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Cellular Site (cellular + site)
Selected AbstractsIntracellular site of ,-secretase cleavage for A,42 generation in Neuro 2a cells harbouring a presenilin 1 mutationFEBS JOURNAL, Issue 7 2000Shinji Sudoh Previously, we reported that mutations in presenilin 1 (PS1) increased the intracellular levels of amyloid ,-protein (A,)42. However, it is still not known at which cellular site or how PS1 mutations exert their effect of enhancing A,42,,-secretase cleavage. In this study, to clarify the molecular mechanisms underlying this enhancement of A,42,,-secretase cleavage, we focused on determining the intracellular site of the cleavage. To address this issue, we used APP,C100 encoding the C-terminal ,-amyloid precursor protein (APP) fragment truncated at the N terminus of A, (C100); C100 requires only ,-secretase cleavage to yield A,. Mutated PS1 (M146L)-induced Neuro 2a cells showed enhanced A,1,42 generation from transiently expressed C100 as well as from full-length APP, whereas the generation of A,1,40 was not increased. The intracellular generation of A,1,42 from transiently expressed C100 in both mutated PS1 -induced and wild-type Neuro 2a cells was inhibited by brefeldin A. Moreover, the generation of A,1,42 and A,1,40 from a C100 mutant containing a di-lysine endoplasmic reticulum retention signal was greatly decreased, indicating that the major intracellular site of ,-secretase cleavage is not the endoplasmic reticulum. The intracellular generation of A,1,42/40 from C100 was not influenced by monensin treatment, and the level of A,1,42/40 generated from C100 carrying a sorting signal for the trans -Golgi network was higher than that generated from wild-type C100. These results using PS1 -mutation-harbouring and wild-type Neuro 2a cells suggest that A,42/40,,-secretase cleavages occur in the Golgi compartment and the trans -Golgi network, and that the PS1 mutation does not alter the intracelluar site of A,42,,-secretase cleavage in the normal APP proteolytic processing pathway. [source] Mitochondrial Production of Hydrogen Peroxide Regulation by Nitric Oxide and the Role of UbisemiquinoneIUBMB LIFE, Issue 4-5 2000Alberto Boveris Abstract Mitochondria are considered the major cellular site for hydrogen peroxide production, a process that is kinetically controlled by the availability of oxygen and nitric oxide to cytochrome oxidase and of ADP to F1-ATPase. The multisite regulation of mi1 tochondrial respiration and energy-transducing pathways support a critical regulatory role of mitochondrion in cell signaling pathways. The cellular steady-state levels of hydrogen peroxide and the role of mitochondria in maintaining these levels are reviewed. [source] Prion diseases: contribution of high-resolution immunomorphologyJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 4 2001J-G. Fournier Abstract The transmisible spongiform encephalopathies or prion diseases are fatal neurological diseases that occur in animals and humans. They are characterized by the accumulation in the cerebral tissue of the abnormal form of prion protein (PrPsc) produced by a post-translational event involving conformational change of its normal cellular counterpart (PrPc). In this short review, we present some results on the biology of prion proteins which have benefited from morphological approaches combining the electron microscopy techniques and the immunodetection methods. We discuss data concerning in particular the physiological function of the normal cellular prion prion (PrPc) which have allowed to open up new vistas on prion diseases, the biogenesis of amyloid plaque and the cellular site involved in the prion protein conversion process. [source] Actions of Acute and Chronic Ethanol on Presynaptic TerminalsALCOHOLISM, Issue 2 2006Marisa Roberto This article presents the proceedings of a symposium entitled "The Tipsy Terminal: Presynaptic Effects of Ethanol" (held at the annual meeting of the Research Society on Alcoholism, in Santa Barbara, CA, June 27, 2005). The objective of this symposium was to focus on a cellular site of ethanol action underrepresented in the alcohol literature, but quickly becoming a "hot" topic. The chairs of the session were Marisa Roberto and George Robert Siggins. Our speakers were chosen on the basis of the diverse electrophysiological and other methods used to discern the effects of acute and chronic ethanol on presynaptic terminals and on the basis of significant insights that their data provide for understanding ethanol actions on neurons in general, as mechanisms underlying problematic behavioral effects of alcohol. The 5 presenters drew from their recent studies examining the effects of acute and chronic ethanol using a range of sophisticated methods from electrophysiological analysis of paired-pulse facilitation and spontaneous and miniature synaptic currents (Drs. Weiner, Valenzuela, Zhu, and Morrisett), to direct recording of ion channel activity and peptide release from acutely isolated synaptic terminals (Dr. Treistman), to direct microscopic observation of vesicular release (Dr. Morrisett). They showed that ethanol administration could both increase and decrease the probability of release of different transmitters from synaptic terminals. The effects of ethanol on synaptic terminals could often be correlated with important behavioral or developmental actions of alcohol. These and other novel findings suggest that future analyses of synaptic effects of ethanol should attempt to ascertain, in multiple brain regions, the role of presynaptic terminals, relevant presynaptic receptors and signal transduction linkages, exocytotic mechanisms, and their involvement in alcohol's behavioral actions. Such studies could lead to new treatment strategies for alcohol intoxication, alcohol abuse, and alcoholism. [source] Complex patterns of mitochondrial dynamics in human pancreatic cells revealed by fluorescent confocal imagingJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 1-2 2010Andrey V. Kuznetsov Abstract Mitochondrial morphology and intracellular organization are tightly controlled by the processes of mitochondrial fission,fusion. Moreover, mitochondrial movement and redistribution provide a local ATP supply at cellular sites of particular demands. Here we analysed mitochondrial dynamics in isolated primary human pancreatic cells. Using real time confocal microscopy and mitochondria-specific fluorescent probes tetramethylrhodamine methyl ester and MitoTracker Green we documented complex and novel patterns of spatial and temporal organization of mitochondria, mitochondrial morphology and motility. The most commonly observed types of mitochondrial dynamics were (i) fast fission and fusion; (ii) small oscillating movements of the mitochondrial network; (iii) larger movements, including filament extension, retraction, fast (0.1,0.3 ,m/sec.) and frequent oscillating (back and forth) branching in the mitochondrial network; (iv) as well as combinations of these actions and (v) long-distance intracellular translocation of single spherical mitochondria or separated mitochondrial filaments with velocity up to 0.5 ,m/sec. Moreover, we show here for the first time, a formation of unusual mitochondrial shapes like rings, loops, and astonishingly even knots created from one or more mitochondrial filaments. These data demonstrate the presence of extensive heterogeneity in mitochondrial morphology and dynamics in living cells under primary culture conditions. In summary, this study reports new patterns of morphological changes and dynamic motion of mitochondria in human pancreatic cells, suggesting an important role of integrations of mitochondria with other intracellular structures and systems. [source] Entamoeba histolytica sirtuin EhSir2a deacetylates tubulin and regulates the number of microtubular assemblies during the cell cycleCELLULAR MICROBIOLOGY, Issue 7 2010Somasri Dam Summary We have discovered four sirtuin genes in Entamoeba histolytica, two of which are similar to eukaryotic sirtuins and two to bacterial and archaeal sirtuins. The eukaryotic sirtuin homologue, EhSir2a, showed NAD+ -dependent deacetylase activity and was sensitive to class III HDAC inhibitors. Localization of EhSir2a at different cellular sites suggested that this deacetylase could have multiple targets. Using an E. histolytica cDNA library in the yeast two-hybrid genetic screen, we identified several proteins that bound to EhSir2a. These proteins included Eh ,-tubulin, whose interaction with EhSir2a was validated in E. histolytica. We have shown that EhSir2a deacetylated tubulin and localized with microtubules in E. histolytica. Increased expression levels of EhSir2a in stable transformants led to reduced number of microtubular assemblies in serum synchronized cells. This effect was abrogated by mutations in the deacetylase domain of EhSir2a, showing that EhSir2a deacetylase activity affected the stability and number of microtubular assemblies during the cell cycle of E. histolytica. Our results suggest that epigenetic modification of tubulin by EhSir2a is one of the mechanisms that regulates microtubular assembly in E. histolytica. [source] | |||||||||||||