Pathology-dependent effects linked to small heat shock proteins expression: an update

Novel mycoplasma nucleomodulin MbovP475 decreased cell viability by regulating expression of CRYAB and MCF2L2

Nucleomodulins are secreted bacterial proteins whose molecular targets are located in host cell nuclei. They are gaining attention as critical virulence factors that either modify the epigenetics of host cells or directly regulate host gene expression. Mycoplasma bovis is a major veterinary pathogen that secretes several potential virulence factors. The aim of this study was to determine whether any of their secreted proteins might function as nucleomodulins. After an initial in silico screening, the nuclear localization of the secreted putative lipoprotein MbovP475 of M. bovis was demonstrated in bovine macrophage cell line (BoMac) experimentally infected with M. bovis. Through combined application of ChIP-seq, Electrophoretic mobility shift assay (EMSA) and surface plasmon resonance (SPR) analysis, MbovP475 was determined to bind the promoter regions of the cell cycle central regulatory genes CRYAB and MCF2L2. MbovP475 has similar secondary structures with the transcription activator-like effectors (TALEs). Screening of various mutants affecting the potential DNA binding sites indicated that the residues ²⁴²NI²⁴³ within MbovP475 loop region of the helix-loop-helix domain were essential to its DNA binding activity, thereby contributing to decrease in BoMac cell viability. In conclusion, this is the first report to confirm M. bovis secretes a conserved TALE-like nucleomodulin that binds the promoters of CRYAB and MCF2L2 genes, and subsequently down-regulates their expression and decreases BoMac cell viability. Therefore, this study offers a new understanding of mycoplasma pathogenesis.

Differential Expression of Heat Shock Protein 27 in Oral Epithelial Dysplasias and Squamous Cell Carcinoma

Background:

Oral squamous cell carcinoma (OSCC) is the most devastating neoplasm with dramatic increase in morbidity and mortality. The detection and prognostic evaluation of precancerous lesions could aid in early control of cancer. Heat shock protein (HSP) 27 has found to be a biomarker and therapeutic target in different types of cancer.

Aim:

This study aims to investigate the role of HSP 27 as prognostic molecular indicator of malignant transformation in oral epithelial dysplasias.

Materials and Methods:

Thirty samples of epithelial dysplasia (10 mild dysplasia, 10 moderate dysplasia, and 10 severe dysplasia/carcinoma in situ cases), 10 samples each of well-differentiated OSCC and normal oral mucosa were routinely processed, formalin-fixed, paraffin-embedded, and analyzed for HSP27 expression by immunohistochemistry. Statistical analysis was done by one way-ANOVA and Mann–Whitney test to assess the differences between two individual groups.

Results:

Normal mucosa showed intense, but nonuniform, expression of HSP27. An initial decline was noted in dysplasias. A significant correlation of HSP27 expression was observed with the severity of dysplasia and well-differentiated OSCC (P < 0.05).

Conclusion:

Low HSP 27 expression can be considered as early molecular indicator of initial dysplastic change in normal mucosa. An overexpression of HSP 27 in clinically and histologically confirmed dysplasia could indicate likely transformation to well-differentiated OSCC and could be of prognostic value. However, further studies with a larger sample size are required to confirm the role of HSP 27 as predictive indicator.

Intrarectally administered polaprezinc attenuates the development of dextran sodium sulfate-induced ulcerative colitis in mice

Polaprezinc (PZ), a chelate of zinc and L-carnosine, has been widely used in the treatment of gastric ulcers since 1994. In recent years, researchers have found PZ to have a beneficial effect on various experimentally induced models of colitis in mice. In the present study, 6% dextran sodium sulfate (DSS) was used to induce a model of ulcerative colitis (UC) in Institute of Cancer Research mice. The therapeutic effect and mechanism of PZ action in a model of UC was studied in order to provide an experimental basis for the clinical application of PZ in UC treatment. The effect of PZ on UC was evaluated in five groups of mice: A vehicle control only group, a DSS model control group (DSS, 6%), a validated treatment control group (DSS 6% + Mesalamine), a low-dose PZ treatment group (DSS 6% + PZ 60 mg/kg) and a high-dose PZ group (DSS 6% + PZ 120 mg/kg). After the animals were sacrificed, blood was collected and the serum levels of NF-κB and tumor necrosis factor-α (TNF-α) were measured. Changes in histology were observed by light microscopy. The protein levels of AKT, phosphorylated AKT and heat shock protein 70 (HSP70) were determined by western blot analysis. The results suggested that PZ reduced the DSS-induced increase in the inflammatory proteins TNF-α and NF-κB in the UC model. The high-dose of PZ also increased the HSP70 protein level, inhibited AKT phosphorylation in a DSS-induced UC animal model, and decreased white blood cell and neutrophil % counts compared to levels in an untreated DSS control group. Histopathology indicated that the mice of the DSS model group had irregular colonic villi, a large number of inflammatory cells and mucosal damage, whereas mice of the group treated with PZ had small intestinal villus morphology and their villi showed signs of recovery from the damage of UC. The results of the present study indicated that PZ significantly alleviates DSS-induced UC in mice, relieves diarrhea, and inhibits the phosphorylation of inflammatory factors and the inflammatory AKT signaling pathway.

Heat shock protein beta 3 (HSPB3) is an unfavorable molecular biomarker in colorectal adenocarcinoma

Small heat shock proteins (sHSPs) participate in numerous cellular functions including cell signaling, differentiation, and apoptosis. Deregulation of the physiological expression level of sHSPs has been associated with several malignancies. Heat shock protein beta 3 (HSPB3) is the third member of the sHSP family in human and is mainly expressed in skeletal and smooth muscles. In this study, we investigated the potential prognostic significance of HSPB3 expression in colorectal adenocarcinoma, the most frequent type of colorectal cancer. For this purpose, we isolated total RNA from 188 colorectal adenocarcinoma specimens and 68 paired noncancerous ones. After reverse transcription of 2 μg total RNA, we quantified HSPB3 levels by using an in-house-developed real-time quantitative polymerase chain reaction method, based on the SYBR Green chemistry. Comparison of HSPB3 levels among 68 pairs of colorectal tumors and their adjacent noncancerous mucosae uncovered the downregulation of HSPB3 expression in the majority of malignant colorectal tumors. More importantly, high HSPB3 expression is associated with poor relapse-free survival (RFS) and overall survival (OS) of patients with colorectal adenocarcinoma. Multivariable Cox regression analysis revealed that HSPB3 overexpression could serve as an adverse prognostic biomarker in colorectal adenocarcinoma, independent of tumor location, histological grade, and TNM stage. Patients' stratification according to tumor location, histological grade, and TNM stage revealed that high HSPB3 messenger RNA expression retains its unfavorable prognostic potential regarding OS, in particular groups of patients with substantially different prognosis. In conclusion, high HSPB3 expression is associated with poor RFS and OS of patients with colorectal adenocarcioma, independently of clinicopathological prognosticators.

CRYAB protects cardiomyocytes against heat stress by preventing caspase-mediated apoptosis and reducing F-actin aggregation

CRYAB is a small heat shock protein (sHSP) that has previously been shown to protect the heart against various cellular stresses; however, its precise function in myocardial cell injury caused by heat stress remains unclear. This study aimed to investigate the molecular mechanism by which CRYAB protects cardiomyocytes against heat stress. We constructed two H9C2 cell lines that stably express CRYAB protein to differing degrees: CRYAB-5 and CRYAB-7. Both CRYAB-5 and CRYAB-7 showed significantly reduced granular degeneration and vacuolar degeneration following heat stress compared to control cells. In addition, CRYAB overexpression in H9C2 cells relieved cell cycle proportion at the G0/G1 phase following heat stress compared to control cells. These protective effects were associated with the level of CRYAB protein expression. Our immunofluorescence analysis showed CRYAB could translocate from the cytoplasm to the nucleus under heat stress conditions, but that CRYAB co-localized with F-actin (which accumulates under stress conditions). Indeed, overexpression of CRYAB significantly reduced the aggregation of F-actin in H9C2 cells caused by heat stress. Furthermore, overexpressing CRYAB protein significantly reduced the apoptosis of cardiomyocytes induced by heat stress, likely by reducing the expression of cleaved-caspase 3. Collectively, our results show overexpression of CRYAB significantly increases the heat resistance of H9C2 cardiomyocytes, likely by reducing F-actin aggregation (thus stabilizing the cytoskeleton), regulating the cell cycle, and preventing caspase-mediated apoptosis.

Analysis of HspB1 (Hsp27) Oligomerization and Phosphorylation Patterns and Its Interaction with Specific Client Polypeptides

Human HspB1 (also denoted as Hsp27) belongs to the family of small (or stress) proteins (sHsps). The family, which contains ten members including αA,B-crystallin polypeptides, is characterized by a conserved C-terminal α-crystallin domain and molecular weights ranging from 20 to 40 kDa. Here, procedures are described for analyzing the dynamic oligomerization and phosphorylation patterns of HspB1 in cells exposed to different environments. Changes in the structural organization of HspB1 can reprogram its interaction with specific partner/client polypeptides. Methods are presented to analyze these interactions using tissue culture cells genetically modified to express different levels of this protein. In addition, the laboratory approaches presented here could be used to test the nine other human sHsp members as well as sHsps from other species.

Mammalian HspB1 (Hsp27) is a molecular sensor linked to the physiology and environment of the cell

Constitutively expressed small heat shock protein HspB1 regulates many fundamental cellular processes and plays major roles in many human pathological diseases. In that regard, this chaperone has a huge number of apparently unrelated functions that appear linked to its ability to recognize many client polypeptides that are subsequently modified in their activity and/or half-life. A major parameter to understand how HspB1 is dedicated to interact with particular clients in defined cellular conditions relates to its complex oligomerization and phosphorylation properties. Indeed, HspB1 structural organization displays dynamic and complex rearrangements in response to changes in the cellular environment or when the cell physiology is modified. These structural modifications probably reflect the formation of structural platforms aimed at recognizing specific client polypeptides. Here, I have reviewed data from the literature and re-analyzed my own studies to describe and discuss these fascinating changes in HspB1 structural organization.

Phosphorylation of alphaB-crystallin in epiretinal membrane of human proliferative diabetic retinopathy

AIM

To examine phosphorylation of alphaB-crystallin (p-αBC), a vascular endothelial growth factor (VEGF) chaperone, and immunohistochemically investigate relationship between p-αBC, VEGF and phosphorylated p38-mitogen-activated protein kinase (p-p38 MAPK) in the epiretinal membrane of human proliferative diabetic retinopathy (PDR).

METHODS

Eleven epiretinal membranes of PDR surgically excised were included in this study. Two normal retinas were also collected from enucleation tissues due to choroidal melanoma. Paraformaldehyde-fixed, paraffin-embedded tissue sections were processed for immunohistochemistry with anti-p-αBC, VEGF, CD31, and p-p38 MAPK antibodies.

RESULTS

Immunoreactivity for p-αBC was observed in all of the epiretinal membranes examined, where phosphorylation on serine (Ser) 59 showed strongest immunoreactivity in over 70% of the membranes. The immunolocalization of p-αBC was detected in the CD31-positive endothelial cells, and co-localized with VEGF and p-p38 MAPK in PDR membranes. Immunoreactivity for p-αBC, however, was undetectable in endothelial cells of the normal retinas, where p-p38 MAPK immunoreactivity was less marked than PDR membranes.

CONCLUSION

Phosphorylation of αBC, in particular, phosphorylation on Ser59 by p-p38 MAPK may play a potential role as a molecular chaperon for VEGF in the pathogenesis of epiretinal membranes in PDR.

Introducing differential expression of human heat shock protein 27 in hepatocellular carcinoma: moving toward identification of cancer biomarker

Previously, it has to be acknowledged that overexpressed heat shock protein B27 (HSPB27) have been implicated in the etiology of wide range of human cancers. However, the molecular mechanism leading to the disease initiation to progression in liver cancer is still unknown. Present work was undertaken to investigate the differentially expressed HSPB27 in association with those damages that lead to liver cancer development. For the identification of liver cancer biomarker, samples were subjected to comparative proteomic analysis using two-dimensional gel electrophoresis (2-DE) and were further validated by Western blot and immunohistochemical analysis. After validation, in silico studies were applied to demonstrate the significantly induced phosphorylated and S-nitrosylated signals. The later included the interacting partner of HSPB27, i.e., mitogen-activated protein kinase-3 and 5 (MAPK3 and 5), ubiquitin C (UBC), v-akt murine thymoma viral oncogene homolog 1 (AKT1), mitogen-activated protein kinase 14 (MAPK14), and tumor protein p53 (TP53), which bestowed with critical capabilities, namely, apoptosis, cell cycling, stress activation, tumor suppression, cell survival, angiogenesis, proliferation, and stress resistance. Taking together, these results shed new light on the potential biomarker HSPB27 that overexpression of HSPB27 did lead to upregulation of their interacting partner that together demonstrate their possible role as a novel tumor progressive agent for the treatment of metastasis in liver cancer. HSPB27 is a promising diagnostic marker for liver cancer although further large-scale studies are required. Also, molecular profiling may help pave the road to the discovery of new therapies.

HspB1, HspB5 and HspB4 in Human Cancers: Potent Oncogenic Role of Some of Their Client Proteins

Human small heat shock proteins are molecular chaperones that regulate fundamental cellular processes in normal unstressed cells as well as in many cancer cells where they are over-expressed. These proteins are characterized by cell physiology dependent changes in their oligomerization and phosphorylation status. These structural changes allow them to interact with many different client proteins that subsequently display modified activity and/or half-life. Nowdays, the protein interactomes of small Hsps are under intense investigations and will represent, when completed, key parameters to elaborate therapeutic strategies aimed at modulating the functions of these chaperones. Here, we have analyzed the potential pro-cancerous roles of several client proteins that have been described so far to interact with HspB1 (Hsp27) and its close members HspB5 (αB-crystallin) and HspB4 (αA-crystallin).

Analysis of the dominant effects mediated by wild type or R120G mutant of αB-crystallin (HspB5) towards Hsp27 (HspB1)

Several human small heat shock proteins (sHsps) are phosphorylated oligomeric chaperones that enhance stress resistance. They are characterized by their ability to interact and form polydispersed hetero-oligomeric complexes. We have analyzed the cellular consequences of the stable expression of either wild type HspB5 or its cataracts and myopathies inducing R120G mutant in growing and oxidative stress treated HeLa cells that originally express only HspB1. Here, we describe that wild type and mutant HspB5 induce drastic and opposite effects on cell morphology and oxidative stress resistance. The cellular distribution and phosphorylation of these polypeptides as well as the oligomerization profile of the resulting hetero-oligomeric complexes formed by HspB1 with the two types of exogenous polypeptides revealed the dominant effects induced by HspB5 polypeptides towards HspB1. The R120G mutation enhanced the native size and salt resistance of HspB1-HspB5 complex. However, in oxidative conditions the interaction between HspB1 and mutant HspB5 was drastically modified resulting in the aggregation of both partners. The mutation also induced the redistribution of HspB1 phosphorylated at serine 15, originally observed at the level of the small oligomers that do not interact with wild type HspB5, to the large oligomeric complex formed with mutant HspB5. This phosphorylation stabilized the interaction of HspB1 with mutant HspB5. A dominant negative effect towards HspB1 appears therefore as an important event in the cellular sensitivity to oxidative stress mediated by mutated HspB5 expression. These observations provide novel data that describe how a mutated sHsp can alter the protective activity of another member of this family of chaperones.