Prohibitin regulates TGF-beta induced apoptosis as a downstream effector of Smad-dependent and -independent signaling

Loss of prohibitin 2 in Schwann cells dysregulates key transcription factors controlling developmental myelination

Schwann cells are critical for the proper development and function of the peripheral nervous system (PNS), where they form a collaborative relationship with axons. Past studies highlighted that a pair of proteins called the prohibitins play major roles in Schwann cell biology. Prohibitins are ubiquitously expressed and versatile proteins. We have previously shown that while prohibitins play a crucial role in Schwann cell mitochondria for long-term myelin maintenance and axon health, they may also be present at the Schwann cell-axon interface during development. Here, we expand on this, showing that drug-mediated modulation of prohibitins in vitro disrupts myelination and confirming that Schwann cell-specific ablation of prohibitin 2 (Phb2) in vivo results in severe defects in radial sorting and myelination. We show in vivo that Phb2-null Schwann cells cannot effectively proliferate and the transcription factors EGR2 (KROX20), POU3F1 (OCT6), and POU3F2 (BRN2), necessary for proper Schwann cell maturation, are dysregulated. Schwann cell-specific deletion of Jun, a transcription factor associated with negative regulation of myelination, confers partial rescue of the developmental defect seen in mice lacking Schwann cell Phb2. Finally, we identify a pool of candidate PHB2 interactors that change their interaction with PHB2 depending on neuronal signals, and thus are potential mediators of PHB2-associated developmental defects. This work develops our understanding of Schwann cell biology, revealing that Phb2 may modulate the timely expression of transcription factors necessary for proper PNS development, and proposing candidates that may play a role in PHB2-mediated integration of axon signals in the Schwann cell.

Phosphoglycerate mutase 5 exacerbates alcoholic cardiomyopathy in male mice by inducing prohibitin-2 dephosphorylation and impairing mitochondrial quality control

BACKGROUND

The induction of mitochondrial quality control (MQC) mechanisms is essential for the re-establishment of mitochondrial homeostasis and cellular bioenergetics during periods of stress. Although MQC activation has cardioprotective effects in various cardiovascular diseases, its precise role and regulatory mechanisms in alcoholic cardiomyopathy (ACM) remain incompletely understood.

METHODS

We explored whether two mitochondria-related proteins, phosphoglycerate mutase 5 (Pgam5) and prohibitin 2 (Phb2), influence MQC in male mice during ACM.

RESULTS

Myocardial Pgam5 expression was upregulated in a male mouse model of ACM. Notably, following ACM induction, heart dysfunction was markedly reversed in male cardiomyocyte-specific Pgam5 knockout (Pgam5cKO) mice. Meanwhile, in alcohol-treated male mouse-derived neonatal cardiomyocytes, Pgam5 depletion preserved cell survival and restored mitochondrial dynamics, mitophagy, mitochondrial biogenesis and the mitochondrial unfolded protein response (mtUPR). We further found that in alcohol-treated cardiomyocyte, Pgam5 binds Phb2 and induces its dephosphorylation at Ser91. Alternative transduction of phospho-mimetic (Phb2S91D) and phospho-defective (Phb2S9A) Phb2 mutants attenuated and enhanced, respectively, alcohol-related mitochondrial dysfunction in cardiomyocytes. Moreover, transgenic male mice expressing Phb2S91D were resistant to alcohol-induced heart dysfunction.

CONCLUSIONS

We conclude that ACM-induced Pgam5 upregulation results in Pgam5-dependent Phb2S91 dephosphorylation, leading to MQC destabilisation and mitochondrial dysfunction in heart. Therefore, modulating the Pgam5/Phb2 interaction could potentially offer a novel therapeutic strategy for ACM in male mice.

HIGHLIGHTS

Pgam5 knockout attenuates alcohol-induced cardiac histopathology and heart dysfunction in male mice. Pgam5 KO reduces alcohol-induced myocardial inflammation, lipid peroxidation and metabolic dysfunction in male mice. Pgam5 depletion protects mitochondrial function in alcohol-exposed male mouse cardiomyocytes. Pgam5 depletion normalises MQC in ACM. EtOH impairs MQC through inducing Phb2 dephosphorylation at Ser91. Pgam5 interacts with Phb2 and induces Phb2 dephosphorylation. Transgenic mice expressing a Ser91 phospho-mimetic Phb2 mutant are resistant to ACM.

Antileukemia Activity of Human Natural Killer Cell-Derived Nanomagic Bullets against Acute Myeloid Leukemia (AML)

Background: Cancer is among the serious health problems of the medical world, for treatment of which severe treatments are used. However, the prognosis of cancer patients is still poor. The application of NK cell-derived exosomes (NK-Exo) is a new method for cancer immunotherapy. These nanoparticles with a size range of 30-120 nm are a small model of mother cells. In this study, the anti-tumor activity of NK-Exo and LAK-Exo (activated NK cell-derived exosome) against acute myeloid leukemia (AML) is investigated in vitro. Materials and Methods: The MACS method was performed for the separation of NK cells from the buffy coats of healthy donors, and an EXOCIBE kit was used for the isolation of NK-Exo. After treating the KG-1 cell line with different doses of NK-Exo, MTT assay, and annexin V-PE were done to evaluate cell proliferation and apoptosis, respectively, and for confirmation of involved proteins, Real-Time PCR and western blotting were performed. Results: Anti-tumor activity of NK-Exo and LAK-Exo was dose- and time-dependent. Their highest activities were observed following 48 hours of incubation with 50 µg/ml exosome (p<0.0001). However, this cytotoxic activity was also seen over a short period of time with low concentrations of NK-Exo (p<0.05) and LAK-Exo (p<0.001).The cytotoxic effect of LAK-Exo on target cells was significantly higher than NK-EXO. The induction of apoptosis by different pathways was time-point dependent. Total apoptosis was 34.56% and 51.6% after 48 hours of tumor cell coculture with 50µg/ml NK-Exo and LAK-Exo, respectively. Significant expression of CASPASE3, P38, and CYTOCHROME C genes was observed in the cells treated with 50 µg/ml NK-Exo and LAK-Exo. Conclusion: Our study confirmed the antileukemia activity of NK-Exo against AML tumor cells in vitro. Therefore, NK-Exo can be considered as a promising and effective treatment for leukemia therapy.

Loss of prohibitin 2 in Schwann cells dysregulates key transcription factors controlling developmental myelination

Schwann cells are critical for the proper development and function of the peripheral nervous system, where they form a mutually beneficial relationship with axons. Past studies have highlighted that a pair of proteins called the prohibitins play major roles in Schwann cell biology. Prohibitins are ubiquitously expressed and versatile proteins. We have previously shown that while prohibitins play a crucial role in Schwann cell mitochondria for long-term myelin maintenance and axon health, they may also be present at the Schwann cell-axon interface during development. Here, we expand on this work, showing that drug-mediated modulation of prohibitins in vitro disrupts myelination and confirming that Schwann cell-specific ablation of prohibitin 2 (Phb2) in vivo results in early and severe defects in peripheral nerve development. Using a proteomic approach in vitro, we identify a pool of candidate PHB2 interactors that change their interaction with PHB2 depending on the presence of axonal signals. Furthermore, we show in vivo that loss of Phb2 in mouse Schwann cells causes ineffective proliferation and dysregulation of transcription factors EGR2 (KROX20), POU3F1 (OCT6) and POU3F2 (BRN2) that are necessary for proper Schwann cell maturation. Schwann cell-specific deletion of Jun, a transcription factor associated with negative regulation of myelination, confers partial rescue of the development defect seen in mice lacking Schwann cell Phb2. This work develops our understanding of Schwann cell biology, revealing that Phb2 may directly or indirectly modulate the timely expression of transcription factors necessary for proper peripheral nervous system development, and proposing candidates that may play a role in PHB2-mediated integration of axon signals in the Schwann cell.

Novel effects of prohibitin 1 expression level on cholesterol and lipid homeostasis

Prohibitin 1 (PHB1) plays an important role in maintaining liver health and function. The PHB1 level is decreased in patients with various liver diseases. In this study, liver cancer was induced in liver-specific Phb1 knock-out mice, which were then subjected to hepatic gene and metabolomic analysis. The reduced expression of mRNA expression level of Phb1 induced down-regulation of cholesterol and lipid metabolism. This result was confirmed in a cell model. The expression of Hmgcr and Srebp2 in normal cells decreased when they were treated with cholesterol. In HepG2 cells in which the expression of Phb1 was lowered using siPhb1, the mRNA expression of Hmgcr and Srebp2 also decreased when the cells were treated with cholesterol. Furthermore, in the Phb1 knock-out group, the expression of Fasn and Srebp1 related to lipid metabolism increased but the expression of Ldlr decreased. The expression of Cat and Gpx in cells increased when the expression of Phb1 decreased. Altogether, a decreased expression of Phb1 induces down-regulation of cholesterol- and lipid metabolism-related genes and cholesterol homeostasis is not achieved, particularly in a cholesterol-rich environment. The decrease in Phb1 expression causes excessive oxidative stress in cholesterol and lipid metabolism. Therefore, maintaining a normal level of PHB1 expression is crucial for maintaining cholesterol homeostasis in the liver. Thus, PHB1 may become an important target for non-alcoholic fatty liver disease and lipid metabolism in the future.

Targeting PHB1 to inhibit castration-resistant prostate cancer progression in vitro and in vivo

BACKGROUND

Castration-resistant prostate cancer (CRPC) is currently the main challenge for prostate cancer (PCa) treatment, and there is an urgent need to find novel therapeutic targets and drugs. Prohibitin (PHB1) is a multifunctional chaperone/scaffold protein that is upregulated in various cancers and plays a pro-cancer role. FL3 is a synthetic flavagline drug that inhibits cancer cell proliferation by targeting PHB1. However, the biological functions of PHB1 in CRPC and the effect of FL3 on CRPC cells remain to be explored.

METHODS

Several public datasets were used to analyze the association between the expression level of PHB1 and PCa progression as well as outcome in PCa patients. The expression of PHB1 in human PCa specimens and PCa cell lines was examined by immunohistochemistry (IHC), qRT-PCR, and Western blot. The biological roles of PHB1 in castration resistance and underlying mechanisms were investigated by gain/loss-of-function analyses. Next, in vitro and in vivo experiments were conducted to investigate the anti-cancer effects of FL3 on CRPC cells as well as the underlying mechanisms.

RESULTS

PHB1 expression was significantly upregulated in CRPC and was associated with poor prognosis. PHB1 promoted castration resistance of PCa cells under androgen deprivation condition. PHB1 is an androgen receptor (AR) suppressive gene, and androgen deprivation promoted the PHB1 expression and its nucleus-cytoplasmic translocation. FL3, alone or combined with the second-generation anti-androgen Enzalutamide (ENZ), suppressed CRPC cells especially ENZ-sensitive CRPC cells both in vitro and in vivo. Mechanically, we demonstrated that FL3 promoted trafficking of PHB1 from plasma membrane and mitochondria to nucleus, which in turn inhibited AR signaling as well as MAPK signaling, yet promoted apoptosis in CRPC cells.

CONCLUSION

Our data indicated that PHB1 is aberrantly upregulated in CRPC and is involved in castration resistance, as well as providing a novel rational approach for treating ENZ-sensitive CRPC.

PGAM5-Mediated PHB2 Dephosphorylation Contributes to Diabetic Cardiomyopathy by Disrupting Mitochondrial Quality Surveillance

Disruption of the mitochondrial quality surveillance (MQS) system contributes to mitochondrial dysfunction in diabetic cardiomyopathy (DCM). In this study, we observed that cardiac expression of phosphoglycerate mutase 5 (PGAM5), a mitochondrial Ser/Thr protein phosphatase, is upregulated in mice with streptozotocin-induced DCM. Notably, DCM-related cardiac structural and functional deficits were negated in cardiomyocyte-specific Pgam5 knockout (Pgam5CKO ) mice. Hyperglycemic stress impaired adenosine triphosphate production, reduced respiratory activity, and prolonged mitochondrial permeability transition pore opening in acutely isolated neonatal cardiomyocytes from control Pgam5f/f mice, and these effects were markedly prevented in cardiomyocytes from Pgam5CKO mice. Likewise, three main MQS-governed processes-namely, mitochondrial fission/fusion cycling, mitophagy, and biogenesis-were disrupted by hyperglycemia in Pgam5f/f , but not in Pgam5CKO , cardiomyocytes. On the basis of bioinformatics prediction of interaction between PGAM5 and prohibitin 2 (PHB2), an inner mitochondrial membrane-associated scaffolding protein, co-immunoprecipitation, and immunoblot assays demonstrated that PGAM5 dephosphorylates PHB2 on Ser91. Transfection of cardiomyocytes with phosphodefective or phosphomimetic Ser91 mutants of PHB2 confirmed a critical role for PGAM5-mediated dephosphorylation of PHB2 in mitochondrial dysfunction associated with hyperglycemic stress. Furthermore, knockin mice expressing phosphomimetic PHB2S91D were resistant to diabetes-induced cardiac dysfunction. Our findings highlight the PGAM-PHB2 axis as a novel and critical regulator of mitochondrial dysfunction in DCM.

Molecular mechanism of the TGF‑β/Smad7 signaling pathway in ulcerative colitis

Aberrant TGF‑β/Smad7 signaling has been reported to be an important mechanism underlying the pathogenesis of ulcerative colitis. Therefore, the present study aimed to investigate the effects of a number of potential anti‑colitis agents on intestinal epithelial permeability and the TGF‑β/Smad7 signaling pathway in an experimental model of colitis. A mouse model of colitis was first established before anti‑TNF‑α and 5‑aminosalicyclic acid (5‑ASA) were administered intraperitoneally and orally, respectively. Myeloperoxidase (MPO) activity, histological index (HI) of the colon and the disease activity index (DAI) scores were then detected in each mouse. Transmission electron microscopy (TEM), immunohistochemical and functional tests, including Evans blue (EB) and FITC‑dextran (FD‑4) staining, were used to evaluate intestinal mucosal permeability. The expression of epithelial phenotype markers E‑cadherin, occludin, zona occludens (ZO‑1), TGF‑β and Smad7 were measured. In addition, epithelial myosin light chain kinase (MLCK) expression and activity were measured. Anti‑TNF‑α and 5‑ASA treatments was both found to effectively reduce the DAI score and HI, whilst decreasing colonic MPO activity, plasma levels of FD‑4 and EB permeation of the intestine. Furthermore, anti‑TNF‑α and 5‑ASA treatments decreased MLCK expression and activity, reduced the expression of Smad7 in the small intestine epithelium, but increased the expression of TGF‑β. In mice with colitis, TEM revealed partial epithelial injury in the ileum, where the number of intercellular tight junctions and the expression levels of E‑cadherin, ZO‑1 and occludin were decreased, all of which were alleviated by anti‑TNF‑α and 5‑ASA treatment. In conclusion, anti‑TNF‑α and 5‑ASA both exerted protective effects on intestinal epithelial permeability in an experimental mouse model of colitis. The underlying mechanism may be mediated at least in part by the increase in TGF‑β expression and/or the reduction in Smad7 expression, which can inhibit epithelial MLCK activity and in turn reduce mucosal permeability during the pathogenesis of ulcerative colitis.

Prohibitin-1 Is a Dynamically Regulated Blood Protein With Cardioprotective Effects in Sepsis

Background In sepsis, circulating cytokines and lipopolysaccharide elicit mitochondrial dysfunction and cardiomyopathy, a major cause of morbidity and mortality with this condition. Emerging research places the PHB1 (lipid raft protein prohibitin-1) at the nexus of inflammation, metabolism, and oxidative stress. PHB1 has also been reported in circulation, though its function in this compartment is completely unknown. Methods and Results Using a wide-ranging approach across multiple in vitro and in vivo models, we interrogated the functional role of intracellular and circulating PHB1 in the heart during sepsis, and elucidated some of the mechanisms involved. Upon endotoxin challenge or sepsis induction in rodent models, PHB1 translocates from mitochondria to nucleus in cardiomyocytes and is secreted into the circulation from the liver in a manner dependent on nuclear factor (erythroid-derived 2)-like 2, a key transcriptional regulator of the antioxidant response. Overexpression or treatment with recombinant human PHB1 enhances the antioxidant/anti-inflammatory response and protects HL-1 cardiomyocytes from mitochondrial dysfunction and toxicity from cytokine stress. Importantly, administration of recombinant human PHB1 blunted inflammation and restored cardiac contractility and ATP production in mice following lipopolysaccharide challenge. This cardioprotective, anti-inflammatory effect of recombinant human PHB1 was determined to be independent of nuclear factor (erythroid-derived 2)-like 2, but partially dependent on PI3K/AKT  signaling in the heart. Conclusions These findings reveal a previously unknown cardioprotective effect of PHB1 during sepsis, and illustrate a pro-survival, protective role for PHB1 in the circulation. Exploitation of circulating PHB1 as a biomarker and/or therapeutic could have widespread benefit in the clinical management of sepsis and other severe inflammatory disorders.

Prohibitin ligands: a growing armamentarium to tackle cancers, osteoporosis, inflammatory, cardiac and neurological diseases

Over the last three decades, the scaffold proteins prohibitins-1 and -2 (PHB1/2) have emerged as key signaling proteins regulating a myriad of signaling pathways in health and diseases. Small molecules targeting PHBs display promising effects against cancers, osteoporosis, inflammatory, cardiac and neurodegenerative diseases. This review provides an updated overview of the various classes of PHB ligands, with an emphasis on their mechanism of action and therapeutic potential. We also describe how these ligands have been used to explore PHB signaling in different physiological and pathological settings.

Comparative proteomics study of proteins involved in induction of higher rates of cell death in mitoxantrone-resistant breast cancer cells MCF-7/MX exposed to TNF-α

Objective(s):

Resistance to medications is one of the main complications in chemotherapy of cancer. It has been shown that some multidrug resistant cancer cells indicate more sensitivity against cytotoxic effects of TNF-α compared to their parental cells. Our previous findings indicated vulnerability of the mitoxantrone-resistant breast cancer cells MCF-7/MX to cell death induced by TNF-α compared to the parent cells MCF-7. In this study, we performed a comparative proteomics analysis for identification of proteins involved in induction of higher susceptibility of MCF-7/MX cells to cytotoxic effect of TNF-α.

Materials and Methods:

Intensity of protein spots in 2D gel electrophoresis profiles of MCF-7 and MCF-7/MX cells were compared with Image Master Platinum 6.0 software. Selected differential protein-spots were identified with MALDI-TOF/TOF mass spectrometry and database searching. Pathway analyses of identified proteins were performed using PANTHER, KEGG PATHWAY, Gene MANIA and STRING databases. Western blot was performed for confirmation of the proteomics results.

Results:

Our results indicated that 48 hr exposure to TNF-α induced 87% death in MCF-7/MX cells compared to 19% death in MCF-7 cells. Forty landmarks per 2D gel electrophoresis were matched by Image Master Software. Six proteins were identified with mass spectrometry. Western blot showed that 14-3-3γ and p53 proteins were expressed higher in MCF-7/MX cells treated with TNF-α compared to MCF-7 cells treated with TNF-α.

Conclusion:

Our results showed that 14-3-3 γ, prohibitin, peroxiredoxin 2 and P53 proteins which were expressed differentially in MCF-7/MX cells treated with TNF-α may involve in the induction of higher rates of cell death in these cells compared to TNF-α-treated MCF-7 cells.

Dual role of RACK1 in airway epithelial mesenchymal transition and apoptosis

Airway epithelial apoptosis and epithelial mesenchymal transition (EMT) are two crucial components of asthma pathogenesis, concomitantly mediated by TGF‐β1. RACK1 is the downstream target gene of TGF‐β1 shown to enhancement in asthma mice in our previous study. Balb/c mice were sensitized twice and challenged with OVA every day for 7 days. Transformed human bronchial epithelial cells, BEAS‐2B cells were cultured and exposed to recombinant soluble human TGF‐β1 to induced apoptosis (30 ng/mL, 72 hours) and EMT (10 ng/mL, 48 hours) in vitro, respectively. siRNA and pharmacological inhibitors were used to evaluate the regulation of RACK1 protein in apoptosis and EMT. Western blotting analysis and immunostaining were used to detect the protein expressions in vivo and in vitro. Our data showed that RACK1 protein levels were significantly increased in OVA‐challenged mice, as well as TGF‐β1‐induced apoptosis and EMT of BEAS‐2B cells. Knockdown of RACK1 (siRACK1) significantly inhibited apoptosis and decreased TGF‐β1 up‐regulated EMT related protein levels (N‐cadherin and Snail) in vitro via suppression of JNK and Smad3 activation. Moreover, siSmad3 or siJNK impaired TGF‐β1‐induced N‐cadherin and Snail up‐regulation in vitro. Importantly, JNK gene silencing (siERK) also impaired the regulatory effect of TGF‐β1 on Smad3 activation. Our present data demonstrate that RACK1 is a concomitant regulator of TGF‐β1 induces airway apoptosis and EMT via JNK/Smad/Snail signalling axis. Our findings may provide a new insight into understanding the regulation mechanism of RACK1 in asthma pathogenesis.

A Putative Prohibitin-Calcium Nexus in β-Cell Mitochondria and Diabetes

The role of mitochondria in apoptosis is well known; however, the mechanisms linking mitochondria to the proapoptotic effects of proinflammatory cytokines, hyperglycemia, and glucolipotoxicity are not completely understood. Complex Ca²⁺ signaling has emerged as a critical contributor to these proapoptotic effects and has gained significant attention in regulating the signaling processes of mitochondria. In pancreatic β-cells, Ca²⁺ plays an active role in β-cell function and survival. Prohibitin (PHB), a mitochondrial chaperone, is actively involved in maintaining the architecture of mitochondria. However, its possible interaction with Ca²⁺-activated signaling pathways has not been explored. The present review aims to examine potential crosstalk between Ca²⁺ signaling and PHB function in pancreatic β-cells. Moreover, this review will focus on the effects of cytokines and glucolipotoxicity on Ca²⁺ signaling and its possible interaction with PHB. Improved understanding of this important mitochondrial protein may aid in the design of more targeted drugs to identify specific pathways involved with stress-induced dysfunction in the β-cell.

The Effects of TGF-β Signaling on Cancer Cells and Cancer Stem Cells in the Bone Microenvironment

BACKGROUND

Transforming growth factor-β (TGF-β) plays a key role in bone metastasis formation; we hypothesized the possible involvement of TGF-β in the induction of cancer stem cells (CSCs) in the bone microenvironment (micro-E), which may be responsible for chemo-resistance.

METHODS

Mouse mammary tumor cells were implanted under the dorsal skin flap over the calvaria and into a subcutaneous (subQ) lesions in female mice, generating tumors in the bone and subQ micro-Es. After implantation of the tumor cells, mice were treated with a TGF-β R1 kinase inhibitor (R1-Ki).

RESULTS

Treatment with R1-Ki decreased tumor volume and cell proliferation in the bone micro-E, but not in the subQ micro-E. R1-Ki treatment did not affect the induction of necrosis or apoptosis in either bone or subQ micro-E. The number of cells positive for the CSC markers, SOX2, and CD166 in the bone micro-E, were significantly higher than those in the subQ micro-E. R1-Ki treatment significantly decreased the number of CSC marker positive cells in the bone micro-E but not in the subQ micro-E. TGF-β activation of the MAPK/ERK and AKT pathways was the underlying mechanism of cell proliferation in the bone micro-E. BMP signaling did not play a role in cell proliferation in either micro-E.

CONCLUSION

Our results indicated that the bone micro-E is a key niche for CSC generation, and TGF-β signaling has important roles in generating CSCs and tumor cell proliferation in the bone micro-E. Therefore, it is critically important to evaluate responses to chemotherapeutic agents on both cancer stem cells and proliferating tumor cells in different tumor microenvironments in vivo.

Cytotoxicity analysis of ambient fine particle in BEAS-2B cells on an air-liquid interface (ALI) microfluidics system

Ambient fine particle is a crucial indicator of air pollution brought into the air by sundry natural and public events. However, a comprehensive understanding of the PM_2.5-induced cytotoxicity especially the contribution of bioaerosol part is still undiscovered. Herein, an ALI microfluidics system integrated multi-omics (iTRAQ & RNA-seq) was successfully utilized to recognize the molecular mechanisms induced by microorganisms carried bioaerosol in human lung epithelial cells. The cells viability was above 98% within 21 days on this system. Moreover, the results showed that eight microorganisms-related pathways (e.g., Salmonella, amoebiasis, HTLV-1) were activated after exposure to PM_2.5 for 24 h, which played a certain proportion in contributing to inflammation reaction. In addition, multi-omics demonstrated that three inflammation-related signal transduction cascades including MAPK signaling pathway, TNF signaling pathway, and TGF signaling pathway were triggered by fine particles, ultimately leading to apoptosis-related process disorder by associated cytokines like TNF, IL6, and TGF-β. Furthermore, flow cytometry analysis showed that the cell apoptosis rate increased from 3.8% to 66.7% between the cells exposed to PM_2.5 (10 μg/cm²) for 24 h and untreated control cells, which indicated that the fine particles had the ability to activate apoptosis-related signal cascades and result in apoptosis. ELISA assay and western blot indicated that HO-1, JNK, IL6, TNF, NF-κB, and FGF14 were significantly increased after exposure to PM_2.5 while Casp3 and FGFR were decreased, which were consistent with the multi-omics. Moreover, PM_2.5 components (OC, EC, 16PAHs, As, Cu, Mn, Cl^-, and NO₃^-) were significantly correlated to the inflammation related proteins and cytokines, which played a vital role in the inflammation and apoptosis related signaling pathways. These findings pointed to strong links among microorganisms infection, inflammation, and apoptosis in cell response to PM_2.5 carried microorganisms. It also provided a new approach for understanding PM_2.5-induced cytotoxicity and health risks.

Prohibitins: A Critical Role in Mitochondrial Functions and Implication in Diseases

Prohibitin 1 (PHB1) and prohibitin 2 (PHB2) are proteins that are ubiquitously expressed, and are present in the nucleus, cytosol, and mitochondria. Depending on the cellular localization, PHB1 and PHB2 have distinctive functions, but more evidence suggests a critical role within mitochondria. In fact, PHB proteins are highly expressed in cells that heavily depend on mitochondrial function. In mitochondria, these two proteins assemble at the inner membrane to form a supra-macromolecular structure, which works as a scaffold for proteins and lipids regulating mitochondrial metabolism, including bioenergetics, biogenesis, and dynamics in order to determine the cell fate, death, or life. PHB alterations have been found in aging and cancer, as well as neurodegenerative, cardiac, and kidney diseases, in which significant mitochondrial impairments have been observed. The molecular mechanisms by which prohibitins regulate mitochondrial function and their role in pathology are reviewed and discussed herein.

Genetic Variants in HSD17B3, SMAD3, and IPO11 Impact Circulating Lipids in Response to Fenofibrate in Individuals With Type 2 Diabetes

Individuals with type 2 diabetes (T2D) and dyslipidemia are at an increased risk of cardiovascular disease. Fibrates are a class of drugs prescribed to treat dyslipidemia, but variation in response has been observed. To evaluate common and rare genetic variants that impact lipid responses to fenofibrate in statin-treated patients with T2D, we examined lipid changes in response to fenofibrate therapy using a genomewide association study (GWAS). Associations were followed-up using gene expression studies in mice. Common variants in SMAD3 and IPO11 were marginally associated with lipid changes in black subjects (P < 5 × 10-6 ). Rare variant and gene expression changes were assessed using a false discovery rate approach. AKR7A3 and HSD17B13 were associated with lipid changes in white subjects (q < 0.2). Mice fed fenofibrate displayed reductions in Hsd17b13 gene expression (q < 0.1). Associations of variants in SMAD3, IPO11, and HSD17B13, with gene expression changes in mice indicate that transforming growth factor-beta (TGF-β) and NRF2 signaling pathways may influence fenofibrate effects on dyslipidemia in patients with T2D.

Small-molecule screening yields a compound that inhibits the cancer-associated transcription factor Hes1 via the PHB2 chaperone

The transcription factor Hes family basic helix-loop-helix transcription factor 1 (Hes1) is a downstream effector of Notch signaling and plays a crucial role in orchestrating developmental processes during the embryonic stage. However, its aberrant signaling in adulthood is linked to the pathogenesis of cancer. In the present study, we report the discovery of small organic molecules (JI051 and JI130) that impair the ability of Hes1 to repress transcription. Hes1 interacts with the transcriptional corepressor transducing-like enhancer of split 1 (TLE1) via an interaction domain comprising two tryptophan residues, prompting us to search a chemical library of 1,800 small molecules enriched for indole-like π-electron-rich pharmacophores for a compound that blocks Hes1-mediated transcriptional repression. This screening identified a lead compound whose extensive chemical modification to improve potency yielded JI051, which inhibited HEK293 cell proliferation with an EC₅₀ of 0.3 μm Unexpectedly, using immunomagnetic isolation and nanoscale LC-MS/MS, we found that JI051 does not bind TLE1 but instead interacts with prohibitin 2 (PHB2), a cancer-associated protein chaperone. We also found that JI051 stabilizes PHB2's interaction with Hes1 outside the nucleus, inducing G₂/M cell-cycle arrest. Of note, JI051 dose-dependently reduced cell growth of the human pancreatic cancer cell line MIA PaCa-2, and JI130 treatment significantly reduced tumor volume in a murine pancreatic tumor xenograft model. These results suggest a previously unrecognized role for PHB2 in the regulation of Hes1 and may inform potential strategies for managing pancreatic cancer.

The mechanisms of graphene-based materials-induced programmed cell death: a review of apoptosis, autophagy, and programmed necrosis

Graphene-based materials (GBMs) are widely used in many fields, including biomedicine. To date, much attention had been paid to the potential unexpected toxic effects of GBMs. Here, we review the recent literature regarding the impact of GBMs on programmed cell death (PCD). Apoptosis, autophagy, and programmed necrosis are three major PCDs. Mechanistic studies demonstrated that the mitochondrial pathways and MAPKs (JNK, ERK, and p38)- and TGF-β-related signaling pathways are implicated in GBMs-induced apoptosis. Autophagy, unlike apoptosis and necroptosis which are already clear cell death types, plays a vital pro-survival role in cell homeostasis, so its role in cell death should be carefully considered. However, GBMs always induce unrestrained autophagy accelerating cell death. GBMs trigger autophagy through inducing autophagosome accumulation and lysosome impairment. Mitochondrial dysfunction, ER stress, TLRs signaling pathways, and p38 MAPK and NF-κB pathways participate in GBMs-induced autophagy. Programmed necrosis can be activated by RIP kinases, PARP, and TLR-4 signaling in macrophages after GBMs exposure. Though apoptosis, autophagy, and necroptosis are distinguished by some characteristics, their numerous signaling pathways comprise an interconnected network and correlate with each other, such as the TLRs, p53 signaling pathways, and the Beclin-1 and Bcl-2 interaction. A better understanding of the mechanisms of PCD induced by GBMs may allow for a thorough study of the toxicology of GBMs and a more precise determination of the consequences of human exposure to GBMs. These determinations will also benefit safety assessments of the biomedical and therapeutic applications of GBMs.

Prohibitin: targeting peptide coupled to ovarian cancer, luteinization and TGF-β pathways

Background

Ovarian epithelial tumor (OET) is a silent disease of late diagnosis and poor prognosis. Currently treatment options are limited and patient response to treatment is difficult to predict so there is a serious need to delineate the real pathogenesis to predict tumour prognosis. Prohibitin (PHB) is an evolutionarily protein that regulates the cell cycle. TGF-β has been shown to be a positive and negative regulator of cellular proliferation and differentiation.

The present study provides an overview on the role played by PHB1, TGF-β and LH in ovarian cancer.

Methods

The study was conducted on 60 patients with ovarian tumors (benign, borderline and malignant) and 20 healthy volunteers. LH and TGF-β serum levels were measured by ELISA. Expression of prohibitin and LHR-mRNA were assessed by IHC and TaqMan® real time gene expression assay, respectively.

Results

Serum levels of LH and TGF-β were significantly decreased among borderline and malignant groups. There was significant over-expression of LHRmRNA in malignant group. Prohibitin expression was significantly increased in malignant ovarian tissue. Strong negative correlations were found between LHR mRNA expression and serum LH levels, and between IHC score of prohibitin and serum levels of LH among patients with borderline ovarian tumors.

Conclusion

Steady decline of LH and TGF-B serum levels, from benign cystadenoma to borderline tumor to carcinoma, suggests their inhibitory role against OET cell growth. Increased PHB1 expression in OET suggests its proliferative activity that can be regulated by luteinisation and/or TGF-β. Furthermore increased LHR mRNA tissue expression can provide hope for using LH in treatment of some types of ovarian cancers.

Altered Cytoskeleton as a Mitochondrial Decay Signature in the Retinal Pigment Epithelium

Mitochondria mediate energy metabolism, apoptosis, and aging, while mitochondrial disruption leads to age-related diseases that include age-related macular degeneration. Descriptions of mitochondrial morphology have been non-systematic and qualitative, due to lack of knowledge on the molecular mechanism of mitochondrial dynamics. The current study analyzed mitochondrial size, shape, and position quantitatively in retinal pigment epithelial cells (RPE) using a systematic computational model to suggest mitochondrial trafficking under oxidative environment. Our previous proteomic study suggested that prohibitin is a mitochondrial decay biomarker in the RPE. The current study examined the prohibitin interactome map using immunoprecipitation data to determine the indirect signaling on cytoskeletal changes and transcriptional regulation by prohibitin. Immunocytochemistry and immunoprecipitation demonstrated that there is a positive correlation between mitochondrial changes and altered filaments as well as prohibitin interactions with kinesin and unknown proteins in the RPE. Specific cytoskeletal and nuclear protein-binding mechanisms may exist to regulate prohibitin-mediated reactions as key elements, including vimentin and p53, to control apoptosis in mitochondria and the nucleus. Prohibitin may regulate mitochondrial trafficking through unknown proteins that include 110 kDa protein with myosin head domain and 88 kDa protein with cadherin repeat domain. Altered cytoskeleton may represent a mitochondrial decay signature in the RPE. The current study suggests that mitochondrial dynamics and cytoskeletal changes are critical for controlling mitochondrial distribution and function. Further, imbalance of retrograde versus anterograde mitochondrial trafficking may initiate the pathogenic reaction in adult-onset neurodegenerative diseases.

The role of lipid raft translocation of prohibitin in regulation of Akt and Raf-protected apoptosis of HaCaT cells upon ultraviolet B irradiation

Prohibitin (PHB) plays a role in regulation of ultraviolet B light (UVB)-induced apoptosis of human keratinocytes, HaCaT cells. The regulatory function of PHB appears to be associated with its lipid raft translocation. However, the detailed mechanism for PHB-mediated apoptosis of these keratinocytes upon UVB irradiation is not clear. In this report, we determined the role of lipid raft translocation of PHB in regulation of UVB-induced apoptosis. Our data show that upon UVB irradiation PHB is translocated from the non-raft membrane to the lipid rafts, which is correlated with a release of both Akt and Raf from membrane. Overexpression of Akt and/or Raf impedes UVB-induced lipid raft translocation of PHB. Immunoprecipitation analysis indicates that UVB alters the interactions among PHB, Akt, and Raf. Reduced expression of PHB leads to a decreased phosphorylation of Akt and ERK, as well as a decreased activity of Akt, and increased apoptosis of the cells upon UVB irradiation. These results suggest that PHB regulates UVB-induced apoptosis of keratinocytes via a mechanism that involves detachment from Akt and Raf on the plasma membrane, and sequential lipid raft translocation.

Multifaceted role of prohibitin in cell survival and apoptosis

Human eukaryotic prohibitin (prohibitin-1 and prohibitin-2) is a membrane protein with different cellular localizations. It is involved in multiple cellular functions, including energy metabolism, proliferation, apoptosis, and senescence. The subcellular localization of prohibitin may determine its functions. Membrane prohibitin regulate the cellular signaling of membrane transport, nuclear prohibitin control transcription activation and the cell cycle, and mitochondrial prohibitin complex stabilize the mitochondrial genome and modulate mitochondrial dynamics, mitochondrial morphology, mitochondrial biogenesis, and the mitochondrial intrinsic apoptotic pathway. Moreover, prohibitin can translocates into the nucleus or the mitochondria under apoptotic signals and the subcellular shuttling of prohibitin is necessary for apoptosis process. Apoptosis is the process of programmed cell death that is important for the maintenance of normal physiological functions. Consequently, any alteration in the content, post-transcriptional modification (i.e. phosphorylation) or the nuclear or mitochondrial translocation of prohibitin may influence cell fate. Understanding the mechanisms of the expression and regulation of prohibitin may be useful for future research. This review provides an overview of the multifaceted and essential roles played by prohibitin in the regulation of cell survival and apoptosis.

Prohibitins role in cellular survival through Ras-Raf-MEK-ERK pathway

Prohibitins are members of a highly conserved protein family containing the stomatin/prohibitin/flotillin/HflK/C (SPFH) domain (also known as the prohibitin [PHB] domain) found in unicellular eukaryotes, fungi, plants, animals, and humans. Two highly homologous members of prohibitins expressed in eukaryotes are prohibitin (PHB; B-cell receptor associated protein-32, BAP-32) and prohibitin 2/repressor of estrogen receptor activity (PHB2, REA, BAP-37). Both PHB and REA/PHB2 are ubiquitously expressed and are present in multiple cellular compartments including the mitochondria, nucleus, and the plasma membrane. Multiple functions have been attributed to the mitochondrial and nuclear PHB and PHB2/REA including cellular differentiation, anti-proliferation, and morphogenesis. One of the major functions of the prohibitins are in maintaining the functional integrity of the mitochondria and protecting cells from various stresses. In the present review, we focus on the recent research developments indicating that PHB and PHB2/REA are involved in maintaining cellular survival through the Ras-Raf-MEK-Erk pathway. Understanding the molecular mechanisms by which the intracellular signaling pathways utilize prohibitins in governing cellular survival is likely to result in development of therapeutic strategies to overcome various human pathological disorders such as diabetes, obesity, neurological diseases, inflammatory bowel disease, and cancer.

Differential expression and regulation of prohibitin during curcumin-induced apoptosis of immortalized human epidermal HaCaT cells

Prohibitin (PHB), also known as inhibin, is important in cell proliferation, differentiation and apoptosis. This protein localizes to the inner membrane of mitochondria, where it acts as a chaperone protein, and is also found in the nucleus, where it negatively regulates transcription. The tumor-suppressive role of PHB in cell proliferation appears to be contradictory. In this study, we investigated the existence, localization and alterations in the expression of PHB in the whole cell and nuclear matrix and analyzed its co-localization with the expression products of related genes. The western blot analysis results revealed that PHB exists in the composition of nuclear matrix proteins and that the expression level of PHB is significantly increased in the whole cell and markedly decreased in the nuclear matrix after curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) treatment. The laser confocal scanning microscope results demonstrated the co-localization of PHB with p53, c-Myc, Bax, and Fas in HaCaT cells, and this co-localization region was transferred as a result of curcumin treatment. In addition, the results of the GST pull-down assay demonstrated the direct interaction of PHB with p53, c-Myc and Bax but not Fas in vitro. Results of the present study confirmed that the expression and distribution of PHB, which is a nuclear matrix protein, affect the apoptosis of HaCaT cells and its co-localization with specific gene products connected with cell apoptosis.

The aberrant expression and localization of prohibitin during apoptosis of human cholangiocarcinoma Mz-ChA-1 cells

In this study, we aimed to investigate the aberrant expression and shift in localization of prohibitin (PHB) during apoptosis of human cholangiocarcinoma cells. Our study demonstrated that PHB was expressed primarily in the cytoplasm and only a little in the nucleus. However, PHB expression significantly decreased, and its localization shifted from the cytoplasm to the nucleus during apoptosis. PHB co-localized with AIF, Rb, p53, and c-Fos, but the region of co-localization was altered after treatment. Meanwhile, we detected a direct interaction between PHB and both p53 and Rb in Mz-ChA-1 cells. These results suggest that the altered localization and expression of PHB, as well as its co-localization with related oncogenes and tumor suppressor genes, can affect the apoptosis of Mz-ChA-1 cells.

Proteomic analysis of rat proximal tubule cells following stretch-induced apoptosis in an in vitro model of kidney obstruction

Urinary tract obstruction (UTO) is a commonly noted disorder on prenatal ultrasound that has the potential to lead to permanent loss of renal function. To study the molecular processes of the disease, an in vitro model has been developed which involves mechanical stretch of proximal tubule cells grown on flexible plates which mimics the physiological conditions during UTO. This study employs a one dimensional SDS-PAGE fractionation procedure, followed by in-gel digest and LC-MS/MS analysis in a semi-quantitative experiment using spectral counting to relatively quantify changes in protein expression following the established model of UTO. Quantitative analysis shows 317 of the 1630 identified proteins express altered abundance, with 135 increased and 182 decreased in abundance as a result of stretch. Gene ontology (GO) and KEGG annotations implicate a number of physiological processes that have been previously shown in addition to some potentially novel processes in UTO. The quantitative proteomic analysis we performed here provides a more complete characterization of changes in protein abundance as a result of stretch than previous studies, and provides a number of previously undescribed proteins in proximal tubule cells that may play a role in UTO.

BIOLOGICAL SIGNIFICANCE

Urinary tract obstruction (UTO) is a commonly noted abnormality on prenatal ultrasound that can either resolve spontaneously or require surgical intervention to prevent permanent renal damage or loss of function. While targeted studies of UTO have shown a number of pathological responses in proximal tubule cells, there are currently no large-scale quantitative studies that aim to elucidate a global cellular response. This study uses a semi-quantitative approach and applies a well characterized model of UTO to determine a number of cellular processes affected by UTO simulation and identifies a number of proteins with altered abundance that have not been noted previously in UTO. This article is part of a Special Issue entitled: Can Proteomics Fill the Gap Between Genomics and Phenotypes?

Prohibitin ligands in cell death and survival: mode of action and therapeutic potential

Prohibitins (PHBs) are scaffold proteins that modulate many signaling pathways controlling cell survival, metabolism, and inflammation. Several drugs that target PHBs have been identified and evaluated for various clinical applications. Preclinical and clinical studies indicate that these PHB ligands may be useful in oncology, cardiology, and neurology, as well as against obesity. This review covers the physiological role of PHBs in health and diseases and current developments concerning PHB ligands.

Prohibitin-2 binding modulates insulin-like growth factor-binding protein-6 (IGFBP-6)-induced rhabdomyosarcoma cell migration

Insulin-like growth factor (IGF)-binding protein (IGFBP)-6 decreases cancer cell proliferation and survival by inhibiting the effects of IGF-II. More recently, IGFBP-6 was found to promote the migration of rhabdomyosarcoma (RMS) cells in an IGF-independent manner, and MAPK pathways were involved in this process. However, the precise molecular mechanisms of these IGF-independent migratory actions of IGFBP-6 are largely unknown. Here, we report that prohibitin-2 (PHB2), a single-span membrane protein, is a key regulator of IGFBP-6-induced RMS cell migration. PHB2 and IGFBP-6 co-localize on the RMS cell surface, and they specifically interact, as demonstrated by affinity chromatography, co-immunoprecipitation, biosensor analysis, and confocal microscopy. Binding affinities for PHB2 are 9.0 ± 1.0 nM for IGFBP-6 and 10.2 ± 0.5 nM for mIGFBP-6, a non-IGF-binding mutant of IGFBP-6. The C-domain but not the N-domain of IGFBP-6 is involved in PHB2 binding. In addition, IGFBP-6 indirectly increases PHB2 tyrosine phosphorylation on RMS membranes. Importantly, PHB2 knockdown completely abolished IGFBP-6-mediated RMS cell migration. In contrast, IGFBP-6-induced MAPK pathway activation was not affected, suggesting that PHB2 may act as a downstream effector of these pathways. These results indicate that PHB2 plays a key role in this IGF-independent action of IGFBP-6 and suggest a possible therapeutic target for RMS.

Proteomic analysis of protein expression profiles during hyperthermia-induced apoptosis in Tca8113 cells

The aim of the present study was to explore protein expression profiles during cancer cell apoptosis induced by hyperthermia. A hyperthermia-induced apoptosis model was established using a Tca8113 cell line derived from a human tongue squamous cell carcinoma, which underwent fluorescent differential display two-dimensional (2D) gel electrophoresis at 2, 6, 8, 12 and 24 h following the induction of hyperthermia. Proteins were identified by mass spectrometry analysis. Expression changes in the proteins were detected by western blot analysis. A total of 107 proteins were detected that exhibited different expression levels in the hyperthermia-treated cells compared with the controls, and 57 of these proteins were identified. Expression changes in the representative proteins were further verified by western blot analysis. These 57 proteins were identified according to the following functional groups: energy metabolism-related enzymes, cytoskeleton-related proteins, chaperones, transcription factors, protein synthesis-related proteins and cell division- and proliferation-related proteins. These groups included 44 upregulated and 13 downregulated proteins. Among the 44 upregulated proteins, 27 were upregulated continuously, eight were upregulated at an early time-point and nine were upregulated at a middle to late time-point. Among the 13 downregulated proteins, five were downregulated continuously, six were downregulated at an early time-point and two were downregulated at a middle to late time-point. These results indicate that hyperthermia-induced Tca8113 cell apoptosis is controlled by multiple factors, which include time and regulatory proteins.

MicroRNA-26a promotes tumor growth and angiogenesis in glioma by directly targeting prohibitin

BACKGROUNDS AND AIMS

Glioma accounts for the majority of primary malignant brain tumors in adults. Upregulation of microRNA-26a (miR-26a) has been observed in glioma. However, the biological function and molecular mechanism of miR-26a in glioma remain to be elucidated.

METHODS

Glioma cells stably overexpressing or down-expressing miR-26a were analyzed for both in vitro and in vivo biological functions. Novel target of miR-26a was identified by bioinformatics searching and molecular biological assays. Glioma specimens and normal brain tissues were analyzed for both expression levels of miR-26a and its target.

RESULTS

Forced expression of miR-26a in glioma cells significantly increased both growth rate and colony formation in vitro and tumor growth and angiogenesis in vivo, while reduced expression of miR-26a played opposite roles. MiR-26a directly targeted prohibitin (PHB) whose expression levels were downregulated in glioma specimens. The levels of miR-26a were inversely correlated with PHB expression levels in glioma samples and strongly correlated with clinical WHO grades of glioma.

CONCLUSION

These results reveal that miR-26a regulates PHB and promotes glioma progression both in vitro and in vivo and that miR-26a and its target PHB are associated with glioma development, which can be helpful in developing microRNA-based treatment for glioma in the future.

TGF-Beta suppresses VEGFA-mediated angiogenesis in colon cancer metastasis

The FET cell line, derived from an early stage colon carcinoma, is non-tumorigenic in athymic nude mice. Engineered FET cells that express TGF-α (FETα) display constitutively active EGFR/ErbB signaling. These cells readily formed xenograft tumors in athymic nude mice. Importantly, FETα cells retained their response to TGF-beta-mediated growth inhibition, and, like the parental FET cells, expression of a dominant negative TGF-beta type II receptor (DNRII) in FETα cells (FETα/DNRII) abrogated responsiveness to TGF-beta-induced growth inhibition and apoptosis under stress conditions in vitro and increased metastatic potential in an orthotopic model in vivo, which indicates metastasis suppressor activity of TGF-beta signaling in this model. Cancer angiogenesis is widely regarded as a key attribute for tumor formation and progression. Here we show that TGF-beta signaling inhibits expression of vascular endothelial growth factor A (VEGFA) and that loss of autocrine TGF-beta in FETα/DNRII cells resulted in increased expression of VEGFA. Regulation of VEGFA expression by TGF-beta is not at the transcriptional level but at the post-transcriptional level. Our results indicate that TGF-beta decreases VEGFA protein stability through ubiquitination and degradation in a PKA- and Smad3-dependent and Smad2-independent pathway. Immunohistochemical (IHC) analyses of orthotopic tumors showed significantly reduced TGF-beta signaling, increased CD31 and VEGFA staining in tumors of FETα/DNRII cells as compared to those of vector control cells. These results indicate that inhibition of TGF-beta signaling increases VEGFA expression and angiogenesis, which could potentially contribute to enhanced metastasis of those cells in vivo. IHC studies performed on human colon adenocarcinoma specimens showed that TGF-beta signaling is inversely correlated with VEGFA expression, indicating that TGF-beta-mediated suppression of VEGFA expression exists in colon cancer patients.

Identification of the genes chemosensitizing hepatocellular carcinoma cells to interferon-α/5-fluorouracil and their clinical significance

The incidence of advanced hepatocellular carcinoma (HCC) is increasing worldwide, and its prognosis is extremely poor. Interferon-alpha (IFN-α)/5-fluorouracil (5-FU) therapy is reportedly effective in some HCC patients. In the present study, to improve HCC prognosis, we identified the genes that are sensitizing to these agents. The screening strategy was dependent on the concentration of ribozymes that rendered HepG2 cells resistant to 5-FU by the repeated transfection of ribozymes into the cells. After 10 cycles of transfection, which was initiated by 5,902,875 sequences of a ribozyme library, three genes including protein kinase, adenosine monophosphate (AMP)-activated, gamma 2 non-catalytic subunit (PRKAG2); transforming growth factor-beta receptor II (TGFBR2); and exostosin 1 (EXT1) were identified as 5-FU-sensitizing genes. Adenovirus-mediated transfer of TGFBR2 and EXT1 enhanced IFN-α/5-FU-induced cytotoxicity as well as 5-FU, although the overexpression of these genes in the absence of IFN-α/5-FU did not induce cell death. This effect was also observed in a tumor xenograft model. The mechanisms of TGFBR2 and EXT1 include activation of the TGF-β signal and induction of endoplasmic reticulum stress, resulting in apoptosis. In HCC patients treated with IFN-α/5-FU therapy, the PRKAG2 mRNA level in HCC tissues was positively correlated with survival period, suggesting that PRKAG2 enhances the effect of IFN-α/5-FU and serves as a prognostic marker for IFN-α/5-FU therapy. In conclusion, we identified three genes that chemosensitize the effects of 5-FU and IFN-α/5-FU on HCC cells and demonstrated that PRKAG2 mRNA can serve as a prognostic marker for IFN-α/5-FU therapy.

Less expression of prohibitin is associated with increased caspase-3 expression and cell apoptosis in renal interstitial fibrosis rats

AIMS

Prohibitin (PHB), a ubiquitous protein, is involved in a variety of molecular functions. Renal interstitial fibrosis (RIF) is a hallmark of common progressive chronic diseases that lead to renal failure. This study was performed to investigate whether PHB was associated with caspase-3 expression/cell apoptosis in RIF rats.

METHODS

Twenty-four male Wistar rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 12, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14 days and 28 days after surgery. RIF index, cell apoptosis index, protein expression of PHB, transforming growth factor-βl (TGF-β1), collagen-IV (Col-IV), fibronectin (FN) or caspase-3 in renal interstitium, and mRNA expression of PHB in renal tissue were detected.

RESULTS

Compared with that in the SHO group, the PHB expression (mRNA and protein) was significantly reduced (P < 0.01). Protein expressions of TGF-β1, Col-IV, FN and caspase-3, and RIF index or cell apoptosis index in GU group were markedly elevated compared with those in SHO group (all P < 0.01). The protein expression of PHB had a negative correlation with the protein expression of TGF-β1, Col-IV, FN or caspase-3, and RIF index or cell apoptosis index (each P < 0.01).

CONCLUSIONS

Less expression of PHB is associated with increased caspase-3 expression/cell apoptosis in RIF rats. However, further research is needed to determine the effect of PHB on caspase-3 expression/cell apoptosis and to determine the potential of PHB as a therapeutic target.

Androgen-regulated processing of the oncomir miR-27a, which targets Prohibitin in prostate cancer

MicroRNAs (miRs) play an important role in the development of many complex human diseases and may have tumour suppressor or oncogenic (oncomir) properties. Prostate cancer is initially an androgen-driven disease, and androgen receptor (AR) remains a key driver of growth even in castration-resistant tumours. However, AR-mediated oncomiR pathways remain to be elucidated. We demonstrate that miR-27a is an androgen-regulated oncomir in prostate cancer, acting via targeting the tumour suppressor and AR corepressor, Prohibitin (PHB). Increasing miR-27a expression results in reduced PHB mRNA and protein levels, and increased expression of AR target genes and prostate cancer cell growth. This involves a novel mechanism for androgen-mediated miR regulation, whereby AR induces a transient increase in miR-23a27a24-2 transcription, but more significantly accelerates processing of the primiR-23a27a24-2 cluster. Androgens therefore regulate miR-27a expression both transcriptionally (via AR binding to the cluster promoter) and post-transcriptionally (accelerating primiR processing to the mature form). We further show that a miR-27a anti-sense oligonucleotide, by opposing the effects of mir-27a, has therapeutic potential in prostate cancer.

STGC3 inhibits xenograft tumor growth of nasopharyngeal carcinoma cells by altering the expression of proteins associated with apoptosis

STGC3 is a potential tumor suppressor that inhibits the growth of the nasopharyngeal carcinoma cell line CNE2; the expression of this protein is reduced in nasopharyngeal carcinoma compared with normal nasopharyngeal tissue. In this study, we investigated the tumor-suppressing activity of STGC3 in nude mice injected subcutaneously with Tet/pTRE-STGC3/CNE2 cells. STGC3 expression was induced by the intraperitoneal injection of doxycycline (Dox). The volume mean of Tet/pTRE-STGC3/CNE2+Dox xenografts was smaller than that of Tet/pTRE/CNE2+Dox xenografts. In addition, Tet/pTRE-STGC3/CNE2+Dox xenografts showed an increase in the percentage of apoptotic cells, a decrease in Bcl-2 protein expression and an increase in Bax protein expression. A proteomic approach was used to assess the protein expression profile associated with STGC3-mediated apoptosis. Western blotting confirmed the differential up-regulation of prohibitin seen in proteomic analysis. These results indicate that overexpression of STGC3 inhibits xenograft growth in nude mice by enhancing apoptotic cell death through altered expression of apoptosis-related proteins such as Bcl-2, Bax and prohibitin. These data contribute to our understanding of the function of STGC3 in human nasopharyngeal carcinoma and provide new clues for investigating other STGC3-associated tumors.

All-trans retinoic acid treatment is associated with prohibitin expression in renal interstitial fibrosis rats

This study was performed to investigate the association of prohibitin with renal interstitial fibrosis (RIF) lesion and to explore the association of all-trans retinoic acid (ATRA) treatment with prohibitin expression in RIF rats. Rats were divided into three groups: the sham operation group (SHO), the model group subjected to unilateral ureteral obstruction (UUO), and the model group treated with ATRA (GA). Renal tissues were collected at 14 and 28 days after surgery, and the relevant indicators were detected. In comparison with the SHO group, the RIF index in the UUO group was markedly elevated (p < 0.01), and the RIF index in the GA group was alleviated compared with that in the UUO group (p < 0.01). Compared with the SHO group, the expression of prohibitin (protein or mRNA) in the UUO group was significantly reduced (each p < 0.01). Prohibitin expression in the GA group was markedly increased when compared with that in the UUO (p < 0.01). The expression of TGF-β1 (protein and mRNA), protein expressions of Col-IV, fibronectin, α-SMA and cleaved Caspase-3, ROS generation and cell apoptosis index in the UUO group were markedly higher than those in the SHO group (all p < 0.01), and their expressions in the GA group were markedly down-regulated compared to those in the UUO group (all p < 0.01, respectively). The protein expression of prohibitin was negatively correlated with the RIF index, protein expression of TGF-β1, Col-IV, fibronectin, α-SMA or cleaved Caspase-3, ROS generation and the cell apoptosis index (each p < 0.01). In conclusion, lower expression of prohibitin is associated with the RIF, and ATRA treatment is associated with increased prohibitin, which can prevent the progression of RIF.

Restoration of transforming growth factor-beta receptor II expression in colon cancer cells with microsatellite instability increases metastatic potential in vivo

Microsatellite instability (MSI), which occurs in 15% of colorectal cancer, has been shown to have a lower incidence of metastasis and better patient survival rates compared with microsatellite stable colorectal cancer. However, a mechanistic understanding of the basis for this difference is very limited. Here, we show that restoration of TGFβ signaling by re-expression of TGFβ receptor II in MSI colon cancer cells increased PI3K/AKT activation, conferred resistance to growth factor deprivation stress-induced apoptosis, and promoted cell motility in vitro. Treatment with a potent PI3K inhibitor (LY294002) blocked the prosurvival and promotility effects of TGFβ, indicating that TGFβ-mediated promotion of cell survival and motility is dependent upon activation of the PI3K/AKT pathway. Analysis of apoptotic effectors that are affected by TGFβ signaling indicated that Bim is an effector of TGFβ-mediated survival. In addition, TGFβ-induced down-regulation of E-cadherin contributed to the prosurvival effect of TGFβ, and restoration of TGFβ signaling in MSI colon cancer cells increased liver metastasis in an orthotopic model in vivo. Taken together, our results demonstrate that restoration of TGFβ signaling promotes cell survival, motility, and metastatic progression in MSI colon cancer cells and indicate that TGFβ receptor II mutations contribute to the favorable outcomes in colon cancer patients with MSI.

Proteomic analysis of myocardial tissue from the border zone during early stage post-infarct remodelling in rats

AIMS

Long-term outcome of patients after myocardial infarction (MI) largely depends on the extent of post-infarct remodelling. To explore the molecular mechanism of remodelling, comparative proteomic analysis was undertaken to identify differential myocardial proteome profiles expressed in the border zone of the post-MI heart.

METHODS AND RESULTS

Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry were used to identify the differential protein profiles expressed in the border zone at specific time points (Days 0, 1, 4, and 10 post-infarction) in a permanent rat MI model. We identified 96 differential protein spots, corresponding to 69 proteins. Cluster analysis exhibited five main temporal expression patterns corresponding to the three phases of early stage remodelling. The alteration in expression was supported by reverse transcription-polymerase chain reaction, western blotting, and immunohistochemical analysis of three selected proteins. Bioinformatics analysis revealed that the proteins in each pattern were functionally related to specific cell processes in remodelling, such as ischaemia, inflammation, and proliferation.

CONCLUSION

A differential myocardial proteome profile was identified in the border zone during early stage post-infarct remodelling. Bioinformatics analysis indicated a possible role of these proteins in remodelling. Proteomics data provided the basis for further functional study of these proteins and for identifying potential molecular targets with therapeutic anti-remodelling effects.

Phosphatase PRL-3 is a direct regulatory target of TGFbeta in colon cancer metastasis

Metastasis causes most deaths from cancer yet mechanistic understanding and therapeutic options remain limited. Overexpression of the phosphatase PRL-3 (phosphatase of regenerating liver) is associated with metastasis of colon cancer. Here, we show that PRL-3 is a direct target of signaling by TGFβ, which is broadly implicated in progression and metastasis. We found that suppression of PRL-3 expression by TGFβ was mediated by Smad-dependent inhibition of PRL-3 transcription at the level of promoter activity. PRL-3 activation stimulated PI3K/AKT signaling that caused resistance to stress-induced apoptosis. PRL-3 overexpression promoted metastatic colonization in an orthotopic mouse model of colon cancer, whereas PRL-3 knockdown reduced metastatic potential. Altered metastatic phenotypes were not derivative of primary tumor development or local invasion but could be attributed to PRL-3-mediated cell survival. Our findings suggest that inhibiting PRL-3 expression might be an important mechanism through which TGFβ suppresses metastasis in colon cancer. In addition, our findings suggest that loss of TGFβ signaling, which occurs commonly during colon cancer progression, is sufficient to activate a PRL-3-mediated cell survival pathway that can selectively promote metastasis. Therefore, a major implication of our findings is that PRL-3 antagonists may offer significant value for antimetastatic therapy in patients with colon cancer.

The role of prohibitin in cell signaling

Prohibitin-1 (PHB, also known as PHB1), a member of the Band-7 family of proteins, is highly conserved evolutionarily, widely expressed, and present in different cellular compartments. Genetic studies with different organism models have provided strong evidence for an important biological role of PHB in mitochondrial function, cell proliferation, and development. Recent discoveries regarding the involvement of PHB in phophatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) and transforming growth factor-β (TGF-β)/signal transducers and activators of transcription signaling pathways, and earlier reports on the interaction of PHB with Raf and its critical role in Ras/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling opened up the possibility that PHB has functions outside of the mitochondria (extramitochondrial) and may be a multifunctional protein. The PI3K/Akt and Ras/MAPK/ERK signaling cascades are versatile signaling processes that diverge from the same receptor tyrosine kinase root, and are involved in cell metabolism, proliferation, and development. Here, we review the emerging role of PHB and its post-translational modifications in signal transduction pathways, especially in PI3K/Akt and Ras/MAPK/ERK signaling. A recent discovery of opposing effects of PHB on longevity under different metabolic states and its potential connection with insulin/insulin-like growth factor-I signaling is also discussed.

Prohibitin is expressed in pancreatic beta-cells and protects against oxidative and proapoptotic effects of ethanol

Pancreatic beta-cell dysfunction is a prerequisite for the development of type 2 diabetes. Alcoholism is a diabetes risk factor and ethanol increases oxidative stress in beta-cells, whereas the mitochondrial chaperone prohibitin (PHB) has antioxidant effects in several cell types. In the present study we investigated whether PHB is expressed in beta-cells and protects these cells against deleterious effects of ethanol, using INS-1E and RINm5F beta-cell lines. Endogenous PHB was detected by western blot and immunocytochemistry. Reactive oxygen species were determined by 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate fluorescence assay, and mitochondrial activity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) reduction, uncoupling protein 2 expression and ATP production. Cell death was determined by Hoechst 33342 staining, cleaved caspase-3 levels and flow cytometry. PHB was expressed in beta-cells under normal conditions and colocalized with Hoechst 33342 in the nucleus and with the mitochondrial probe Mitofluor in the perinuclear area. In ethanol-treated cells, MTT reduction and ATP production decreased, whereas reactive oxygen species, uncoupling protein 2 and cleaved caspase-3 levels increased. In addition, flow cytometry analysis showed an increase of apoptotic cells. Ethanol treatment increased PHB expression and induced PHB translocation from the nucleus to the mitochondria. PHB overexpression decreased the apoptotic effects of ethanol, whereas PHB knockdown enhanced these effects. The protective effects of endogenous PHB were recapitulated by incubation of the cells with recombinant human PHB. Thus, PHB is expressed in beta-cells, increases with oxidative stress and protects the cells against deleterious effects of ethanol.