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891.
The mechanisms that govern receptor coalescence into functional clusters--often a critical step in their stimulation by ligand--are poorly understood. We used single-molecule tracking to investigate the dynamics of CD36, a clustering-responsive receptor that mediates oxidized LDL uptake by macrophages. We found that CD36 motion in the membrane was spatially structured by the cortical cytoskeleton. A subpopulation of receptors diffused within linear confinement regions whose unique geometry simultaneously facilitated freedom of movement along one axis while increasing the effective receptor density. Co-confinement within troughs enhanced the probability of collisions between unligated receptors and promoted their clustering. Cytoskeleton perturbations that inhibited diffusion in linear confinement regions reduced receptor clustering in the absence of ligand and, following ligand addition, suppressed CD36-mediated signaling and internalization. These observations demonstrate a role for the cytoskeleton in controlling signal transduction by structuring receptor diffusion within membrane regions that increase their collision frequency. 相似文献
892.
Directed conversion of Alzheimer's disease patient skin fibroblasts into functional neurons 总被引:2,自引:0,他引:2
893.
Fernández S Eritja R Aviñó A Jaumot J Gargallo R 《International journal of biological macromolecules》2011,49(4):729-736
The influence of pH, temperature and the cationic porphyrin TMPyP4 on the conformational equilibria of the cytosine-rich strand of the human telomeric sequence 5′-(C3TA2)4-3′, as well as those of the sequence 5′-(C3TT2)4-3′, was studied. The presence of adenine bases at the loops causes the formation of two different intramolecular i-motif structures with a pH-transition midpoint around 4.6, which stability is lower than the i-motif formed by the sequence 5′-(C3TT2)4-3′. The stoichiometries of the complexes formed by these i-motif structures with TMPyP4 are also influenced by the presence of adenine at the loops. 相似文献
894.
895.
Trevisol ET Panek AD Mannarino SC Eleutherio EC 《Applied microbiology and biotechnology》2011,90(2):697-704
The fermentation process offers a wide variety of stressors for yeast, such as temperature, aging, and ethanol. To evaluate
a possible beneficial effect of trehalose on ethanol production, we used mutant strains of Saccharomyces cerevisiae possessing different deficiencies in the metabolism of this disaccharide: in synthesis, tps1; in transport, agt1; and in degradation, ath1 and nth1. According to our results, the tps1 mutant, the only strain tested unable to synthesize trehalose, showed the lowest fermentation yield, indicating that this
sugar is important to improve ethanol production. At the end of the first fermentation cycle, only the strains deficient in
transport and degradation maintained a significant level of the initial trehalose. The agt1, ath1, and nth1 strains showed the highest survival rates and the highest proportions of non-petites. Accumulation of petites during fermentation
has been correlated to low ethanol production. When recycled back for a subsequent fermentation, those mutant strains produced
the highest ethanol yields, suggesting that trehalose is required for improving fermentative capacity and longevity of yeasts,
as well as their ability to withstand stressful industrial conditions. Finally, according to our results, the mechanism by
which trehalose improves ethanol production seems to involve mainly protection against protein oxidation. 相似文献
896.
Guaragnella N Antonacci L Passarella S Marra E Giannattasio S 《Biochemical Society transactions》2011,39(5):1538-1543
The use of non-mammalian model organisms, including yeast Saccharomyces cerevisiae, can provide new insights into eukaryotic PCD (programmed cell death) pathways. In the present paper, we report recent achievements in the elucidation of the events leading to PCD that occur as a response to yeast treatment with AA (acetic acid). In particular, ROS (reactive oxygen species) generation, cyt c (cytochrome c) release and mitochondrial function and proteolytic activity will be dealt with as they vary along the AA-PCD time course by using both wild-type and mutant yeast cells. Two AA-PCD pathways are described sharing common features, but distinct from one another with respect to the role of ROS and mitochondria, the former in which YCA1 acts upstream of cyt c release and caspase-like activation in a ROS-dependent manner and the latter in which cyt c release does not occur, but caspase-like activity increases, in a ROS-independent manner. 相似文献
897.
Bejarano I Espino J Marchena AM Barriga C Paredes SD Rodríguez AB Pariente JA 《Molecular and cellular biochemistry》2011,353(1-2):167-176
Melatonin is an indoleamine secreted by the pineal gland that shows multiple tasks. This ubiquitously acting free radical scavenger has recently been shown to stimulate the production of reactive oxygen species (ROS) in tumour cells, making them undergo apoptosis, whilst it prevents apoptosis in healthy cells. The mechanisms by which melatonin exerts these dual actions are, however, not yet clearly understood. Thus, the aim of this study was to further investigate how melatonin can enhance oxidative stress-induced apoptosis in a leukaemia cell line. The results show that melatonin increased the apoptotic effects of H(2)O(2) in human myeloid HL-60 cells as assessed by cellular viability, mitochondrial permeability transition induction, mitochondrial membrane depolarization, ROS generation, caspases 3, 8 and 9 activity, phosphatidylserine externalization, and DNA fragmentation techniques. When healthy leucocytes were exposed to H(2)O(2), melatonin increased the viability of the cells. Taken together, the findings indicate that melatonin is a potential physiological tool capable of protecting healthy cells from chemotherapy-induced ROS production as well as inducing tumour cell death. Because cancer cells manifest increased oxidative stress as a result of their elevated metabolism, the use of melatonin may be useful in impairing their ROS buffering capacity. 相似文献
898.
Daniela Basso Eliana Greco Andrea Padoan Paola Fogar Michele Scorzeto Elisa Fadi Dania Bozzato Stefania Moz Filippo Navaglia Carlo‐Federico Zambon Roberta Seraglia Eugenio De Carlo Anna Valerio Carlo Reggiani Sergio Pedrazzoli Mario Plebani 《Journal of cellular physiology》2011,226(2):456-468
After isolating NT‐S100A8 from pancreatic cancer (PC) tissue of diabetic patients, we verified whether this peptide alters PC cell growth and invasion and/or insulin release and [Ca2+]i oscillations of insulin secreting cells and/or insulin signaling. BxPC3, Capan1, MiaPaCa2, Panc1 (PC cell lines) cell growth, and invasion were assessed in the absence or presence of 50, 200, and 500 nM NT‐S100A8. In NT‐S100A8 stimulated β‐TC6 (insulinoma cell line) culture medium, insulin and [Ca2+] were measured at 2, 3, 5, 10, 15, 30, and 60 min, and [Ca2+]i oscillations were monitored (epifluorescence) for 3 min. Five hundred nanomolars NT‐S100A8 stimulated BxPC3 cell growth only and dose dependently reduced MiaPaCa2 and Panc1 invasion. Five hundred nanomolars NT‐S100A8 induced a rapid insulin release and enhanced β‐TC6 [Ca2+]i oscillations after both one (F = 6.05, P < 0.01) and 2 min (F = 7.42, P < 0.01). In the presence of NT‐S100A8, [Ca2+] in β‐TC6 culture medium significantly decreased with respect to control cells (F = 6.3, P < 0.01). NT‐S100A8 did not counteract insulin induced phosphorylation of the insulin receptor, Akt and IκB‐α, but it independently activated Akt and NF‐κB signaling in PC cells. In conclusion, NT‐S100A8 exerts a mild effect on PC cell growth, while it reduces PC cell invasion, possibly by Akt and NF‐κB signaling, NT‐S100A8 enhances [Ca2+]i oscillations and insulin release, probably by inducing Ca2+ influx from the extracellular space, but it does not interfere with insulin signaling. J. Cell. Physiol. 226: 456–468, 2011. © 2010 Wiley‐Liss, Inc. 相似文献
899.
Renier A De Faria SM Jourand P Giraud E Dreyfus B Rapior S Prin Y 《Journal of experimental botany》2011,62(10):3693-3697
Crotalaria are plants of the Fabaceae family whose nodulation characteristics have been little explored despite the recent discovery of their unexpected ability to be efficiently nodulated in symbiosis with bacteria of the genus Methylobacterium. It has been shown that methylotrophy plays a key role in this unusual symbiotic system, as it is expressed within the nodule and as non-methylotroph mutants had a depleting effect on plant growth response. Within the nodule, Methylobacterium is thus able to obtain carbon both from host plant photosynthesis and from methylotrophy. In this context, the aim of the present study was to show the histological and cytological impacts of both symbiotic and methylotrophic metabolism within Crotalaria podocarpa nodules. It was established that if Crotalaria nodules are multilobed, each lobe has the morphology of indeterminate nodules but with a different anatomy; that is, without root hair infection or infection threads. In the fixation zone, bacteroids display a spherical shape and there is no uninfected cell. Crotalaria nodulation by Methylobacterium displayed some very unusual characteristics such as starch storage within bacteroid-filled cells of the fixation zone and also the complete lysis of apical nodular tissues (where bacteria have a free-living shape and express methylotrophy). This lysis could possibly reflect the bacterial degradation of plant wall pectins through bacterial pectin methyl esterases, thus producing methanol as a substrate, allowing bacterial multiplication before release from the nodule. 相似文献
900.