Molecular interactions of Bcl-2 and Bcl-xL with mortalin: identification and functional characterization

Mitochondria-targeting folic acid-modified nanoplatform based on mesoporous carbon and a bioactive peptide for improved colorectal cancer treatment

Oral colon-targeted drug delivery systems (OCDDs) are designed to deliver the therapeutic agents to colonic disease sites to improve the effectiveness of drug treatment, increase bioavailability, and reduce systemic side effects and are beneficial for the treatment of colorectal cancer (CRC) and inflammatory bowel disease (IBD). However, concerns about the biosafety of OCDDs are increasing, and changes in the physiological environment of the gastrointestinal tract can affect the therapeutic efficacy of the drug. Herein, we report about an orally administered colon-accumulating mitochondria-targeted drug delivery nanoplatform (M27-39@FA-MCNs), which was synthesized using the small peptide, M27-39, and folic acid (FA)-modified mesoporous carbon nanoparticles (FA-MCNs). The phenolic resin polymerized with phloroglucinol and formaldehyde (PF) was used for fabricating MCNs using a one-step soft-template method. Folic acid (FA) can be covalently combined with chitosan-modified MCNs to obtain FA-MCNs. The M27-39@FA-MCNs were stable with a spherical morphology and an average diameter of 129 nm. The cumulative release rate of M27-39@FA-MCNs in the artificial gastric fluid (pH = 1.2) and intestinal fluid (pH = 6.8) for 6 h was 87.77%. This nanoplatform maintains the advantages of both FA and MCNs to improve the bioactivity of M27-39 with high drug accumulation in colorectal tumor tissues and the ease of excretion, thus ameliorating its biosafety and targetability. Furthermore, M27-39@FA-MCNs induced tumor-cell apoptosis and inhibited tumor growth by disrupting mitochondrial energy metabolism and regulating the mitochondrial apoptosis signaling pathway and immune inflammatory response. Thus, such a mitochondria-targeting FA-modified nanoplatform based on mesoporous carbon and a bioactive peptide may provide a precise strategy for CRC treatment. STATEMENT OF SIGNIFICANCE: In this study, we constructed an orally administered colon-accumulating mitochondria-targeted drug delivery nanoplatform (M27-39@FA-MCNs), which was synthesized using the small peptide (M27-39) and folic acid-modified mesoporous carbon nanoparticles (FA-MCNs). M27-39@FA-MCNs increased the targeting ability of M27-39 toward mitochondria and colon based on the properties of FA-MCNs; they also increased M27-39 accumulation and residence time in colon tumors. Oral administration of M27-39@FA-MCNs remarkably alleviated colorectal cancer (CRC) by targeting tumor cell mitochondria and interfering with the mitochondrial energy metabolism process, and inducing apoptosis related P53/Caspase-3 mitochondrial pathway activation. Therefore, M27-39@FA-MCNs may provide a safe and precise therapeutic strategy for CRC.

Bcl-2 Family of Proteins in the Control of Mitochondrial Calcium Signalling: An Old Chap with New Roles

Bcl-2 family proteins are considered as one of the major regulators of apoptosis. Indeed, this family is known to control the mitochondrial outer membrane permeabilization (MOMP): a central step in the mitochondrial pathway of apoptosis. However, in recent years Bcl-2 family members began to emerge as a new class of intracellular calcium (Ca²⁺) regulators. At mitochondria-ER contacts (MERCs) these proteins are able to interact with major Ca²⁺ transporters, thus controlling mitochondrial Ca²⁺ homeostasis and downstream Ca²⁺ signalling pathways. Beyond the regulation of cell survival, this Bcl-2-dependent control over the mitochondrial Ca²⁺ dynamics has far-reaching consequences on the physiology of the cell. Here, we review how the Bcl-2 family of proteins mechanistically regulate mitochondrial Ca²⁺ homeostasis and how this regulation orchestrates cell death/survival decisions as well as the non-apoptotic process of cell migration.

Identification and Characterization of MortaparibPlus-A Novel Triazole Derivative That Targets Mortalin-p53 Interaction and Inhibits Cancer-Cell Proliferation by Wild-Type p53-Dependent and -Independent Mechanisms

p53 has an essential role in suppressing the carcinogenesis process by inducing cell cycle arrest/apoptosis/senescence. Mortalin/GRP75 is a member of the Hsp70 protein family that binds to p53 causing its sequestration in the cell cytoplasm. Hence, p53 cannot translocate to the nucleus to execute its canonical tumour suppression function as a transcription factor. Abrogation of mortalin-p53 interaction and subsequent reactivation of p53's tumour suppression function has been anticipated as a possible approach in developing a novel cancer therapeutic drug candidate. A chemical library was screened in a high-content screening system to identify potential mortalin-p53 interaction disruptors. By four rounds of visual assays for mortalin and p53, we identified a novel synthetic small-molecule triazole derivative (4-[(1E)-2-(2-phenylindol-3-yl)-1-azavinyl]-1,2,4-triazole, henceforth named Mortaparib^Plus). Its activities were validated using multiple bioinformatics and experimental approaches in colorectal cancer cells possessing either wild-type (HCT116) or mutant (DLD-1) p53. Bioinformatics and computational analyses predicted the ability of Mortaparib^Plus to competitively prevent the interaction of mortalin with p53 as it interacted with the p53 binding site of mortalin. Immunoprecipitation analyses demonstrated the abrogation of mortalin-p53 complex formation in Mortaparib^Plus-treated cells that showed growth arrest and apoptosis mediated by activation of p21^WAF1, or BAX and PUMA signalling, respectively. Furthermore, we demonstrate that Mortaparib^Plus-induced cytotoxicity to cancer cells is mediated by multiple mechanisms that included the inhibition of PARP1, up-regulation of p73, and also the down-regulation of mortalin and CARF proteins that play critical roles in carcinogenesis. Mortaparib^Plus is a novel multimodal candidate anticancer drug that warrants further experimental and clinical attention.

Molecular Docking Study of Naturally Derived Flavonoids with Antiapoptotic BCL-2 and BCL-XL Proteins toward Ovarian Cancer Treatment

The naturally derived flavonoids are well known to have anticarcinogenic effects. Flavonoids could be an alternative strategy for ovarian cancer treatment, due to existing platinum-based drugs are reported to develop resistance with low survival rates. Inhibition of antiapoptotic proteins, namely B-cell lymphoma (Bcl-2) and B-cell lymphoma-extra large (Bcl-xl), is the key target to stimulate apoptosis process in cancer cells. This study aimed to determine the binding interaction of five naturally derived flavonoids (biochanin A, myricetin, apigenin, galangin, and fisetin) with potential antiapoptotic target proteins (Bcl-2 and Bcl-xl). The molecular docking study was conducted using AutoDock Vina program. The binding affinity and the presence of hydrogen bonds between the flavonoids and target proteins were predicted. Our findings showed that all the flavonoids showed better binding affinity with Bcl-xl than that of Bcl-2 proteins. The highest binding affinity was recorded in fisetin-Bcl-xl protein complex (-8.8 kcal/mol). Meanwhile, the other flavonoids docked with Bcl-xl protein showed binding affinities, ranging from -8.0 to -8.6 kcal/mol. A total of four hydrogen bonds, four hydrophobic contacts, and one electrostatic interaction were detected in the docked fisetin-Bcl-xl complex, explaining its high binding affinity with Bcl-xl. The present results indicate that all flavonoids could potentially serve as Bcl-xl protein inhibitors, which would consequently lead to apoptotic process in ovarian cancers.

Wild-type p53-modulated autophagy and autophagic fibroblast apoptosis inhibit hypertrophic scar formation

Hypertrophic scarring is a serious fibrotic skin disease, and the abnormal activation of hypertrophic scar fibroblasts (HSFs) intensifies its pathogenesis. Our previous studies have demonstrated that the dysregulation of autophagy in HSFs is associated with fibrosis. However, knowledge regarding the regulation of HS fibrosis by p53-modulated autophagy is limited. Here, we investigated the effect of p53-modulated autophagy on HS fibrosis. The overexpression of wtp53 (Adp53) promoted autophagic capacity and inhibited collagen and α-SMA expression in HSFs. In contrast, LC3 (AdLC3) overexpression did not suppress Col 1, Col 3, or α-SMA expression, but LC3 (shLC3) knockdown downregulated collagen expression. Adp53-modulated autophagy altered Bcl-2 and Bcl-xL expression, but AdLC3 affected only Bcl-xL expression. Silencing Bcl-xL suppressed collagen expression, but autophagy was also inhibited. Flow cytometry showed that the silencing of Bcl-2 (sibcl-2), Bcl-xL (sibcl-xL), and Adp53 significantly increased apoptosis in the HSFs. Therefore, wtp53 inhibited fibrosis in the HSFs by modulating autophagic HSF apoptosis; moreover, the inhibition of autophagy by sibcl-xL had antifibrotic effects. In addition, treatment with Adp53, AdLC3, shLC3, sibcl-2, and sibcl-xL reduced scar formation in a rabbit ear scar model. These data confirm that wtp53-modulated autophagy and autophagic HSF apoptosis can serve as potential molecular targets for HS therapy.

Characterization and prognostic significance of mortalin, Bcl-2 and Bax in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is an aggressive type of cancer, and its incidence and mortality rates are increasing worldwide. Mortalin is a highly conserved chaperone protein involved in multiple pathological and physiological processes, including anti-apoptosis, carcinogenesis and metastasis. The Bcl-2 family of proteins can be divided into pro-survival and pro-apoptotic members, including B-cell lymphoma 2 (Bcl-2) and Bcl-2-like protein 4 (Bax). The aim of the present study was to investigate the association between mortalin, Bcl-2 and Bax, as well as the prognostic significance of the combined expression of mortalin, Bcl-2 and Bax in ICC. Immunohistochemistry was used to determine the expression of mortalin, Bcl-2 and Bax in 116 ICC samples and to assess the association between expression of 3 markers and clinicopathological features of ICC patients. This revealed that ICC tumor tissues overexpressed mortalin and Bcl-2 and exhibited low expression of Bax in ICC tumor tissues compared with that in corresponding peritumoral samples. According to Pearson's correlation coefficient analysis, high expression of mortalin in ICC was positively correlated with Bcl-2 expression and negatively correlated with Bax expression. Furthermore, multiple linear regression analysis demonstrated that mortalin was positively associated with Bcl-2, but not with Bax, in patients with ICC. Patients with ICC exhibiting high expression of mortalin/Bcl-2 or low expression of Bax were closely associated with a malignant ICC phenotype, a relatively low overall survival rate and a high recurrence rate. Multivariate analysis indicated that mortalin and Bcl-2 were independent prognostic indicators for ICC patients. Meanwhile, the concomitant overexpression of mortalin and Bcl-2 and the low expression of Bax were independent markers for predicting a relatively poor prognosis of ICC. The overexpression of mortalin and Bcl-2 and/or the low expression of Bax are implicated in the anti-apoptotic effect and tumor progression of ICC. Mortalin or Bcl-2, or a combination of mortalin, Bcl-2 and Bax may be used to predict the prognosis of ICC, as well as potential therapeutic targets.

Mortalin deficiency suppresses fibrosis and induces apoptosis in keloid spheroids

Mortalin (Mot) is a mitochondrial chaperone of the heat shock protein 70 family and it’s pro-proliferative and anti-apoptosis functions could be associated with keloid pathogenesis, and blocking of mortalin and its interaction with p53 might be a potential novel target for the treatment of keloid. Therefore, we generated mortalin-specific small hairpin (sh) RNAs (dE1-RGD/GFP/shMot) and introduced into keloid spheroids for examination of its apoptotic and anti-fibrotic effect. On keloid tissues, mortalin expression was higher than adjacent normal tissues and it’s protein expressions were activated keloid fibroblasts (KFs). After primary keloid spheroid were transduced with dE1-RGD/GFP/shMot for knockdown of mortalin, expression of type I, III collagen, fibronectin, and elastin was significantly reduced and transforming growth factor-β1, epidermal growth factor receptor (EGFR), Extracellular Signal-Regulated Kinases 1 and 2 (Erk 1/2), and Smad 2/3 complex protein expression were decreased. In addition, increased TUNEL activities and cytochrome C were observed. Further, for examine of mortalin and p53 interaction, we performed immunofluorescence analysis. Knockdown of mortalin relocated p53 to the cell nucleus in primary keloid spheroids by dE1-RGD/GFP/shMot transduction. These results support the utility of knockdown of mortalin to induce apoptosis and reduce ECMs expression in keloid spheroid, which may be highly beneficial in treating keloids.

Autophagy protein LC3 regulates the fibrosis of hypertrophic scar by controlling Bcl-xL in dermal fibroblasts

Hypertrophic scar (HS) is a serious skin fibrotic disease characterized by excessive hypercellularity and extracellular matrix (ECM) component deposition. Autophagy is a tightly regulated physiological process essential for cellular maintenance, differentiation, development and homeostasis. However, during the formation of HS, whether and how autophagy is regulated in dermal fibroblasts are still far from elucidated. Here we detected the autophagic capacity in HS and normal skin (NS) counterparts, explored and verified the key regulatory molecules of autophagy in HS-derived fibroblasts (HSFs), and validated the data using rabbit ear scar model. Transmission electron microscopy (TEM) and immunostaining data showed that LC3-positive cells and autophagosomes in HS/HSFs were more intensive relative to those in NS/NSFs groups. Knockdown of LC3 (shLC3) could significantly block the expressionof type I collagen (Col 1, p < 0.01) and type III collagen (Col 3, p < 0.01) and thus inhibit the fibrosis of HSFs. shLC3 resistant to autophagy was shown to be Bcl-xL-, not Bcl-2-dependent, and silencing of Bcl-xL (sibcl-xL) significantly increased apoptosis of HSFs (p < 0.01). Immunofluorescence results showed that instead of inhibiting α-SMA protein expression, shLC3 could change its architecture arrangement in HSFs. sibcl-xL showed that Bcl-xL was a key signaling molecule involved in HSFs autophagy. More importantly, both shLC3 and sibcl-xL obviously improved the appearance and architecture of the rabbit ear scar, and reduced scar formation on the rabbit ear. Therefore, the aberration of LC3 protein processing compromised autophagy in HS might associate with its pathogenesis in wound repair. LC3 regulated HS fibrosis by controlling the expression of Bcl-xL in HSFs. Thus, Bcl-xL might serve as a potential molecular target, providing a novel strategy for HS therapy.

Molecular dynamics-based identification of novel natural mortalin-p53 abrogators as anticancer agents

INTRODUCTION

Cancer is one of the leading causes of mortality worldwide that requires attention in terms of extensive study and research. Eradication of mortalin-p53 interaction that leads to the inhibition of transcriptional activation or blocking of p53 from functioning as a suppressor and induction of nuclear translocation of p53 can prove to be one of the useful approaches for cancer management.

RESULTS

In this study, we used structure-based approach to target the p53-binding domain of mortalin in order to prevent mortalin-p53 complex formation. We screened compounds from ZINC database against the modeled mortalin protein using Glide virtual screening. The top two compounds, DTOM (ZINC 28639308) and TTOM (ZINC 38143676) with Glide score of -12.27 and -12.16, respectively, were identified with the potential to abrogate mortalin-p53 interaction. Finally, molecular dynamics simulations were used to analyze the dynamic stability of the ligand-bound complex and it was observed that residues Tyr196, Asn198, Val264 and Thr267 were involved in intermolecular interactions in both the simulated ligand-bound complexes, and thus, these residues may have a paramount role in stabilizing the binding of the ligands with the protein.

CONCLUSION

These detailed insights can further facilitate the development of potent inhibitors against mortalin-p53 complex.

Abrogation of AuroraA-TPX2 by novel natural inhibitors: molecular dynamics-based mechanistic analysis

INTRODUCTION

Cancer is characterized by uncontrolled cell growth and genetic instabilities. The human Aurora-A kinase protein plays a crucial role in spindle assembly during mitosis and is activated by another candidate oncogene, targeting protein for Xklp2 (TPX2). It has been proposed that dissociation of Aurora A-TPX2 complex leads to disruption of mitotic spindle apparatus, thereby preventing cell division and further tumor growth.

MATERIALS AND METHODS

A large natural compound library was docked against the active site of Aurora A-TPX2 complex. The protein-ligand complexes were subjected to molecular dynamics simulation to ascertain their binding stability. The drug properties of the compounds were analyzed to observe their drug-like properties.

RESULTS

The virtual screening of natural compound library yielded two high scoring compounds, the first compound CTOM [ZINC ID: 38143674] (Glide score: -9.49) was stable for 17 ns while the second TTOM (Glide score: -9.07) was stable for 15 ns. While CTOM interacted with His280, Thr288 of Aurora A and Tyr34, Lys38 of TPX2, TTOM interacted with Arg285 and Arg286 in addition to the residues involved with CTOM.

CONCLUSIONS

We report two natural compounds as potential drugs leads for the disruption of this complex. These ligands show a preferable docking score and have many drugs like properties within in the range of 95% of known drugs. The study provides evidence that CTOM and TTOM can efficiently inhibit the TPX2-mediated activation of Aurora A. Thus, it paves way for an elaborate investigation and establishes the importance of computational approaches as time- and cost-effective techniques.

Structural investigations of T854A mutation in EGFR and identification of novel inhibitors using structure activity relationships

BACKGROUND

The epidermal growth factor receptor (EGFR) is a member of the ErbB family that is involved in a number of processes responsible for cancer development and progression such as angiogenesis, apoptosis, cell proliferation and metastatic spread. Malfunction in activation of protein tyrosine kinases has been shown to result in uncontrolled cell growth. The EGFR TK domain has been identified as suitable target in cancer therapy and tyrosine kinase inhibitors such as erlotinib have been used for treatment of cancer. Mutations in the region of the EGFR gene encoding the tyrosine kinase (TK) domain causes altered responses to EGFR TK inhibitors (TKI). In this paper we perform molecular dynamics simulations and PCA analysis on wild-type and mutant (T854A) structures to gain insight into the structural changes observed in the target protein upon mutation. We also report two novel inhibitors identified by combined approach of QSAR model development.

RESULTS

The wild-type and mutant structure was observed to be stable for 26 ns and 24 ns respectively. In PCA analysis, the mutant structure proved to be more flexible than wild-type. We developed a 3D-QSAR model using 38 thiazolyl-pyrazoline compounds which was later used for prediction of inhibitory activity of natural compounds of ZINC library. The 3D-QSAR model was proved to be robust by the statistical parameters such as r2 (0.9751), q2(0.9491) and pred_r2(0.9525).

CONCLUSION

Analysis of molecular dynamics simulations results indicate stability loss and increased flexibility in the mutant structure. This flexibility results in structural changes which render the mutant protein drug resistant against erlotinib. We report two novel compounds having high predicted inhibitory activity to EGFR TK domain with both wild-type and mutant structure.

Effects of PDTC on NF-κB expression and apoptosis in rats with severe acute pancreatitis-associated lung injury

We investigated the effects of pyrrolidine dithiocarbamate (PDTC) on intrapulmonary expression of nuclear factor-κB (NF-κB), and apoptosis in rats with severe acute pancreatitis (SAP). We induced SAP, then used immunohistochemistry, TUNEL staining, quantitative PCR assays and western blotting to examine PDTC effects. Treatment with PDTC resulted in interstitial edema and widening of the basement membrane, with swollen mitochondria and aggregation of nuclear chromatin. Expression of NF-κB, Fas, Bcl-2 and TNF-α in lung tissues of SAP rats was increased, with NF-κB, Fas and TNF-α levels maximal after 6 h. PDTC appeared to ameliorate pathological changes, with low levels of NF-κB, Fas, TNF-α, and Caspase-3 mRNA observed and a lower apoptosis index compared with that seen in SAP rats. Expression of NF-κB could be involved in lung tissue apoptosis during SAP. We postulate that PDTC inhibits the activation of NF-κB and apoptosis, effectively alleviating the severity of lung injury.

Fucoxanthin induces growth arrest and apoptosis in human bladder cancer T24 cells by up-regulation of p21 and down-regulation of mortalin

Fucoxanthin, a natural carotenoid, has been reported to have anti-cancer activity in human colon cancer cells, human prostate cancer cells, human leukemia cells, and human epithelial cervical cancer cells. This study was undertaken to evaluate the molecular mechanisms of fucoxanthin against human bladder cancer T24 cell line. MTT analysis results showed that 5 and 10 μM fucoxanthin inhibited the proliferation of T24 cells in a dose- and time-dependent manner accompanied by the growth arrest at G0/G1 phase of cell cycle, which is mediated by the up-regulation of p21, a cyclin-dependent kinase (CDK)-inhibitory protein and the down-regulation of CDK-2, CDK-4, cyclin D1, and cyclin E. In addition, 20 and 40 μM fucoxanthin induced apoptosis of T24 cells by the abrogation of mortalin-p53 complex and the reactivation of nuclear mutant-type p53, which also had tumor suppressor function as wild-type p53. All these results demonstrated that the anti-cancer activity of fucoxanthin on T24 cells was associated with cell cycle arrest at G0/G1 phase by up-regulation of p21 at low doses and apoptosis via decrease in the expression level of mortalin, which is a stress regulator and a member of heat shock protein 70, followed by up-regulation of cleaved caspase-3 at high doses.

Positive immunohistochemical expression of bcl-2 in hormone-independent breast carcinomas is associated with a greater lymph node involvement and poor outcome

To study the immunohistochemical expression of bcl-2 in patients with hormone-independent breast infiltrating ductal carcinomas (IDC) and its possible association with other clinico-biological parameters and outcome. Our study group included 72 females with hormone-independent (ER and PgR negative) infiltrating ductal breast carcinomas. Age, tumor size, axillary lymph node involvement (N), distant metastasis and histological grade, as well as the immunohistochemical expression of Ki67, p53 and androgen receptor (AR), were analyzed. We follow up 57 patients during a period of time ranged between 20 and 193 months (80.2 ± 58.3; median 78 months). Of all IDCs included in our study, 18 were ER-/PgR-/bcl-2+ and 54 ER-/PgR-/bcl-2-. The percentages of slightly bcl-2-positive (+) and bcl-2-strong positive (++) cases were 25 and 19 %, respectively, values lower than those observed in ER+/PgR+ tumors (79.3 and 86.8 %, respectively). Breast IDC with positivity (+) for bcl-2 showed, exclusively, greater lymph node involvement higher than 3 nodes (N+ >3) (p 0.021) and a great number of deaths due to the tumor (p 0.011). Same results were obtained when we compared bcl-2-negative and bcl-2-strong positive (++) subgroups. Our results led us to consider that the positive (+ or ++) immunohistochemical expression of bcl-2 in hormone-independent (ER and PgR negative) breast carcinomas is associated with greater axillary lymph node involvement and a greater number of deaths in the follow-up, being these data opposite to that observed in hormone-dependent tumors.

TP53 status regulates ACSL5-induced expression of mitochondrial mortalin in enterocytes and colorectal adenocarcinomas

Acyl-CoA synthetase 5 (ACSL5), a mitochondrially localized enzyme, catalyzes the synthesis of long-chain fatty acid thioesters and is physiologically involved in pro-apoptotic sensing of enterocytes. The aim of the present study is to identify an ACSL5-dependent regulation of mitochondrially expressed proteins and the characterization of related pathways in normal and diseased human intestinal mucosa. Proteomics of isolated mitochondria from ACSL5 transfectants and CaCo2 controls were performed. ACSL5-dependent protein synthesis was verified with quantitative reverse transcription plus the polymerase chain reaction, Western blotting, short-interfering-RNA-mediated gene silencing and additional cell culture experiments. Lipid changes were analyzed with tandem mass spectrometry. ACSL5-related pathways were characterized in normal mucosa and sporadic adenocarcinomas of the human intestine. In CaCo2 cells transfected with ACSL5, mortalin (HSPA9) was about two-fold increased in mitochondria, whereas cytoplasmic mortalin levels were unchanged. Disturbance of acyl-CoA/sphingolipid metabolism, induced by ACSL5 over-expression, was characterized as crucial. ACSL5-related over-expression of mitochondrial mortalin was found in HEK293 and Lovo (wild-type TP53 [tumor protein p53]) and CaCo2 (p53-negative; TP53 mutated) cells but not in Colo320DM cells (mutated TP53). In normal human intestinal mucosa, an increasing gradient of both ACSL5 and mortalin from bottom to top was observed, whereas p53 (wild-type TP53) decreased. In sporadic intestinal adenocarcinomas with strong p53 immunostaining (mutated TP53), ACSL5-related mortalin expression was heterogeneous. ACSL5-induced mitochondrial mortalin expression is assumed to be a stress response to ACSL5-related changes in lipid metabolism and is regulated by the TP53 status. Uncoupling of ACSL5 and mitochondrial mortalin by mutated TP53 could be important in colorectal carcinogenesis.