosis. More importantly, HSPB6 deletion attenuated cofilin activity, leading to excessive smooth muscle cell stiffness and eventually resulting in the development of aortic dissection and rupture. Our data suggest that excessive stiffness of vascular smooth muscle cells caused by HSPB6 deficiency is a new pathogenetic mechanism leading to aortic dissection.

Overexpression of HSPB6 inhibits osteosarcoma progress through the ERK signaling pathway

Heat shock protein B6 (HSPB6) plays a certain role in the formation of several cancers, whereas its effect on osteosarcoma remains unclear. In this study, the effect of HSPB6 on osteosarcoma was validated through numerous experiments. HSPB6 was down-regulated in osteosarcoma. As indicated by the result of CCK-8 and colony formation assays, HSPB6 overexpression was likely to inhibit the osteosarcoma cells proliferation, whereas the flow cytometry analysis suggested that apoptosis of osteosarcoma cells was increased after HSPB6 overexpression. Furthermore, transwell and wound healing assays suggested that when HSPB6 was overexpressed, osteosarcoma cells migration and invasion were declined. Moreover, the western blotting assay suggested that the protein level of p-ERK1/2 was down-regulated in osteosarcoma when HSPB6 was overexpressed. Besides, the effect of HSPB6 on osteosarcoma in vivo was examined. As indicated by the result, HSPB6 overexpression was likely to prevent osteosarcoma growth and lung metastasis in vivo. As revealed by the findings of this study, HSPB6 overexpression exerted anticancer effects in osteosarcoma through the ERK signaling pathway and HSPB6 may be suitable target for osteosarcoma molecular therapies.

HSPB6 Is Depleted in Colon Cancer Patients and Its Expression Is Induced by 5-aza-2'-Deoxycytidine In Vitro

Background and Objectives: Colon cancer (CC) is the second most common cancer in Saudi Arabia, and the number of new cases is expected to increase by 40% by 2040. Sixty percent of patients with CC are diagnosed in the late stage, causing a reduced survival rate. Thus, identifying a new biomarker could contribute to diagnosing CC in the early stages, leading to delivering better therapy and increasing the survival rate. Materials and Methods: HSPB6 expression was investigated in extracted RNA taken from 10 patients with CC and their adjacent normal tissues, as well as in DMH-induced CC and a colon treated with saline taken from a male Wistar rat. Additionally, the DNA of the LoVo and Caco-2 cell lines was collected, and bisulfite was converted to measure the DNA methylation level. This was followed by applying 5-aza-2'-deoxycytidine (AZA) to the LoVo and Caco-2 cell lines for 72 h to see the effect of DNA methylation on HSPB6 expression. Finally, the GeneMANIA database was used to find the interacted genes at transcriptional and translational levels with HSPB6. Results: We found that the expression of HSPB6 was downregulated in 10 CC tissues compared to their adjacent normal colon tissues, as well as in the in vivo study, where its expression was lower in the colon treated with the DMH agent compared to the colon treated with saline. This suggests the possible role of HSPB6 in tumor progression. Moreover, HSPB6 was methylated in two CC cell lines (LoVo and Caco-2), and demethylation with AZA elevated its expression, implying a mechanistic association between DNA methylation and HSPB6 expression. Conclusions: Our findings indicate that HSPB6 is adversely expressed with tumor progression, and its expression may be controlled by DNA methylation. Thus, HSPB6 could be a good biomarker employed in the CC diagnostic process.

Prevalence of HSPB6 gene variants in peripartum cardiomyopathy: Data from the German PPCM registry

BACKGROUND

Heat shock protein family B (small) member 6 (HSPB6) mediates cardioprotective effects against stress-induced injury. In humans two gene variants of HSPB6 have been identified with a prevalence of 1% in patients with dilated cardiomyopathy (DCM). Peripartum cardiomyopathy (PPCM) is a potentially life-threatening heart disease of unknown etiology in previously healthy women of whom 16-20% of PPCM carry gene variants associated with cardiomyopathy. This study was designed to analyze the prevalence of pathogenic HSPB6 gene variants in PPCM.

METHODS AND RESULTS

Whole-exome sequencing was performed in whole blood samples of PPCM patients (n = 65 PPCM patients from the German PPCM registry) and screened subsequently for HSPB6 gene variants. In this PPCM cohort one PPCM patient carries a HSPB6 gene variant of uncertain significance (VUS), which was not associated with changes in the amino acid sequence and no likely pathogenic or pathogenic variants were detected.

CONCLUSION

HSPB6 gene variants did not occur more frequently in a cohort of PPCM patients from the German PPCM registry, compared to DCM patients. Genetic analyses in larger cohorts and in cohorts of different ethiologies of PPCM patients are needed to address the role of the genetic background in the pathogenesis of PPCM.

Heat shock proteins are differentially expressed in brain and spinal cord: implications for multiple sclerosis

Multiple sclerosis (MS) is a chronic neurodegenerative disease characterized by demyelination, inflammation and neurodegeneration throughout the central nervous system. Although spinal cord pathology is an important factor contributing to disease progression, few studies have examined MS lesions in the spinal cord and how they differ from brain lesions. In this study we have compared brain and spinal cord white (WM) and grey (GM) matter from MS and control tissues, focusing on small heat shock proteins (HSPB) and HSP16.2. Western blotting was used to examine protein levels of HSPB1, HSPB5, HSPB6, HSPB8 and HSP16.2 in brain and spinal cord from MS and age-matched non-neurological controls. Immunohistochemistry was used to examine expression of the HSPs in MS spinal cord lesions and controls. Expression levels were quantified using ImageJ. Western blotting revealed significantly higher levels of HSPB1, HSPB6 and HSPB8 in MS and control spinal cord compared to brain tissues. No differences in HSPB5 and HSP16.2 protein levels were observed, although HSPB5 protein levels were higher in brain WM versus GM. In MS spinal cord lesions, increased HSPB1 and HSPB5 expression was observed in astrocytes, and increased neuronal expression of HSP16.2 was observed in normal-appearing GM and type 1 GM lesions. The high constitutive expression of several HSPBs in spinal cord and increased expression of HSPBs and HSP16.2 in MS illustrate differences between brain and spinal cord in health and upon demyelination. Regional differences in HSP expression may reflect differences in astrocyte cytoskeleton composition and influence inflammation, possibly affecting the effectiveness of pharmacological agents.

Regulation of BECN1-mediated autophagy by HSPB6: Insights from a human HSPB6S10F mutant

HSPB6/Hsp20 (heat shock protein family B [small] member 6) has emerged as a novel cardioprotector against stress-induced injury. We identified a human mutant of HSPB6 (HSPB6^S10F) exclusively present in dilated cardiomyopathy (DCM) patients. Cardiac expression of this mutant in mouse hearts resulted in remodeling and dysfunction, which progressed to heart failure and early death. These detrimental effects were associated with reduced interaction of mutant HSPB6^S10F with BECN1/Beclin 1, leading to BECN1 ubiquitination and its proteosomal degradation. As a result, autophagy flux was substantially inhibited and apoptosis was increased in HSPB6^S10F-mutant hearts. In contrast, overexpression of wild-type HSPB6 (HSPB6 WT) not only increased BECN1 levels, but also competitively suppressed binding of BECN1 to BCL2, resulting in stimulated autophagy. Indeed, preinhibition of autophagy attenuated the cardioprotective effects of HSPB6 WT. Taken together, these findings reveal a new regulatory mechanism of HSPB6 in cell survival through its interaction with BECN1. Furthermore, Ser10 appears to be crucial for the protective effects of HSPB6 and transversion of this amino acid to Phe contributes to cardiomyopathy.

Study of HSPB6: Insights into the Properties of the Multifunctional Protective Agent

HSPB6(Heat shock protein B6), is also referred to as P20/HSP20. Unlike other many other members of sHSP(small Heat shock protein) family, which tend to form high-molecular-mass oligomers, in solution, human HSPB6 only forms dimers. However, it still exhibits chaperon-like activity comparable with that of HSPB5. It is expressed ubiquitously, with high and constitutive expression in muscular tissues. sHSPs characteristically function as molecular chaperones and HSPB6 also has a molecular chaperone activity. HSPB6 is up-regulated in response to diverse cellular stress or damage and protect cells from otherwise lethal conditions. HSPB6 is widely recognized as a principle mediator of cardioprotective signaling and recent studies have unraveled the protective role of HSPB6 in disease or injury to the central nervous system. Moreover, accumulating evidence has implicated HSPB6 as a key mediator of diverse vital physiological processes, such as smooth muscle relaxation, platelet aggregation. The versatility of HSPB6 can be explained by its direct involvement in regulating different client proteins and its ability to form heterooligomer with other sHSPs, which seems to be dependent on HSPB6 phosphorylation. This review focuses on the properties including expression and regulation pattern, phosphorylation, chaperon activity, multiple cellular targets of HSPB6, as well as its possible role in physical and pathological conditions.

Molecular characterization and SNP identification in HSPB6 gene in Karan Fries (Bos taurus x Bos indicus) cattle

Heat shock proteins (HSPs) act as molecular chaperones which are preferentially transcribed in response to severe perturbations of the cellular homeostasis such as heat stress. The present study was undertaken for molecular characterization and detection of genetic polymorphisms of HSPB6 gene in 100 Karan Fries Cattle. HSPB6 gene was mapped on Bos taurus autosome 18 (BTA 18), comprising three exons and two introns. Four sets of primers for HSPB6 gene were designed using Primer3 software (version 0.4.0). For detecting single nucleotide polymorphisms (SNPs), sequence data was analyzed using BioEdit software (version 7.2). Comparative sequence analysis of HSPB6 gene showed five nucleotide polymorphisms, which included three transitions viz. g.161A > G, g.436G > A and g.2152A > G and two transversions viz. g.1743C > G and g.2417A > T compared to B. taurus (NCBI GenBank: AC_000175.1). HSPB6 gene of Karan Fries cattle exhibited a high percentage of nucleotide identity (47.0-100.0%) with the corresponding mammalian homologue. The present study indicated a high degree of genetic variability in the HSPB6 gene in the Karan Fries cattle populations.

Lysine deacetylase inhibition promotes relaxation of arterial tone and C-terminal acetylation of HSPB6 (Hsp20) in vascular smooth muscle cells

There is increasing interest in establishing the roles that lysine acetylation of non nuclear proteins may exert in modulating cell function. Lysine deacetylase 8 (KDAC8), for example, has been suggested to interact with α-actin and control the differentiation of smooth muscle cells. However, a direct role of smooth muscle non nuclear protein acetylation in regulating tone is unresolved. We sought to define the actions of two separate KDAC inhibitors on arterial tone and identify filament-interacting protein targets of acetylation and association with KDAC8. Compound 2 (a specific KDAC8 inhibitor) or Trichostatin A (TSA, a broad-spectrum KDAC inhibitor) inhibited rat arterial contractions induced by phenylephrine (PE) or high potassium solution. In contrast to the predominantly nuclear localization of KDAC1 and KDAC2, KDAC8 was positioned in extranuclear areas of native vascular smooth muscle cells. Several filament-associated proteins identified as putative acetylation targets colocalized with KDAC8 by immunoprecipitation (IP): cortactin, α-actin, tropomyosin, HSPB1 (Hsp27) and HSPB6 (Hsp20). Use of anti-acetylated lysine antibodies showed that KDAC inhibition increased acetylation of each protein. A custom-made antibody targeting the C-terminal acetylated lysine of human HSPB6 identified this as a novel target of acetylation that was increased by KDAC inhibition. HSPB6 phosphorylation, a known vasodilatory modification, was concomitantly increased. Interrogation of publicly available mass spectrometry data identified 50 other proteins with an acetylated C-terminal lysine. These novel data, in alliance with other recent studies, alert us to the importance of elucidating the mechanistic links between changes in myofilament-associated protein acetylation, in conjunction with other posttranslational modifications, and the regulation of arterial tone.