Biology of the Cell
0248-4900
Cơ quản chủ quản: WILEY , Wiley-Blackwell
Lĩnh vực:
Medicine (miscellaneous)Cell Biology
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Các bài báo tiêu biểu
Conducting the initiation of protein synthesis: the role of eIF4G Abstract The eukaryotic initiation factor eIF4G is a large modular protein which serves as a docking site for initiation factors and proteins involved in RNA translation. Together with eIF4E and eIF4A, eIF4G constitutes the eIF4F complex which is a key component in promoting ribosome binding to the mRNA. Thus, the central role of eIF4G in initiation makes it a valid target for events aimed at modulating translation. Such events occur during viral infection by picornaviruses and lentiviruses and result in the hijack of the translational machinery through cleavage of eIF4G. Proteolysis of eIF4G is also mediated by caspases during the onset of apoptosis causing inhibition of protein synthesis. We will review the role of eIF4G and protein partners as well as the cellular and viral events that modulate eIF4G activity in the initiation of translation.
Tập 95 Số 3-4 - Trang 141-156 - 2003
Subcellular distribution of the inositol 1,4,5‐trisphosphate receptors: functional relevance and molecular determinants Abstract The inositol 1,4,5‐trisphosphate receptor (IP3 R) is an intracellular Ca2+ channel that is for the largest part expressed in the endoplasmic reticulum. Its precise subcellular localization is an important factor for the correct initiation and propagation of Ca2+ signals. The relative position of the IP3 Rs, and thus of the IP3 ‐sensitive Ca2+ stores, to mitochondria, nucleus or plasma membrane determines in many cases the physiological consequences of IP3 ‐induced Ca2+ release. Most cell types express more than one IP3 R isoform and their subcellular distribution is cell‐type dependent. Moreover, it was recently demonstrated that depending on the physiological status of the cell redistribution of IP3 Rs and/or of IP3 ‐sensitive Ca2+ stores could occur. This indicates that the cell must be able to regulate not only IP3 R expression but also its distribution. The various proteins potentially determining IP3 R localization and redistribution will therefore be discussed.
Tập 96 Số 1 - Trang 3-17 - 2004
Activity‐dependent regulation of the sumoylation machinery in rat hippocampal neurons Abstract Background information Sumoylation is a key post‐translational modification by which the Small Ubiquitin‐like MOdifier (SUMO) polypeptide is covalently attached to specific lysine residues of substrate proteins through a specific enzymatic pathway. Although sumoylation participates in the regulation of nuclear homeostasis, the sumoylation machinery is also expressed outside of the nucleus where little is still known regarding its non‐nuclear functions, particularly in the Central Nervous System (CNS). We recently reported that the sumoylation process is developmentally regulated in the rat CNS. Results Here, we demonstrate that there is an activity‐dependent redistribution of endogenous sumoylation enzymes in hippocampal neurons. By performing biochemical and immunocytochemical experiments on primary cultures of rat hippocampal neurons, we show that sumoylation and desumoylation enzymes are differentially redistributed in and out of synapses upon neuronal stimulation. This enzymatic redistribution in response to a neuronal depolarisation results in the transient decrease of sumoylated protein substrates at synapses. Conclusions Taken together, our data identify an activity‐dependent regulation of the sumoylation machinery in neurons that directly impacts on synaptic sumoylation levels. This process may provide a mechanism for neurons to adapt their physiological responses to changes occurring during neuronal activation.
Tập 105 Số 1 - Trang 30-45 - 2013
Timing the phases of the microtubule cycles involved in cytoplasmic and nuclear divisions in cells of undisturbed onion root meristems Summary— The duration of the different phases of the microtubule and chromosome cycles were estimated in the native diploid cell populations of Allium cepa L root meristems proliferating undisturbed, under steady state conditions, at the physiological temperature of 15°C. The cycles were coupled by considering their fitting in relation to the short process of nuclear envelope breakdown. In the cycle related to cytoplasmic division, the preprophase band which predicts the future position of the phragmoplast made its appearance, as a wide band, 16 mm before the G2 to prophase transition, ie it was only present during the final 5% of the total G2 timing (5 h 30 mm). The band became narrow only 6 mm after prophase had started and it was present in this form for the remaining prophase time (2 h 24 mm). Its disappearance occurred strictly coinciding with nuclear envelope breakdown, at the end of prophase. No microtubules related to cytoplasmic division were apparent until 9 mm after telophase had initiated. The two initial stages of phragmoplast formation which followed occupied, respectively, 27 mm and 54.5 mm of the 2‐h long telophase. On the other hand, the third and last stage in phragmoplast formation covered both the final 35 mm of mitosis and the 6 initial mm of the G1 of the next interphase. A very short (less than 4 mm) stage of microtubular nucleation around the nuclear envelope took place immediately afterwards, before the cortical array of microtubules appeared. The microtubule cycle related to nuclear division started with the apparent activation of the future spindle poles 7.4 mm before prophase was over. The mitotic spindle developed in the 5.6 mm long prometaphase. The spindle functioned in metaphase for the 42 mm it lasted, half spindles being separated for the 37 mm anaphase occupied in these cells.
Tập 78 - Trang 235-241 - 1993
The aquaporin-Z water channel gene of Escherichia coli: Structure, organization and phylogeny
Tập 89 - Trang 321-329 - 1997
The biased lamellipodium development and microtubule organizing center position in vascular endothelial cells migrating under the influence of fluid flow<sup>*</sup> Summary— To analytically study the morphological responses of vascular endothelial cells (ECs) to fluid flow, we designed a parallel plate flow culture chamber in which cells were cultured under fluid shear stress ranging from 0.01 to 2.0 Pa for several days. Via a viewing window of the chamber, EC responses to known levels of fluid shear stress were monitored either by direct observations or by a video‐enhanced time‐lapse microscopy. Among the responses of cultured ECs to flow, morphological responses take from hours to days to be fully expressed, except for the fluid shear stress‐dependent motility pattern change we reported earlier which could be detected within 30 min of flow changes. We report here that ECs exposed to more than 1.0 Pa of fluid shear shear stress have developed lamellipodia in the direction of flow in 10 min. This is the fastest structurally identifiable EC response to fluid shear stress. This was a reversible response. When the flow was stopped or reduced to the level which exerted less than 0.1 Pa of fluid shear stress, the biased lamellipodium development was lost within several minutes. The microtubule organizing center was located posterior to the nucleus in ECs under the influence of flow. However, this position was established only in ECs responding to fluid shear stress for longer than 1 h, indicating that positioning of the microtubule organizing center was not the reason for, but rather the result of, the biased lamellipodium response. Colcemid‐treated ECs responded normally to flow, indicating that microtubules were not involved in both flow sensing and the flow‐induced, biased lamellipodium development.
Tập 77 Số 3 - Trang 237-245 - 1993
Immunodetection of annexins 1 and 2 in ciliated cells from quail oviduct* Summary— Annexins I and 2 are Ca2+ ‐binding proteins related to the cytoskeletal proteins which have been reported to bind in a calcium‐dependent manner to F‐actin and phospholipids in vitro . Proteins immunologically related to the brain 37‐kDa annexin I and 36‐kDa annexin 2 were characterized by immunoblotting epithelial ciliated cells from quail oviduct. They were detected by immunofluorescence in ciliated as well as glandular cells, using antisera and purified antibodies directed against pig brain annexins. The pattern of labeling was found in the apical part of both cell types, with close membrane association. However, a wider distribution was observed in mature ciliated cells: annexins were localized in the well developed cytoskeletal meshwork in which the ciliary apparatus is tightly anchored. After immunogold labeling, annexins 1 and 2 were located in the same area as spectrin 240/235 and at the connection sites of F‐actin; both these cytoskeletals proteins were associated with the appendages of the basal body. In contrast, annexins were not detected in immature epithelial cells, while actin and spectrin were present. During ciliogenesis, the staining gradually appeared associated with the lateral and apical membranes. In this cellular model, the annexins may function during exocytosis in gland epithelial cells, where a close cytoskeleton‐membrane association is observed; moreover, in ciliated cells, a relationship between cytoskeletal elements of the terminal web and annexins may exist.
Tập 75 - Trang 45-54 - 1992
Cytoplasmic vacuolation, adaptation and cell death: A view on new perspectives and features Summry— This review focuses on a widely‐observed morphological phenomenon, a unique class of cytoplasmic vacuolation, found in cultured (mammalian) cells. This vacuolation is quite distinct from autophagosomal and heterophagosomal, ie excessive lysosomal vacuolation, and occurs in most cell types spontaneously or via a wide range of inductive stimuli. Apart from vacuolation arising artefactually (usually due to poor fixation), spontaneous vacuolation occurs in individual or small clusters of cultured cells without apparent change in their local environment, while neighbouring cells remain completely unaffected. Since spontaneous vacuolation is unpredictable, the process of vacuolation — or ‘vacuolisation’ — (‘Vacuolation’ is the state of being with vacuoles; ‘vacuolisation’ therefore implies the process of becoming vacuolated. However, only the quicker term vacuolation will be used throughout this review to refer to the process of vacuole development.) induced experimentally, and hence relatively reproducibly by a range of substances and disturbances, offers an experimental approach which should give further insight into its physiology and pathophysiology. Unfortunately, our knowledge here remains woefully inadequate compared with the purely morphological aspects of the phenomenon. Vacuolation following disturbances could have an underlying common mechanism; however, a review of the literature suggests that this is not the case, and that it occurs via several different pathways, involving many different cell organelles and structures. All cells appear to retain the capacity to vacuolate for some physiological purpose, and it can be a permanent feature in many cell types, particularly ‘lower’ organisms and plants. Vacuolation in cells is generally seen as an adaptive physiological response, presumably for ‘damage limitation’, but very little is known about the intracellular homeostatic mechanisms which operate to restore the status quo. Where damage limitation fails, cells usually die quickly, but no clear evidence has been found that this is in any way ‘programmed’. It is argued that the demise which occurs via the vacuolation route may, in fact, be a distinct form of cell death which is difficult to fit into the conventional lytic and apoptotic modes.
Tập 91 Số 7 - Trang 485-498 - 1999
Cytoskeleton of the unfertilized sea urchin egg Unfertilized Paracentrotus lividus egg cytoskeleton is prepared by mild, nonionic detergent extraction at 4 degrees C in buffer systems containing either 2‐methyl‐2,4‐pentanediol (hexylene glycol) or glycerol. These extractions allow the isolation of cytomatrices that maintain the egg form and are 70‐80 micron in diameter. DNase inhibition assays show that actin is in polymerized form in these cytomatrices. Ultrastructural observations reveal that the cytoskeletons are made up essentially of 2 categories of filaments, 7‐8‐nm and 2‐4‐nm in diameter, respectively. After heavy meromyosin labelling, short, radiating actin filaments are seen in the cortical region, while longer actin filaments are found in the internal region of these cytomatrices. The 2‐4‐nm filaments of still unknown biochemical nature are organized in a meshwork. In contrast to results found with fertilized eggs, bundles of actin filaments and microtubules are absent; 8‐13‐nm filaments are not detected.
Tập 60 Số 1 - Trang 63-69 - 1987