Heat shock protein 90-α mediates aldo-keto reductase 1B10 (AKR1B10) protein secretion through secretory lysosomes

Aldo-keto reductase 1B10 as a Carcinogenic but Not a Prognostic Factor in Colorectal Cancer

Colorectal cancer (CRC) is the leading cause of cancer death, but little is known about its etiopathology. Aldo-keto reductase 1B10 (AKR1B10) protein is primarily expressed in intestinal epithelial cells, but lost in colorectal cancer tissues. This study revealed that AKR1B10 may not be a prognostic but an etiological factor in colorectal tumorigenesis. Using a tissue microarray, we investigated the expression of AKR1B10 in tumor tissues of 592 colorectal cancer patients with a mean follow-up of 25 years. Results exhibited that AKR1B10 protein was undetectable in 374 (63.13%), weakly positive in 146 (24.66%), and positive 72 (12.16%) of 592 tumor tissues. Kaplan-Meier analysis showed that AKR1B10 expression was not correlated with overall survival or disease-free survival. Similar results were obtained in various survival analyses stratified by clinicopathological parameters. AKR1B10 was not correlated with tumor T-pathology, N-pathology, TNM stages, cell differentiation and lymph node/regional/distant metastasis either. However, AKR1B10 silencing in culture cells enhanced carbonyl induced protein and DNA damage; and in ulcerative colitis tissues, AKR1B10 deficiency was associated acrolein-protein lesions. Together this study suggests that AKR1B10 downregulation may not be a prognostic but a carcinogenic factor of colorectal cancer.

Serum AKR1B10 as an indicator of unfavorable survival of hepatocellular carcinoma

BACKGROUND AND AIMS

A large-scale multicenter study validated aldo-keto reductase 1B10 (AKR1B10) as a new serum marker of hepatocellular carcinoma (HCC). This study aimed to evaluate the prognostic value of serum AKR1B10 in HCC.

METHODS

273 naïve HCC patients enrolled for serum AKR1B10 tests were followed up for 2 years. Survival and clinical data were collected. Kaplan-Meier survival analysis and log-rank tests were used to estimate correlation of patient survival with serum AKR1B10. Univariate and multivariate COX regression analyses were used to evaluate the prognostic value of serum AKR1B10 level independently or in combination with other clinicopathological factors. α-fetoprotein (AFP) was analyzed in parallel for comparison.

RESULTS

Serum AKR1B10 associated with tumor stage (p = 0.012), size (p = 0.004), primary tumor number (p = 0.019), and Child-Pugh classification (p = 0.003). HCC patients with a high level of serum AKR1B10 (≥ 267.9 pg/ml) had median survival (MS) of 25 months (95% confidence interval [CI] 20.788-29.212) vs. MS of 34 months (CI 28.911-39.089) in patients with normal serum AKR1B10 (p < 0.001). Univariate and multivariate COX regression analyses showed that serum AKR1B10 level was an unfavorable prognostic marker of HCC independently (HR 1.830, 95% CI 1.312-2.552; p < 0.001) or in combination with other clinical factors (HR 1.883, 95% CI 1.264-2.806; p = 0.002), such as TNM stage, tumor size and portal invasion. In the same cohort of HCC patients, AFP exhibited prognostic value at a cut-off of 400 ng/ml, but not at 20 ng/ml and 200 ng/ml.

CONCLUSIONS

Serum AKR1B10 is a new prognostic marker of HCC, better than AFP.

Aldo-keto reductase family 1 member B10 is regulated by nucleos(t)ide analogues for chronic hepatitis B

The number of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) patients persists even under nucleos(t)ide analogues (NAs) treatment. Aldo-keto reductase family 1 member B10 (AKR1B10) expression has been reported in advanced chronic liver diseases as well as cancer tissues. We observed an association between related to HCC incidence and serum AKR1B10 by analyzing patients under treatment with NAs. Serum AKR1B10 levels measured by ELISA were higher in HCC cases under NA treatment compared with non-HCC cases and were associated with lamivudine- and adefovir pivoxil-, but not entecavir- or tenofovir alafenamide-treated cases. The latter drugs did not increase AKR1B10 values even in HCC cases, suggesting that they influence the reduction of AKR1B10 in any cases. This analysis was supported by in-vitro examination, which showed reduced AKR1B10 expression by entecavir and tenofovir via immunofluorescence staining. In conclusion there was a relationship between HBV-related HCC incidence and AKR1B10 under nucleos(t)ide analogues, especially in the use of lamivudine and adefovir pivoxil, but entecavir and tenofovir had suppressive effects of AKR1B10.

Characterization of human oxidoreductases involved in aldehyde odorant metabolism

Oxidoreductases are major enzymes of xenobiotic metabolism. Consequently, they are essential in the chemoprotection of the human body. Many xenobiotic metabolism enzymes have been shown to be involved in chemosensory tissue protection. Among them, some were additionally shown to be involved in chemosensory perception, acting in signal termination as well as in the generation of metabolites that change the activation pattern of chemosensory receptors. Oxidoreductases, especially aldehyde dehydrogenases and aldo-keto reductases, are the first barrier against aldehyde compounds, which include numerous odorants. Using a mass spectrometry approach, we characterized the most highly expressed members of these families in the human nasal mucus sampled in the olfactory vicinity. Their expression was also demonstrated using immunohistochemistry in human epitheliums sampled in the olfactory vicinity. Recombinant enzymes corresponding to three highly expressed human oxidoreductases (ALDH1A1, ALDH3A1, AKR1B10) were used to demonstrate the high enzymatic activity of these enzymes toward aldehyde odorants. The structure‒function relationship set based on the enzymatic parameters characterization of a series of aldehyde odorant compounds was supported by the X-ray structure resolution of human ALDH3A1 in complex with octanal.

Regulation of Protein Transport Pathways by the Cytosolic Hsp90s

The highly conserved molecular chaperone heat shock protein 90 (Hsp90) is well-known for maintaining metastable proteins and mediating various aspects of intracellular protein dynamics. Intriguingly, high-throughput interactome studies suggest that Hsp90 is associated with a variety of other pathways. Here, we will highlight the potential impact of Hsp90 in protein transport. Currently, a limited number of studies have defined a few mechanistic contributions of Hsp90 to protein transport, yet the relevance of hundreds of additional connections between Hsp90 and factors known to aide this process remains unresolved. These interactors broadly support transport pathways including endocytic and exocytic vesicular transport, the transfer of polypeptides across membranes, or unconventional protein secretion. In resolving how Hsp90 contributes to the protein transport process, new therapeutic targets will likely be obtained for the treatment of numerous human health issues, including bacterial infection, cancer metastasis, and neurodegeneration.

AKR1B10 as a Potential Novel Serum Biomarker for Breast Cancer: A Pilot Study

Background

Aldo-keto reductase 1B10 (AKR1B10) is a secretory protein that is upregulated in breast cancer.

Objective

This case-controlled pilot study evaluated the serum level of AKR1B10 in healthy women and patients with a localized or metastatic breast cancer.

Methods

AKR1B10 levels were measured by ELISA and IHC in several patient cohorts.

Results

Our data showed that serum AKR1B10 was significantly elevated in patients with localized (6.72 ± 0.92 ng/ml) or metastatic (7.79 ± 1.13 ng/ml) disease compared to cancer-free healthy women (1.69 ± 0.17 ng/ml) (p<0.001); the serum AKR1B10 was correlated with its expression in tumor tissues, but not with the tumor burden, molecular subtypes or histological stages. After surgical removal of primary tumors, the serum AKR1B10 was rapidly decreased within 3 days and plateaued at a level similar to that of healthy controls in most patients. ROC curve analysis suggested the optimal diagnostic cut-off value of serum AKR1B10 at 3.456 ng/ml with AUC 0.9045 ± 0.0337 (95% CI 0.8384 - 0.9706), sensitivity 84.75% (95% CI 73.01% to 92.78%), and specificity 93.88% (95% CI 83.13% to 98.72%).

Conclusions

These data indicate the potential value of serum AKR1B10 as a biomarker of breast cancer.

AKR1B10, One of the Triggers of Cytokine Storm in SARS-CoV2 Severe Acute Respiratory Syndrome

Preventing the cytokine storm observed in COVID-19 is a crucial goal for reducing the occurrence of severe acute respiratory failure and improving outcomes. Here, we identify Aldo-Keto Reductase 1B10 (AKR1B10) as a key enzyme involved in the expression of pro-inflammatory cytokines. The analysis of transcriptomic data from lung samples of patients who died from COVID-19 demonstrates an increased expression of the gene encoding AKR1B10. Measurements of the AKR1B10 protein in sera from hospitalised COVID-19 patients suggests a significant link between AKR1B10 levels and the severity of the disease. In macrophages and lung cells, the over-expression of AKR1B10 induces the expression of the pro-inflammatory cytokines Interleukin-6 (IL-6), Interleukin-1β (IL-1β) and Tumor Necrosis Factor a (TNFα), supporting the biological plausibility of an AKR1B10 involvement in the COVID-19-related cytokine storm. When macrophages were stressed by lipopolysaccharides (LPS) exposure and treated by Zopolrestat, an AKR1B10 inhibitor, the LPS-induced production of IL-6, IL-1β, and TNFα is significantly reduced, reinforcing the hypothesis that the pro-inflammatory expression of cytokines is AKR1B10-dependant. Finally, we also show that AKR1B10 can be secreted and transferred via extracellular vesicles between different cell types, suggesting that this protein may also contribute to the multi-organ systemic impact of COVID-19. These experiments highlight a relationship between AKR1B10 production and severe forms of COVID-19. Our data indicate that AKR1B10 participates in the activation of cytokines production and suggest that modulation of AKR1B10 activity might be an actionable pharmacological target in COVID-19 management.

AKR1B10 inhibits the proliferation and migration of gastric cancer via regulating epithelial-mesenchymal transition

Gastric cancer (GC) is a common malignancy around the world with a poor prognosis. Aldo-keto reductase family 1 member B10 (AKR1B10) is indispensable to cancer development and progression, which has served as a diagnostic biomarker for tumors. In our study, we demonstrated that the expression of AKR1B10 in GC tissues was significantly lower compared with normal gastric tissues. Subgroup analysis showed that, according to the clinic-pathological factors, the effect of the AKR1B10 expression level on the prognosis of GC patients was significantly different. Moreover, reduced expression of AKR1B10 promoted the ability of GC cells in proliferation and migration. Furthermore, increased AKR1B10 levels resulted in the opposite trend in vitro. Moreover, AKR1B10 was correlated with epithelial-mesenchymal transition (EMT) in a significant way. In vivo experiment, knockdown of AKR1B10 promoted the growth of tumor, increased Vimentin, and E-cadherin significantly. In summary, AKR1B10 is considered as a tumor suppressor in GC and is a promising therapeutic target.

The Role of AKR1B10 in Physiology and Pathophysiology

AKR1B10 is a human nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reductase belonging to the aldo-keto reductase (AKR) 1B subfamily. It catalyzes the reduction of aldehydes, some ketones and quinones, and interacts with acetyl-CoA carboxylase and heat shock protein 90α. The enzyme is highly expressed in epithelial cells of the stomach and intestine, but down-regulated in gastrointestinal cancers and inflammatory bowel diseases. In contrast, AKR1B10 expression is low in other tissues, where the enzyme is upregulated in cancers, as well as in non-alcoholic fatty liver disease and several skin diseases. In addition, the enzyme's expression is elevated in cancer cells resistant to clinical anti-cancer drugs. Thus, growing evidence supports AKR1B10 as a potential target for diagnosing and treating these diseases. Herein, we reviewed the literature on the roles of AKR1B10 in a healthy gastrointestinal tract, the development and progression of cancers and acquired chemoresistance, in addition to its gene regulation, functions, and inhibitors.

AKR1B10 negatively regulates autophagy through reducing GAPDH upon glucose starvation in colon cancer

Autophagy is considered to be an important switch for facilitating normal to malignant cell transformation during colorectal cancer development. Consistent with other reports, we found that the membrane receptor Neuropilin1 (NRP1) is greatly upregulated in colon cancer cells that underwent autophagy upon glucose deprivation. However, the mechanism underlying NRP1 regulation of autophagy is unknown. We found that knockdown of NRP1 inhibits autophagy and largely upregulates the expression of aldo-keto reductase family 1 B10 (AKR1B10). Moreover, we demonstrated that AKR1B10 interacts with and inhibits the nuclear importation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and then subsequently represses autophagy. Interestingly, we also found that an NADPH-dependent reduction reaction could be induced when AKR1B10 interacts with GAPDH, and the reductase activity of AKR1B10 is important for its repression of autophagy. Together, our findings unravel a novel mechanism of NRP1 in regulating autophagy through AKR1B10.

AKR1B10 Inhibitor Epalrestat Facilitates Sorafenib-Induced Apoptosis and Autophagy Via Targeting the mTOR Pathway in Hepatocellular Carcinoma

Sorafenib is the standard systemic treatment for advanced hepatocellular carcinoma (HCC), and improving its therapeutic effects is crucial for addressing cancer aggression. We previously reported that epalrestat, an aldo-keto reductase 1B10 inhibitor, enhanced sorafenib's inhibitory effects on HCC xenograft in nude mice. This study aimed to elucidate the mechanism of epalrestat's anti-tumour enhancing effects on sorafenib. HepG2 cells were treated with sorafenib, epalrestat, and their combination. Cell proliferation was assessed with Cell Counting Kit-8 and colony formation assays. AKR1B10 supernate concentration and enzyme activity were detected by ELISA assay and the decrease of optical density of NADPH at 340 nm. Cell cycle and apoptosis analyses were performed with flow cytometry. Western blots clarified the molecular mechanism underlying effects on cell cycle, apoptosis, and autophagy. The anti-tumour mechanism was then validated in vivo through TUNEL and immunohistochemistry staining of HCC xenograft sections. Epalrestat combined with sorafenib inhibited HepG2 cellular proliferation in vitro, arrested the cell cycle at G0/G1, and promoted apoptosis and autophagy. Treatment with a specific mTOR activator MHY-1485 increased mTOR phosphorylation, while suppressing apoptosis and autophagy. Consistent with in vitro results, data from the HCC-xenograft nude mouse model also indicated that combined treatment inhibited the mTOR pathway and promoted apoptosis and autophagy. In conclusion, epalrestat heightens sorafenib's anti-cancer effects via blocking the mTOR pathway, thus inducing cell cycle arrest, apoptosis, and autophagy.

Genome-wide screening diagnostic biomarkers and the construction of prognostic model of hepatocellular carcinoma

Although methods in diagnosis and therapy of hepatocellular carcinoma (HCC) have made significant progress in decades, the overall survival (OS) of HCC remains dissatisfactory, so it is particularly important to find better diagnostic and prognostic biomarkers. In this study, we found a more reliable potential diagnostic biomarkers and constructed a more accurate prognostic evaluation model based on integrated transcriptome sequencing analysis of multiple independent data sets. First, we performed quality evaluation and differential analysis on seven Gene Expression Omnibus (GEO) data sets, and then comprehensively analyzed the differentially expressed genes with a robust rank aggregation algorithm. Next, Least absolute shrinkage and selection operator (LASSO) regression was used to establish an 8-gene prognostic risk score (RS) model. Finally, the prognostic model was further validated in the GEO data set. Also, RS has independence on other clinicopathological characteristics but has similarities in prognostic assessment compared with the T stage. Moreover, the combination of T stage and prognostic RS model based on the 8-gene had a better prognostic evaluation effect. In brief, our research suggest that the prognostic risk model of 8 genes has important clinical significance in HCC patients, and can further enrich the prognostic guidance value of the traditional T stage.

Sugar Alcohols of Polyol Pathway Serve as Alarmins to Mediate Local-Systemic Innate Immune Communication in Drosophila

Interorgan immunological communication is critical to connect the local-systemic innate immune response and orchestrate a homeostatic host defense. However, the factors and their roles in this process remain unclear. We find Drosophila IMD response in guts can sequentially trigger a systemic IMD reaction in the fat body. Sugar alcohols of the polyol pathway are essential for the spatiotemporal regulation of gut-fat body immunological communication (GFIC). IMD activation in guts causes elevated levels of sorbitol and galactitol in hemolymph. Aldose reductase (AR) in hemocytes, the rate-limiting enzyme of the polyol pathway, is necessary and sufficient for the increase of plasma sugar alcohols. Sorbitol relays GFIC by subsequent activation of Metalloprotease 2, which cleaves PGRP-LC to activate IMD response in fat bodies. Thus, this work unveils how GFIC relies on the intermediate activation of the polyol pathway in hemolymph and demonstrates that AR provides a critical metabolic checkpoint in the global inflammatory response.

Serum aldo-keto reductase family 1 member B10 predicts advanced liver fibrosis and fatal complications of nonalcoholic steatohepatitis

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is associated with liver inflammation in patients with nonalcoholic fatty liver disease, and it can progress to liver fibrosis at an advanced stage, as well as hepatocellular carcinoma (HCC) and portal hypertension. Although liver fibrosis is accurately diagnosed via biopsy, noninvasive methods are preferable. Aldo-keto reductase family 1 member B10 (AKR1B10) is associated with HCC and is secreted into the blood by liver cells via a lysosome-mediated nonclassical pathway. Accordingly, we analyzed whether secretion of AKR1B10 protein is associated with advanced NASH.

METHODS

We performed histological staging in 85 Matteoni classification type III and IV NASH patients and evaluated the incidence of HCC, formation of gastroesophageal varices, and prognosis according to serum AKR1B10 and Wisteria floribunda agglutinin-positive Mac-2 binding protein (WFA(+)-M2BP)(M2BPGi) and by comparison with conventional markers of fibrosis.

RESULTS

 A positive correlation was found between the Brunt classification and serum AKR1B10 level. In Brunt stage 4 patients, AKR1B10 levels were higher than those of other liver fibrosis markers, with higher specificity. The cutoff values for AKR1B10 and WFA(+)-M2BP for stage 4 fibrosis were 1.03 and 3.11, respectively. The rates of stage 4 fibrosis, HCC incidence, and gastroesophageal varix formation were significantly different between the two groups subdivided according to these cutoff levels. Moreover, the patients in the higher value group had significantly worse prognosis after NASH diagnosis CONCLUSION: AKR1B10 is a useful serum biomarker for advanced liver fibrosis in NASH and, combined with serum WFA(+)-M2BP, can predict HCC development, gastroesophageal varix formation, and poor prognosis.

A Large-Scale Multicenter Study Validates Aldo-Keto Reductase Family 1 Member B10 as a Prevalent Serum Marker for Detection of Hepatocellular Carcinoma

Aldo-keto reductase family 1 member B10 (AKR1B10) is a secretory protein overexpressed in hepatocellular carcinoma (HCC). We aimed to evaluate AKR1B10 as a serum marker for detection of HCC. Herein, we conducted a cohort study that consecutively enrolled 1,244 participants from three independent hospitals, including HCC, healthy controls (HCs), benign liver tumors (BLTs), chronic hepatitis B (CHB), and liver cirrhosis (LC). Serum AKR1B10 was tested by time-resolved fluorescent assays. Data were plotted for receiver operating characteristic (ROC) curve analyses. Alpha-fetoprotein (AFP) was analyzed for comparison. An exploratory discovery cohort demonstrated that serum AKR1B10 increased in patients with HCC (1,567.3 ± 292.6 pg/mL; n = 69) compared with HCs (85.7 ± 10.9 pg/mL; n = 66; P < 0.0001). A training cohort of 519 participants yielded an optimal diagnostic cutoff of serum AKR1B10 at 267.9 pg/mL. When ROC curve was plotted for HCC versus all controls (HC + BLT + CHB + LC), serum AKR1B10 had diagnostic parameters of the area under the curve (AUC) 0.896, sensitivity 72.7%, and specificity 95.7%, which were better than AFP with AUC 0.816, sensitivity 65.1%, and specificity 88.9%. Impressively, AKR1B10 showed promising diagnostic potential in early-stage HCC and AFP-negative HCC. Combination of AKR1B10 with AFP increased diagnostic accuracy for HCC compared with AKR1B10 or AFP alone. A validation cohort of 522 participants confirmed these findings. An independent cohort of 68 patients with HCC who were followed up showed that serum AKR1B10 dramatically decreased 1 day after operation and was nearly back to normal 3 days after operation. Conclusion: AKR1B10 is a potent serum marker for detection of HCC and early-stage HCC, with better diagnostic performance than AFP.

Potential of AKR1B10 as a Biomarker and Therapeutic Target in Type 2 Leprosy Reaction

The AKR1B10 (aldo-keto reductase family 1 member B10) gene has important functions in carcinogen-induced neoplasia. AKR1B10 is also expressed in type 2 reaction leprosy patients (R2). We measured the expression of AKR1B10 in the skin lesions of patients with leprosy by immunohistochemistry from biopsies that encompassed the spectrum of types of leprosy, based on the Ridley and Jopling classification [10 samples each of tuberculoid (TT), borderline tuberculoid (BT), mid-borderline (BB), and borderline lepromatous (BL) lesions; four samples of lepromatous lesions (LL)], reactional leprosy [14 samples of type 1 Reaction (R1) and 10 samples of type 2 Reaction (R2)], and biopsies from 9 healthy control (HC) subjects. In addition, 46 lepromatous lesions (BL and LL), 45 lepromatous lesions in regression, and 115 R2 lesions were included. Eight of 10 R2 samples (80%), 3 of 46 active BL and LL samples (6%), 23 of 45 BL and LL samples in regression (51%), and 107 of 115 R2 samples (93%) were positive for AKR1B10, differing significantly between all groups (p < 0.05). AKR1B10 expression was highest in the cytoplasm of macrophages. Thus, AKR1B10 is overexpressed on the lepromatous side (BL and LL) in samples that are in regression, especially type 2 reaction-associated lesions, rendering it a potential marker of type 2 reactional episodes of leprosy and a target of drugs against reactional episodes.

AKR1B10-inhibitory Selaginella tamariscina extract and amentoflavone decrease the growth of A549 human lung cancer cells in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Selaginella tamariscina (P.Beauv.) Spring is a traditional medicinal plant used to treat various human diseases, including cancer, in Asia. The detailed molecular mechanism underlying the anti-cancer effects of this plant and the anti-cancer action of the combinatorial treatment of S. tamariscina and doxorubicin have not yet been investigated.

AIM OF THE STUDY

We evaluated the inhibitory activity of S. tamariscina extract (STE) and its major compound, amentoflavone, on human aldo-keto reductase family 1B10 (AKR1B10), which is a detoxification enzyme involved in drug resistance, to evaluate their anti-cancer effects and their potential as adjuvant agents for doxorubicin cancer chemotherapy.

MATERIALS AND METHODS

We tested the AKR1B10 inhibitory activity of STE and amentoflavone via an in vitro biochemical assay using recombinant human AKR1B10. We tested the anti-proliferative activity in A549, NCI-H460, SKOV-3, and MCF-7 human cancer cells, which contain different expression levels of AKR1B10, and determined the combination index to evaluate whether the addition of STE and amentoflavone is synergistic or antagonistic to the anti-cancer action of doxorubicin. We finally evaluated the in vivo anti-tumor effects of STE in a nude mouse xenograft model of A549 cells.

RESULTS

STE and amentoflavone potently inhibited human AKR1B10 and synergistically increased the doxorubicin anti-proliferative effect in A549 and NCI-H460 human lung cancer cells that express a high level of AKR1B10 mRNA and protein. STE also significantly inhibited A549 tumor growth in animal experiments.

CONCLUSION

Our results suggest that STE and amentoflavone could be potential anti-cancer agents that target AKR1B10 and might be candidate adjuvant agents to boost the anti-cancer effect of doxorubicin.

Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β

Overexpression of plasma membrane multidrug resistance-associated protein 1 (MRP-1) in Ewing's sarcoma (ES) predicts poor outcome. MRP-1 is also expressed in mitochondria, and we have examined the submitochondrial localization of MRP-1 and investigated the mechanism of MRP-1 transport and role of this organelle in the response to doxorubicin. The mitochondrial localization of MRP-1 was examined in ES cell lines by differential centrifugation and membrane solubilization by digitonin. Whether MRP-1 is chaperoned by heat shock proteins (HSPs) was investigated by immunoprecipitation, immunofluorescence microscopy, and HSP knockout using small hairpin RNA and inhibitors (apoptozole, 17-AAG, and NVPAUY). The effect of disrupting mitochondrial MRP-1-dependent efflux activity on the cytotoxic effect of doxorubicin was investigated by counting viable cell number. Mitochondrial MRP-1 is glycosylated and localized to the outer mitochondrial membrane, where it is coexpressed with HSP90. MRP-1 binds to both HSP90 and HSP70, although only inhibition of HSP90β decreases expression of MRP-1 in the mitochondria. Disruption of mitochondrial MRP-1-dependent efflux significantly increases the cytotoxic effect of doxorubicin (combination index, <0.9). For the first time, we have demonstrated that mitochondrial MRP-1 is expressed in the outer mitochondrial membrane and is a client protein of HSP90β, where it may play a role in the doxorubicin-induced resistance of ES.-Roundhill, E., Turnbull, D., Burchill, S. Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β.

Proteomic analysis of mesenchymal stem cells from normal and deep carious dental pulp

Dental pulp stem cells (DPSCs), precursor cells of odontoblasts, are ideal seed cells for tooth tissue engineering and regeneration. Our previous study has demonstrated that stem cells exist in dental pulp with deep caries and are called carious dental pulp stem cells (CDPSCs). The results indicated that CDPSCs had a higher proliferative and stronger osteogenic differentiation potential than DPSCs. However, the molecular mechanisms responsible for the biological differences between DPSCs and CDPSCs are poorly understood. The aim of this study was to define the molecular features of DPSCs and CDPSCs by comparing the proteomic profiles using two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) in combination with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Our results revealed that there were 18 protein spots differentially expressed between DPSCs and CDPSCs in a narrow pH range of 4 to 7. These differently expressed proteins are mostly involved in the regulation of cell proliferation, differentiation, cell cytoskeleton and motility. In addition, our results suggested that CDPSCs had a higher expression of antioxidative proteins that might protect CDPSCs from oxidative stress. This study explores some potential proteins responsible for the biological differences between DPSCs and CDPSCs and expands our understanding on the molecular mechanisms of mineralization of DPSCs in the formation of the dentin-pulp complex.