scholarly journals Morphology of the Yeast Endocytic Pathway

1998 ◽  
Vol 9 (1) ◽  
pp. 173-189 ◽  
Author(s):  
Cristina Prescianotto-Baschong ◽  
Howard Riezman
Keyword(s):  
Time Course ◽  
Strong Support ◽  
Multivesicular Body ◽  
Endocytic Pathway ◽  
Dependent Manner ◽  
Uniform Size ◽  
Endocytic Vesicles ◽  
Energy Dependent ◽  
Mutant Cells ◽  
Positively Charged

Positively charged Nanogold (Nanoprobes, Stony Brook, NY) has been developed as a new marker to follow the endocytic pathway in yeast. Positively charged Nanogold binds extensively to the surface of yeast spheroplasts and is internalized in an energy-dependent manner. Internalization of gold is blocked in the end3 mutant. During a time course of incubation of yeast spheroplasts with positively charged Nanogold at 15°C, the gold was detected sequentially in small vesicles, a peripheral, vesicular/tubular compartment that we designate as an early endosome, a multivesicular body corresponding to the late endosome near the vacuole, and in the vacuole. Experiments examining endocytosis in the sec18mutant showed an accumulation of positively charged Nanogold in approximately 30–50 nm diameter vesicles. These vesicles most likely represent the primary endocytic vesicles as no other intermediates were detected in the mutant cells, and they correspond in size to the first vesicles detected in wild-type spheroplasts at 15°C. These data lend strong support to the idea that the internalization step of endocytosis in yeast involves formation of small vesicles of uniform size from the plasma membrane.

scholarly journals Endosomal maturation by Rab conversion in Aspergillus nidulans is coupled to dynein-mediated basipetal movement

2012 ◽  
Vol 23 (10) ◽  
pp. 1889-1901 ◽  
Author(s):  
Juan F. Abenza ◽  
Antonio Galindo ◽  
Mario Pinar ◽  
Areti Pantazopoulou ◽  
Vivian de los Ríos ◽  
...  
Keyword(s):  
Aspergillus Nidulans ◽  
Multivesicular Body ◽  
Endocytic Pathway ◽  
Dependent Manner ◽  
Long Distance ◽  
Genetic Studies ◽  
Late Endosomes ◽  
Early Endosomes ◽  
A Minor ◽  
Long Distance Movement

We exploit the ease with which highly motile early endosomes are distinguished from static late endosomes in order to study Aspergillus nidulans endosomal traffic. RabSRab7 mediates homotypic fusion of late endosomes/vacuoles in a homotypic fusion- and vacuole protein sorting/Vps41–dependent manner. Progression across the endocytic pathway involves endosomal maturation because the end products of the pathway in the absence of RabSRab7 are minivacuoles that are competent in multivesicular body sorting and cargo degradation but retain early endosomal features, such as the ability to undergo long-distance movement and propensity to accumulate in the tip region if dynein function is impaired. Without RabSRab7, early endosomal Rab5s—RabA and RabB—reach minivacuoles, in agreement with the view that Rab7 homologues facilitate the release of Rab5 homologues from endosomes. RabSRab7 is recruited to membranes already at the stage of late endosomes still lacking vacuolar morphology, but the transition between early and late endosomes is sharp, as only in a minor proportion of examples are RabA/RabB and RabSRab7 detectable in the same—frequently the less motile—structures. This early-to-late endosome/vacuole transition is coupled to dynein-dependent movement away from the tip, resembling the periphery-to-center traffic of endosomes accompanying mammalian cell endosomal maturation. Genetic studies establish that endosomal maturation is essential, whereas homotypic vacuolar fusion is not.

scholarly journals A Yeast t-SNARE Involved in Endocytosis

1998 ◽  
Vol 9 (10) ◽  
pp. 2873-2889 ◽  
Author(s):  
Karin Séron ◽  
Ville Tieaho ◽  
Cristina Prescianotto-Baschong ◽  
Thomas Aust ◽  
Marie-Odile Blondel ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Secretory Pathway ◽  
Essential Gene ◽  
Specific Interaction ◽  
Endocytic Pathway ◽  
Intracellular Membrane ◽  
Atpase Subunit ◽  
Early Endosomes ◽  
Endocytic Vesicles ◽  
Positively Charged

The ORF YOL018c (TLG2) of Saccharomyces cerevisiae encodes a protein that belongs to the syntaxin protein family. The proteins of this family, t-SNAREs, are present on target organelles and are thought to participate in the specific interaction between vesicles and acceptor membranes in intracellular membrane trafficking. TLG2 is not an essential gene, and its deletion does not cause defects in the secretory pathway. However, its deletion in cells lacking the vacuolar ATPase subunit Vma2p leads to loss of viability, suggesting that Tlg2p is involved in endocytosis. In tlg2Δ cells, internalization was normal for two endocytic markers, the pheromone α-factor and the plasma membrane uracil permease. In contrast, degradation of α-factor and uracil permease was delayed intlg2Δ cells. Internalization of positively charged Nanogold shows that the endocytic pathway is perturbed in the mutant, which accumulates Nanogold in primary endocytic vesicles and shows a greatly reduced complement of early endosomes. These results strongly suggest that Tlg2p is a t-SNARE involved in early endosome biogenesis.

scholarly journals A Chinese hamster ovary cell mutant defective in the non-endocytic uptake of fluorescent analogs of phosphatidylserine: isolation using a cytosol acidification protocol.

1995 ◽  
Vol 128 (5) ◽  
pp. 793-804 ◽  
Author(s):  
K Hanada ◽  
R E Pagano
Keyword(s):  
Plasma Membrane ◽  
Cho Cells ◽  
Screening Method ◽  
Endocytic Pathway ◽  
Ovary Cell ◽  
Acidic Ph ◽  
Intact Cells ◽  
Energy Dependent ◽  
Mutant Cells ◽  
Cytosolic Acidification

Transmembrane movement of phosphatidylserine (PS) and various PS analogs at the plasma membrane is thought to occur by an ATP-dependent, protein-mediated process. To isolate mutant CHO cells defective in this activity, we first obtained conditions which inhibited the endocytic, but not the non-endocytic pathway of lipid internalization since PS may enter cells by a combination of these two pathways. We found that acidic treatment of cells, which blocks clathrin-dependent endocytosis, enhanced the energy-dependent uptake of 1-palmitoyl-2-(6-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]caproyl -sn- glycero-3-phosphoserine (C6-NBD-PS) in CHO cells from donor vesicles (liposomes) by about twofold. Control experiments demonstrated that the enhanced uptake of C6-NBD-PS at acidic pH was not due to: (a) an increase in the capacity of the plasma membrane to incorporate C6-NBD-PS from the donor vesicles; (b) a decrease in the rate of loss of C6-NBD-PS from the cells; or (c) fusion or engulfment of the donor vesicles. When cytosolic acidification (to pH 6.3) was imposed without acidification of the extracellular medium, C6-NBD-PS uptake by intact cells was increased by about 50% compared to control values determined in the absence of acidification. These results suggested that a protein and energy dependent system(s) for transbilayer movement of the fluorescent PS was stimulated by cytosolic acidification. A screening method for mutant cells defective in the non-endocytic uptake of fluorescent PS analogs with replica cell colonies at acidic pH was then devised. After selection of mutagenized CHO-K1 cells by in situ screening, we obtained a mutant cell line in which uptake of fluorescent PS analogs was reduced to about 25% of the wild type level at either pH 6.0 or 7.4. Control experiments demonstrated that the reduced uptake of fluorescent PS analogs in the mutant cells was unrelated to multidrug resistance, and that endocytosis of another plasma membrane lipid marker occurred normally in the mutant cells. These results suggested that a non-endocytic pathway responsible for uptake of fluorescent PS analogs was specifically affected in the mutant cells.

The Time Course of the Aversive Conflict Signal

2015 ◽  
Vol 62 (1) ◽  
pp. 30-39 ◽  
Author(s):  
Julia Fritz ◽  
Gesine Dreisbach
Keyword(s):  
Time Course ◽  
Strong Support ◽  
Short Soas ◽  
Priming Effects ◽  
Presentation Time ◽  
Psychological Evidence ◽  
Study Participants ◽  
Direct Investigation

The idea that conflicts are aversive signals recently has gained strong support by both physiological as well as psychological evidence. However, the time course of the aversive signal has not been subject to direct investigation. In the present study, participants had to judge the valence of neutral German words after being primed with conflict or non-conflict Stroop stimuli in three experiments with varying SOA (200 ms, 400 ms, 800 ms) and varying prime presentation time. Conflict priming effects (i.e., increased frequencies of negative judgments after conflict as compared to non-conflict primes) were found for SOAs of 200 ms and 400 ms, but absent (or even reversed) with a SOA of 800 ms. These results imply that the aversiveness of conflicts is evaluated automatically with short SOAs, but is actively counteracted with prolonged prime presentation.

scholarly journals Annexin A6 modulates TBC1D15/Rab7/StARD3 axis to control endosomal cholesterol export in NPC1 cells

2019 ◽  
Vol 77 (14) ◽  
pp. 2839-2857 ◽  
Author(s):  
Elsa Meneses-Salas ◽  
Ana García-Melero ◽  
Kristiina Kanerva ◽  
Patricia Blanco-Muñoz ◽  
Frederic Morales-Paytuvi ◽  
...  
Keyword(s):  
Late Endosome ◽  
Dependent Manner ◽  
Lipid Transfer ◽  
Cholesterol Accumulation ◽  
Membrane Contact Sites ◽  
Late Endosomes ◽  
Membrane Contact ◽  
Domain 3 ◽  
Niemann Pick ◽  
Mutant Cells

Abstract Cholesterol accumulation in late endosomes is a prevailing phenotype of Niemann-Pick type C1 (NPC1) mutant cells. Likewise, annexin A6 (AnxA6) overexpression induces a phenotype reminiscent of NPC1 mutant cells. Here, we demonstrate that this cellular cholesterol imbalance is due to AnxA6 promoting Rab7 inactivation via TBC1D15, a Rab7-GAP. In NPC1 mutant cells, AnxA6 depletion and eventual Rab7 activation was associated with peripheral distribution and increased mobility of late endosomes. This was accompanied by an enhanced lipid accumulation in lipid droplets in an acyl-CoA:cholesterol acyltransferase (ACAT)-dependent manner. Moreover, in AnxA6-deficient NPC1 mutant cells, Rab7-mediated rescue of late endosome-cholesterol export required the StAR-related lipid transfer domain-3 (StARD3) protein. Electron microscopy revealed a significant increase of membrane contact sites (MCS) between late endosomes and ER in NPC1 mutant cells lacking AnxA6, suggesting late endosome-cholesterol transfer to the ER via Rab7 and StARD3-dependent MCS formation. This study identifies AnxA6 as a novel gatekeeper that controls cellular distribution of late endosome-cholesterol via regulation of a Rab7-GAP and MCS formation.

scholarly journals Decoding the temporal nature of brain GR activity in the NFκB signal transition leading to depressive-like behavior

2021 ◽  
Author(s):  
Young-Min Han ◽  
Min Sun Kim ◽  
Juyeong Jo ◽  
Daiha Shin ◽  
Seung-Hae Kwon ◽  
...  
Keyword(s):  
Inhibitory Action ◽  
Time Course ◽  
Molecular Mechanisms ◽  
Late Phase ◽  
Fine Tuning ◽  
Dependent Manner ◽  
Middle Phase ◽  
Temporal Shift

AbstractThe fine-tuning of neuroinflammation is crucial for brain homeostasis as well as its immune response. The transcription factor, nuclear factor-κ-B (NFκB) is a key inflammatory player that is antagonized via anti-inflammatory actions exerted by the glucocorticoid receptor (GR). However, technical limitations have restricted our understanding of how GR is involved in the dynamics of NFκB in vivo. In this study, we used an improved lentiviral-based reporter to elucidate the time course of NFκB and GR activities during behavioral changes from sickness to depression induced by a systemic lipopolysaccharide challenge. The trajectory of NFκB activity established a behavioral basis for the NFκB signal transition involved in three phases, sickness-early-phase, normal-middle-phase, and depressive-like-late-phase. The temporal shift in brain GR activity was differentially involved in the transition of NFκB signals during the normal and depressive-like phases. The middle-phase GR effectively inhibited NFκB in a glucocorticoid-dependent manner, but the late-phase GR had no inhibitory action. Furthermore, we revealed the cryptic role of basal GR activity in the early NFκB signal transition, as evidenced by the fact that blocking GR activity with RU486 led to early depressive-like episodes through the emergence of the brain NFκB activity. These results highlight the inhibitory action of GR on NFκB by the basal and activated hypothalamic-pituitary-adrenal (HPA)-axis during body-to-brain inflammatory spread, providing clues about molecular mechanisms underlying systemic inflammation caused by such as COVID-19 infection, leading to depression.

scholarly journals Uptake and Distribution of Administered Bone Marrow Mesenchymal Stem Cell Extracellular Vesicles in Retina

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 730
Author(s):  
Biji Mathew ◽  
Leianne A. Torres ◽  
Lorea Gamboa Gamboa Acha ◽  
Sophie Tran ◽  
Alice Liu ◽  
...  
Keyword(s):  
Stem Cell ◽  
Mesenchymal Stem Cell ◽  
Extracellular Vesicles ◽  
Time Course ◽  
Ganglion Cells ◽  
Ex Vivo ◽  
Dependent Manner ◽  
Paracrine Effects

Cell replacement therapy using mesenchymal (MSC) and other stem cells has been evaluated for diabetic retinopathy and glaucoma. This approach has significant limitations, including few cells integrated, aberrant growth, and surgical complications. Mesenchymal Stem Cell Exosomes/Extracellular Vesicles (MSC EVs), which include exosomes and microvesicles, are an emerging alternative, promoting immunomodulation, repair, and regeneration by mediating MSC’s paracrine effects. For the clinical translation of EV therapy, it is important to determine the cellular destination and time course of EV uptake in the retina following administration. Here, we tested the cellular fate of EVs using in vivo rat retinas, ex vivo retinal explant, and primary retinal cells. Intravitreally administered fluorescent EVs were rapidly cleared from the vitreous. Retinal ganglion cells (RGCs) had maximal EV fluorescence at 14 days post administration, and microglia at 7 days. Both in vivo and in the explant model, most EVs were no deeper than the inner nuclear layer. Retinal astrocytes, microglia, and mixed neurons in vitro endocytosed EVs in a dose-dependent manner. Thus, our results indicate that intravitreal EVs are suited for the treatment of retinal diseases affecting the inner retina. Modification of the EV surface should be considered for maintaining EVs in the vitreous for prolonged delivery.

scholarly journals IL-8 and MCP Gene Expression and Production by LPS-Stimulated Human Corneal Stromal Cells

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
Roni M. Shtein ◽  
Susan G. Elner ◽  
Zong-Mei Bian ◽  
Victor M. Elner
Keyword(s):  
Gene Expression ◽  
Northern Blot ◽  
Stromal Cells ◽  
Blot Analysis ◽  
Time Course ◽  
Northern Blot Analysis ◽  
Statistical Significance ◽  
Dependent Manner ◽  
Corneal Inflammation ◽  
Chemotactic Protein

Purpose. To determine time course of effect of lipopolysaccharide (LPS) on production of interleukin-8 (IL-8) and monocyte chemotactic protein (MCP) by cultured human corneal stromal cells.Methods. Human corneal stromal cells were harvested from donor corneal specimens, and fourth to sixth passaged cells were used. Cell cultures were stimulated with LPS for 2, 4, 8, and 24 hours. Northern blot analysis of IL-8 and MCP gene expression and ELISA for IL-8 and MCP secretion were performed. ELISA results were analyzed for statistical significance using two-tailed Student'st-test.Results. Northern blot analysis demonstrated significantly increased IL-8 and MCP gene expression after 4 and 8 hours of exposure to LPS. ELISA for secreted IL-8 and MCP demonstrated statistically significant increases (P<0.05) after corneal stromal cell stimulation with LPS.Conclusions. This paper suggests that human corneal stromal cells may participate in corneal inflammation by secreting potent leukocyte chemotactic and activating proteins in a time-dependent manner when exposed to LPS.

Nuclear import of glycoconjugates is distinct from the classical NLS pathway

1995 ◽  
Vol 108 (4) ◽  
pp. 1325-1332 ◽  
Author(s):  
E. Duverger ◽  
C. Pellerin-Mendes ◽  
R. Mayer ◽  
A.C. Roche ◽  
M. Monsigny
Keyword(s):  
Nuclear Localization ◽  
Nuclear Import ◽  
Nuclear Localization Signal ◽  
Peptide Sequence ◽  
Nuclear Pore ◽  
Dependent Manner ◽  
Permeabilized Cells ◽  
Localization Signal ◽  
Energy Dependent ◽  
Cytosolic Factors

The nuclear import of many proteins depends on a short peptide sequence called the nuclear localization signal. However, glycosylated proteins, which lack such a nuclear localization signal, upon their injection into the cytosol by electroporation, enter the nucleus in a sugar-dependent manner. This paper brings new insights on the mechanism of this process, based on a study of neoglycoprotein nuclear uptake by digitonin-permeabilized cells. The nuclear import of neoglycoproteins is energy dependent: it does not occur when cells are maintained at 4 degrees C or when cells are ATP-depleted by treatment with apyrase. The nuclear import of neoglycoproteins occurs through the nuclear pore: it is inhibited by preincubation of cells with wheat germ agglutinin, a lectin which binds the nuclear pore glycoproteins and blocks the translocation step of nuclear localization signal bearing proteins through the nuclear pore. Furthermore, the nuclear import of neoglycoproteins does not use the pathway of nuclear localization signal bearing proteins: nuclear import of nuclear localization signal bearing proteins depends on cytosolic factors and is inhibited by treatment of cells with N-ethylmaleimide, while the nuclear import of neoglycoproteins neither requires added cytosolic factors nor is sensitive to alkylation by N-ethylmaleimide. In addition, upon incubation in the presence of a large excess of nuclear localization signal bearing protein, the nuclear import of neoglycoproteins is not inhibited.

Abstract P204: Epithelial Sodium Channel Stimulation by Glucose

Hypertension ◽  
2016 ◽  
Vol 68 (suppl_1) ◽  
Author(s):  
Parijat S Joy ◽  
Peter M. Snyder
Keyword(s):  
Diabetes Mellitus ◽  
Cell Surface ◽  
Collecting Duct ◽  
Short Circuit ◽  
Primary Cultures ◽  
Endocytic Pathway ◽  
Sodium Absorption ◽  
Dependent Manner ◽  
Elevated Glucose ◽  
Underlying Mechanisms

There is a link between diabetes mellitus and hypertension, but the underlying mechanisms are poorly understood. The epithelial Na + channel ENaC plays an important role in blood pressure control; ENaC mutations cause Liddle’s syndrome, an inherited form of hypertension. Previous work suggests that ENaC abundance is increased in diabetes mellitus, but the underlying mechanisms are unclear. Here we tested the effect of glucose on ENaC regulation. In Ussing chamber experiments using mouse kidney collecting duct cells (mCCD) and primary cultures of human lung epithelia, elevated glucose increased ENaC-mediated short-circuit current by 2-3 times in a dose-dependent manner from 100mg/dl to 400mg/dl of glucose. This was caused by an increase in ENaC abundance at the cell surface. We hypothesized that hyperglycemia might enhance ENaC cell surface abundance by altering activity of Nedd4-2, an E3 ubiquitin-protein ligase that binds to PY motifs within ENaC. Consistent with this hypothesis, we found that mutation of the PY motifs abolished ENaC stimulation by elevated glucose. Moreover, using a biotinylation assay, we found that elevated glucose (300 mg/dl) slowed ENaC endocytosis and reduced its degradation in the endocytic pathway. These changes in trafficking are explained by our finding that glucose reduced ENaC binding to Nedd4-2, and hence, reduced ENaC ubiquitination. O-GlcNAcylation plays a role in insulin signaling and glucose toxicity due to increased O-GlcNAcylation of target proteins. To test a role for O-GlcNAcylation in ENaC stimulation by glucose, we used 6-Diazo-5-oxo-l-norleucine (DON) to inhibit O-GlcNAcylation. DON abolished ENaC stimulation by elevated glucose. Using anti-O-GlcNAc antibody, we found that Nedd4-2 is a substrate for O-GlcNAcylation, and this modification was increased by elevated glucose. DON also reversed the reduction in binding of Nedd4-2 to ENaC at high glucose levels. Together, our data suggest a model in which hyperglycemia stimulates ENaC through O-GlcNAcylation of Nedd4-2, increasing ENaC abundance at cell surface thus increasing epithelial sodium absorption.

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