Bcl-2 expression decreases cadherin-mediated cell-cell adhesion

Development and Characterization of a Human Mammary Epithelial Cell Culture Model for the Blood-Milk Barrier-A Contribution from the ConcePTION Project

It is currently impossible to perform an evidence-based risk assessment for medication use during breastfeeding. The ConcePTION project aims to provide information about the use of medicines during lactation. The study aimed to develop and characterize an in vitro model of the blood-milk barrier to determine the extent of the milk transfer of xenobiotics, relying on either on human mammary epithelial cells (hMECs) or immortalized cell lines derived from breast tissue. The hMECs were cultured and characterized for epithelial markers; further, the ability to form an epithelial barrier was investigated. Drug transporter functionality in the cultured hMECs was analyzed with specific probe substrates. The hMECs showed an epithelial morphology and the expression of epithelial markers and tight junctions. They formed a reproducible tight barrier with a transepithelial electrical resistance greater than 400 Ωcm2, unlike immortalized cell lines. Different levels of mRNA expression were detected for 81 genes of membrane transporters. Functional assays showed no evidence for the transporter-mediated secretion of medicines across the hMECs. Nevertheless, the hMEC-based in vitro model covered a 50-fold range of permeability values, differentiating between passive transcellular and paracellular-mediated transport. The cultured hMECs proved to be a promising in vitro model for biorelevance; the wide characterization of hMECs makes them useful for studying medicine partitioning in milk.

Transcriptome Analysis Reveals Vimentin-Induced Disruption of Cell-Cell Associations Augments Breast Cancer Cell Migration

In advanced metastatic cancers with reduced patient survival and poor prognosis, expression of vimentin, a type III intermediate filament protein is frequently observed. Vimentin appears to suppress epithelial characteristics and augments cell migration but the molecular basis for these changes is not well understood. Here, we have ectopically expressed vimentin in MCF-7 and investigated its genomic and functional implications. Vimentin changed the cell shape by decreasing major axis, major axis angle and increased cell migration, without affecting proliferation. Vimentin downregulated major keratin genes KRT8, KRT18 and KRT19. Transcriptome-coupled GO and KEGG analyses revealed that vimentin-affected genes were linked to either cell-cell/cell-ECM or cell cycle/proliferation specific pathways. Using shRNA mediated knockdown of vimentin in two cell types; MCF-7FV (ectopically expressing) and MDA-MB-231 (endogenously expressing), we identified a vimentin-specific signature consisting of 13 protein encoding genes (CDH5, AXL, PTPRM, TGFBI, CDH10, NES, E2F1, FOXM1, CDC45, FSD1, BCL2, KIF26A and WISP2) and two long non-coding RNAs, LINC00052 and C15ORF9-AS1. CDH5, an endothelial cadherin, which mediates cell-cell junctions, was the most downregulated protein encoding gene. Interestingly, downregulation of CDH5 by shRNA significantly increased cell migration confirming our RNA-Seq data. Furthermore, presence of vimentin altered the lamin expression in MCF-7. Collectively, we demonstrate, for the first time, that vimentin in breast cancer cells could change nuclear architecture by affecting lamin expression, which downregulates genes maintaining cell-cell junctions resulting in increased cell migration.

Study of long non-coding RNA highly upregulated in liver cancer (HULC) in breast cancer: A clinical & in vitro investigation

Background & objectives:

Breast cancer remains the most common malignancy among women worldwide. Long non-coding RNAs (lncRNAs) have been shown to play critical roles in tumour initiation and progression. This study was aimed to evaluate the potential role of lncRNA highly upregulated in liver cancer (HULC) in breast cancer.

Methods:

The expression of HULC was evaluated in breast cancer patients and cell lines using real-time quantitative reverse transcription polymerase chain reaction. Small interfering RNA-based knockdown was also employed to study the potential role of HULC in breast cancer cell lines including ZR-75-1, MCF7 and MDA-MB-231.

Results:

HULC was significantly upregulated in tumour tissues compared to non-tumoural margins (P<0.001). The receiver operating characteristic (ROC) curve analysis demonstrated the biomarker potential of HULC (ROC^AUC=0.78, P<0.001). The HULC knockdown induced apoptosis and suppressed cellular migration in breast cancer cell lines.

Interpretation & conclusions:

Our results indicated that HULC was upregulated in breast cancer and might play a role in tumourigenesis. The HULC may have a potential to be exploited as a new biomarker and therapeutic target in breast cancer.

Long non‑coding RNA NNT‑AS1 knockdown represses the progression of gastric cancer via modulating the miR‑142‑5p/SOX4/Wnt/β‑catenin signaling pathway

Patients with advanced gastric cancer (GC) have a poor prognosis with a median overall survival of 10–12 months. Long non-coding RNA nicotinamide nucleotide transhydrogenase-antisense RNA1 (NNT-AS1) and sex-determining region Y-related high mobility group box 4 (SOX4) have been reported to be associated with the progression of various types of cancer; however, the regulatory mechanism between NNT-AS1 and SOX4 in GC is not completely understood. Reverse transcription-quantitative PCR was used to detect the expression levels of NNT-AS1, microRNA (miR)-142-5p and SOX4. Western blotting was performed to assess the protein expression levels of SOX4, β-catenin, c-Myc, Bcl-2 and E-cadherin. The proliferation, apoptosis, migration and invasion of GC cells were determined using MTT, flow cytometry and Transwell assays. The relationship between miR-142-5p and NNT-AS1 or SOX4 was investigated using a dual-luciferase reporter assay. NNT-AS1 and SOX4 were upregulated, whereas miR-142-5p was downregulated in GC tissues and cells compared with normal tissues and cells. Both NNT-AS1 and SOX4 knockdown inhibited GC cell proliferation, migration and invasion, and enhanced GC cell apoptosis. Moreover, the results indicated that NNT-AS1 modulated SOX4 expression by sponging miR-142-5p. In addition, SOX4 overexpression reversed NNT-AS1 knockdown-mediated effects on GC cell proliferation, apoptosis, migration and invasion. NNT-AS1 knockdown blocked the Wnt/β-catenin signaling pathway via the miR-142-5p/SOX4 axis. Collectively, the present study indicated that NNT-AS1 knockdown decreased GC cell proliferation, migration and invasion, and induced GC cell apoptosis by regulating the miR-142-5p/SOX4/Wnt/β-catenin signaling pathway axis.

Estrogen matters in metastasis

Metastatic cancer cells meet several physical, biochemical and immunological barriers before colonizing a new territory. Cancerous cells turn invasive, mobile and eventually disengage from their native niche. This is followed by their intravasation, extravasation, survival, proliferation, and colonization into distant organs. Unlike well-confined tumors, which respond favorably to anti-cancer therapeutics, metastatic tumors are life-threatening and incurable. More than 90% of cancer-related mortality is caused by metastases, hence the emphasis is now on developing the strategies to block or reverse the process of metastasis. This has ensued intensive research with a focus on the mechanisms underlying metastasis. Substantial work carried out in this direction has led to the identification of specific enzymes, proteins, cytokines, chemokines, growth factors, exosomes, miRNA and lipids, etc. as the facilitators of metastasis. Metastatic cells are exposed to a diverse array of local and systemic signals. Among these, estrogens are of great relevance. Estrogens have been strongly linked to cancers, especially of breast and uterine origin. Recent data hint that estrogens, well recognized for their role in proliferation, may have a role in metastasis also. It is proposed that influence of estrogen on metastasis may be independent of its proliferation-inducing ability. Data are emerging to suggest that estrogens have potential to modulate various events of the metastatic cascade such as local invasion, intravasation, anoikis, immune evasion, extravasation, angiogenesis and metastatic colonization. This review summarizes some of the recent advances in our knowledge on the role of estrogens in the metastatic cascade of cancerous cells.

A model for cell migration in non-isotropic fibrin networks with an application to pancreatic tumor islets

Cell migration, known as an orchestrated movement of cells, is crucially important for wound healing, tumor growth, immune response as well as other biomedical processes. This paper presents a cell-based model to describe cell migration in non-isotropic fibrin networks around pancreatic tumor islets. This migration is determined by the mechanical strain energy density as well as cytokines-driven chemotaxis. Cell displacement is modeled by solving a large system of ordinary stochastic differential equations where the stochastic parts result from random walk. The stochastic differential equations are solved by the use of the classical Euler–Maruyama method. In this paper, the influence of anisotropic stromal extracellular matrix in pancreatic tumor islets on T-lymphocytes migration in different immune systems is investigated. As a result, tumor peripheral stromal extracellular matrix impedes the immune response of T-lymphocytes through changing direction of their migration.

Comparison of transepithelial resistance measurement techniques: Chopsticks vs. Endohm

Background

TER measurements across confluent cellular monolayers provide a useful indication of TJ strength between epithelial and endothelial cells in culture. Having a reliable and accurate method of measuring cell-to-cell adhesion is critical to studies in pathophysiology and cancer metastasis. However, the use of different technical approaches to measure TER has reportedly yielded inconsistent measurements within the same cell lines.

Methods

In the current study, we compared the peak TER values for the MDCK (canine kidney) and MCF-7 (human breast cancer) epithelial cell lines using two common approaches (Chopstick and Endohm) and two types of polymer inserts (PC and PET).

Results

Both cell lines demonstrated a statistically significant difference in the peak TERs obtained using the two different approaches. Further, the MDCK (but not the MCF-7) cells demonstrated a statistically significant difference between the peak TERs when using the same approach but different inserts.

Conclusion

Our study indicates the importance of using a single approach when seeking to measure and compare the TER values of cultured cell lines.

Cold Shock Proteins Mediate GN with Mesangioproliferation

DNA binding protein A (DbpA) is a member of the human cold shock domain-containing protein superfamily, with known functions in cell proliferation, differentiation, and stress responses. DbpA mediates tight junction-associated activities in tubular epithelial cells, but the function of DbpA in mesangial cells is unknown. Here, we found DbpA protein expression restricted to vascular smooth muscle cells in healthy human kidney tissue but profound induction of DbpA protein expression within the glomerular mesangial compartment in mesangioproliferative nephritis. In vitro, depletion or overexpression of DbpA using lentiviral constructs led to inhibition or promotion, respectively, of mesangial cell proliferation. Because platelet-derived growth factor B (PDGF-B) signaling has a pivotal role in mesangial cell proliferation, we examined the regulatory effect of PDGF-B on DbpA. In vitro studies of human and rat mesangial cells confirmed a stimulatory effect of PDGF-B on DbpA transcript numbers and protein levels. Additional in vivo investigations showed DbpA upregulation in experimental rat anti-Thy1.1 nephritis and murine mesangioproliferative nephritis models. To interfere with PDGF-B signaling, we injected nephritic rats with PDGF-B neutralizing aptamers or the MEK/ERK inhibitor U0126. Both interventions markedly decreased DbpA protein expression. Conversely, continuous PDGF-B infusion in healthy rats induced DbpA expression predominantly within the mesangial compartment. Taken together, these results indicate that DbpA is a novel target of PDGF-B signaling and a key mediator of mesangial cell proliferation.

miR-34a inhibits migration and invasion of tongue squamous cell carcinoma via targeting MMP9 and MMP14

Background

miR-34a is an important tumor suppressor gene in various cancer types. But little is known about the dysregulation of miR-34a in tongue squamous cell carcinoma (TSCC). In this study, we investigate the expression and potential role of miR-34a in TSCC.

Methods

We evaluated miR-34a expression and its relationship with clinicopathological characters in 75 pairs of TSCC samples, and confirmed the role of miR-34a for predicting lymph node metastases from a further 15 pairs of paraffin-embedded TSCC specimens with stringent clinicopathological recruitment criteria using quantitative reverse transcription polymerase chain reaction (qRT-PCR). The effects of miR-34a on cell proliferation, migration and invasion were examined in TSCC cell lines using Cell Counting Kit-8 assay, wound healing assay and transwell assay, respectively. The effects of miR-34a on the expression of matrix metalloproteinase (MMP) 9 and 14 were detected by luciferase reporter assays and Western blot analysis. The expression of miR-34a, MMP9 and MMP14 were also confirmed in TSCC samples by in situ hybridization and immunohistochemistry.

Results

miR-34a expression in tumor tissues from TSCC patients with positive lymph node metastases was significantly lower than that with negative lymph node metastases. Overexpression of miR-34a significantly suppressed migration and invasion in TSCC cells and simultaneously inhibited the expression of MMP9 and MMP14 through targeting the coding region and the 3′untranslated region, respectively. Moreover, miR-34a expression in TSCC was inversely correlated with protein expression of MMP9 and MMP14 in the TSCC samples.

Conclusions

miR-34a plays an important role in lymph node metastases of TSCC through targeting MMP9 and MMP14 and may have potential applications in prognosis prediction and gene therapy for lymph node metastases of TSCC patients.

Minireview: Steroid/nuclear receptor-regulated dynamics of occluding and anchoring junctions

A diverse set of physiological signals control intercellular interactions by regulating the structure and function of occluding junctions (tight junctions) and anchoring junctions (adherens junctions and desmosomes). These plasma membrane junctions are comprised of multiprotein complexes of transmembrane and cytoplasmic peripheral plasma membrane proteins. Evidence from many hormone-responsive tissues has shown that expression, modification, molecular interactions, stability, and localization of junctional complex-associated proteins can be targeted by nuclear hormone receptors and their ligands through transcriptional and nontranscriptional mechanisms. The focus of this minireview is to discuss molecular, cellular, and physiological studies that directly link nuclear receptor- and ligand-triggered signaling pathways to the regulation of occluding and anchoring junction dynamics.

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.

Prognostic implications of micoRNA miR-195 expression in human tongue squamous cell carcinoma

Background

miR-195 is aberrantly expressed in multiple types of disease. But little is known about the dysregulation of miR-195 in tongue squamous cell carcinoma (TSCC). In this study, we investigated the roles of miR-195 in the development and progression of TSCC.

Methods

Using quantitative reverse transcription-polymerase chain reaction (qRT-PCR), we evaluated miR-195 expression in TSCC samples from 81 patients. Overall survival of these patients was examined using Kaplan–Meier curves with log-rank tests and the Cox proportional hazards model. The expression of two known miR-195 target genes, Cyclin D1 and Bcl-2, was also examined in the TSCC samples by immunohistochemistry. The effects of miR-195 overexpression on cell cycle progression and apoptosis and its effects on the expression of Cyclin D1 and Bcl-2 were examined in transfected TSCC cell lines (SCC-15 and Cal27) using fluorescence-activated cell sorting assays, luciferase reporter assays, and Western blots.

Results

Reduced miR-195 expression was associated with tumor size and the clinical stage of TSCC tumors. Kaplan–Meier survival analysis indicated that the TSCC patients with reduced expression of miR-195 had poor overall survival and in multivariable analyses low levels of miR-195 emerged as an independent prognostic factor for this clinical outcome. Levels of miR-195 expression were inversely correlated with the expression of Cyclin D1 and Bcl-2. Overexpression of miR-195 inhibited cell cycle progression, promoted apoptosis, and reduced Cyclin D1 and Bcl-2 expression in two TSCC cell lines.

Conclusions

miR-195 may have potential applications as a prognostic factor for TSCC patients.

Slit-Robo signaling induces malignant transformation through Hakai-mediated E-cadherin degradation during colorectal epithelial cell carcinogenesis

The Slit family of guidance cues binds to Roundabout (Robo) receptors and modulates cell migration. We report here that ectopic expression of Slit2 and Robo1 or recombinant Slit2 treatment of Robo1-expressing colorectal epithelial carcinoma cells recruited an ubiquitin ligase Hakai for E-cadherin (E-cad) ubiquitination and lysosomal degradation, epithelial-mesenchymal transition (EMT), and tumor growth and liver metastasis, which were rescued by knockdown of Hakai. In contrast, knockdown of endogenous Robo1 or specific blockade of Slit2 binding to Robo1 prevented E-cad degradation and reversed EMT, resulting in diminished tumor growth and liver metastasis. Ectopic expression of Robo1 also triggered a malignant transformation in Slit2-positive human embryonic kidney 293 cells. Importantly, the expression of Slit2 and Robo1 was significantly associated with an increased metastatic risk and poorer overall survival in colorectal carcinoma patients. We conclude that engagement of Robo1 by Slit2 induces malignant transformation through Hakai-mediated E-cad ubiquitination and lysosomal degradation during colorectal epithelial cell carcinogenesis.

Odontoblast-targeted Bcl-2 overexpression impairs dentin formation

Apoptosis has been described extensively in tooth development, which is under tight control of multiple apoptosis regulators, including anti-apoptotic protein Bcl-2. However, it is totally unclear how Bcl-2 is related to odontogenesis, especially dentinogenesis. Using a transgenic mouse Col2.3Bcl-2 in which human Bcl-2 was overexpressed in odontoblasts, the effect of Bcl-2 on dentinogenesis was investigated. Overexpression of Bcl-2 was detected by immunohistochemistry and Western blot. Odontoblast apoptosis was evaluated by TUNEL and Western blot detection of cleaved caspase-3. Odontoblast differentiation was assessed by real-time PCR detection of dentin matrix expression. Dentin mineralization was evaluated by micro-CT in vivo, and alizarin red S staining and calcium content analysis in vitro. Bcl-2 was found to be overexpressed in odontoblasts and prevent their apoptosis. Odontoblast differentiation and mineralization was inhibited by Bcl-2, as evidenced by lower expressions of DMP-1, OC, and DSPP, and decreased odontoblast mineralization in vitro, as well as decreased dentin thickness and mineral density in vivo when compared to the wild-type animals. Inhibition of odontoblast differentiation by Bcl-2 occurs, at least partially, via a suppression of MEK-ERK1/2 signaling pathway. In conclusion, Bcl-2 overexpression prevents odontoblast apoptosis and impairs dentin formation, partially via an inhibition of odontoblast differentiation. This study revealed some novel functions of Bcl-2 in dentinogenesis in addition to its anti-apoptotic effect, which shed some light on the genetic complexity of tooth development.

BCL2 interaction with actin in vitro may inhibit cell motility by enhancing actin polymerization

In addition to its well-defined role as an antagonist in apoptosis, we propose that BCL2 may act as an intracellular suppressor of cell motility and adhesion under certain conditions. Our evidence shows that, when over-expressed in both cancer and non-cancer cells, BCL2 can form a complex with actin and gelsolin that functions to decrease gelsolin-severing activity to increase actin polymerization, and, thus, suppress cell adhesive processes. The linkage between increased BCL2 and increased actin polymerization on the one hand, and suppression of cell adhesion, spreading, and motility on the other hand, is a novel observation that may provide a plausible explanation for why BCL2 over-expression in some tumors is correlated with improved patient survival. In addition, we have identified conditions in vitro in which F-actin polymerization can be increased while cell motility is reduced. These findings underscore the possibility that BCL2 may be involved in modulating cytoskeleton reorganization, and may provide an opportunity to explore signal transduction pathways important for cell adhesion and migration and to develop small molecule therapies for suppression of cancer metastasis.

The exploitation of differential endocytic pathways in normal and tumor cells in the selective targeting of nanoparticulate chemotherapeutic agents

Polymeric micelles with cross-linked ionic cores of poly(methacrylic acid) and nonionic shell of poly(ethylene oxide) (cl-micelles) are shown here to readily internalize in epithelial cancer cells but not in normal epithelial cells that form tight junctions (TJ). The internalization of such cl-micelles in the cancer cells proceeded mainly through caveolae-mediated endocytosis. In confluent normal epithelial cells this endocytosis route was absent at the apical side and the cl-micelles sequestered in TJ regions of the cell membrane without entering the cells for at least 24h. Disruption of the TJ by calcium deprivation resulted in redistribution of cl-micelles inside the cells. In cancer cells following initial cellular entry the cl-micelles bypassed the early endosomes and reached the lysosomes within 30min. This allowed designing cl-micelles with cytotoxic drug, doxorubicin, linked via pH-sensitive hydrazone bonds, which were cleaved in the acidic environment of lysosomes resulting in accumulation of the drug in the nucleus after 5h. Such pH-sensitive cl-micelles displayed selective toxicity to cancer cells but were non-toxic to normal epithelial cells. In conclusion, we describe major difference in interactions of cl-micelles with cancer and normal cells that can lead to development of novel drug delivery system with reduced side effects and higher efficacy in cancer chemotherapy.

TNF-alpha downregulates E-cadherin and sensitizes response to γ-irradiation in Caco-2 cells

PURPOSE

The purpose of the present study was to assess the biological effects of TNF-alpha in Caco-2 well-differentiated colon adenocarcinoma cells and to determine radiation sensitivity in order to develop TNF-alpha into a cancer therapeutic agent.

MATERIALS AND METHODS

A cell viability test was conducted via a colorimetric and colony forming assay after 1 day and 3 days of incubation with TNF-alpha. Western blotting analysis and immunofluorescence staining were conducted to explore TNF-alpha-induced morphological and molecular changes in the adhesion molecules, E-cadherin and claudin-4. The effects of γ-irradiation at a dose of 2 Gy on cell survival were evaluated by a clonogenic assay. The molecular changes in apoptosis-regulatory proteins were assessed by Western blotting.

RESULTS

Caco-2 cells were highly resistant to TNF alpha-induced cell death and 2 Gy of γ-irradiation. However, we observed the downregulation of the adherens junctional protein, E-cadherin and translocation of tight junctional protein, claudin-4 from the membrane to the cytosol induced by TNF-alpha treatment which would indicate cell-cell junction disruptions. These alterations of junctional proteins influenced the regulation of cell death in response to 2 Gy of γ-irradiation. The combined treatment of TNF-alpha with 2 Gy of γ-irradiation reduced the survival of Caco-2 cells by down-regulating bcl-xl and activating JNK pathways.

CONCLUSION

These results suggest that TNF-alpha might be potentially applied as a therapeutic agent in order to enhance sensitivity to 2 Gy of γ-irradiation administered in radiotherapy for the treatment of human colon cancer.

Biological relevance of ion energy in performance of human endothelial cells on ion-implanted flexible polyurethane surfaces

To improve the biocompatibility of polyurethane (PUR), we modified the surface by irradiation with different ions (Carbon; C, Oxygen; O, Nitrogen; N, or Argon; Ar) at 0.3-50 keV energy and doses of 1,00E+13 - 1,00E+15 ions/cm(2). The effects of ion implantation using different ion energies and densities were observed on adhesion, proliferation, and viability of human umbilical vein endothelial cells (HUVECs). The long-term in vitro stability of ion-implanted PUR was also investigated. Ion irradiation moderately affected the surface roughness (R(a)), but strongly enhanced the work of adhesion (W(a)). Cell adhesion was markedly improved on O-, N-, and Ar-, but not on C-implanted PUR surfaces. Medium ion energies and lower ion doses produced the best HUVEC attachment and proliferation, indicating the importance of choosing the proper range of energy applied during ion irradiation. In addition, apoptosis rates were significantly reduced when compared with unmodified PUR (uPUR). N implantation significantly protected the surface, although C implantation led to stronger surface erosions than on uPUR. In total, ion implantation on flexible PUR surfaces strongly improved the material surface characteristics and biocompatibility. Electron beam ion implantation within an appropriate energy window is thus a key to improving flexible PUR surfaces for clinical use to support endothelial cell performance. Thus, it can contribute to designing small-diameter grafts, which are in great demand, towards vascular tissue engineering applications.

Regulation of mitochondrial respiratory chain biogenesis by estrogens/estrogen receptors and physiological, pathological and pharmacological implications

There has been increasing evidence pointing to the mitochondrial respiratory chain (MRC) as a novel and important target for the actions of 17beta-estradiol (E(2)) and estrogen receptors (ER) in a number of cell types and tissues that have high demands for mitochondrial energy metabolism. This novel E(2)-mediated mitochondrial pathway involves the cooperation of both nuclear and mitochondrial ERalpha and ERbeta and their co-activators on the coordinate regulation of both nuclear DNA- and mitochondrial DNA-encoded genes for MRC proteins. In this paper, we have: 1) comprehensively reviewed studies that reveal a novel role of estrogens and ERs in the regulation of MRC biogenesis; 2) discussed their physiological, pathological and pharmacological implications in the control of cell proliferation and apoptosis in relation to estrogen-mediated carcinogenesis, anti-cancer drug resistance in human breast cancer cells, neuroprotection for Alzheimer's disease and Parkinson's disease in brain, cardiovascular protection in human heart and their beneficial effects in lens physiology related to cataract in the eye; and 3) pointed out new research directions to address the key questions in this important and newly emerging area. We also suggest a novel conceptual approach that will contribute to innovative regimens for the prevention or treatment of a wide variety of medical complications based on E(2)/ER-mediated MRC biogenesis pathway.

Lack of Bax prevents influenza A virus-induced apoptosis and causes diminished viral replication

The ectopic overexpression of Bcl-2 restricts both influenza A virus-induced apoptosis and influenza A virus replication in MDCK cells, thus suggesting a role for Bcl-2 family members during infection. Here we report that influenza A virus cannot establish an apoptotic response without functional Bax, a downstream target of Bcl-2, and that both Bax and Bak are directly involved in influenza A virus replication and virus-induced cell death. Bak is substantially downregulated during influenza A virus infection in MDCK cells, and the knockout of Bak in mouse embryonic fibroblasts yields a dramatic rise in the rate of apoptotic death and a corresponding increase in levels of virus replication, suggesting that Bak suppresses both apoptosis and the replication of virus and that the virus suppresses Bak. Bax, however, is activated and translocates from the cytosol to the mitochondria; this activation is required for the efficient induction of apoptosis and virus replication. The knockout of Bax in mouse embryonic fibroblasts blocks the induction of apoptosis, restricts the infection-mediated activation of executioner caspases, and inhibits virus propagation. Bax knockout cells still die but by an alternative death pathway displaying characteristics of autophagy, similarly to our previous observation that influenza A virus infection in the presence of a pancaspase inhibitor leads to an increase in levels of autophagy. The knockout of Bax causes a retention of influenza A virus NP within the nucleus. We conclude that the cell and virus struggle to control apoptosis and autophagy, as appropriately timed apoptosis is important for the replication of influenza A virus.

Heterotrimeric G proteins and apoptosis: intersecting signaling pathways leading to context dependent phenotypes

Apoptosis, a programmed cell death mechanism, is a fundamental process during the normal development and somatic maintenance of all multicellular organisms and thus is highly conserved and tightly regulated through numerous signaling pathways. Apoptosis is of particular clinical importance as its dysregulation contributes significantly to numerous human diseases, primarily through changes in the expression and activation of key apoptotic regulators. Each of the four families of heterotrimeric G proteins (G(s), G(i/o), G(q/11) and G(12/13)) has been implicated in numerous cellular signaling processes, including proliferation, transformation, migration, differentiation, and apoptosis. Heterotrimeric G protein signaling is an important but not widely studied mechanism regulating apoptosis. G protein Signaling and Apoptosis broadly cover two large bodies of literature and share numerous signaling pathways. Examination of the intersection between these two areas is the focus of this review. Several studies have implicated signaling through each of the four heterotrimeric G protein families to regulate apoptosis within numerous disease contexts, but the mechanism(s) are not well defined. Each G protein family has been shown to stimulate and/or inhibit apoptosis in a context-dependent fashion through regulating numerous downstream effectors including the Bcl-2 family, NF-kappaB, PI3 Kinase, MAP Kinases, and small GTPases. These cell-type specific and G protein coupled receptor dependent effects have led to a complex body of literature of G protein regulation of apoptosis. Here, we review the literature and summarize apoptotic signaling through each of the four heterotrimeric G protein families (and the relevant G protein coupled receptors), and discuss limitations and future directions for research on regulating apoptosis through G protein coupled mechanisms. Continued investigation in this field is essential for the identification of important targets for pharmacological intervention in numerous diseases.

Regulation of energy metabolism pathways by estrogens and estrogenic chemicals and potential implications in obesity associated with increased exposure to endocrine disruptors

The prevalence of obesity among children, adolescents and adults has been dramatically increasing worldwide during the last several decades. The obesity epidemic has been recognized as one of the major global health problems, because its health hazard is linked to a number of common diseases including breast and prostate cancers. Obesity is caused by combination of genetic and environmental factors. While genetic contribution to obesity has been known to be significant, the genetic factors remain relatively unchanged. Recent studies have highlighted the involvement of environmental "obesogens", i.e. the xenobiotic chemicals that can disrupt the normal development and homeostatic control over adipogenesis and energy balance. Several lines of evidence suggest that increasing exposure to chemicals with endocrine-disrupting activities (endocrine-disrupting chemicals, EDCs) contributes to the increased obesity. The cellular and molecular mechanisms underlying obesogen-associated obesity are just now being appreciated. In this paper, we comprehensively reviewed current knowledge about the role of estrogen receptors alpha and beta (ERalpha and ERbeta) in regulation of energy metabolism pathways, including glucose transport, glycolysis, tricarboxylic acid (TCA) cycle, mitochondrial respiratory chain (MRC), adenosine nucleotide translocator (ANT) and fatty acid beta-oxidation and synthesis, by estrogens; and then examined the disturbance of E(2)/ER-mediated energy metabolism pathways by environmental obesogens; and finally, we discussed the potential implications of disturbance of energy metabolism pathways by obesogens in obesity and pointed out several key aspects of this area that need to be further explored. A better understanding of the cellular and molecular mechanisms underlying obesogen-associated obesity will lead to new approaches for slow down and/or prevention of the increased trend of obesity associated with exposure to obesogens.

Oncogenic K-Ras regulates proliferation and cell junctions in lung epithelial cells through induction of cyclooxygenase-2 and activation of metalloproteinase-9

Expression of oncogenic K-Ras is frequently observed in non-small-cell lung cancer. However, oncogenic K-Ras is not sufficient to transform lung epithelial cells and requires collaborating signals that have not been defined. To examine the biological effects of K-Ras in nontransformed lung epithelial cells, stable transfectants were generated in RL-65 cells, a spontaneously immortalized lung epithelial cell line. Expression of K-Ras resulted in extracellular signal-regulated kinase (ERK) activation, which mediated induction of cyclooxygenase (COX)-2 and increased prostaglandin E(2) production. Epithelial cells expressing oncogenic K-Ras showed increased proliferation in two- and three-dimensional tissue culture and delayed formation of hollow acinar structures in three-dimensional matrigel cultures. These affects were mediated through COX-2-dependent activation of beta-catenin signaling and inhibition of apoptosis. ERK activation also led to induction of metalloproteinase (MMP)-9 and cleavage of E-cadherin at two specific sites. This resulted in partial disruption of adherens junctions as determined by decreased transepithelial resistance (TER), and disruption of E-cadherin/beta-catenin interactions. An MMP-9 inhibitor reversed the decrease in TER and inhibited beta-catenin signaling. These data indicate that although expression of oncogenic K-Ras does not transform lung epithelial cells, it alters the phenotype of the cells by increasing proliferation and decreasing cell-cell contacts characteristic of epithelial cells.

Tamoxifen and ICI 182,780 increase Bcl-2 levels and inhibit growth of breast carcinoma cells by modulating PI3K/AKT, ERK and IGF-1R pathways independent of ERalpha

We recently showed that estrogen withdrawal from the ERalpha(+), high Bcl-2-expressing breast carcinoma cells (MCF-7B) reduced Bcl-2 protein levels while increasing cell-cell adhesion, and junction formation. Here we compared these cells with the ERalpha(+) and low Bcl-2-expressing MCF-7 cells and with the normal mammary epithelial cell line MCF-10-2A not expressing ERalpha or Bcl-2. All cell lines expressed normal HER2. Antiestrogen (Tamoxifen and ICI 182,780) treatment increased Bcl-2 levels in both MCF-7 and -7B cells and led to the formation of acinar structures. This treatment led to the dissociation of junctions and redistribution of junctional components to the cytoplasm in MCF-10-2A and -7 cells, while in MCF-7B cells junctional proteins redistributed to membranes. Antiestrogen treatment decreased PI3K/Akt activation and increased ERK activation regardless of ERalpha status. IGF-1R was inactivated in the antiestrogen-treated MCF-7 cells while it was activated in MCF-7B cells. Our data show that Tamoxifen and ICI 182,780 can induce growth inhibitory effects via the sustained activation/inactivation of signaling pathways that regulate cell survival, cell death and differentiation in the absence of ERalpha. Furthermore, Bcl-2 overexpression may alter the functional interactions among these pathways in response to antiestrogens, which also may provide a potential explanation for the observation that Bcl-2 overexpressing tumors have a better prognosis.

Posttranslational truncation of E-cadherin and significance for tumour progression

Stable intraepithelial adhesion complexes are essential for the maintenance of epithelial integrity. Alterations in these complexes are key events in the development and progression of many diseases. One of the major proteins involved in maintaining epithelial cell-cell adhesion is the cell-adhesion junction protein E-cadherin, a member of the cadherin family of transmembrane adhesion proteins. E-cadherin is involved in many cellular processes including morphogenesis, adhesion, recognition, communication and oncogenesis. Inactivation of its adhesive properties is often a key step in tumour progression and metastasis, leading to its recent description as a tumour suppressor gene. Mutations of the E-cadherin gene CDH1 in gastric and mammary cancers have been well documented and reports of transcriptional repression during tumour progression are increasing. This review examines the role of posttranslational truncation of E-cadherin in cancer cells focusing on implications for tumour progression. The various proteins involved in the directed cleavage of E-cadherin and consequences of these truncations are discussed.

Bone-targeted overexpression of Bcl-2 increases osteoblast adhesion and differentiation and inhibits mineralization in vitro

Apoptosis is a process important for the development and homeostasis of self-renewing tissues, including bone. However, little is known about the function of Bcl-2, a key player of apoptosis, in the regulation of osteoblast activity. Ex vivo cultures of osteoblasts from Col2.3Bcl-2 mice, in which human Bcl-2 was targeted to bone by the 2.3 kb fragment of the type I collagen promoter, were used to study the effect of Bcl-2 in osteoblasts. During 35 days of culture, hBcl-2 expression increased without any effect on endogenous mouse Bcl-2 and Bax expression. Adhesion of transgenic (TG) osteoblasts was twofold more than that of wild-type (WT) cells, with significantly higher expression of integrins alpha(1), alpha(2), and alpha(5) but similar levels of alpha(v) and beta(1) relative to WT cells. Proliferation of osteoblasts was not affected. Overexpression of hBcl-2 promoted the differentiation of osteoblasts, as shown by increased message levels of alkaline phosphatase, type I collagen, bone sialoprotein, and osteocalcin in the TG compared to WT cells throughout the culture period. The two transcription factors essential for osteoblast differentiation, core binding factor alpha 1 (Cbfa-1) and osterix, had significantly higher expression in TG than WT cells during the early culture period. ss-Catenin, a central player in the canonical Wnt pathway, also had higher expression in TG than WT cultures. Mineralization was significantly decreased in TG cultures, with less osteoblast apoptosis, compared to WT. Thus, Bcl-2 seems to have multiple roles in modulating osteoblast activities.

An NF-kappaB and slug regulatory loop active in early vertebrate mesoderm

Background

In both Drosophila and the mouse, the zinc finger transcription factor Snail is required for mesoderm formation; its vertebrate paralog Slug (Snai2) appears to be required for neural crest formation in the chick and the clawed frog Xenopus laevis. Both Slug and Snail act to induce epithelial to mesenchymal transition (EMT) and to suppress apoptosis.

Methodology & Principle Findings

Morpholino-based loss of function studies indicate that Slug is required for the normal expression of both mesodermal and neural crest markers in X. laevis. Both phenotypes are rescued by injection of RNA encoding the anti-apoptotic protein Bcl-xL; Bcl-xL's effects are dependent upon IκB kinase-mediated activation of the bipartite transcription factor NF-κB. NF-κB, in turn, directly up-regulates levels of Slug and Snail RNAs. Slug indirectly up-regulates levels of RNAs encoding the NF-κB subunit proteins RelA, Rel2, and Rel3, and directly down-regulates levels of the pro-apopotic Caspase-9 RNA.

Conclusions/Significance

These studies reveal a Slug/Snail–NF-κB regulatory circuit, analogous to that present in the early Drosophila embryo, active during mesodermal formation in Xenopus. This is a regulatory interaction of significance both in development and in the course of inflammatory and metastatic disease.

Bcl-2 overexpression disrupts the morphology of PC12 cells through reduced ERK activation

Bcl-2 has been hypothesized to regulate many cellular functions in addition to its well-characterized role in the prevention of programmed cell death. To understand the role of Bcl-2 in regulating cell morphology and to explore the mechanism of this effect, we examined the effects of Bcl-2 overexpression on the morphology of PC12 cells in culture. We demonstrate that the overexpression of Bcl-2 in PC12 cells results in altered cell morphology and reduced actin expression. Analysis of extracellular signal-regulated kinase (ERK) 1/2 phosphorylation reveals that the morphological changes seen after bcl-2 transfection are associated with reduced ERK activation. Treatment of control (mock-transfected) PC12 cells with the mitogen-activated ERK-activating kinase (MEK) inhibitor PD98059 converts their flat, process-bearing morphology into the rounded, process-free morphology of bcl-2-transfected cells, further confirming the association of ERK activation with altered cell shape. In conclusion, the present study describes a novel function of Bcl-2 in regulating cell shape through reduced ERK activation.

SUMOylation attenuates sensitivity toward hypoxia- or desferroxamine-induced injury by modulating adaptive responses in salivary epithelial cells

Hypoxic stress activates various signal transduction pathways including posttranslational modification with the ubiquitin-like SUMO protein (SUMOylation). However, the molecular mechanisms by which SUMOylation regulates hypoxic responses remain unclear. Here, we investigated the ability of rat salivary Pa-4 epithelial cells to resist cell injury elicited by 1% O(2)- or hypoxia-mimetic desferroxamine (DFO)-stimulated SUMOylation processes. By using Pa-4 cells stably transduced with lenti-SUMO-1 and a cell-permeant peptide harboring SUMO-binding motif to interfere with SUMO-dependent protein-protein interactions, we demonstrate that SUMOylation augments cell survival against DFO treatment. This appeared to be partly mediated through attenuation of Protein Kinase C (PKC)-delta activation and caspase-3 cleavage, hallmarks of pro-apoptotic signaling. Intriguingly, DFO-induced phosphorylation of DNA damage marker ataxia-telangiectasia-mutated protein S1981 preceded activation of PKCdelta and caspase-3. Constitutive SUMOylation facilitated 1% O(2)- or DFO-induced nuclear factor kappaB transactivation, possibly via activation of genotoxic signaling cascade. In addition, we observed transient preservation of transepithelial electrical resistance during the early stage of hypoxia (1% O(2)) as well as enhanced transepithelial electrical resistance recovery after prolonged hypoxia in SUMO-1-expressing cell monolayers. In conclusion, our results unveil a previously unrecognized mechanism by which SUMOylation and activation of ataxia-telangiectasia-mutated protein, PKCdelta, caspase-3, and nuclear factor kappaB signaling pathways modulate salivary adaptive responses to stress in cells exposed to either 1% O(2) or DFO.

Association of connexin36 and zonula occludens-1 with zonula occludens-2 and the transcription factor zonula occludens-1-associated nucleic acid-binding protein at neuronal gap junctions in rodent retina

Most gap junctions between neurons in mammalian retina contain abundant connexin36, often in association with the scaffolding protein zonula occludens-1. We now investigate co-association of connexin36, zonula occludens-1, zonula occludens-2 and Y-box transcription factor 3 (zonula occludens-1-associated nucleic acid-binding protein) in mouse and rat retina. By immunoblotting, zonula occludens-1-associated nucleic acid-binding protein and zonula occludens-2 were both detected in retina, and zonula occludens-2 in retina was found to co-immunoprecipitate with connexin36. By immunofluorescence, the four proteins appeared as puncta distributed in the plexiform layers. In the inner plexiform layer, most connexin36-puncta were co-localized with zonula occludens-1, and many were co-localized with zonula occludens-1-associated nucleic acid-binding protein. Moreover, zonula occludens-1-associated nucleic acid-binding protein was often co-localized with zonula occludens-1. Nearly all zonula occludens-2-puncta were positive for connexin36, zonula occludens-1 and zonula occludens-1-associated nucleic acid-binding protein. In the outer plexiform layer, connexin36 was also often co-localized with zonula occludens-1-associated nucleic acid-binding protein. In connexin36 knockout mice, labeling of zonula occludens-1 was slightly reduced in the inner plexiform layer, zonula occludens-1-associated nucleic acid-binding protein was decreased in the outer plexiform layer, and both zonula occludens-1-associated nucleic acid-binding protein and zonula occludens-2 were markedly decreased in the inner sublamina of the inner plexiform layer, whereas zonula occludens-1, zonula occludens-2 and zonula occludens-1-associated nucleic acid-binding protein puncta persisted and remained co-localized in the outer sublamina of the inner plexiform layer. By freeze-fracture replica immunogold labeling, connexin36 was found to be co-localized with zonula occludens-2 within individual neuronal gap junctions. In addition, zonula occludens-1-associated nucleic acid-binding protein was abundant in a portion of ultrastructurally-defined gap junctions throughout the inner plexiform layer, and some of these junctions contained both connexin36 and zonula occludens-1-associated nucleic acid-binding protein. These distinct patterns of connexin36 association with zonula occludens-1, zonula occludens-2 and zonula occludens-1-associated nucleic acid-binding protein in different sublaminae of retina, and differential responses of these proteins to connexin36 gene deletion suggest differential regulatory and scaffolding roles of these gap junction accessory proteins. Further, the persistence of a subpopulation of zonula occludens-1/zonula occludens-2/zonula occludens-1-associated nucleic acid-binding protein co-localized puncta in the outer part of the inner plexiform layer of connexin36 knockout mice suggests close association of these proteins with other structures in retina, possibly including gap junctions composed of an as-yet-unidentified connexin.

Relationship of p53, Bcl-2, Ki-67 index and E-cadherin expression in early invasive breast cancers with comedonecrosis as an accelerated apoptosis

AIMS

To study the relationship between comedonecrosis formation and morphology, apoptosis, and p53, Bcl-2, Ki-67 index and E-cadherin expression in early invasive breast cancer.

EXPERIMENTAL DESIGN

Early invasive breast cancers were first divided into two groups according to the presence (CN+ tumours) or absence (CN- tumours) of comedonecrosis. The histological grade, apoptosis, and expression of E-cadherin, Ki-67, p53 and Bcl-2 in the cancer-affected area, and in normal ducts from the specimen, were then examined.

RESULTS

Less tubule and gland formation was seen in CN+ tumours than in CN- tumours, although the histological grade between the groups was not different. During early comedonecrosis, cells undergo apoptosis and subsequent necrosis. p53 was higher in CN+ tumours than in CN- tumours and normal ducts, whereas Bcl-2 was lower in CN+ tumours than in CN- tumours and normal ducts. Both tumours had higher Ki-67 than in normal ducts, but no difference was evident between the tumours. CN+ tumours had slightly higher E-cadherin than that in CN- tumours, but lower than that in normal ducts. The level of comedonecrosis was positively correlated with p53, but inversely correlated with Bcl-2 in all tumours, and p53 and Bcl-2 were inversely correlated with each other. Furthermore, comedonecrosis and p53 were correlated with Ki-67 in CN+ tumours, and Bcl-2 was correlated with Ki-67 in CN- tumours.

CONCLUSION

Comedonecrosis may be actively regulated through an apoptotic procedure in massive cancers for their survival and progression, and the above proteins may be associated cooperatively in this process. CN+ and CN- tumours may have opposite proliferative systems under the p53-Bcl-2 pathway.

Sodium/potasium ATPase (Na+, K+-ATPase) and ouabain/related cardiac glycosides: a new paradigm for development of anti- breast cancer drugs?

Prolonged exposure to 17beta-estradiol (E2) is a key etiological factor for human breast cancer. The biological effects and carcinogenic effects of E2 are mediated via estrogen receptors (ERs), ERalpha and ERbeta. Anti-estrogens, e.g. tamoxifen, and aromatase inhibitors have been used to treat ER-positive breast cancer. While anti-estrogen therapy is initially successful, a major problem is that most tumors develop resistance and the disease ultimately progresses, pointing to the need of developing alternative drugs targeting to other critical targets in breast cancer cells. We have identified that Na+, K+-ATPase, a plasma membrane ion pump, has unique/valuable properties that could be used as a potentially important target for breast cancer treatment: (a) it is a key player of cell adhesion and is involved in cancer progression; (b) it serves as a versatile signal transducer and is a target for a number of hormones including estrogens and (d) its aberrant expression and activity are implicated in the development and progression of breast cancer. There are several lines of evidence indicating that ouabain and related digitalis (the potent inhibitors of Na+, K+-ATPase) possess potent anti-breast cancer activity. While it is not clear how the suggested anti-cancer activity of these drugs work, several observations point to ouabain and digitalis as being potential ER antagonists. We critically reviewed many lines of evidence and postulated a novel concept that Na+, K+-ATPase in combination with ERs could be important targets of anti-breast cancer drugs. Modulators, e.g. ouabain and related digitalis could be useful to develop valuable anti-breast cancer drugs as both Na+, K+-ATPase inhibitors and ER antagonists.

The zebrafish bcl-2 homologue Nrz controls development during somitogenesis and gastrulation via apoptosis-dependent and -independent mechanisms

Although the role of the b-cell lymphoma (Bcl)-2 family of apoptosis inhibitors is well documented in tumor cells and tissue morphogenesis, their role during the early development of vertebrates is unknown. Here, we characterize Nrz, a new Bcl-2-related inhibitor of apoptosis in zebrafish. Nrz is a mitochondrial protein, antagonizing the death-accelerator Bax. The nrz gene is mainly expressed during gastrulation and somitogenesis. The knockdown of nrz with antisense morpholinos leads to alterations of the somites, correlated with an increase in apoptosis. In addition, earlier during development, in the zebrafish gastrula, nrz knockdown results in an increase of snail-1 expression at the margin and frequent gastrulation arrest at the shield stage, independently of apoptosis. Together these data suggest that Nrz, in addition to its effect on apoptosis, contributes to cell movements during gastrulation by negatively regulating the expression of Snail-1, a transcription factor that controls cell adhesion.

Identification of individual genes altered in squamous cell carcinoma of the vulva

Chromosome rearrangements in squamous cell carcinoma of the vulva (SCV) have indicated common consistent regions of loss and gain. The overall aim of our research was to define and characterize individual genes that underlie the pathogenesis of SCV. Thirteen cell lines from 12 SCV patients were evaluated for loss and gain of 122 genes distributed throughout the genome. Individual genes were analyzed for genetic alterations using a novel genomewide strategy, the multiplex ligation-dependent probe amplification assay. Our candidate gene approach identified several altered loci. Most frequent was the loss of 1 copy of TMSB10, observed in 11 of 12 SCV patients, followed by loss of CTNNB1 and BCL2, which occurred in 7 of 12 patients. Frequent gains/amplifications included CCND1, observed in 8 of 12 patients, and IL12A, in 7 of the 12 patients. Loss and gain of specific genes observed in our study were generally concordant with the results of previous studies of cytogenetics and CGH utilizing the same SCV cell lines. Genetic alterations are hallmarks of tumorigenesis, and there is wide agreement that recurrent altered genomic loci contain genes important for tumor development and progression. Understanding the interplay of cancer genes and the pathways they utilize can lead to the detection of novel molecular targets in the diagnosis, prognosis, and treatment of SCV.

WT1-interacting protein and ZO-1 translocate into podocyte nuclei after puromycin aminonucleoside treatment

Podocyte differentiation is required for normal glomerular filtration barrier function and is regulated by the transcription factor WT1. We identified WT1-interacting protein (WTIP) and hypothesized that it functions as both a scaffold for slit diaphragm proteins and a corepressor of WT1 transcriptional activity by shuttling from cell-cell junctions to the nucleus after injury. Endogenous WTIP colocalizes with zonula occludens-1 (ZO-1) in cultured mouse podocyte adherens junctions. To model podocyte injury in vitro, we incubated differentiated podocytes with puromycin aminonucleoside (PAN; 100 microg/ml) for 24 h, which disassembled cell-cell contacts, rearranged actin cytoskeleton, and caused process retraction. Podocyte synaptopodin expression diminished after PAN treatment, consistent with podocyte dedifferentiation in some human glomerular diseases. To assess podocyte function, we measured albumin flux across differentiated podocytes cultured on collagen-coated Transwell filters. Albumin transit across PAN-treated cells increased to levels observed with undifferentiated podocytes. Consistent with our hypothesis, WTIP, as well as ZO-1, translocated from podocyte adherens junctions to nuclei in PAN-treated cells. Because WTIP is a transcriptional corepressor for WT1, we examined the effect of PAN on expression of retinoblastoma binding protein Rbbp7 (also known as RbAp46), a WT1 target gene expressed in S-shaped bodies during nephrogenesis. Rbbp7 expression in PAN-treated podocytes was reduced compared with untreated cells. In conclusion, WTIP translocates from cell-cell junctions to the nucleus in PAN-treated podocytes. We suggest that WTIP monitors slit diaphragm protein assembly and shuttles into the nucleus after podocyte injury, translating changes in slit diaphragm structure into altered gene expression and a less differentiated phenotype.

Enteropathogenic Escherichia coli EspF is targeted to mitochondria and is required to initiate the mitochondrial death pathway

Enteropathogenic Escherichia coli (EPEC) is a causative agent of infant diarrhoea in developing countries. The EspF protein is the product of the espF gene found on the locus of enterocyte effacement, the key pathogenicity island carried by EPEC and enterohemorrhagic E. coli. EspF is injected from adherent EPEC into host cells via a type III secretion system and was previously shown to induce apoptotic cell death and to be required for disruption of host intestinal barrier function. In this work, we show by immunofluorescence and fractionation studies that EspF is targeted to host mitochondria. The N-terminal region of EspF serves as a mitochondrial import signal and, when expressed within cells, can target hybrid green fluorescent protein to mitochondria. Assessment of mitochondrial membrane potential in infected epithelial cells indicated that EspF plays a role in the mitochondrial membrane permeabilization induced by EPEC infection. Furthermore, EspF was associated with the release of cytochrome c from mitochondria into the cytoplasm and with caspase-9 and caspase-3 cleavage. These findings indicate a role for EspF in initiating the mitochondrial death pathway.

Modeling the effect of deregulated proliferation and apoptosis on the growth dynamics of epithelial cell populations in vitro

We present a three-dimensional individual cell-based, biophysical model to study the effect of normal and malfunctioning growth regulation and control on the spatial-temporal organization of growing cell populations in vitro. The model includes explicit representations of typical epithelial cell growth regulation and control mechanisms, namely 1), a cell-cell contact-mediated form of growth inhibition; 2), a cell-substrate contact-dependent cell-cycle arrest; and 3), a cell-substrate contact-dependent programmed cell death (anoikis). The model cells are characterized by experimentally accessible biomechanical and cell-biological parameters. First, we study by variation of these cell-specific parameters which of them affect the macroscopic morphology and growth kinetics of a cell population within the initial expanding phase. Second, we apply selective knockouts of growth regulation and control mechanisms to investigate how the different mechanisms collectively act together. Thereby our simulation studies cover the growth behavior of epithelial cell populations ranging from undifferentiated stem cell populations via transformed variants up to tumor cell lines in vitro. We find that the cell-specific parameters, and in particular the strength of the cell-substrate anchorage, have a significant impact on the population morphology. Furthermore, they control the efficacy of the growth regulation and control mechanisms, and consequently tune the transition from controlled to uncontrolled growth that is induced by the failures of these mechanisms. Interestingly, however, we find the qualitative and quantitative growth kinetics to be remarkably robust against variations of cell-specific parameters. We compare our simulation results with experimental findings on a number of epithelial and tumor cell populations and suggest in vitro experiments to test our model predictions.

Tunicamycin preserves intercellular junctions, cytoarchitecture, and cell-substratum interactions in ATP-depleted epithelial cells

Pretreatment with the nucleoside antibiotic tunicamycin was found to protect cultured renal epithelial cells in the face of ATP-depletion, in large part by preserving junctional and cellular architecture. Tunicamycin pretreatment of Madin-Darby canine kidney cells not only preserved E-cadherin staining at the plasma membrane, but also inhibited ATP-depletion-mediated E-cadherin degradation. Electron microscopic analysis, together with the preservation of the staining patterns of the tight junction marker ZO-1, the apical/microvillar marker gp135, and basolateral marker Na/K-ATPase suggested that tunicamycin preserved the junctional complex and the polarized epithelial cell phenotype. Tunicamycin pretreatment also prevented reductions in the filamentous actin content of the cells, as well as preserving Golgi architecture. Moreover, a quantitative measure of cell adhesion demonstrated that tunicamycin pretreatment resulted in a fivefold increase in attachment of cells to the substratum (77% versus 16%). Thus, pretreatment with tunicamycin protects polarized epithelial cells from ischemic injury through the preservation of epithelial cell architecture, intercellular junctions, and cell-substratum interactions in the setting of intracellular ATP-depletion.