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1.  The A3 Adenosine Receptor Mediates Cell Spreading, Reorganization of Actin Cytoskeleton, and Distribution of Bcl-xL: Studies in Human Astroglioma Cells 
The pathophysiological role of the adenosine A3 receptor in the central nervous system is largely unknown. We have investigated the effects of the selective A3 receptor agonist 2-chloro-N6-(3-iodobenzyl)-adenosine, Cl-IB-MECA, in cells of the astroglial lineage (human astrocytoma ADF cells). A marked reorganization of the cytoskeleton, with appearance of stress fibers and numerous cell protrusions, was found following exposure of cells to low (nM) concentrations of Cl-IB-MECA. These “trophic” effects were accompanied by induction of the expression of Rho, a small GTP-binding protein, which was virtually absent in control cells, and by changes of the intracellular distribution of the antiapoptotic protein Bcl-xL, that, in agonist-exposed cells, became specifically associated to cell protrusions. This is the first demonstration that the intracellular organization of Bcl-xL can be modulated by the activation of a G-protein-coupled membrane receptor, such as the A3 adenosine receptor. Moreover, modulation of the astrocytic cytoskeleton by adenosine may have intriguing implications in both nervous system development and in the response of the brain to trauma and ischemia.
doi:10.1006/bbrc.1997.7705
PMCID: PMC4248308  PMID: 9425266
2.  HRES-1/Rab4-mediated depletion of Drp1 impairs mitochondrial homeostasis and represents a target for treatment in SLE 
Annals of the rheumatic diseases  2013;73(10):1888-1897.
Objective
Accumulation of mitochondria underlies T-cell dysfunction in systemic lupus erythematosus (SLE). Mitochondrial turnover involves endosomal traffic regulated by HRES-1/Rab4, a small GTPase that is overexpressed in lupus T cells. Therefore, we investigated whether (1) HRES-1/Rab4 impacts mitochondrial homeostasis and (2) Rab geranylgeranyl transferase inhibitor 3-PEHPC blocks mitochondrial accumulation in T cells, autoimmunity and disease development in lupus-prone mice.
Methods
Mitochondria were evaluated in peripheral blood lymphocytes (PBL) of 38 SLE patients and 21 healthy controls and mouse models by flow cytometry, microscopy and western blot. MRL/lpr mice were treated with 125 μg/kg 3-PEHPC or 1 mg/kg rapamycin for 10 weeks, from 4 weeks of age. Disease was monitored by antinuclear antibody (ANA) production, proteinuria, and renal histology.
Results
Overexpression of HRES-1/Rab4 increased the mitochondrial mass of PBL (1.4-fold; p=0.019) and Jurkat cells (2-fold; p=0.000016) and depleted the mitophagy initiator protein Drp1 both in human (−49%; p=0.01) and mouse lymphocytes (−41%; p=0.03). Drp1 protein levels were profoundly diminished in PBL of SLE patients (−86±3%; p=0.012). T cells of 4-week-old MRL/lpr mice exhibited 4.7-fold over-expression of Rab4A (p=0.0002), the murine homologue of HRES-1/ Rab4, and depletion of Drp1 that preceded the accumulation of mitochondria, ANA production and nephritis. 3-PEHPC increased Drp1 (p=0.03) and reduced mitochondrial mass in T cells (p=0.02) and diminished ANA production (p=0.021), proteinuria (p=0.00004), and nephritis scores of lupus-prone mice (p<0.001).
Conclusions
These data reveal a pathogenic role for HRES-1/Rab4-mediated Drp1 depletion and identify endocytic control of mitophagy as a treatment target in SLE.
doi:10.1136/annrheumdis-2013-203794
PMCID: PMC4047212  PMID: 23897774
3.  Low-dose oral imatinib in the treatment of systemic sclerosis interstitial lung disease unresponsive to cyclophosphamide: a phase II pilot study 
Arthritis Research & Therapy  2014;16(4):R144.
Introduction
Pulmonary involvement represents a major cause of death of systemic sclerosis (SSc) patients. Recent data suggest that tyrosine kinase inhibitors, such as imatinib, may be a therapeutic option for SSc patients. However, preliminary published clinical trials were inconclusive about imatinib efficacy and showed side effects. The purpose of this study was to verify efficacy and tolerability of low-dose imatinib on interstitial lung disease in a cohort of SSc patients unresponsive to cyclophosphamide therapy.
Methods
Thirty consecutive SSc patients with active pulmonary involvement, unresponsive to cyclophosphamide, were treated with imatinib 200 mg/day for 6 months followed by a 6-month follow-up. A “good response” was defined as an increase of forced vital capacity (FVC) by more of 15% and/or increase of diffusing capacity of carbon monoxide (DLCO) >15% and PaO2 > 90% of initial value and high-resolution computed tomography (HRCT)-scan pattern unchanged or improved.
Results
Twenty-six patients completed the study. Three patients died and one patient was lost to follow-up. Four patients (15.32%) had a good response, 7 worsened and 15 had a stabilized lung disease. Overall, 19 (73.07%) patients had an improved or stabilized lung disease. After a 6-month follow-up, 12 (54.5%) of the 22 patients showed an improved or stabilized lung disease.
Conclusions
Lung function was stabilized in a large proportion of patients unresponsive to cyclophosphamide therapy and a beneficial outcome emerged from the analysis of HRCT lung scans. There was no significant improvement of skin involvement, and the low dose was well tolerated. These data provide useful suggestions to design future randomized clinical trials for SSc therapeutics.
Trial registration
ClinicalTrials.gov NCT00573326. Registered 13 December 2007.
doi:10.1186/ar4606
PMCID: PMC4227120  PMID: 25007944
4.  Mitochondria hyperfusion and elevated autophagic activity are key mechanisms for cellular bioenergetic preservation in centenarians 
Aging (Albany NY)  2014;6(4):296-310.
Mitochondria have been considered for long time as important determinants of cell aging because of their role in the production of reactive oxygen species. In this study we investigated the impact of mitochondrial metabolism and biology as determinants of successful aging in primary cultures of fibroblasts isolated from the skin of long living individuals (LLI) (about 100 years old) compared with those from young (about 27 years old) and old (about 75 years old) subjects. We observed that fibroblasts from LLI displayed significantly lower complex I-driven ATP synthesis and higher production of H2O2 in comparison with old subjects. Despite these changes, bioenergetics of these cells appeared to operate normally. This lack of functional consequences was likely due to a compensatory phenomenon at the level of mitochondria, which displayed a maintained supercomplexes organization and an increased mass. This appears to be due to a decreased mitophagy, induced by hyperfused, elongated mitochondria. The overall data indicate that longevity is characterized by a preserved bioenergetic function likely attained by a successful mitochondria remodeling that can compensate for functional defects through an increase in mass, i.e. a sort of mitochondrial “hypertrophy”.
PMCID: PMC4032796  PMID: 24799450
mitochondria; reactive oxygen species; dermal fibroblasts; human aging; longevity; bioenergetics; autophagy; mitophagy
5.  Autoantibodies to Estrogen Receptor α in Systemic Sclerosis (SSc) as Pathogenetic Determinants and Markers of Progression 
PLoS ONE  2013;8(9):e74332.
Systemic sclerosis (SSc) is a multisystem autoimmune disease of unknown etiology characterized by inflammation, autoantibody production, and fibrosis. It predominantly affects women, this suggesting that female sex hormones such as estrogens may play a role in disease pathogenesis. However, up to date, the role of estrogens in SSc has been scarcely explored. The activity of estrogens is mediated either by transcription activity of the intracellular estrogen receptors (ER), ERα and ERβ, or by membrane-associated ER. Since the presence of autoantibodies to ERα and their role as estrogen agonists interfering with T lymphocyte homeostasis were demonstrated in other autoimmune diseases, we wanted to ascertain whether anti-ERα antibodies were detectable in sera from patients with SSc. We detected anti-ERα antibody serum immunoreactivity in 42% of patients with SSc (30 out of 71 analyzed). Importantly, a significant association was found between anti-ERα antibody values and key clinical parameters of disease activity and severity. Fittingly, anti-ERα antibody levels were also significantly associated with alterations of immunological features of SSc patients, including increased T cell apoptotic susceptibility and changes in T regulatory cells (Treg) homeostasis. In particular, the percentage of activated Treg (CD4+CD45RA− FoxP3brightCD25bright) was significantly higher in anti-ERα antibody positive patients than in anti-ERα antibody negative patients. Taken together our data clearly indicate that anti-ERα antibodies, probably via the involvement of membrane-associated ER, can represent: i) promising markers for SSc progression but, also, ii) functional modulators of the SSc patients’ immune system.
doi:10.1371/journal.pone.0074332
PMCID: PMC3776852  PMID: 24058548
7.  Cell Surface Estrogen Receptor Alpha Is Upregulated during Subchronic Metabolic Stress and Inhibits Neuronal Cell Degeneration 
PLoS ONE  2012;7(7):e42339.
In addition to the classical nuclear estrogen receptor, the expression of non-nuclear estrogen receptors localized to the cell surface membrane (mER) has recently been demonstrated. Estrogen and its receptors have been implicated in the development or progression of numerous neurodegenerative disorders. Furthermore, the pathogenesis of these diseases has been associated with disturbances of two key cellular programs: apoptosis and autophagy. An excess of apoptosis or a defect in autophagy has been implicated in neurodegeneration. The aim of this study was to clarify the role of ER in determining neuronal cell fate and the possible implication of these receptors in regulating either apoptosis or autophagy. The human neuronal cell line SH-SY5Y and mouse neuronal cells in primary culture were thus exposed to chronic minimal peroxide treatment (CMP), a form of subcytotoxic minimal chronic stress previously that mimics multiple aspects of long-term cell stress and represents a limited molecular proxy for neurodegenerative processes. We actually found that either E2 or E2-bovine serum albumin construct (E2BSA, i.e. a non-permeant form of E2) was capable of modulating intracellular cell signals and regulating cell survival and death. In particular, under CMP, the up-regulation of mERα, but not mERβ, was associated with functional signals (ERK phosphorylation and p38 dephosphorylation) compatible with autophagic cytoprotection triggering and leading to cell survival. The mERα trafficking appeared to be independent of the microfilament system cytoskeletal network but was seemingly associated with microtubular apparatus network, i.e., to MAP2 molecular chaperone. Importantly, antioxidant treatments, administration of siRNA to ERα, or the presence of antagonist of ERα hindered these events. These results support that the surface expression of mERα plays a pivotal role in determining cell fate, and that ligand-induced activation of mER signalling exerts a powerful cell-survival signal. These results shed new light on the pathogenetic mechanisms leading to neuronal cell degeneration.
doi:10.1371/journal.pone.0042339
PMCID: PMC3409197  PMID: 22860116
8.  Recruitment of cellular prion protein to mitochondrial raft-like microdomains contributes to apoptosis execution 
Molecular Biology of the Cell  2011;22(24):4842-4853.
PrPC is identified as a new component of mitochondrial raft-like microdomains in T cells undergoing CD95/Fas–mediated apoptosis, and microtubular network integrity and function could play a role in the redistribution of PrPC from the plasma membrane to the mitochondria.
We examined the possibility that cellular prion protein (PrPC) plays a role in the receptor-mediated apoptotic pathway. We first found that CD95/Fas triggering induced a redistribution of PrPC to the mitochondria of T lymphoblastoid CEM cells via a mechanism that brings into play microtubular network integrity and function. In particular, we demonstrated that PrPC was redistributed to raft-like microdomains at the mitochondrial membrane, as well as at endoplasmic reticulum-mitochondria–associated membranes. Our in vitro experiments also demonstrated that, although PrPC had such an effect on mitochondria, it induced the loss of mitochondrial membrane potential and cytochrome c release only after a contained rise of calcium concentration. Finally, the involvement of PrPC in apoptosis execution was also analyzed in PrPC-small interfering RNA–transfected cells, which were found to be significantly less susceptible to CD95/Fas–induced apoptosis. Taken together, these results suggest that PrPC might play a role in the complex multimolecular signaling associated with CD95/Fas receptor–mediated apoptosis.
doi:10.1091/mbc.E11-04-0348
PMCID: PMC3237627  PMID: 22031292
9.  Dynamics of mitochondrial raft-like microdomains in cell life and death 
On the basis of the biochemical nature of lipid rafts, composed by glycosphingolipids, cholesterol and signaling proteins, it has been suggested that they are part of the complex framework of subcellular intermixing activities that lead to CD95/Fas-triggered apoptosis. We demonstrated that, following CD95/Fas triggering, cellular prion protein (PrPC), which represents a paradigmatic component of lipid rafts, was redistributed to mitochondrial raft-like microdomains via endoplasmic reticulum (ER)-mitochondria associated membranes (MAM) and microtubular network.
 
Raft-like microdomains appear to be involved in a series of intracellular functions, such as: (1) the membrane “scrambling” that participates in cell death execution pathways, (2) the remodeling of organelles, (3) the recruitment of proteins to the mitochondria; (4) the mitochondrial oxidative phosphorylation and ATP production.
In conclusion, we suggest that lipid raft components can exert their regulatory activity in apoptosis execution at three different levels: (1) in the DISC formation at the plasma membrane; (2) in the intracellular redistribution at cytoplasmic organelles, and, (3) in the structural and functional mitochondrial modifications associated with apoptosis execution.
doi:10.4161/cib.19145
PMCID: PMC3376069  PMID: 22808338
Apoptosis; gangliosides; microdomains; mitochondria; prion protein; rafts; scrambling
10.  Mitochondrial fission and cristae disruption increase the response of cell models of Huntington's disease to apoptotic stimuli 
EMBO molecular medicine  2010;2(12):490-503.
Huntington's disease (HD), a genetic neurodegenerative disease caused by a polyglutamine expansion in the Huntingtin (Htt) protein, is accompanied by multiple mitochondrial alterations. Here we show that mitochondrial fragmentation and cristae alterations characterize cellular models of HD and participate in their increased susceptibility to apoptosis. In HD cells the increased basal activity of the phosphatase calcineurin dephosphorylates the pro-fission dynamin related protein 1 (Drp1), increasing its mitochondrial translocation and activation, and ultimately leading to fragmentation of the organelle. The fragmented HD mitochondria are characterized by cristae alterations that are aggravated by apoptotic stimulation. A genetic analysis indicates that correction of mitochondrial elongation is not sufficient to rescue the increased cytochrome c release and cell death observed in HD cells. Conversely, the increased apoptosis can be corrected by manoeuvres that prevent fission and cristae remodelling. In conclusion, the cristae remodelling of the fragmented HD mitochondria contributes to their hypersensitivity to apoptosis.
doi:10.1002/emmm.201000102
PMCID: PMC3044888  PMID: 21069748
apoptosis; cristae remodelling; fission; Huntington's disease; mitochondria
11.  The Red Blood Cell as a Gender-Associated Biomarker in Metabolic Syndrome: A Pilot Study 
In the present pilot study (56 patients), some red blood cell parameters in samples from patients with metabolic syndrome and subclinical atherosclerosis, but without any sign of coronary artery disease, have been analyzed. The main goal of this work was to determine, in this preclinical state, new peripheral gender-associated bioindicators of possible diagnostic or prognostic value. In particular, three different “indicators” of red blood cell injury and aging have been evaluated: glycophorin A, CD47, and phosphatidylserine externalization. Interestingly, all these determinants appeared significantly modified and displayed gender differences. These findings could provide novel and useful hints in the research for gender-based real-time bioindicators in the progression of metabolic syndrome towards coronary artery disease. Further, more extensive studies are, however, necessary in order to validate these findings.
doi:10.1155/2011/204157
PMCID: PMC3176426  PMID: 21941552
12.  Survival features of EBV-stabilized cells from centenarians: morpho-functional and transcriptomic analyses 
Age  2011;34(6):1341-1359.
In the present work, we analyzed the survival features of six different Epstein–Barr virus (EBV)-stabilized lymphoid cell lines obtained from adult subjects and from subjects of more than 95 years. For the first, we found that lymphoid B cells from centenarians were more resistant to apoptosis induction and displayed a more developed lysosomal compartment, the most critical component of phagic machinery, in comparison with lymphoid B cells from adult subjects. In addition, cells from centenarians were capable of engulfing and digesting other cells, i.e., their siblings (even entire cells), whereas lymphoid cells from “control samples”, i.e., from adults, did not. This behavior was improved by nutrient deprivation but, strikingly, it was unaffected by the autophagy-modulating drug, rapamycin, an autophagy inducer, and 3-methyladenine, an autophagy inhibitor. Transcriptomic analyses indicated that: (1) aspartyl proteases, (2) cell surface molecules such as integrins and cadherins, and (3) some components of cytoskeletal network could contribute to establish this survival phenotype. Also, Kyoto Encyclopedia of Genes and Genomes pathways such as Wnt signaling pathway, an essential contributor to cell migration and actin cytoskeleton remodeling, appeared as prominent. Although we cannot rule out the possibility that EBV-immortalization could play a role, since we observed this phagic behavior in cells from centenarians but not in those from adults, we hypothesize that it may represent an important survival determinant in cells from centenarians.
Electronic supplementary material
The online version of this article (doi:10.1007/s11357-011-9307-4) contains supplementary material, which is available to authorized users.
doi:10.1007/s11357-011-9307-4
PMCID: PMC3528377  PMID: 21904824
Lymphoid cells; Centenarians; Apoptosis; Cannibalism; Autophagy; Transcriptomic analysis
13.  Mitochondrial fission and cristae disruption increase the response of cell models of Huntington's disease to apoptotic stimuli 
EMBO Molecular Medicine  2010;2(12):490-503.
Huntington's disease (HD), a genetic neurodegenerative disease caused by a polyglutamine expansion in the Huntingtin (Htt) protein, is accompanied by multiple mitochondrial alterations. Here, we show that mitochondrial fragmentation and cristae alterations characterize cellular models of HD and participate in their increased susceptibility to apoptosis. In HD cells, the increased basal activity of the phosphatase calcineurin dephosphorylates the pro-fission dynamin related protein 1 (Drp1), increasing its mitochondrial translocation and activation, and ultimately leading to fragmentation of the organelle. The fragmented HD mitochondria are characterized by cristae alterations that are aggravated by apoptotic stimulation. A genetic analysis indicates that correction of mitochondrial elongation is not sufficient to rescue the increased cytochrome c release and cell death observed in HD cells. Conversely, the increased apoptosis can be corrected by manoeuvres that prevent fission and cristae remodelling. In conclusion, the cristae remodelling of the fragmented HD mitochondria contributes to their hypersensitivity to apoptosis.
doi:10.1002/emmm.201000102
PMCID: PMC3044888  PMID: 21069748
apoptosis; cristae remodelling; fission; Huntington's disease; mitochondria
14.  Cathepsin B inhibition interferes with metastatic potential of human melanoma: an in vitro and in vivo study 
Molecular Cancer  2010;9:207.
Background
Cathepsins represent a group of proteases involved in determining the metastatic potential of cancer cells. Among these are cysteinyl- (e.g. cathepsin B and cathepsin L) and aspartyl-proteases (e.g. cathepsin D), normally present inside the lysosomes as inactive proenzymes. Once released in the extracellular space, cathepsins contribute to metastatic potential by facilitating cell migration and invasiveness.
Results
In the present work we first evaluated, by in vitro procedures, the role of cathepsins B, L and D, in the remodeling, spreading and invasiveness of eight different cell lines: four primary and four metastatic melanoma cell lines. Among these, we considered two cell lines derived from a primary cutaneous melanoma and from a supraclavicular lymph node metastasis of the same patient. To this purpose, the effects of specific chemical inhibitors of these proteases, i.e. CA-074 and CA-074Me for cathepsin B, Cathepsin inhibitor II for cathepsin L, and Pepstatin A for cathepsin D, were evaluated. In addition, we also analyzed the effects of the biological inhibitors of these cathepsins, i.e. specific antibodies, on cell invasiveness. We found that i) cathepsin B, but not cathepsins L and D, was highly expressed at the surface of metastatic but not of primary melanoma cell lines and that ii) CA-074, or specific antibodies to cathepsin B, hindered metastatic cell spreading and dissemination, whereas neither chemical nor biological inhibitors of cathepsins D and L had significant effects. Accordingly, in vivo studies, i.e. in murine xenografts, demonstrated that CA-074 significantly reduced human melanoma growth and the number of artificial lung metastases.
Conclusions
These results suggest a reappraisal of the use of cathepsin B inhibitors (either chemical or biological) as innovative strategy in the management of metastatic melanoma disease.
doi:10.1186/1476-4598-9-207
PMCID: PMC2925371  PMID: 20684763
15.  Endosomal compartment contributes to the propagation of CD95/Fas-mediated signals in type II cells 
The Biochemical journal  2008;413(3):467-478.
Participation of diverse organelles in the intracellular signalling that follows CD95/Fas receptor ligation encompasses a series of subcellular changes that are mandatory for, or even bolster, the apoptotic cascade. In the present study, we analysed the role of endocytosis in the propagation of cell death signalling after CD95/Fas engagement in type II cells (CEM cells). We show that this receptor–ligand interaction triggers endocytosis independently of any caspase activation. This FasL (Fas ligand)-induced endocytosis also leads to an early and directional ‘movement’ of endocytic vesicles towards the mitochondrial compartment. In turn, this cross-talk between endosomal and mitochondrial compartments was followed by the loss of the mitochondrial membrane potential and apoptosis execution. This cell remodelling was absent in receptor-independent cell death, such as that induced by the mitochondriotropic drug staurosporine, and in a CEM cell line selected for its multidrug resistance (CEM VBL100). In these cells a reduced FasL (Fas ligand)-induced endocytosis and a reduced organelle cross-talk corresponded to a reduced apoptosis. Altogether, these findings suggest a key role of endocytosis in the propagation and amplification of the CD95/Fas-activated signalling leading to type II cell demise.
doi:10.1042/BJ20071704
PMCID: PMC2819661  PMID: 18442358
apoptosis; CD95/Fas; endocytosis; mitochondrial membrane potential (MMP); multidrug resistance; type II cell
16.  Role of GD3-CLIPR-59 Association in Lymphoblastoid T Cell Apoptosis Triggered by CD95/Fas 
PLoS ONE  2010;5(1):e8567.
We previously found that a directional movement of the raft component GD3 towards mitochondria, by its association with microtubules, was mandatory to late apoptogenic events triggered by CD95/Fas. Since CLIPR-59, CLIP-170-related protein, has recently been identified as a microtubule binding protein associated with lipid rafts, we analyzed the role of GD3-CLIPR-59 association in lymphoblastoid T cell apoptosis triggered by CD95/Fas. To test whether CLIPR-59 could play a role at the raft-microtubule junction, we performed a series of experiments by using immunoelectron microscopy, static or flow cytometry and biochemical analyses. We first assessed the presence of CLIPR-59 molecule in lymphoblastoid T cells (CEM). Then, we demonstrated that GD3-microtubule interaction occurs via CLIPR-59 and takes place at early time points after CD95/Fas ligation, preceding the association GD3-tubulin. GD3-CLIPR-59 association was demonstrated by fluorescence resonance energy transfer (FRET) analysis. The key role of CLIPR-59 in this dynamic process was clarified by the observation that silencing CLIPR-59 by siRNA affected the kinetics of GD3-tubulin association, spreading of GD3 towards mitochondria and apoptosis execution. We find that CLIPR-59 may act as a typical chaperone, allowing a prompt interaction between tubulin and the raft component GD3 during cell apoptosis triggered by CD95/Fas. On the basis of the suggested role of lipid rafts in conveying pro-apoptotic signals these results disclose new perspectives in the understanding of the mechanisms by which raft-mediated pro-apoptotic signals can directionally reach their target, i.e. the mitochondria, and trigger apoptosis execution.
doi:10.1371/journal.pone.0008567
PMCID: PMC2797139  PMID: 20052288
17.  Activation of Cyclin-Dependent Kinase 5 Is a Consequence of Cell Death 
Cyclin-dependent kinase 5 (Cdk5) is similar to other Cdks but is activated during cell differentiation and cell death rather than cell division. Since activation of Cdk5 has been reported in many situations leading to cell death, we attempted to determine if it was required for any form of cell death. We found that Cdk5 is activated during apoptotic deaths and that the activation can be detected even when the cells continue to secondary necrosis. This activation can occur in the absence of Bim, calpain, or neutral cathepsins. The kinase is typically activated by p25, derived from p35 by calpain-mediated cleavage, but inhibition of calpain does not affect cell death or the activation of Cdk5. Likewise, RNAi-forced suppression of the synthesis of Cdk5 does not affect the incidence or kinetics of cell death. We conclude that Cdk5 is activated as a consequence of metabolic changes that are common to many forms of cell death. Thus its activation suggests processes during cell death that will be interesting or important to understand, but activation of Cdk5 is not necessary for cells to die.
doi:10.1155/2009/805709
PMCID: PMC2760396  PMID: 19830249
18.  Fas Death Receptor Enhances Endocytic Membrane Traffic Converging into the Golgi Region 
Molecular Biology of the Cell  2009;20(2):600-615.
The death receptor Fas/CD95 initiates apoptosis by engaging diverse cellular organelles including endosomes. The link between Fas signaling and membrane traffic has remained unclear, in part because it may differ in diverse cell types. After a systematic investigation of all known pathways of endocytosis, we have clarified that Fas activation opens clathrin-independent portals in mature T cells. These portals drive rapid internalization of surface proteins such as CD59 and depend upon actin-regulating Rho GTPases, especially CDC42. Fas-enhanced membrane traffic invariably produces an accumulation of endocytic membranes around the Golgi apparatus, in which recycling endosomes concentrate. This peri-Golgi polarization has been documented by colocalization analysis of various membrane markers and applies also to active caspases associated with internalized receptor complexes. Hence, T lymphocytes show a diversion in the traffic of endocytic membranes after Fas stimulation that seems to resemble the polarization of membrane traffic after their activation.
doi:10.1091/mbc.E08-09-0925
PMCID: PMC2626565  PMID: 19037097
19.  Guidelines for the use and interpretation of assays for monitoring autophagy in higher eukaryotes 
Klionsky, Daniel J. | Abeliovich, Hagai | Agostinis, Patrizia | Agrawal, Devendra K. | Aliev, Gjumrakch | Askew, David S. | Baba, Misuzu | Baehrecke, Eric H. | Bahr, Ben A. | Ballabio, Andrea | Bamber, Bruce A. | Bassham, Diane C. | Bergamini, Ettore | Bi, Xiaoning | Biard-Piechaczyk, Martine | Blum, Janice S. | Bredesen, Dale E. | Brodsky, Jeffrey L. | Brumell, John H. | Brunk, Ulf T. | Bursch, Wilfried | Camougrand, Nadine | Cebollero, Eduardo | Cecconi, Francesco | Chen, Yingyu | Chin, Lih-Shen | Choi, Augustine | Chu, Charleen T. | Chung, Jongkyeong | Clarke, Peter G.H. | Clark, Robert S.B. | Clarke, Steven G. | Clavé, Corinne | Cleveland, John L. | Codogno, Patrice | Colombo, María I. | Coto-Montes, Ana | Cregg, James M. | Cuervo, Ana Maria | Debnath, Jayanta | Demarchi, Francesca | Dennis, Patrick B. | Dennis, Phillip A. | Deretic, Vojo | Devenish, Rodney J. | Di Sano, Federica | Dice, J. Fred | DiFiglia, Marian | Dinesh-Kumar, Savithramma | Distelhorst, Clark W. | Djavaheri-Mergny, Mojgan | Dorsey, Frank C. | Dröge, Wulf | Dron, Michel | Dunn, William A. | Duszenko, Michael | Eissa, N. Tony | Elazar, Zvulun | Esclatine, Audrey | Eskelinen, Eeva-Liisa | Fésüs, László | Finley, Kim D. | Fuentes, José M. | Fueyo, Juan | Fujisaki, Kozo | Galliot, Brigitte | Gao, Fen-Biao | Gewirtz, David A. | Gibson, Spencer B. | Gohla, Antje | Goldberg, Alfred L. | Gonzalez, Ramon | González-Estévez, Cristina | Gorski, Sharon | Gottlieb, Roberta A. | Häussinger, Dieter | He, You-Wen | Heidenreich, Kim | Hill, Joseph A. | Høyer-Hansen, Maria | Hu, Xun | Huang, Wei-Pang | Iwasaki, Akiko | Jäättelä, Marja | Jackson, William T. | Jiang, Xuejun | Jin, Shengkan | Johansen, Terje | Jung, Jae U. | Kadowaki, Motoni | Kang, Chanhee | Kelekar, Ameeta | Kessel, David H. | Kiel, Jan A.K.W. | Kim, Hong Pyo | Kimchi, Adi | Kinsella, Timothy J. | Kiselyov, Kirill | Kitamoto, Katsuhiko | Knecht, Erwin | Komatsu, Masaaki | Kominami, Eiki | Kondo, Seiji | Kovács, Attila L. | Kroemer, Guido | Kuan, Chia-Yi | Kumar, Rakesh | Kundu, Mondira | Landry, Jacques | Laporte, Marianne | Le, Weidong | Lei, Huan-Yao | Lenardo, Michael J. | Levine, Beth | Lieberman, Andrew | Lim, Kah-Leong | Lin, Fu-Cheng | Liou, Willisa | Liu, Leroy F. | Lopez-Berestein, Gabriel | López-Otín, Carlos | Lu, Bo | Macleod, Kay F. | Malorni, Walter | Martinet, Wim | Matsuoka, Ken | Mautner, Josef | Meijer, Alfred J. | Meléndez, Alicia | Michels, Paul | Miotto, Giovanni | Mistiaen, Wilhelm P. | Mizushima, Noboru | Mograbi, Baharia | Monastyrska, Iryna | Moore, Michael N. | Moreira, Paula I. | Moriyasu, Yuji | Motyl, Tomasz | Münz, Christian | Murphy, Leon O. | Naqvi, Naweed I. | Neufeld, Thomas P. | Nishino, Ichizo | Nixon, Ralph A. | Noda, Takeshi | Nürnberg, Bernd | Ogawa, Michinaga | Oleinick, Nancy L. | Olsen, Laura J. | Ozpolat, Bulent | Paglin, Shoshana | Palmer, Glen E. | Papassideri, Issidora | Parkes, Miles | Perlmutter, David H. | Perry, George | Piacentini, Mauro | Pinkas-Kramarski, Ronit | Prescott, Mark | Proikas-Cezanne, Tassula | Raben, Nina | Rami, Abdelhaq | Reggiori, Fulvio | Rohrer, Bärbel | Rubinsztein, David C. | Ryan, Kevin M. | Sadoshima, Junichi | Sakagami, Hiroshi | Sakai, Yasuyoshi | Sandri, Marco | Sasakawa, Chihiro | Sass, Miklós | Schneider, Claudio | Seglen, Per O. | Seleverstov, Oleksandr | Settleman, Jeffrey | Shacka, John J. | Shapiro, Irving M. | Sibirny, Andrei | Silva-Zacarin, Elaine C.M. | Simon, Hans-Uwe | Simone, Cristiano | Simonsen, Anne | Smith, Mark A. | Spanel-Borowski, Katharina | Srinivas, Vickram | Steeves, Meredith | Stenmark, Harald | Stromhaug, Per E. | Subauste, Carlos S. | Sugimoto, Seiichiro | Sulzer, David | Suzuki, Toshihiko | Swanson, Michele S. | Tabas, Ira | Takeshita, Fumihiko | Talbot, Nicholas J. | Tallóczy, Zsolt | Tanaka, Keiji | Tanaka, Kozo | Tanida, Isei | Taylor, Graham S. | Taylor, J. Paul | Terman, Alexei | Tettamanti, Gianluca | Thompson, Craig B. | Thumm, Michael | Tolkovsky, Aviva M. | Tooze, Sharon A. | Truant, Ray | Tumanovska, Lesya V. | Uchiyama, Yasuo | Ueno, Takashi | Uzcátegui, Néstor L. | van der Klei, Ida | Vaquero, Eva C. | Vellai, Tibor | Vogel, Michael W. | Wang, Hong-Gang | Webster, Paul | Wiley, John W. | Xi, Zhijun | Xiao, Gutian | Yahalom, Joachim | Yang, Jin-Ming | Yap, George | Yin, Xiao-Ming | Yoshimori, Tamotsu | Yu, Li | Yue, Zhenyu | Yuzaki, Michisuke | Zabirnyk, Olga | Zheng, Xiaoxiang | Zhu, Xiongwei | Deter, Russell L.
Autophagy  2007;4(2):151-175.
Research in autophagy continues to accelerate,1 and as a result many new scientists are entering the field. Accordingly, it is important to establish a standard set of criteria for monitoring macroautophagy in different organisms. Recent reviews have described the range of assays that have been used for this purpose.2,3 There are many useful and convenient methods that can be used to monitor macroautophagy in yeast, but relatively few in other model systems, and there is much confusion regarding acceptable methods to measure macroautophagy in higher eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers of autophagosomes versus those that measure flux through the autophagy pathway; thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from fully functional autophagy that includes delivery to, and degradation within, lysosomes (in most higher eukaryotes) or the vacuole (in plants and fungi). Here, we present a set of guidelines for the selection and interpretation of the methods that can be used by investigators who are attempting to examine macroautophagy and related processes, as well as by reviewers who need to provide realistic and reasonable critiques of papers that investigate these processes. This set of guidelines is not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to verify an autophagic response.
PMCID: PMC2654259  PMID: 18188003
autolysosome; autophagosome; flux; lysosome; phagophore; stress; vacuole
20.  Impairment of Human Immunodeficiency Virus Type 1 (HIV-1) Entry into Jurkat T Cells by Constitutive Expression of the HIV-1 Vpr Protein: Role of CD4 Down-Modulation 
Journal of Virology  2000;74(21):10207-10211.
Jurkat T-cell clones, stably expressing the human immunodeficiency virus type 1 (HIV-1) Vpr protein, exhibited an impaired susceptibility to HIV-1 infection. A marked down-modulation of surface CD4 receptors was detected in Vpr-expressing clones with respect to control cells. Likewise, a reduced CD4 expression was also observed in parental Jurkat cells infected with wild-type but not with Vpr-mutant HIV-1. Notably, Vpr-expressing clones were fully susceptible to infection with a vesicular stomatitis virus G protein-pseudotyped HIV-1 virus, indicating that a block at the level of viral entry was responsible for the inhibition of viral replication. The effect exerted by Vpr on HIV replication and CD4 expression suggests that this protein can regulate both the establishment of a productive HIV-1 infection and CD4-mediated T-cell functions.
PMCID: PMC102060  PMID: 11024150
21.  Mitochondrial fission and cristae disruption increase the response of cell models of Huntington's disease to apoptotic stimuli 
EMBO Molecular Medicine  2010;2(12):490-503.
Huntington's disease (HD), a genetic neurodegenerative disease caused by a polyglutamine expansion in the Huntingtin (Htt) protein, is accompanied by multiple mitochondrial alterations. Here, we show that mitochondrial fragmentation and cristae alterations characterize cellular models of HD and participate in their increased susceptibility to apoptosis. In HD cells, the increased basal activity of the phosphatase calcineurin dephosphorylates the pro-fission dynamin related protein 1 (Drp1), increasing its mitochondrial translocation and activation, and ultimately leading to fragmentation of the organelle. The fragmented HD mitochondria are characterized by cristae alterations that are aggravated by apoptotic stimulation. A genetic analysis indicates that correction of mitochondrial elongation is not sufficient to rescue the increased cytochrome c release and cell death observed in HD cells. Conversely, the increased apoptosis can be corrected by manoeuvres that prevent fission and cristae remodelling. In conclusion, the cristae remodelling of the fragmented HD mitochondria contributes to their hypersensitivity to apoptosis.
doi:10.1002/emmm.201000102
PMCID: PMC3044888  PMID: 21069748
apoptosis; cristae remodelling; fission; Huntington's disease; mitochondria
22.  HRES-1/Rab4-mediated depletion of Drp1 impairs mitochondrial homeostasis and represents a target for treatment in SLE 
Annals of the Rheumatic Diseases  2013;73(10):1888-1897.
Objective
Accumulation of mitochondria underlies T-cell dysfunction in systemic lupus erythematosus (SLE). Mitochondrial turnover involves endosomal traffic regulated by HRES-1/Rab4, a small GTPase that is overexpressed in lupus T cells. Therefore, we investigated whether (1) HRES-1/Rab4 impacts mitochondrial homeostasis and (2) Rab geranylgeranyl transferase inhibitor 3-PEHPC blocks mitochondrial accumulation in T cells, autoimmunity and disease development in lupus-prone mice.
Methods
Mitochondria were evaluated in peripheral blood lymphocytes (PBL) of 38 SLE patients and 21 healthy controls and mouse models by flow cytometry, microscopy and western blot. MRL/lpr mice were treated with 125 μg/kg 3-PEHPC or 1 mg/kg rapamycin for 10 weeks, from 4 weeks of age. Disease was monitored by antinuclear antibody (ANA) production, proteinuria, and renal histology.
Results
Overexpression of HRES-1/Rab4 increased the mitochondrial mass of PBL (1.4-fold; p=0.019) and Jurkat cells (2-fold; p=0.000016) and depleted the mitophagy initiator protein Drp1 both in human (−49%; p=0.01) and mouse lymphocytes (−41%; p=0.03). Drp1 protein levels were profoundly diminished in PBL of SLE patients (−86±3%; p=0.012). T cells of 4-week-old MRL/lpr mice exhibited 4.7-fold over-expression of Rab4A (p=0.0002), the murine homologue of HRES-1/Rab4, and depletion of Drp1 that preceded the accumulation of mitochondria, ANA production and nephritis. 3-PEHPC increased Drp1 (p=0.03) and reduced mitochondrial mass in T cells (p=0.02) and diminished ANA production (p=0.021), proteinuria (p=0.00004), and nephritis scores of lupus-prone mice (p<0.001).
Conclusions
These data reveal a pathogenic role for HRES-1/Rab4-mediated Drp1 depletion and identify endocytic control of mitophagy as a treatment target in SLE.
doi:10.1136/annrheumdis-2013-203794
PMCID: PMC4047212  PMID: 23897774
Autoimmune Diseases; Autoimmunity; Systemic Lupus Erythematosus
23.  Activation of Rho GTPases by Cytotoxic Necrotizing Factor 1 Induces Macropinocytosis and Scavenging Activity in Epithelial Cells 
Molecular Biology of the Cell  2001;12(7):2061-2073.
Macropinocytosis, a ruffling-driven process that allows the capture of large material, is an essential aspect of normal cell function. It can be either constitutive, as in professional phagocytes where it ends with the digestion of captured material, or induced, as in epithelial cells stimulated by growth factors. In this case, the internalized material recycles back to the cell surface. We herein show that activation of Rho GTPases by a bacterial protein toxin, the Escherichia coli cytotoxic necrotizing factor 1 (CNF1), allowed epithelial cells to engulf and digest apoptotic cells in a manner similar to that of professional phagocytes. In particular, we have demonstrated that 1) the activation of all Rho, Rac, and Cdc42 by CNF1 was essential for the capture and internalization of apoptotic cells; and 2) such activation allowed the discharge of macropinosomal content into Rab7 and lysosomal associated membrane protein-1 acidic lysosomal vesicles where the ingested particles underwent degradation. Taken together, these findings indicate that CNF1-induced “switching on” of Rho GTPases may induce in epithelial cells a scavenging activity, comparable to that exerted by professional phagocytes. The activation of such activity in epithelial cells may be relevant, in mucosal tissues, in supporting or integrating the scavenging activity of resident macrophages.
PMCID: PMC55656  PMID: 11452003

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