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1.  Mutations of C19orf12, coding for a transmembrane glycine zipper containing mitochondrial protein, cause mis-localization of the protein, inability to respond to oxidative stress and increased mitochondrial Ca2+ 
Frontiers in Genetics  2015;6:185.
Mutations in C19orf12 have been identified in patients affected by Neurodegeneration with Brain Iron Accumulation (NBIA), a clinical entity characterized by iron accumulation in the basal ganglia. By using western blot analysis with specific antibody and confocal studies, we showed that wild-type C19orf12 protein was not exclusively present in mitochondria, but also in the Endoplasmic Reticulum (ER) and MAM (Mitochondria Associated Membrane), while mutant C19orf12 variants presented a different localization. Moreover, after induction of oxidative stress, a GFP-tagged C19orf12 wild-type protein was able to relocate to the cytosol. On the contrary, mutant isoforms were not able to respond to oxidative stress. High mitochondrial calcium concentration and increased H2O2 induced apoptosis were found in fibroblasts derived from one patient as compared to controls. C19orf12 protein is a 17 kDa mitochondrial membrane-associated protein whose function is still unknown. Our in silico investigation suggests that, the glycine zipper motifs of C19orf12 form helical regions spanning the membrane. The N- and C-terminal regions with respect to the transmembrane portion, on the contrary, are predicted to rearrange in a structural domain, which is homologs to the N-terminal regulatory domain of the magnesium transporter MgtE, suggesting that C19orf12 may act as a regulatory protein for human MgtE transporters. The mutations here described affect respectively one glycine residue of the glycine zipper motifs, which are involved in dimerization of transmembrane helices and predicted to impair the correct localization of the protein into the membranes, and one residue present in the regulatory domain, which is important for protein-protein interaction.
PMCID: PMC4470416  PMID: 26136767
mitochondria; oxidative stress; neurodegeneration with brain iron accumulation; endoplasmic reticulum-mitochondria associated membranes (ER-MAM); molecular modeling; simulation
2.  Study of PTEN subcellular localization 
Methods (San Diego, Calif.)  2015;77-78:92-103.
The tumor suppressor PTEN is a key regulator of a plethora of cellular processes that are crucial in cancer development. Through its lipid phosphatase activity PTEN suppresses the PI3K/AKT pathway to govern cell proliferation, growth, migration, energy metabolism and death. The repertoire of roles fulfilled by PTEN has recently been expanded to include crucial functions in the nucleus, where it favors genomic stability and restrains cell cycle progression, as well as protein phosphatase dependent activity at the endoplasmic reticulum (ER) and mitochondria-associated membranes (MAMs), where PTEN interacts with the inositol 1,4,5-trisphosphate receptors (IP3Rs) and regulates Ca2+ release from the ER and sensitivity to apoptosis. Indeed, PTEN is present in definite subcellular locations where it performs distinct functions acting on specific effectors. In this review, we summarize recent advantages in methods to study PTEN subcellular localization and the distinct biological functions of PTEN in different cellular compartments. A deeper understanding of PTEN’s compartmentalized-functions will guide the rational design of novel therapies.
PMCID: PMC4396696  PMID: 25312582
AKAP, A kinase anchoring protein; ArA, arachidonic acid; Ca2+, calcium; CLS, cytoplasmic localization signal; Co-IP, co-immunoprecipitation; COX, cytochrome c oxidase; ER, endoplasmic reticulum; ER-RFP, endoplasmic reticulum-targeted red fluorescent protein; FRAP, fluorescence recovery after photobleaching; GFP, green fluorescent protein; HAUSP, herpesvirus-associated ubiquitin-specific protease; HK-I, hexokinase I; IF, immunofluorescence; IP3R, inositol 1,4,5-trisphosphate receptor; IPC, ischemic preconditioning; I/R, ischemia–reperfusion; MAMs, mitochondria-associated membranes; mtDsRED, mitochondria-targeted red fluorescent protein; Ndfip1, NEDD4 family-interacting protein 1; NEDD4, neural precursor cell expressed developmentally downregulated-4; NES, nuclear export signal; NLS, nuclear localization signal; OMM, outer mitochondrial membrane; PAM, plasma membrane–associated membranes; PIP2, phosphatidylinositol-4,5-bisphosphate; PIP3, phosphatidylinositol-3,4,5-trisphosphate; PK, proteinase K; PM, plasma membrane; PML, promyelocytic leukemia; PTEN, phosphatase and tensin homolog deleted on chromosome 10; RFP, red fluorescent protein; ROS, reactive oxygen species; STS, staurosporine; YFP, yellow fluorescent protein; VDAC, voltage-dependent anion channel; Mitochondria; Endoplasmic reticulum; Cancer; Calcium; Cell death; Apoptosis
3.  Cancer-associated PTEN mutants act in a dominant negative manner to suppress PTEN protein function 
Cell  2014;157(3):595-610.
PTEN dysfunction plays a crucial role in the pathogenesis of hereditary and sporadic cancers. Here we show that PTEN homo-dimerizes, and in this active conformation exerts lipid phosphatase activity on PtdIns(3,4,5)P3. We demonstrate that catalytically inactive cancer-associated PTEN mutants hetero-dimerize with wild-type PTEN and constrain its phosphatase activity in a dominant-negative manner. To study the consequences of homo- and hetero-dimerization of wild-type and mutant PTEN in vivo, we generated Pten knock-in mice harboring two cancer-associated PTEN mutations (PtenC124S and PtenG129E). Heterozygous PtenC124S/+ and PtenG129E/+ cells and tissues exhibit increased sensitivity to PI3-K/Akt activation compared to wild-type and Pten+/- counterparts, while this difference is no longer apparent between PtenC124S/- and Pten-/- cells. Notably, PtenKI mice are more tumor-prone and display features reminiscent of complete Pten loss. Our findings reveal that PTEN loss and PTEN mutations are not synonymous, and define a new working model for the function and regulation of PTEN.
PMCID: PMC4098792  PMID: 24766807
4.  A Unified Nomenclature and Amino Acid Numbering for Human PTEN 
Science signaling  2014;7(332):pe15.
The tumor suppressor PTEN is a major brake for cell transformation, mainly due to its phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] phosphatase activity that directly counteracts the oncogenicity of phosphoinositide 3-kinase (PI3K). PTEN mutations are frequent in tumors and in the germ line of patients with tumor predisposition or with neurological or cognitive disorders, which makes the PTEN gene and protein a major focus of interest in current biomedical research. After almost two decades of intense investigation on the 403-residue-long PTEN protein, a previously uncharacterized form of PTEN has been discovered that contains 173 amino-terminal extra amino acids, as a result of an alternate translation initiation site. To facilitate research in the field and to avoid ambiguities in the naming and identification of PTEN amino acids from publications and databases, we propose here a unifying nomenclature and amino acid numbering for this longer form of PTEN.
PMCID: PMC4367864  PMID: 24985344
5.  Intravital imaging reveals p53-dependent cancer cell death induced by phototherapy via calcium signaling 
Oncotarget  2014;6(3):1435-1445.
One challenge in biology is signal transduction monitoring in a physiological context. Intravital imaging techniques are revolutionizing our understanding of tumor and host cell behaviors in the tumor environment. However, these deep tissue imaging techniques have not yet been adopted to investigate the second messenger calcium (Ca2+). In the present study, we established conditions that allow the in vivo detection of Ca2+ signaling in three-dimensional tumor masses in mouse models. By combining intravital imaging and a skinfold chamber technique, we determined the ability of photodynamic cancer therapy to induce an increase in intracellular Ca2+ concentrations and, consequently, an increase in cell death in a p53-dependent pathway.
PMCID: PMC4359305  PMID: 25544762
Calcium (Ca2+); cell death; apoptosis; TRP53 (p53); mitochondria
6.  Mitochondrial Ca2+ Remodeling is a Prime Factor in Oncogenic Behavior 
Frontiers in Oncology  2015;5:143.
Cancer is sustained by defects in the mechanisms underlying cell proliferation, mitochondrial metabolism, and cell death. Mitochondrial Ca2+ ions are central to all these processes, serving as signaling molecules with specific spatial localization, magnitude, and temporal characteristics. Mutations in mtDNA, aberrant expression and/or regulation of Ca2+-handling/transport proteins and abnormal Ca2+-dependent relationships among the cytosol, endoplasmic reticulum, and mitochondria can cause the deregulation of mitochondrial Ca2+-dependent pathways that are related to these processes, thus determining oncogenic behavior. In this review, we propose that mitochondrial Ca2+ remodeling plays a pivotal role in shaping the oncogenic signaling cascade, which is a required step for cancer formation and maintenance. We will describe recent studies that highlight the importance of mitochondria in inducing pivotal “cancer hallmarks” and discuss possible tools to manipulate mitochondrial Ca2+ to modulate cancer survival.
PMCID: PMC4479728  PMID: 26161362
mitochondrial dysfunction; cancer; Ca2+ signaling; oncogene and oncosuppressor
7.  Selective Augmentation of Stem Cell Populations in Structural Fat Grafts for Maxillofacial Surgery 
PLoS ONE  2014;9(11):e110796.
Structural fat grafting utilizes the centrifugation of liposuction aspirates to create a graded density of adipose tissue. This study was performed to qualitatively investigate the effects of centrifugation on stem cells present in adipose tissue. Liposuction aspirates were obtained from healthy donors and either not centrifuged or centrifuged at 1,800 rpm for 3 minutes. The obtained fat volumes were divided into three layers and then analyzed. The results demonstrate that centrifugation induces a different distribution of stem cells in the three layers. The high-density layer displays the highest expression of mesenchymal stem cell and endothelial markers. The low-density layer exhibits an enrichment of multipotent stem cells. We conclude that appropriate centrifugation concentrates stem cells. This finding may influence the clinical practice of liposuction aspirate centrifugation and enhance graft uptake.
PMCID: PMC4222876  PMID: 25375632
8.  Differential expression of microRNA501-5p affects the aggressiveness of clear cell renal carcinoma 
FEBS Open Bio  2014;4:952-965.
•Low expression of miR501-5p correlates with good prognosis for patients with ccRCC.•miRNA501-5p downregulation stimulates apoptosis by p53 activation.•miR501-5p upregulation promotes cell proliferation and survival.•Increased cell growth occurs by activation of mTOR kinase and MDM2 expression.•This miRNA modulates apoptosis/cell growth, making it a prognostic biomarker for ccRCC.
Renal cell carcinoma is a common neoplasia of the adult kidney that accounts for about 3% of adult malignancies. Clear cell renal carcinoma is the most frequent subtype of kidney cancer and 20–40% of patients develop metastases. The absence of appropriate biomarkers complicates diagnosis and prognosis of this disease. In this regard, small noncoding RNAs (microRNAs), which are mutated in several neoplastic diseases including kidney carcinoma, may be optimal candidates as biomarkers for diagnosis and prognosis of this kind of cancer. Here we show that patients with clear cell kidney carcinoma that express low levels of miR501-5p exhibited a good prognosis compared with patients with unchanged or high levels of this microRNA. Consistently, in kidney carcinoma cells the downregulation of miR501-5p induced an increased caspase-3 activity, p53 expression as well as decreased mTOR activation, leading to stimulation of the apoptotic pathway. Conversely, miR501-5p upregulation enhanced the activity of mTOR and promoted both cell proliferation and survival. These biological processes occurred through p53 inactivation by proteasome degradation in a mechanism involving MDM2-mediated p53 ubiquitination. Our results support a role for miR501-5p in balancing apoptosis and cell survival in clear cell renal carcinoma. In particular, the downregulation of microRNA501-5p promotes a good prognosis, while its upregulation contributes to a poor prognosis, in particular, if associated with p53 and MDM2 overexpression and mTOR activation. Thus, the expression of miR501-5p is a possible biomarker for the prognosis of clear cell renal carcinoma.
PMCID: PMC4241533  PMID: 25426415
ccRCC, clear cell renal cell carcinoma; MDM2, mouse double minute 2 homolog; mTOR, mammalian target of rapamycin; pRCC, papillary renal cell carcinoma; MicroRNA501-5p; mTOR signaling; p53; Apoptosis; Cell survival
9.  PLCB3 is a key modulator of IL-8 expression in cystic fibrosis bronchial epithelial cells 
Respiratory insufficiency is the major cause of morbidity and mortality in patients affected by cystic fibrosis. An excessive neutrophilic inflammation, mainly orchestrated by the release of IL-8 from bronchial epithelial cells and amplified by chronic bacterial infection with Pseudomonas aeruginosa, leads to progressive tissue destruction. The anti-inflammatory drugs presently utilized in cystic fibrosis patients have several limitations, indicating the need for identifying novel molecular targets. To address this issue, we preliminarily studied the association of 721 single-nucleotide polymorphisms from 135 genes potentially involved in signal transduction implicated in neutrophil recruitment in a cohort of F508del homozygous cystic fibrosis patients with either severe or mild progression of lung disease. The top ranking association was found for a nonsynonymous polymorphism of the phospholipase C beta 3 (PLCB3) gene. Studies in bronchial epithelial cells exposed to P.aeruginosa revealed that PLCB3 is implicated in extra cellular nucleotide–dependent intracellular calcium signaling, leading to activation of the protein kinase C alpha and beta and of the nuclear transcription factor NF-κB p65. The pro-inflammatory pathway regulated by PLCB3 acts by potentiating the Toll-like Receptors’ signaling cascade and represents an interesting molecular target to attenuate the excessive recruitment of neutrophils without completely abolishing the inflammatory response.
PMCID: PMC4166552  PMID: 21411730
10.  STAT3 Activities and Energy Metabolism: Dangerous Liaisons 
Cancers  2014;6(3):1579-1596.
STAT3 mediates cytokine and growth factor receptor signalling, becoming transcriptionally active upon tyrosine 705 phosphorylation (Y-P). Constitutively Y-P STAT3 is observed in many tumors that become addicted to its activity, and STAT3 transcriptional activation is required for tumor transformation downstream of several oncogenes. We have recently demonstrated that constitutively active STAT3 drives a metabolic switch towards aerobic glycolysis through the transcriptional induction of Hif-1α and the down-regulation of mitochondrial activity, in both MEF cells expressing constitutively active STAT3 (Stat3C/C) and STAT3-addicted tumor cells. This novel metabolic function is likely involved in mediating pre-oncogenic features in the primary Stat3C/C MEFs such as resistance to apoptosis and senescence and rapid proliferation. Moreover, it strongly contributes to the ability of primary Stat3C/C MEFs to undergo malignant transformation upon spontaneous immortalization, a feature that may explain the well known causative link between STAT3 constitutive activity and tumor transformation under chronic inflammatory conditions. Taken together with the recently uncovered role of STAT3 in regulating energy metabolism from within the mitochondrion when phosphorylated on Ser 727, these data place STAT3 at the center of a hub regulating energy metabolism under different conditions, in most cases promoting cell survival, proliferation and malignant transformation even though with distinct mechanisms.
PMCID: PMC4190557  PMID: 25089666
STAT3; metabolism; Warburg effect; aerobic glycolysis; cellular transformation; mitochondrial activity
11.  The mitochondrial permeability transition pore is a dispensable element for mitochondrial calcium efflux 
Cell Calcium  2014;56(1):1-13.
Graphical abstract
The mitochondrial permeability transition pore (mPTP) has long been known to have a role in mitochondrial calcium (Ca2+) homeostasis under pathological conditions as a mediator of the mitochondrial permeability transition and the activation of the consequent cell death mechanism. However, its role in the context of mitochondrial Ca2+ homeostasis is not yet clear. Several studies that were based on PPIF inhibition or knock out suggested that mPTP is involved in the Ca2+ efflux mechanism, while other observations have revealed the opposite result.
The c subunit of the mitochondrial F1/FO ATP synthase has been recently found to be a fundamental component of the mPTP. In this work, we focused on the contribution of the mPTP in the Ca2+ efflux mechanism by modulating the expression of the c subunit. We observed that forcing mPTP opening or closing did not impair mitochondrial Ca2+ efflux. Therefore, our results strongly suggest that the mPTP does not participate in mitochondrial Ca2+ homeostasis in a physiological context in HeLa cells.
PMCID: PMC4074345  PMID: 24755650
ANT, adenine nucleotide translocase; [Ca2+]c, cytosolic calcium concentration; [Ca2+]m, mitochondrial calcium concentration; CsA, cyclosporine A; HK, hexokinase II; H2O2, hydrogen peroxide; IB, intracellular milieu; MCU, mitochondrial Ca2+ uniporter; NCLX, mitochondrial Na+/Ca2+ antiporter; MPT, mitochondrial permeability transition; mPTP, mitochondrial permeability transition pore; PiC, inorganic phosphate carrier; PPIF, peptidyl prolyl isomerase; siRNAs, small-interfering RNAs; TSPO, peripheral benzodiazepine receptor; RuR, ruthenium red; VDAC, voltage-dependent anion channel; ATP5G1; Calcium (Ca2+); Cyclophilin F; Cyclosporine A (CsA); Mitochondria; Permeability transition pore (PTP); Peptidyl prolyl isomerase F (PPIF)
12.  Role of the c subunit of the FO ATP synthase in mitochondrial permeability transition 
Cell Cycle  2013;12(4):674-683.
The term “mitochondrial permeability transition” (MPT) refers to an abrupt increase in the permeability of the inner mitochondrial membrane to low molecular weight solutes. Due to osmotic forces, MPT is paralleled by a massive influx of water into the mitochondrial matrix, eventually leading to the structural collapse of the organelle. Thus, MPT can initiate mitochondrial outer membrane permeabilization (MOMP), promoting the activation of the apoptotic caspase cascade as well as of caspase-independent cell death mechanisms. MPT appears to be mediated by the opening of the so-called “permeability transition pore complex” (PTPC), a poorly characterized and versatile supramolecular entity assembled at the junctions between the inner and outer mitochondrial membranes. In spite of considerable experimental efforts, the precise molecular composition of the PTPC remains obscure and only one of its constituents, cyclophilin D (CYPD), has been ascribed with a crucial role in the regulation of cell death. Conversely, the results of genetic experiments indicate that other major components of the PTPC, such as voltage-dependent anion channel (VDAC) and adenine nucleotide translocase (ANT), are dispensable for MPT-driven MOMP. Here, we demonstrate that the c subunit of the FO ATP synthase is required for MPT, mitochondrial fragmentation and cell death as induced by cytosolic calcium overload and oxidative stress in both glycolytic and respiratory cell models. Our results strongly suggest that, similar to CYPD, the c subunit of the FO ATP synthase constitutes a critical component of the PTPC.
PMCID: PMC3594268  PMID: 23343770
ATP5G1; apoptosis; caspases; cytochrome c; mitochondrial respiratory chain; p53; permeability transition pore (PTP)
14.  The Mitochondrial Permeability Transition Pore and Cancer: Molecular Mechanisms Involved in Cell Death 
Frontiers in Oncology  2014;4:302.
Since its discovery in the 1970s, the mitochondrial permeability transition (MPT) has been proposed to be a strategic regulator of cell death. Intense research efforts have focused on elucidating the molecular components of the MPT because this knowledge may help to better understand and treat various pathologies ranging from neurodegenerative and cardiac diseases to cancer. In the case of cancer, several studies have revealed alterations in the activity of the mitochondrial permeability transition pore (mPTP) and have determined its regulatory mechanism; these studies have also suggested that suppression of the activity of the mPTP, rather than its inactivation, commonly occurs in solid neoplasms. This review focuses on the most recent advances in understanding mPTP regulation in cancer and highlights the ability of the mPTP to impede the mechanisms of cell death.
PMCID: PMC4235083  PMID: 25478322
apoptosis; cancer; necrosis; permeability transition pore; ATP synthase; ROS; tumors; PTP
15.  Transglutaminase 2 Contributes to Apoptosis Induction in Jurkat T Cells by Modulating Ca2+ Homeostasis via Cross-Linking RAP1GDS1 
PLoS ONE  2013;8(12):e81516.
Transglutaminase 2 (TG2) is a protein cross-linking enzyme known to be associated with the in vivo apoptosis program of T cells. However, its role in the T cell apoptosis program was not investigated yet.
Here we report that timed overexpression of both the wild type (wt) and the cross-linking mutant of TG2 induced apoptosis in Jurkat T cells, the wt being more effective. Part of TG2 colocalised with mitochondria. WtTG2-induced apoptosis was characterized by enhanced mitochondrial Ca2+ uptake. Ca2+-activated wtTG2 cross-linked RAP1, GTP-GDP dissociation stimulator 1, an unusual guanine exchange factor acting on various small GTPases, to induce a yet uncharacterized signaling pathway that was able to promote the Ca2+ release from the endoplasmic reticulum via both Ins3P and ryanodine sensitive receptors leading to a consequently enhanced mitochondrial Ca2+uptake.
Our data indicate that TG2 might act as a Ca2+ sensor to amplify endoplasmic reticulum-derived Ca2+ signals to enhance mitochondria Ca2+ uptake. Since enhanced mitochondrial Ca2+ levels were previously shown to sensitize mitochondria for various apoptotic signals, our data demonstrate a novel mechanism through which TG2 can contribute to the induction of apoptosis in certain cell types. Since, as compared to knock out cells, physiological levels of TG2 affected Ca2+ signals in mouse embryonic fibroblasts similar to Jurkat cells, our data might indicate a more general role of TG2 in the regulation of mitochondrial Ca2+ homeostasis.
PMCID: PMC3859493  PMID: 24349085
16.  17β-Estradiol Enhances Signalling Mediated by VEGF-A-Delta-Like Ligand 4-Notch1 Axis in Human Endothelial Cells 
PLoS ONE  2013;8(8):e71440.
Estrogens play a protective role in coronary artery disease. The mechanisms of action are still poorly understood, although a role for estrogens in stimulation of angiogenesis has been suggested. In several cell types, estrogens modulate the Notch pathway, which is involved in controlling angiogenesis downstream of vascular endothelial growth factor A (VEGF-A). The goal of our study was to establish whether estrogens modulate Notch activity in endothelial cells and the possible consequences on angiogenesis. Human umbilical vein endothelial cells (HUVECs) were treated with 17β-estradiol (E2) and the effects on Notch signalling were evaluated. E2 increased Notch1 processing as indicated by i) decreased levels of Notch1 transmembrane subunit ii) increased amount of Notch1 in nuclei iii) unaffected level of mRNA. Similarly, E2 increased the levels of the active form of Notch4 without altering Notch4 mRNA. Conversely, protein and mRNA levels of Notch2 were both reduced suggesting transcriptional repression of Notch2 by E2. Under conditions where Notch was activated by upregulation of Delta-like ligand 4 (Dll4) following VEGF-A treatment, E2 caused a further increase of the active form of Notch1, of the number of cells with nuclear Notch1 and of Hey2 mRNA. Estrogen receptor antagonist ICI 182.780 antagonized these effects suggesting that E2 modulation of Notch1 is mediated by estrogen receptors. E2 treatment abolished the increase in endothelial cells sprouting caused by Notch inhibition in a tube formation assay on 3D Matrigel and in mouse aortic ring explants. In conclusion, E2 affects several Notch pathway components in HUVECs, leading to an activation of the VEGF-A-Dll4-Notch1 axis and to a modulation of vascular branching when Notch signalling is inhibited. These results contribute to our understanding of the molecular mechanisms of cardiovascular protection exerted by estrogens by uncovering a novel role of E2 in the Notch signalling-mediated modulation of angiogenesis.
PMCID: PMC3742772  PMID: 23967210
17.  Mitochondrial calcium uniporter, MiRNA and cancer 
Mitochondria receive calcium (Ca2+) signals from endoplasmic reticulum (ER) and decode them into pro-apoptotic inputs, which lead to cell death. Therefore, mitochondrial Ca2+ overload is considered a fundamental trigger of the apoptotic process, and several oncogenes and tumor suppressors modify the activity of protein involved in Ca2+ homeostasis to control apoptosis. The identification of the channel responsible for mitochondrial Ca2+ entry, the Mitochondrial Ca2+Uniporter (MCU), together with its regulatory components, MICU1 and MCUR1, provides new molecular tools to investigate this process. Recent data have also shown that miR-25 decreases mitochondrial Ca2+ uptake through selective MCU downregulation, conferring resistance to apoptotic challenges. MCU appears to be downregulated in human colon cancer samples, and accordingly, miR-25 is aberrantly expressed, indicating the importance of mitochondrial Ca2+ regulation in cancer cell survival.
PMCID: PMC3656015  PMID: 23713134
mitochondria; calcium (Ca2+); Mitochondrial Calcium Uniporter (MCU); MicroRNAs (MiRNA); apoptosis; cell death; cancer
18.  Systemic elevation of PTEN induces a tumor suppressive metabolic state 
Cell  2012;149(1):49-62.
Decremental loss of PTEN results in cancer susceptibility and tumor progression. In turn this raises the possibility that PTEN elevation might be an attractive option for cancer prevention and therapy. We have generated several transgenic mouse lines with variably elevated PTEN expression levels, taking advantage of BAC (Bacterial Artificial Chromosome)-mediated transgenesis. Super-PTEN mutants are viable and show reduced body size due to decreased cell number, with no effect on cell size. Unexpectedly, PTEN elevation at the organism level results in healthy metabolism characterized by increased energy expenditure and reduced body fat accumulation. Cells derived from these mice show reduced glucose and glutamine uptake, increased mitochondrial oxidative phosphorylation, and are resistant to oncogenic transformation. Mechanistically we find that PTEN elevation orchestrates this metabolic switch by regulating PI3K-dependent and independent pathways, and negatively impacts two of the most pronounced metabolic features of tumor cells: glutaminolysis and the Warburg effect.
PMCID: PMC3319228  PMID: 22401813
19.  Oxidative Stress in Cardiovascular Diseases and Obesity: Role of p66Shc and Protein Kinase C 
Reactive oxygen species (ROS) are a byproduct of the normal metabolism of oxygen and have important roles in cell signalling and homeostasis. An imbalance between ROS production and the cellular antioxidant defence system leads to oxidative stress. Environmental factors and genetic interactions play key roles in oxidative stress mediated pathologies. In this paper, we focus on cardiovascular diseases and obesity, disorders strongly related to each other; in which oxidative stress plays a fundamental role. We provide evidence of the key role played by p66Shc protein and protein kinase C (PKC) in these pathologies by their intracellular regulation of redox balance and oxidative stress levels. Additionally, we discuss possible therapeutic strategies aimed at attenuating the oxidative damage in these diseases.
PMCID: PMC3625561  PMID: 23606925
20.  The selective inhibition of nuclear PKCζ restores the effectiveness of chemotherapeutic agents in chemoresistant cells 
Cell Cycle  2012;11(5):1040-1048.
The atypical protein kinase C (PKC) isoform zeta (PKCζ) has been implicated in the intracellular transduction of mitogenic and apoptotic signals by acting on different signaling pathways. The key role of these processes in tumorigenesis suggests a possible involvement of PKCζ in this event. PKCζ is activated by cytotoxic treatments, inhibits apoptotic cell death and reduces the sensitivity of cancer cells to chemotherapeutic agents. Here, using pharmacological and DNA recombinant approaches, we show that oxidative stress triggers nuclear translocation of PKCζ and induces resistance to apoptotic agents. Accordingly, chemoresistant cells show accumulation of PKCζ within the nucleus, and a nuclear-targeted PKCζ transfected in tumor cells decreases sensitivity to apoptosis. We thus developed a novel recombinant protein capable of selectively inhibiting the nuclear fraction of PKCζ that restored the susceptibility to apoptosis in cells in which PKCζ was enriched in the nuclear fraction, including chemoresistant cells. These findings establish the importance of PKCζ as a possible target to increase the effectiveness of anticancer therapies and highlight potential sites of intervention.
PMCID: PMC3323800  PMID: 22333579
protein kinase C; chemoresistance; oxidative stress; nuclear translocation; apoptosis
21.  Hyaluronic Acid Induces Activation of the κ-Opioid Receptor 
PLoS ONE  2013;8(1):e55510.
Nociceptive pain is one of the most common types of pain that originates from an injury involving nociceptors. Approximately 60% of the knee joint innervations are classified as nociceptive. The specific biological mechanism underlying the regulation of nociceptors is relevant for the treatment of symptoms affecting the knee joint. Intra-articular administration of exogenous hyaluronic acid (HA) in patients with osteoarthritis (OA) appears to be particularly effective in reducing pain and improving patient function.
We performed an in vitro study conducted in CHO cells that expressed a panel of opioid receptors and in primary rat dorsal root ganglion (DRG) neurons to determine if HA induces the activation of opioid peptide receptors (OPr) using both aequorin and the fluorescent dye Fura-2/AM.
Selective agonists and antagonists for each OPr expressed on CHO cells were used to test the efficacy of our in vitro model followed by stimulation with HA. The results showed that HA induces stimulatory effects on the κ receptor (KOP). These effects of HA were also confirmed in rat DRG neurons, which express endogenously the OPr.
HA activates the KOP receptor in a concentration dependent manner, with a pEC50 value of 7.57.
PMCID: PMC3557250  PMID: 23383210
22.  Downregulation of the Mitochondrial Calcium Uniporter by Cancer-Related miR-25 
Current Biology  2013;23(1):58-63.
The recently discovered mitochondrial calcium uniporter (MCU) promotes Ca2+ accumulation into the mitochondrial matrix [1, 2]. We identified in silico miR-25 as a cancer-related MCU-targeting microRNA family and demonstrate that its overexpression in HeLa cells drastically reduces MCU levels and mitochondrial Ca2+ uptake, while leaving other mitochondrial parameters and cytosolic Ca2+ signals unaffected. In human colon cancers and cancer-derived cells, miR-25 is overexpressed and MCU accordingly silenced. miR-25-dependent reduction of mitochondrial Ca2+ uptake correlates with resistance to apoptotic challenges and can be reversed by anti-miR-25 overexpression. Overall, the data demonstrate that microRNA targeting of mitochondrial Ca2+ signaling favors cancer cell survival, thus providing mechanistic insight into the role of mitochondria in tumorigenesis and identifying a novel therapeutic target in neoplasia.
► miR-25 regulates intracellular calcium homeostasis ► Mitochondrial calcium uniporter (MCU) is a target of miR-25 ► MCU plays a critical role in apoptosis and tumorigenesis ► MCU is downregulated in different cancer cell lines and in human colonic adenocarcinoma
PMCID: PMC3540261  PMID: 23246404
23.  Chemoresistance and Cancer-Related Inflammation: Two Hallmarks of Cancer Connected by an Atypical Link, PKCζ 
Frontiers in Oncology  2013;3:232.
Atypical protein kinase C isoforms are serine threonine kinases involved in various pathological conditions. In recent years, the PKCζ isoform has emerged as an important regulator of multiple cellular processes operating in cancer. In this review, we will focus on the PKCζ isoform as an oxidative-sensing kinase involved in cancer-related inflammation and chemoresistance. We will discuss its nuclear localization and its possible pivotal role in connecting inflammation with drug resistance.
PMCID: PMC3770915  PMID: 24062985
atypical PKC; PKCζ; cancer; chemoresistance; inflammation; nucleus; apoptosis
24.  Donor Age-Related Biological Properties of Human Dental Pulp Stem Cells Change in Nanostructured Scaffolds 
PLoS ONE  2012;7(11):e49146.
The aim of the present work is to study how biological properties, such as proliferation and commitment ability, of human adult dental pulp stem cells (DPSCs) relate to the age of the donor. Human dental pulps were extracted from molars of healthy adult subjects aged 16 to >66 years. DPSCs were isolated and cultured in the presence of osteogenic, neurogenic, or vasculogenic differentiation medium. Proliferation ability was evaluated by determining doubling time, and commitment ability was evaluated by gene expression and morphological analyses for tissue-specific markers. The results confirm a well-defined proliferative ability for each donor age group at an early in vitro passage (p2). DPSCs from younger donors (up to 35 years) maintain this ability in long-term cultures (p8). Stem cells of all age donor groups maintain their commitment ability during in vitro culture. In vivo tests on the critical size defect repair process confirmed that DPSCs of all donor ages are a potent tool for bone tissue regeneration when mixed with 3D nanostructured scaffolds.
PMCID: PMC3509126  PMID: 23209565
25.  The mitochondrial heme exporter FLVCR1b mediates erythroid differentiation 
The Journal of Clinical Investigation  2012;122(12):4569-4579.
Feline leukemia virus subgroup C receptor 1 (FLVCR1) is a cell membrane heme exporter that maintains the balance between heme levels and globin synthesis in erythroid precursors. It was previously shown that Flvcr1-null mice died in utero due to a failure of erythropoiesis. Here, we identify Flvcr1b, a mitochondrial Flvcr1 isoform that promotes heme efflux into the cytoplasm. Flvcr1b overexpression promoted heme synthesis and in vitro erythroid differentiation, whereas silencing of Flvcr1b caused mitochondrial heme accumulation and termination of erythroid differentiation. Furthermore, mice lacking the plasma membrane isoform (Flvcr1a) but expressing Flvcr1b had normal erythropoiesis, but exhibited hemorrhages, edema, and skeletal abnormalities. Thus, FLVCR1b regulates erythropoiesis by controlling mitochondrial heme efflux, whereas FLVCR1a expression is required to prevent hemorrhages and edema. The aberrant expression of Flvcr1 isoforms may play a role in the pathogenesis of disorders characterized by an imbalance between heme and globin synthesis.
PMCID: PMC3533534  PMID: 23187127

Results 1-25 (59)