scholarly journals Transport through the yeast endocytic pathway occurs through morphologically distinct compartments and requires an active secretory pathway and Sec18p/N-ethylmaleimide-sensitive fusion protein.

1997 ◽  
Vol 8 (1) ◽  
pp. 13-31 ◽  
Author(s):  
L Hicke ◽  
B Zanolari ◽  
M Pypaert ◽  
J Rohrer ◽  
H Riezman
Keyword(s):  
Fusion Protein ◽  
Secretory Pathway ◽  
Protein A ◽  
Brefeldin A ◽  
Early Endosome ◽  
Late Endosome ◽  
Endocytic Pathway ◽  
Early Secretory Pathway ◽  
Late Endosomes

Molecules travel through the yeast endocytic pathway from the cell surface to the lysosome-like vacuole by passing through two sequential intermediates. Immunofluorescent detection of an endocytosed pheromone receptor was used to morphologically identify these intermediates, the early and late endosomes. The early endosome is a peripheral organelle that is heterogeneous in appearance, whereas the late endosome is a large perivacuolar compartment that corresponds to the prevacuolar compartment previously shown to be an endocytic intermediate. We demonstrate that inhibiting transport through the early secretory pathway in sec mutants quickly impedes transport from the early endosome. Treatment of sensitive cells with brefeldin A also blocks transport from this compartment. We provide evidence that Sec18p/N-ethylmaleimide-sensitive fusion protein, a protein required for membrane fusion, is directly required in vivo for forward transport early in the endocytic pathway. Inhibiting protein synthesis does not affect transport from the early endosome but causes endocytosed proteins to accumulate in the late endosome. As newly synthesized proteins and the late steps of secretion are not required for early to late endosome transport, but endoplasmic reticulum through Golgi traffic is, we propose that efficient forward transport in the early endocytic pathway requires delivery of lipid from secretory organelles to endosomes.

Nav1.5 sodium channels in macrophages in multiple sclerosis lesions

2012 ◽  
Vol 19 (5) ◽  
pp. 532-542 ◽  
Author(s):  
Joel A Black ◽  
Jia Newcombe ◽  
Stephen G Waxman
Keyword(s):  
Multiple Sclerosis ◽  
Protein A ◽  
Proteolipid Protein ◽  
Endocytic Pathway ◽  
Late Endosomes ◽  
Myelin Degradation ◽  
Active Multiple Sclerosis

Background: Macrophages are dynamic participants in destruction of white matter in active multiple sclerosis (MS) plaques. Regulation of phagocytosis and myelin degradation along endosomal pathways in macrophages is highly-orchestrated and critically-dependent upon acidification of endosomal lumena. Evidence from in vitro studies with macrophages and THP-1 cells suggests that sodium channel Nav1.5 is present in the limiting membrane of maturing endosomes where it plays a prominent role in the accumulation of protons. However, a contribution of the Nav1.5 channel to macrophage-mediated events in vivo has not been demonstrated. Method: We examined macrophages within active MS lesions by immunohistochemistry to determine whether Nav1.5 is expressed in these cells in situ and, if expressed, whether it is localized to specific compartments along the endocytic pathway. Results: Our results demonstrate that Nav1.5 is expressed within macrophages in active MS lesions, and that it is preferentially expressed in late endosomes and phagolysosomes (Rab7+, LAMP-1+), and sparsely expressed in early (EEA-1+) endosomes. Triple-immunolabeling studies showed localization of Nav1.5 within Rab7+ endosomes containing proteolipid protein, a myelin marker, in macrophages within active MS plaques. Conclusions: These observations support the suggestion that Nav1.5 contributes to the phagocytic pathway of myelin degradation in macrophages in vivo within MS lesions.

Overexpression of the ARF1 exchange factor ARNO inhibits the early secretory pathway and causes the disassembly of the Golgi complex

1998 ◽  
Vol 111 (22) ◽  
pp. 3427-3436 ◽  
Author(s):  
S. Monier ◽  
P. Chardin ◽  
S. Robineau ◽  
B. Goud
Keyword(s):  
Golgi Complex ◽  
Secretory Pathway ◽  
Small Gtpase ◽  
Endocytic Pathway ◽  
Cell Fractionation ◽  
Exchange Factor ◽  
Early Secretory Pathway ◽  
Membrane Budding

The small GTPase ARF1 is a key regulator of intracellular membrane traffic. In its active, GTP-bound form, ARF1 is associated with Golgi membranes and promotes the recruitment of the cytosolic coat protein complex, which will result in membrane budding and vesicle formation. ARNO (ARF nucleotide site opener) has been shown to act in vitro as a GTP exchange factor for ARF1. Here, we have investigated the function of ARNO in vivo. By immunofluorescence and cell fractionation, ARNO was found to be mostly cytosolic in HeLa cells. Its overexpression led to a strong inhibition of the secretion of SEAP (secreted form of alkaline phosphatase). Newly synthesized SEAP failed to acquire endoglycosidase H resistance, indicating a block in the early secretory pathway. This effect on secretion was accompanied by a disassembly of the Golgi complex and a redistribution of Golgi resident proteins into the endoplasmic reticulum (ER). On the other hand, ARNO overexpression did not affect the early endocytic pathway. These results show that ARNO functions in vivo in Golgi to ER transport. Its behavior is then consistent with ARNO being an exchange factor for ARF1.

scholarly journals Saccharomyces cerevisiae Grx6 and Grx7 Are Monothiol Glutaredoxins Associated with the Early Secretory Pathway

2008 ◽  
Vol 7 (8) ◽  
pp. 1415-1426 ◽  
Author(s):  
Alicia Izquierdo ◽  
Celia Casas ◽  
Ulrich Mühlenhoff ◽  
Christopher Horst Lillig ◽  
Enrique Herrero
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Active Site ◽  
Secretory Pathway ◽  
Transmembrane Domain ◽  
Inhibitory Effect ◽  
Protein Accumulation ◽  
Oxidoreductase Activity ◽  
Early Secretory Pathway ◽  
Glycosylation Inhibitor

ABSTRACT Saccharomyces cerevisiae Grx6 and Grx7 are two monothiol glutaredoxins whose active-site sequences (CSYS and CPYS, respectively) are reminiscent of the CPYC active-site sequence of classical dithiol glutaredoxins. Both proteins contain an N-terminal transmembrane domain which is responsible for their association to membranes of the early secretory pathway vesicles, facing the luminal side. Thus, Grx6 localizes at the endoplasmic reticulum and Golgi compartments, while Grx7 is mostly at the Golgi. Expression of GRX6 is modestly upregulated by several stresses (calcium, sodium, and peroxides) in a manner dependent on the Crz1-calcineurin pathway. Some of these stresses also upregulate GRX7 expression under the control of the Msn2/4 transcription factor. The N glycosylation inhibitor tunicamycin induces the expression of both genes along with protein accumulation. Mutants lacking both glutaredoxins display reduced sensitivity to tunicamycin, although the drug is still able to manifest its inhibitory effect on a reporter glycoprotein. Grx6 and Grx7 have measurable oxidoreductase activity in vivo, which is increased in the presence of tunicamycin. Both glutaredoxins could be responsible for the regulation of the sulfhydryl oxidative state at the oxidant conditions of the early secretory pathway vesicles. However, the differences in location and expression responses against stresses suggest that their functions are not totally overlapping.

scholarly journals Trafficking of prion proteins through a caveolae-mediated endosomal pathway

2003 ◽  
Vol 162 (4) ◽  
pp. 703-717 ◽  
Author(s):  
Peter J. Peters ◽  
Alexander Mironov ◽  
David Peretz ◽  
Elly van Donselaar ◽  
Estelle Leclerc ◽  
...  
Keyword(s):  
Prion Proteins ◽  
Protein A ◽  
Subcellular Location ◽  
Cellular Prion Protein ◽  
Endocytic Pathway ◽  
Live Cells ◽  
Trafficking Pathway ◽  
Late Endosomes ◽  
Endosomal Pathway ◽  
Glycosylphosphatidyl Inositol

To understand the posttranslational conversion of the cellular prion protein (PrPC) to its pathologic conformation, it is important to define the intracellular trafficking pathway of PrPC within the endomembrane system. We studied the localization and internalization of PrPC in CHO cells using cryoimmunogold electron microscopy. At steady state, PrPC was enriched in caveolae both at the TGN and plasma membrane and in interconnecting chains of endocytic caveolae. Protein A–gold particles bound specifically to PrPC on live cells. These complexes were delivered via caveolae to the pericentriolar region and via nonclassical, caveolae-containing early endocytic structures to late endosomes/lysosomes, thereby bypassing the internalization pathway mediated by clathrin-coated vesicles. Endocytosed PrPC-containing caveolae were not directed to the ER and Golgi complex. Uptake of caveolae and degradation of PrPC was slow and sensitive to filipin. This caveolae-dependent endocytic pathway was not observed for several other glycosylphosphatidyl inositol (GPI)-anchored proteins. We propose that this nonclassical endocytic pathway is likely to determine the subcellular location of PrPC conversion.

scholarly journals Recycling pathways of glucosylceramide in BHK cells: distinct involvement of early and late endosomes

1992 ◽  
Vol 103 (4) ◽  
pp. 1139-1152
Author(s):  
J.W. Kok ◽  
K. Hoekstra ◽  
S. Eskelinen ◽  
D. Hoekstra
Keyword(s):  
Plasma Membrane ◽  
Intracellular Ph ◽  
Brefeldin A ◽  
Fluid Phase ◽  
Endocytic Pathway ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Recycling Pathway ◽  
Golgi Network ◽  
Extensive Involvement

Recycling pathways of the sphingolipid glucosylceramide were studied by employing a fluorescent analog of glucosylceramide, 6(-)[N-(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]hexanoylglucosyl sphingosine (C6-NBD-glucosylceramide). Direct recycling of the glycolipid from early endosomes to the plasma membrane occurs, as could be shown after treating the cells with the microtubule-disrupting agent nocodazole, which causes inhibition of the glycolipid's trafficking from peripheral early endosomes to centrally located late endosomes. When the microtubuli are intact, at least part of the glucosylceramide is transported from early to late endosomes together with ricin. Interestingly, also N-(lissamine rhodamine B sulfonyl)phosphatidylethanolamine (N-Rh-PE), a membrane marker of the fluid-phase endocytic pathway, is transported to this endosomal compartment. However, in contrast to both ricin and N-Rh-PE, the glucosylceramide can escape from this organelle and recycle to the plasma membrane. Monensin and brefeldin A have little effect on this recycling pathway, which would exclude extensive involvement of early Golgi compartments in recycling. Hence, the small fraction of the glycolipid that colocalizes with transferrin (Tf) in the Golgi area might directly recycle via the trans-Golgi network. When the intracellular pH was lowered to 5.5, recycling was drastically reduced, in accordance with the impeding effect of low intracellular pH on vesicular transport during endocytosis and in the biosynthetic pathway. Our results thus demonstrate the existence of at least two recycling pathways for glucosylceramide and indicate the relevance of early endosomes in recycling of both proteins and lipids.

scholarly journals Chicken Erythroid AE1 Anion Exchangers Associate with the Cytoskeleton During Recycling to the Golgi

1999 ◽  
Vol 10 (2) ◽  
pp. 455-469 ◽  
Author(s):  
Sourav Ghosh ◽  
Kathleen H. Cox ◽  
John V. Cox
Keyword(s):  
Plasma Membrane ◽  
Ammonium Chloride ◽  
Anion Exchanger ◽  
Secretory Pathway ◽  
Brefeldin A ◽  
Endocytic Pathway ◽  
Erythroid Cells ◽  
Anion Exchangers ◽  
Membrane Compartment ◽  
Chloride Treatment

Chicken erythroid AE1 anion exchangers receive endoglycosidase F (endo F)-sensitive sugar modifications in their initial transit through the secretory pathway. After delivery to the plasma membrane, anion exchangers are internalized and recycled to the Golgi where they acquire additional N-linked modifications that are resistant to endo F. During recycling, some of the anion exchangers become detergent insoluble. The acquisition of detergent insolubility correlates with the association of the anion exchanger with cytoskeletal ankyrin. Reagents that inhibit different steps in the endocytic pathway, including 0.4 M sucrose, ammonium chloride, and brefeldin A, block the acquisition of endo F-resistant sugars and the acquisition of detergent insolubility by newly synthesized anion exchangers. The inhibitory effects of ammonium chloride on anion exchanger processing are rapidly reversible. Furthermore, AE1 anion exchangers become detergent insoluble more rapidly than they acquire endo F-resistant modifications in cells recovering from an ammonium chloride block. This suggests that the cytoskeletal association of the recycling anion exchangers occurs after release from the compartment where they accumulate due to ammonium chloride treatment, and prior to their transit through the Golgi. The recycling pool of newly synthesized anion exchangers is reflected in the steady-state distribution of the polypeptide. In addition to plasma membrane staining, anion exchanger antibodies stain a perinuclear compartment in erythroid cells. This perinuclear AE1-containing compartment is also stained by ankyrin antibodies and partially overlaps the membrane compartment stained by NBD C6-ceramide, a Golgi marker. Detergent extraction of erythroid cells in situ has suggested that a substantial fraction of the perinuclear pool of AE1 is cytoskeletal associated. The demonstration that erythroid anion exchangers interact with elements of the cytoskeleton during recycling to the Golgi suggests the cytoskeleton may be involved in the post-Golgi trafficking of this membrane transporter.

scholarly journals Casein Kinase I Regulates Membrane Binding by ARF GAP1

2002 ◽  
Vol 13 (8) ◽  
pp. 2559-2570 ◽  
Author(s):  
Sidney Yu ◽  
Michael G. Roth
Keyword(s):  
Amino Acid ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Membrane Binding ◽  
Casein Kinase ◽  
Protein Domain ◽  
Amino Terminal ◽  
Early Secretory Pathway

ARF GAP1, a 415-amino acid GTPase activating protein (GAP) for ADP-ribosylation factor (ARF) contains an amino-terminal 115-amino acid catalytic domain and no other recognizable features. Amino acids 203–334 of ARF GAP1 were sufficient to target a GFP-fusion protein to Golgi membranes in vivo. When overexpressed in COS-1 cells, this protein domain inhibited protein transport between the ER and Golgi and, in vitro, competed with the full-length ARF GAP1 for binding to membranes. Membrane binding by ARF GAP1 in vitro was increased by a factor in cytosol and this increase was inhibited by IC261, an inhibitor selective for casein kinase Iδ (CKIδ), or when cytosol was treated with antibody to CKIδ. The noncatalytic domain of ARF GAP1 was phosphorylated both in vivo and in vitro by CKI. IC261 blocked membrane binding by ARF GAP1 in vivo and inhibited protein transport in the early secretory pathway. Overexpression of a catalytically inactive CKIδ also inhibited the binding of ARF GAP1 to membranes and interfered with protein transport. Thus, a CKI isoform is required for protein traffic through the early secretory pathway and can modulate the amount of ARF GAP1 that can bind to membranes.

scholarly journals De novo formation of an early endosome during Rab5 to Rab7 transition

2020 ◽  
Author(s):  
Frode Miltzow Skjeldal ◽  
Linda Hofstad Haugen ◽  
Duarte Mateus ◽  
Dominik Frei ◽  
Oddmund Bakke
Keyword(s):  
De Novo ◽  
Early Endosome ◽  
Late Endosome ◽  
Second Phase ◽  
Specific Domain ◽  
Endosomal Membrane ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Main Determinants ◽  
Insight Into

AbstractRab5 and Rab7a are the main determinants of early and late endosomes and are important regulators of endosomal progression. The transport from early endosomes to late endosome seems to be regulated through an endosomal maturation switch where Rab5 is exchanged with Rab7a on the same endosome. Here we provide new insight into the mechanism of endosomal maturation where we have discovered a stepwise Rab5 detachment, sequentially regulated by Rab7a. The initial detachment of Rab5 is Rab7a independent and demonstrate a diffusion-like exchange between cytosol and endosomal membrane, and the second phase is slower where Rab5 converges into a specific domain that specifically detaches as a Rab5 indigenous endosome. Consequently, we show that early endosomal maturation regulated through the Rab5 to Rab7a switch induce the formation of a new fully functional early endosome. Progression through a stepwise early endosomal maturation regulates the direction of the transport and concomitantly regulates the homeostasis of early endosomes.

scholarly journals Annexin A8 Regulates Late Endosome Organization and Function

2008 ◽  
Vol 19 (12) ◽  
pp. 5267-5278 ◽  
Author(s):  
Verena Goebeler ◽  
Michaela Poeter ◽  
Dagmar Zeuschner ◽  
Volker Gerke ◽  
Ursula Rescher
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Actin Filaments ◽  
Late Endosome ◽  
Endocytic Pathway ◽  
Mitogen Activated Protein Kinase ◽  
Late Endosomes ◽  
Endosomal Membranes ◽  
Epidermal Growth ◽  
And Function

Different classes of endosomes exhibit a characteristic intracellular steady-state distribution governed by interactions with the cytoskeleton. Late endosomes, organelles of the degradative lysosomal route, seem to require associated actin filaments for proper localization and function. We show here that the F-actin and phospholipid binding protein annexin A8 is associated specifically with late endosomes. Altering intracellular annexin A8 levels drastically affected the morphology and intracellular distribution of late endosomes. Trafficking through the degradative pathway was delayed in the absence of annexin A8, resulting in attenuated ligand-induced degradation of the epidermal growth factor receptor and prolonged epidermal growth factor-induced activation of mitogen-activated protein kinase. Depletion of annexin A8 reduced the association of late endosomal membranes with actin filaments. These results indicate that the defective cargo transport through the late endocytic pathway and the imbalanced signaling of activated receptors observed in the absence of annexin A8 results from the disturbed association of late endosomal membranes with the actin network, resulting in impaired actin-based late endosome motility.

The endocytic pathway in animal cells

1990 ◽  
Vol 48 (3) ◽  
pp. 41-41
Author(s):  
Gareth Griffiths
Keyword(s):  
Early Endosome ◽  
Endocytic Pathway ◽  
Three Dimensions ◽  
Cell Periphery ◽  
Animal Cells ◽  
The Third ◽  
Negative Stain ◽  
Late Endosomes ◽  
Work Done

Our recent data have provided evidence that the endocytic pathway comprises four structurally and functionally distinct compartments in addition to the clathrin coated vesicles. The most proximal of these compartments, the early endosome, is structurally complex, consists of cisternal, tubular, as well as vesicular domains and is predominantly localized to the cell periphery. We have proposed that the vesicular domains bud off the early endosome to form the spherical endosome (carrier) vesicles that transport material from early to late endosomes, a process that requires microtubules. These endosome vesicles are spherical (0.2-0.4μm diameter) structures whose lumen is packed with thin tubules. The structure of the latter has recently become more evident in negative stain preparations. These vesicles can also be shown to bind microtubules in vitro (work done in collaboration with Jean Gruenberg's group, EMBL). The third compartment, the late endosome or prelysosomal compartment (PLC) is, like the early endosome, complex in three-dimensions.

Sign in / Sign up

Export Citation Format

Share Document