Cellular compartment

About: Cellular compartment is a research topic. Over the lifetime, 1082 publications have been published within this topic receiving 53794 citations. The topic is also known as: cell compartmentation.

Lipidomic processes in homeostatic and LPS-modified cell renewal cycle. Role of phosphatidylinositol 3-kinase pathway in biomembrane synthesis and restitution of apical epithelial membrane.

Abstract: Background Nuclear transcriptome initiates specific proteome that facilitates metabolic events culminating in restitution of cell components and reproduction of the discrete cellular function, but the magnitude of various genes induction and following proteomic, lipidomic, and glycomic processes provide distinctness to the final product and its function. In homeostasis, the challenged cell responds to stimuli in defined and predictable mode but in the disease such as ulcerative erosions the ablation of cell survival signals and cell apoptosis is enhanced. Therefore, to uncover the discreteness and dissimilarity of the pathological processes induced by elicobacter pylori (H. pylori) lipopolysaccharide (LPS), not only measurement of the genomic events is crucial, but a complete cycle of events reproducing the cell specific proteins, lipids, and cell-specific environment created in situ require thorough investigation. Methods An impact of H. pylori LPS-induced processes on posttranslational lipidomic activity in endoplasmic reticulum (ER), Golgi and apical membrane was evaluated in the in vitro paradigm assembled with components of the rat gastric mucosal epithelial cells. Results In ER, the signals commanding synthesis of biomembrane in the presence of control, the LPS-derived or LPS-admixed cytosol was identical. The assembled vesicles contained the same amount of apoprotein and had the same lipid composition. Their biomembrane contained the same amount of sphingolipids in form of ceramide, which is determining factor of the ER-transport vesicle completion. The transport of apoprotein in ER vesicles to Golgi was also not changed. In Golgi, LPS-derived cytosol affected two distinct and concurrent with assembly of Golgi transport vesicles processes. The LPS-derived cytosol affected formation of Golgi transport vesicles destined to apical membrane and the incorporation (fusion) of Golgi vesicles with apical epithelial membrane. The LPS-derived cytosol decreased the production of Golgi vesicles by 15% and their fusion with the apical epithelial membrane by 83%. In contrast with wortmannin, the LPS-derived cytosol had no impact on Golgi transport vesicles association with the epithelial membrane. Conclusions We concluded that LPS interferes with MAPK-dependent activation of cytosolic PLA(2) since MAPKs immunoprecipitate added to the LPS-cytosol restored activation of cytosolic PLA(2)-specific fusion of the Golgi transport vesicles with apical mucosal cell membrane. On the other hand, wortmannin that inhibited the association of Golgi transport vesicles with apical membrane, interferes with cytosolic activity that controls association of PI3K-containing Golgi vesicles with the apical membrane. Together, our studies present evidence that allow to conclude that LPS affects MAPK-specific phosphorylation and PLA(2)-assisted membranes' fusion, whereas wortmannin affects association of PI3K- and PI3P-containing Golgi-derived transport vesicles with the membrane. In the final outcome, both actions result in a diminished or inhibited restitution of apical membrane.

Relationships between membranous organelles in amoebae studied by electron microscopic cytochemical staining.

Abstract: The intracellular location of a variety of enzymes was studied in Amoeba proteus with the use of electron microscopic cytochemical methods, in an attempt to assess the relationships between different membranous organelles. One group of enzymes, including nucleoside diphosphatases (IDPase, UDPase, GDPase, ADPase), carbamoyl phosphatase, alkaline phosphatase, and BAXD oxidase was localized mainly in the rough endoplasmic reticulum, nuclear envelope, and convex side of the Golgi apparatus. Esterase activity had a similar localization except that the Golgi apparatus was "stained" throughout most of its extent. A second group of enzymes was found in Golgi cisternae and vesicles, and in some vacuoles. This group included acid phosphatase, thiamine pyrophosphatase, and aryl sulfatase. Some enzymes previously detected in cytoplasmic membranes of other cells, including glucose-6-phosphatase, showed little or no activity in amoebae. The results suggest that there are chemical similarities and probable functional relationships between the rough endoplasmic reticulum, the nuclear envelope, and the convex side of the Golgi apparatus. On the other hand, the concave pole of the Golgi apparatus, aggregates of smooth tubules and vesicles, and the cell surface appear more closely related to one another than to the endoplasmic reticulum and the convex side of the Golgi apparatus. The cytochemical similarity between the Golgi apparatus and certain vacuoles such as food vacuoles may reflect the role of the Golgi apparatus in the formation of lysosomes. The locations of reaction products of the various enzymes in amoebae are compared with observations reported for other cell types.

Protein Kinase A Activity Is Necessary for Fission and Fusion of Golgi to Endoplasmic Reticulum Retrograde Tubules

Abstract: It is becoming increasingly accepted that together with vesicles, tubules play a major role in the transfer of cargo between different cellular compartments. In contrast to our understanding of the molecular mechanisms of vesicular transport, little is known about tubular transport. How signal transduction molecules regulate these two modes of membrane transport processes is also poorly understood. In this study we investigated whether protein kinase A (PKA) activity regulates the retrograde, tubular transport of Golgi matrix proteins from the Golgi to the endoplasmic reticulum (ER). We found that Golgi-to-ER retrograde transport of the Golgi matrix proteins giantin, GM130, GRASP55, GRASP65, and p115 was impaired in the presence of PKA inhibitors. In addition, we unexpectedly found accumulation of tubules containing both Golgi matrix proteins and resident Golgi transmembrane proteins. These tubules were still attached to the Golgi and were highly dynamic. Our data suggest that both fission and fusion of retrograde tubules are mechanisms regulated by PKA activity.

Platelet-activating factor antagonists enhance intracellular degradation of amyloid-β42 in neurons via regulation of cholesterol ester hydrolases

Abstract: The progressive dementia that is characteristic of Alzheimer’s disease is associated with the accumulation of amyloid-beta (Aβ) peptides in extracellular plaques and within neurons. Aβ peptides are targeted to cholesterol-rich membrane micro-domains called lipid rafts. Observations that many raft proteins undertake recycling pathways that avoid the lysosomes suggest that the accumulation of Aβ in neurons may be related to Aβ targeting lipid rafts. Here we tested the hypothesis that the degradation of Aβ by neurons could be increased by drugs affecting raft formation. Primary neurons were incubated with soluble Aβ preparations. The amounts of Aβ42 in neurons or specific cellular compartments were measured by enzyme-linked immunosorbent assay. The effects of drugs on the degradation of Aβ42 were studied. Aβ42 was targeted to detergent-resistant, low-density membranes (lipid rafts), trafficked via a pathway that avoided the lysosomes, and was slowly degraded by neurons (half-life was greater than 5 days). The metabolism of Aβ42 was sensitive to pharmacological manipulation. In neurons treated with the cholesterol synthesis inhibitor squalestatin, less Aβ42 was found within rafts, greater amounts of Aβ42 were found in lysosomes, and the half-life of Aβ42 was reduced to less than 24 hours. Treatment with phospholipase A2 inhibitors or platelet-activating factor (PAF) antagonists had the same effects on Aβ42 metabolism in neurons as squalestatin. PAF receptors were concentrated in the endoplasmic reticulum (ER) along with enzymes that constitute the cholesterol ester cycle. The addition of PAF to ER membranes triggered activation of cholesterol ester hydrolases and the release of cholesterol from stores of cholesterol esters. An inhibitor of cholesterol ester hydrolases (diethylumbelliferyl phosphate) also increased the degradation of Aβ42 in neurons. We conclude that the targeting of Aβ42 to rafts in normal cells is a factor that affects its degradation. Critically, pharmacological manipulation of neurons can significantly increase Aβ42 degradation. These results are consistent with the hypothesis that the Aβ-induced production of PAF controls a cholesterol-sensitive pathway that affects the cellular localization and hence the fate of Aβ42 in neurons.

Extending roGFP Emission via Förster-Type Resonance Energy Transfer Relay Enables Simultaneous Dual Compartment Ratiometric Redox Imaging in Live Cells

Abstract: Reactive oxygen species (ROS) mediate both intercellular and intraorganellar signaling, and ROS propagate oxidative stress between cellular compartments such as mitochondria and the cytosol. Each cellular compartment contains its own sources of ROS as well as antioxidant mechanisms, which contribute to dynamic fluctuations in ROS levels that occur during signaling, metabolism, and stress. However, the coupling of redox dynamics between cellular compartments has not been well studied because of the lack of available sensors to simultaneously measure more than one subcellular compartment in the same cell. Currently, the redox-sensitive green fluorescent protein, roGFP, has been used extensively to study compartment-specific redox dynamics because it provides a quantitative ratiometric readout and it is amenable to subcellular targeting as a genetically encoded sensor. Here, we report a new family of genetically encoded fluorescent protein sensors that extend the fluorescence emission of roGFP via Forster-ty...