BBA - Molecular Cell Research (v.1843, #6)
Editorial Board (i).
GPI/AMF inhibition blocks the development of the metastatic phenotype of mature multi-cellular tumor spheroids by Juan Carlos Gallardo-Pérez; Nadia Alejandra Rivero-Segura; Alvaro Marín-Hernández; Rafael Moreno-Sánchez; Sara Rodríguez-Enríquez (1043-1053).
Epithelial–mesenchymal transition (EMT) and cellular invasiveness are two pivotal processes for the development of metastatic tumor phenotypes. The metastatic profile of non-metastatic MCF-7 cells growing as multi-cellular tumor microspheroids (MCTSs) was analyzed by determining the contents of the EMT, invasive and migratory proteins, as well as their migration and invasiveness potential and capacity to secrete active cytokines such as the glucose phosphate isomerase/AMF (GPI/AMF). As for the control, the same analysis was also performed in MCF-7 and MDA-MB-231 (highly metastatic, MDA) monolayer cells, and in stage IIIB and IV human metastatic breast biopsies. The proliferative cell layers (PRL) of mature MCF-7 MCTSs, MDA monolayer cells and metastatic biopsies exhibited increased cellular contents (2–15 times) of EMT (β-catenin, SNAIL), migratory (vimentin, cytokeratin, and fibronectin) and invasive (MMP-1, VEGF) proteins versus MCF-7 monolayer cells, quiescent cell layers of mature MCF-7 MCTS and non-metastatic breast biopsies. The increase in metastatic proteins correlated with substantially elevated cellular abilities for migration (18-times) and invasiveness (13-times) and with the higher level (6-times) of the cytokine GPI/AMF in the extracellular medium of PRL, as compared to MCF-7 monolayer cells. Interestingly, the addition of the GPI/AMF inhibitors erythrose-4-phosphate or 6-phosphogluconate at micromolar doses significantly decreased its extracellular activity (> 80%), with a concomitant diminution in the metastatic protein content and migratory tumor cell capacity, and with no inhibitory effect on tumor lactate production or toxicity on 3T3 mouse fibroblasts. The present findings provide new insights into the discovery of metabolic inhibitors to be used as complementary therapy against metastatic and aggressive tumors.Display Omitted
Keywords: Epithelial–mesenchymal transition; Cell migration; Invasiveness; Metastatic phenotype; Glucose phosphate isomerase/autocrine motility factor; Tumor spheroid;
MTOR-independent induction of autophagy in trabecular meshwork cells subjected to biaxial stretch by Kristine M. Porter; Nallathambi Jeyabalan; Paloma B. Liton (1054-1062).
The trabecular meshwork (TM) is part of a complex tissue that controls the exit of aqueous humor from the anterior chamber of the eye, and therefore helps maintaining intraocular pressure (IOP). Because of variations in IOP with changing pressure gradients and fluid movement, the TM and its contained cells undergo morphological deformations, resulting in distention and stretching. It is therefore essential for TM cells to continuously detect and respond to these mechanical forces and adapt their physiology to maintain proper cellular function and protect against mechanical injury. Here we demonstrate the activation of autophagy, a pro-survival pathway responsible for the degradation of long-lived proteins and organelles, in TM cells when subjected to biaxial static stretch (20% elongation), as well as in high-pressure perfused eyes (30 mm Hg). Morphological and biochemical markers for autophagy found in the stretched cells include elevated LC3-II levels, increased autophagic flux, and the presence of autophagic figures in electron micrographs. Furthermore, our results indicate that the stretch-induced autophagy in TM cells occurs in an MTOR- and BAG3-independent manner. We hypothesize that activation of autophagy is part of the physiological response that allows TM cells to cope and adapt to mechanical forces.
Keywords: Autophagy; Glaucoma; Mechanical stress; Trabecular meshwork; MTOR pathway; Chaperon-assisted autophagy;
Mechanism of endoplasmic reticulum stress-induced vascular endothelial dysfunction by Maria Galán; Modar Kassan; Philip J. Kadowitz; Mohamed Trebak; Souad Belmadani; Khalid Matrougui (1063-1075).
We recently reported that ER stress plays a key role in vascular endothelial dysfunction during hypertension. In this study we aimed to elucidate the mechanisms by which ER stress induction and oxidative stress impair vascular endothelial function.We conducted in vitro studies with primary endothelial cells from coronary arteries stimulated with tunicamycin, 1 μg/mL, in the presence or absence of two ER stress inhibitors: tauroursodeoxycholic acid (Tudca), 500 μg/mL, and 4-phenylbutyric acid (PBA), 5 mM. ER stress induction was assessed by enhanced phosphorylation of PERK and eIF2α, and increased expression of CHOP, ATF6 and Grp78/Bip. The ER stress induction increased p38 MAPK phosphorylation, Nox2/4 mRNA levels and NADPH oxidase activity, and decreased eNOS promoter activity, eNOS expression and phosphorylation, and nitrite levels. Interestingly, the inhibition of p38 MAPK pathway reduced CHOP and Bip expressions enhanced by tunicamycin and restored eNOS promoter activation as well as phosphorylation. To study the effects of ER stress induction in vivo, we used C57BL/6J mice and p47phox−/− mice injected with tunicamycin or saline. The ER stress induction in mice significantly impaired vascular endothelium-dependent and independent relaxation in C57BL/6J mice compared with p47phox−/− mice indicating NADPH oxidase activity as an intermediate for ER stress in vascular endothelial dysfunction.We conclude that chemically induced ER stress leads to a downstream enhancement of p38 MAPK and oxidative stress causing vascular endothelial dysfunction. Our results indicate that inhibition of ER stress could be a novel therapeutic strategy to attenuate vascular dysfunction during cardiovascular diseases.
Keywords: Endoplasmic reticulum; Endothelial dysfunction; MAPKinase; Oxidative stress;
The c10orf10 gene product is a new link between oxidative stress and autophagy by Marcus W. Stepp; Rodney J. Folz; Jerry Yu; Igor N. Zelko (1076-1088).
The human c10orf10 gene product, also known as decidual protein induced by progesterone (DEPP), is known to be differentially regulated in mouse tissues in response to hypoxia and oxidative stress, however its biological function remains unknown. We found that mice lacking extracellular superoxide dismutase (EC-SOD) show attenuated expression of DEPP in response to acute hypoxia. DEPP mRNA levels, as well as the activity of a reporter gene expressed under the control of the DEPP 5′-flanking region, were significantly upregulated in Hep3B and Vero cells overexpressing EC-SOD. Subcellular fractionation and immunofluorescent microscopy indicated that overexpressed DEPP is co-localized with both protein aggregates and aggresomes. Further biochemical characterization indicates that DEPP protein is unstable and undergoes rapid degradation. Inhibition of proteasome activities significantly increases DEPP protein levels in soluble and insoluble cytosolic fractions. Attenuation of autophagosomal activity by 3-methyladenine increases DEPP protein levels while activation of autophagy by rapamycin reduced DEPP protein levels. In addition, ectopic overexpression of DEPP leads to autophagy activation, while silencing of DEPP attenuates autophagy. Collectively, these results indicate that DEPP is a major hypoxia-inducible gene involved in the activation of autophagy and whose expression is regulated by oxidative stress.
Keywords: Extracellular superoxide dismutase; DEPP; Autophagy; Aggresomes; Oxidative stress; Hypoxia;
Structural determinants for the ouabain-stimulated increase in Na–K ATPase activity by Syed J. Khundmiri; Sarah A. Salyer; Brandon Farmer; Natia Qipshidze-Kelm; Rebecca D. Murray; Barbara J. Clark; Zijian Xie; Thomas A. Pressley; Eleanor D. Lederer (1089-1102).
Recent studies suggest that at low concentrations, ouabain increases Na–K ATPase and NHE1 activity and activates the Src signaling cascade in proximal tubule cells. Our laboratory demonstrated that low concentrations of ouabain increase blood pressure in rats. We hypothesize that ouabain-induced increase in blood pressure and Na–K ATPase activity requires NHE1 activity and association. To test this hypothesis we treated rats with ouabain (1 μg kg body wt− 1 day− 1) for 9 days in the presence or absence of the NHE1 inhibitor, zoniporide. Ouabain stimulated a significant increase in blood pressure which was prevented by zoniporide. Using NHE1-expressing Human Kidney cells 2 (HK2), 8 (HK8) and 11 (HK11) and Mouse Kidney cells from Wild type (WT) and NHE1 knock-out mice (SWE) cell lines, we show that ouabain stimulated Na–K ATPase activity and surface expression in a Src-dependent manner in NHE1-expressing cells but not in NHE1-deplete cells. Zoniporide prevented ouabain-induced stimulation of 86Rb uptake in the NHE1-expressing cells. FRET and TIRF microscopy showed that ouabain increased association between GFP-NHE1 and mCherry-Na–K ATPase transfected into NHE1-deficient SWE cells. Mutational analysis demonstrated that the caveolin binding motif (CBM) of Na–K ATPase α1 is required for translocation of both Na–K ATPase α1 and NHE1 to the basolateral membrane. Mutations in activity or scaffold domains of NHE1 resulted in loss of ouabain-mediated regulation of Na–K ATPase. These results support that NHE1 is required for the ouabain-induced increase in blood pressure, and that the caveolin binding motif of Na–K ATPase α1 as well as the activity and scaffolding domains of NHE1 are required for their functional association.
Keywords: Ouabain; Blood pressure; Na–K ATPase; NHE1; Src kinase; TIRF microscopy;
Fructose bisphosphate aldolase is involved in the control of RNA polymerase III-directed transcription by Małgorzata Cieśla; Jolanta Mierzejewska; Małgorzata Adamczyk; Ann-Kristin Östlund Farrants; Magdalena Boguta (1103-1110).
Yeast Fba1 (fructose 1,6-bisphosphate aldolase) is a glycolytic enzyme essential for viability. The overproduction of Fba1 enables overcoming of a severe growth defect caused by a missense mutation rpc128-1007 in a gene encoding the C128 protein, the second largest subunit of the RNA polymerase III complex. The suppression of the growth phenotype by Fba1 is accompanied by enhanced de novo tRNA transcription in rpc128-1007 cells. We inactivated residues critical for the catalytic activity of Fba1. Overproduction of inactive aldolase still suppressed the rpc128-1007 phenotype, indicating that the function of this glycolytic enzyme in RNA polymerase III transcription is independent of its catalytic activity.Yeast Fba1 was determined to interact with the RNA polymerase III complex by coimmunoprecipitation. Additionally, a role of aldolase in control of tRNA transcription was confirmed by ChIP experiments. The results indicate a novel direct relationship between RNA polymerase III transcription and aldolase.
Keywords: Aldolase; tRNA transcription; Pol III; Yeast;
ALK1 heterozygosity increases extracellular matrix protein expression, proliferation and migration in fibroblasts by José M. Muñoz-Félix; Nuria Perretta-Tejedor; Nélida Eleno; José M. López-Novoa; Carlos Martínez-Salgado (1111-1122).
Fibrosis is a pathological situation in which excessive amounts of extracellular matrix (ECM) are deposited in the tissue. Myofibroblasts play a crucial role in the development and progress of fibrosis as they actively synthesize ECM components such as collagen I, fibronectin and connective tissue growth factor (CTGF) and cause organ fibrosis. Transforming growth factor beta 1 (TGF-β1) plays a major role in tissue fibrosis. Activin receptor-like kinase 1 (ALK1) is a type I receptor of TGF-β1 with an important role in angiogenesis whose function in cellular biology and TGF-β signaling is well known in endothelial cells, but its role in fibroblast biology and its contribution to fibrosis is poorly studied. We have recently demonstrated that ALK1 regulates ECM protein expression in a mouse model of obstructive nephropathy. Our aim was to evaluate the role of ALK1 in several processes involved in fibrosis such as ECM protein expression, proliferation and migration in ALK1+/+ and ALK1+/− mouse embryonic fibroblasts (MEFs) after TGF-β1 stimulations and inhibitors. ALK1 heterozygous MEFs show increased expression of ECM proteins (collagen I, fibronectin and CTGF/CCN2), cell proliferation and migration due to an alteration of TGF-β/Smad signaling. ALK1 heterozygous disruption shows an increase of Smad2 and Smad3 phosphorylation that explains the increases in CTGF/CCN2, fibronectin and collagen I, proliferation and cell motility observed in these cells. Therefore, we suggest that ALK1 plays an important role in the regulation of ECM protein expression, proliferation and migration.Display Omitted
Keywords: ALK1; Fibrosis; Extracellular matrix; Smads; Proliferation; Migration;
Glucagon induces translocation of glucokinase from the cytoplasm to the nucleus of hepatocytes by transfer between 6-phosphofructo 2-kinase/fructose 2,6-bisphosphatase-2 and the glucokinase regulatory protein by Kirsty S. Cullen; Ziad H. Al-Oanzi; Finbarr P.M. O'Harte; Loranne Agius; Catherine Arden (1123-1134).
Glucokinase activity is a major determinant of hepatic glucose metabolism and blood glucose homeostasis. Liver glucokinase activity is regulated acutely by adaptive translocation between the nucleus and the cytoplasm through binding and dissociation from its regulatory protein (GKRP) in the nucleus. Whilst the effect of glucose on this mechanism is well established, the role of hormones in regulating glucokinase location and its interaction with binding proteins remains unsettled. Here we show that treatment of rat hepatocytes with 25 mM glucose caused decreased binding of glucokinase to GKRP, translocation from the nucleus and increased binding to 6-phosphofructo 2-kinase/fructose 2,6 bisphosphatase-2 (PFK2/FBPase2) in the cytoplasm. Glucagon caused dissociation of glucokinase from PFK2/FBPase2, concomitant with phosphorylation of PFK2/FBPase2 on Ser-32, uptake of glucokinase into the nucleus and increased interaction with GKRP. Two novel glucagon receptor antagonists attenuated the action of glucagon. This establishes an unequivocal role for hormonal control of glucokinase translocation. Given that glucagon excess contributes to the pathogenesis of diabetes, glucagon may play a role in the defect in glucokinase translocation and activity evident in animal models and human diabetes.
Keywords: Glucokinase; Glucokinase regulatory protein; 6-phosphofructo 2-kinase/fructose 2,6 bisphosphatase-2; Hepatocyte; Glucagon;
Phosphorylation of p300 increases its protein degradation to enhance the lung cancer progression by Shao-An Wang; Chia-Yang Hung; Jian-Ying Chuang; Wen-Chang Chang; Tsung-I Hsu; Jan-Jong Hung (1135-1149).
p300 is a transcription cofactor for a number of nuclear proteins. Most studies of p300 have focused on the regulation of its function, which primarily includes its role as a transcription co-factor for a number of nuclear proteins. In this study, we found that p300 was highly phosphorylated and its level was decreased during mitosis and tumorigenesis. In vitro and in vivo experiments aimed showed that cyclin-dependent kinase 1 (CDK1) and ERK1/2 phosphorylated p300 on Ser1038 and Ser2039. Mutations of Ser1038 and Ser2039 increased p300 protein stability and levels. Inhibition of p300 degradation by blocking its phosphorylation decreased the proliferation and metastasis activity of lung cancer cells, indicating that p300 acts as a tumor suppressor in lung cancer tumorigenesis. Investigation of the molecular mechanism showed that blocking p300 phosphorylation disrupted chromatin condensation and the increased the acetylation of histone H3. Analysis of cell cycle progression in HA-p300-S2A-expressing cells by flow cytometry showed that the p300 mutants arrested the cells at S-phase or delayed the mitotic entry and exit. The expression of several important oncogenes, MMP-9, vimentin, β-catenin, N-cadherin and c-myc, was negatively regulated by p300. In conclusion, during lung tumorigenesis, a phosphorylation-mediated decrease in p300 level enhanced oncogene expression during interphase and decreased histone H3 acetylation during mitosis, which promoted lung cancer progression.
Keywords: p300; Phosphorylation; Protein stability; CDK1; Mitosis; Metastasis;
Loss of proteostasis induced by amyloid beta peptide in brain endothelial cells by Ana Catarina Fonseca; Catarina R. Oliveira; Cláudia F. Pereira; Sandra M. Cardoso (1150-1161).
Abnormal accumulation of amyloid-β (Aβ) peptide in the brain is a pathological hallmark of Alzheimer's disease (AD). In addition to neurotoxic effects, Aβ also damages brain endothelial cells (ECs) and may thus contribute to the degeneration of cerebral vasculature, which has been proposed as an early pathogenic event in the course of AD and is able to trigger and/or potentiate the neurodegenerative process and cognitive decline. However, the mechanisms underlying Aβ-induced endothelial dysfunction are not completely understood. Here we hypothesized that Aβ impairs protein quality control mechanisms both in the secretory pathway and in the cytosol in brain ECs, leading cells to death. In rat brain RBE4 cells, we demonstrated that Aβ1–40 induces the failure of the ER stress-adaptive unfolded protein response (UPR), deregulates the ubiquitin–proteasome system (UPS) decreasing overall proteasome activity with accumulation of ubiquitinated proteins and impairs the autophagic protein degradation pathway due to failure in the autophagic flux, which culminates in cell demise. In conclusion, Aβ deregulates proteostasis in brain ECs and, as a consequence, these cells die by apoptosis.
Keywords: Alzheimer's disease; Amyloid-beta; Autophagy; Endoplasmic reticulum stress; Ubiquitin–proteasome system; Apoptosis;
Modulation of calcium-induced cell death in human neural stem cells by the novel peptidylarginine deiminase–AIF pathway by Kin Pong U; Venkataraman Subramanian; Antony P. Nicholas; Paul R. Thompson; Patrizia Ferretti (1162-1171).
PADs (peptidylarginine deiminases) are calcium-dependent enzymes that change protein-bound arginine to citrulline (citrullination/deimination) affecting protein conformation and function. PAD up-regulation following chick spinal cord injury has been linked to extensive tissue damage and loss of regenerative capability. Having found that human neural stem cells (hNSCs) expressed PAD2 and PAD3, we studied PAD function in these cells and investigated PAD3 as a potential target for neuroprotection by mimicking calcium-induced secondary injury responses. We show that PAD3, rather than PAD2 is a modulator of cell growth/death and that PAD activity is not associated with caspase-3-dependent cell death, but is required for AIF (apoptosis inducing factor)-mediated apoptosis. PAD inhibition prevents association of PAD3 with AIF and AIF cleavage required for its translocation to the nucleus. Finally, PAD inhibition also hinders calcium-induced cytoskeleton disassembly and association of PAD3 with vimentin, that we show to be associated also with AIF; together this suggests that PAD-dependent cytoskeleton disassembly may play a role in AIF translocation to the nucleus. This is the first study highlighting a role of PAD activity in balancing hNSC survival/death, identifying PAD3 as an important upstream regulator of calcium-induced apoptosis, which could be targeted to reduce neural loss, and shedding light on the mechanisms involved.Display Omitted
Keywords: Apoptosis inducing factor (AIF); Cell death; Citrullination–deimination; Human neural stem cell; Peptidylarginine deiminase (PAD, PADI); Vimentin;
Non-classical testosterone signaling is mediated by a G-protein-coupled receptor interacting with Gnα11 by Mazen Shihan; Ahmed Bulldan; Georgios Scheiner-Bobis (1172-1181).
Testosterone is known to mediate its effects by two different mechanisms of action. In the so-called “classical” pathway testosterone binds to cytosolic androgen receptors (AR), which essentially function as ligand-activated transcription factors. Once activated, these receptors bind to DNA and activate the expression of target genes. In the “non-classical” pathway, the steroid hormone binds to receptors associated with the plasma membrane and induces signaling cascades mediated through activation of Erk1/2. The precise nature of the membrane-associated AR, however, remains controversial. Although some assume that the membrane and cytosolic AR are identical, others propose that the AR of the membrane is a G-protein-coupled receptor (GPCR). To evaluate these two possibilities we first searched for testosterone-induced signaling cascades in the spermatogenic cell line GC-2. Testosterone was found to cause phosphorylation (activation) of Erk1/2, CREB, and ATF-1, consistent with its non-classical mechanism of action. Silencing of AR expression by means of siRNA did not influence testosterone-induced activation of Erk1/2, CREB, or ATF-1, indicating that this pathway is not activated by the classical cytosolic/nuclear AR. In contrast, when the expression of the G-protein Gnα11 is suppressed, the activation of these signaling molecules is abolished, suggesting that these responses are elicited through a membrane-bound GPCR. The results presented here and the identification of the testosterone-specific GPCR in future investigations will help to reveal and characterize new testosterone-mediated mechanisms associated not only with fertility and reproduction but perhaps also with other physiological processes.
Keywords: Testosterone; Signaling; Erk1/2; CREB; ATF-1; Androgen receptor; GPCR; Gnα11; Spermatogenic cell;
Minimal impact electro-injection of cells undergoing dynamic shape change reveals calpain activation by Kimberley J. Lewis; Benjamin Masterman; Iraj Laffafian; Sharon Dewitt; Jennie S. Campbell; Maurice B. Hallett (1182-1187).
The ability of neutrophils to rapidly change shape underlies their physiological functions of phagocytosis and spreading. A major problem in establishing the mechanism is that conventional microinjection of substances and indicators interferes with this dynamic cell behaviour. Here we show that electroinjection, a “no-touch” point-and-shoot means of introducing material into the cell, is sufficiently gentle to allow neutrophils to be injected whilst undergoing chemokinesis and spreading without disturbing cell shape change behaviour. Using this approach, a fluorogenic calpain-1 selective peptide substrate was introduced into the cytosol of individual neutrophils undergoing shape changes. These data showed that (i) physiologically elevated cytosolic Ca2 + concentrations were sufficient to trigger calpain-1 activation, blockade of Ca2 + influx preventing calpain activation and (ii) calpain-1 activity was elevated in spreading neutrophil. These findings provide the first direct demonstration of a physiological role for Ca2 + elevation in calpain-1 activation and rapid cell spreading. Electroinjection of cells undergoing dynamic shape changes thus opens new avenues of investigation for defining the molecular mechanism underlying dynamic cell shape changes.
Keywords: Cell spreading; Chemokinesis; Cytosolic Ca2 +; Neutrophil; Phagocytosis;
Reversible acetylation of Lin28 mediated by PCAF and SIRT1 by Ling-xia Wang; Jing Wang; Ting-ting Qu; Ye Zhang; Yu-fei Shen (1188-1195).
Lin28 is a small RNA-binding protein that plays an important role in regulating developmental timing, stem cell reprogramming, and oncogenesis. However, the significance of the effect of post-translational modifications on Lin28 activity is not fully understood. In this study, we demonstrated that PCAF directly interacted with and acetylated Lin28. We also showed that the acetylation of Lin28 can be specifically reversed by the deacetylase SIRT1. These findings suggest that the PCAF/SIRT1 balance plays an important role in regulating Lin28 activity. Furthermore, we found that the cold shock domain of Lin28 is the major target of PCAF-mediated acetylation, which leads to a severe reduction in the Lin28 protein levels and an increase in the level of mature let-7a. This study provides the first demonstration that post-translational modification regulates Lin28 activity during let-7a biogenesis and sheds light on the regulation of Lin28 in ES cells and carcinogenesis.
Keywords: Lin28; PCAF; SIRT1; Acetylation; Protein stability;
Specificity protein 4 (Sp4) regulates the transcription of AMPA receptor subunit GluA2 (Gria2) by Anusha Priya; Kaid Johar; Bindu Nair; Margaret T.T. Wong-Riley (1196-1206).
The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are important glutamatergic receptors mediating fast excitatory synaptic transmission in the brain. The regulation of the four subunits of AMPA receptors, GluA1-4, is poorly understood. Excitatory synaptic transmission is highly energy-demanding, and this energy is derived mainly from the oxidative pathway. Recently, we found that specificity factor regulates all subunits of cytochrome c oxidase (COX), a critical energy-generating enzyme. COX is also regulated by nuclear respiratory factor 1 (NRF-1), which transcriptionally controls the Gria2 (GluA2) gene of AMPA receptors. The goal of the present study was to test our hypothesis that Sp-factors (Sp1, Sp3, and/or Sp4) also regulate AMPA subunit genes. If so, we wish to determine if Sp-factors and NRF-1 function via a complementary, concurrent and parallel, or a combination of complementary and concurrent/parallel mechanism. By means of multiple approaches, including electrophoretic mobility shift and supershift assays, chromatin immunoprecipitation, promoter mutations, real-time quantitative PCR, and western blot analysis, we found that Sp4, but not Sp1 or Sp3, regulates the Gria2, but not Gria1, 3, or 4, subunit gene of the AMPA receptor in a concurrent and parallel manner with NRF-1. Thus, Sp4 and NRF-1 both mediate the tight coupling between neuronal activity and energy metabolism at the transcriptional level.
Keywords: AMPA receptor; Gene regulation; GluA2; Sp4; Specificity protein 4; Transcription factor;
The plant decapeptide OSIP108 prevents copper-induced apoptosis in yeast and human cells by Pieter Spincemaille; Gursimran Chandhok; Benjamin Newcomb; Jef Verbeek; Kim Vriens; Andree Zibert; Hartmut Schmidt; Yusuf A. Hannun; Jos van Pelt; David Cassiman; Bruno P.A. Cammue; Karin Thevissen (1207-1215).
We previously identified the Arabidopsis thaliana-derived decapeptide OSIP108, which increases tolerance of plants and yeast cells to oxidative stress. As excess copper (Cu) is known to induce oxidative stress and apoptosis, and is characteristic for the human pathology Wilson disease, we investigated the effect of OSIP108 on Cu-induced toxicity in yeast. We found that OSIP108 increased yeast viability in the presence of toxic Cu concentrations, and decreased the prevalence of Cu-induced apoptotic markers. Next, we translated these results to the human hepatoma HepG2 cell line, demonstrating anti-apoptotic activity of OSIP108 in this cell line. In addition, we found that OSIP108 did not affect intracellular Cu levels in HepG2 cells, but preserved HepG2 mitochondrial ultrastructure. As Cu is known to induce acid sphingomyelinase activity of HepG2 cells, we performed a sphingolipidomic analysis of OSIP108-treated HepG2 cells. We demonstrated that OSIP108 decreased the levels of several sphingoid bases and ceramide species. Moreover, exogenous addition of the sphingoid base dihydrosphingosine abolished the protective effect of OSIP108 against Cu-induced cell death in yeast. These findings indicate the potential of OSIP108 to prevent Cu-induced apoptosis, possibly via its effects on sphingolipid homeostasis.
Keywords: OSIP108; Copper; Apoptosis; Ceramide; Saccharomyces cerevisiae;
The TMEFF2 tumor suppressor modulates integrin expression, RhoA activation and migration of prostate cancer cells by Xiaofei Chen; Joshua M. Corbin; Greg J. Tipton; Li V. Yang; Adam S. Asch; Maria J. Ruiz-Echevarría (1216-1224).
Cell adhesion and migration play important roles in physiological and pathological states, including embryonic development and cancer invasion and metastasis. The type I transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is expressed mainly in brain and prostate and its expression is deregulated in prostate cancer. We have previously shown that TMEFF2 can function as a tumor suppressor by inhibiting cell migration and invasion of prostate cells. However, the molecular mechanisms involved in this inhibition are not clear. In this study we demonstrate that TMEFF2 affects cell adhesion and migration of prostate cancer cells and that this effect correlates with changes in integrin expression and RhoA activation. Deletion of a 13 basic-rich amino acid region in the cytoplasmic domain of TMEFF2 prevented these effects. Overexpression of TMEFF2 reduced cell attachment and migration on vitronectin and caused a concomitant decrease in RhoA activation, stress fiber formation and expression of αv, β1 and β3 integrin subunits. Conversely, TMEFF2 interference in 22Rv1 prostate cancer cells resulted in an increased integrin expression. Results obtained with a double TRAMP/TMEFF2 transgenic mouse also indicated that TMEFF2 expression reduced integrin expression in the mouse prostate. In summary, the data presented here indicate an important role of TMEFF2 in regulating cell adhesion and migration that involves integrin signaling and is mediated by its cytoplasmic domain.
Keywords: TMEFF2; Integrin; Cell migration; Cell attachment; Prostate cancer;
Peroxisome proliferator-activated receptor γ-mediated induction of microRNA-145 opposes tumor phenotype in colorectal cancer by Anna Panza; Carolina Votino; Annamaria Gentile; Maria Rosaria Valvano; Tommaso Colangelo; Massimo Pancione; Lucia Micale; Giuseppe Merla; Angelo Andriulli; Lina Sabatino; Manlio Vinciguerra; Clelia Prattichizzo; Gianluigi Mazzoccoli; Vittorio Colantuoni; Ada Piepoli (1225-1236).
MicroRNAs (miRNAs) regulate diverse biological processes by inhibiting translation or inducing degradation of target mRNAs. miR-145 is a candidate tumor suppressor in colorectal carcinoma (CRC). Colorectal carcinogenesis involves deregulation of cellular processes controlled by a number of intertwined chief transcription factors, such as PPARγ and SOX9. Since PPAR family members are able to modulate complex miRNAs networks, we hypothesized a role of miRNA-145 in the interaction between PPARγ and SOX9 in colorectal carcinogenesis.To address this issue, we evaluated gene expression in tissue specimens of CRC patients and we took advantage of invitro models represented by CRC derived cell lines (CaCo2, SW480, HCT116, and HT-29), employing PPARγ activation and/or miRNA-145 ectopic overexpression to analyze how their interplay impact the expression of SOX9 and the development of a malignant phenotype.PPARγ regulates the expression of miR-145 by directly binding to a PPAR response element (PPRE) in its promoter at − 1207/− 1194 bp from the transcription start site. The binding is essential for miR-145 upregulation by PPARγ upon rosiglitazone treatment. Ectopic expression of miR-145, in turn, regulates SOX9 expression through the binding to specific seed motifs. The PPARγ-miR-145-SOX9 axis overarches cell cycle progression, invasiveness and differentiation of CRC derived cell lines.Together, these results suggest that miR-145 is a novel target of PPARγ, acts as a tumor suppressor in CRC cell lines and is a key regulator of intestinal cell differentiation by directly targeting SOX9, a marker of undifferentiated progenitors in the colonic crypts.
Keywords: miR-145; PPARγ; SOX9; Colorectal cancer; Invasiveness;