scholarly journals Delineation of the endocytic pathway of substance P and its seven-transmembrane domain NK1 receptor.

1995 ◽  
Vol 6 (5) ◽  
pp. 509-524 ◽  
Author(s):  
E F Grady ◽  
A M Garland ◽  
P D Gamp ◽  
M Lovett ◽  
D G Payan ◽  
...  
Keyword(s):  
Substance P ◽  
Cell Surface ◽  
Transmembrane Domain ◽  
Endocytic Pathway ◽  
Atpase Inhibitor ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Endosomal Acidification ◽  
Neurokinin 1 ◽  
New Protein

Many of the actions of the neuropeptide substance P (SP) that are mediated by the neurokinin 1 receptor (NK1-R) desensitize and resensitize, which may be associated with NK1-R endocytosis and recycling. We delineated this endocytic pathway in transfected cells by confocal microscopy using cyanine 3-SP and NK1-R antibodies. SP and the NK1-R were internalized into the same clathrin immunoreactive vesicles, and then sorted into different compartments. The NK1-R was colocalized with a marker of early endosomes, but not with markers of late endosomes or lysosomes. We quantified the NK1-R at the cell surface by incubating cells with an antibody to an extracellular epitope. After exposure to SP, there was a loss and subsequent recovery of surface NK1-R. The loss was prevented by hypertonic sucrose and potassium depletion, inhibitors of clathrin-mediated endocytosis. Recovery was independent of new protein synthesis because it was unaffected by cycloheximide. Recovery required endosomal acidification because it was prevented by an H(+)-ATPase inhibitor. The fate of internalized 125I-SP was examined by chromatography. SP was intact at the cell surface and in early endosomes, but slowly degraded in perinuclear vesicles. We conclude that SP induces clathrin-dependent internalization of the NK1-R. The SP/NK1-R complex dissociates in acidified endosomes. SP is degraded, whereas the NK1-R recycles to the cell surface.

scholarly journals The Early Phagosomal Stage of Francisella tularensis Determines Optimal Phagosomal Escape and Francisella Pathogenicity Island Protein Expression

2008 ◽  
Vol 76 (12) ◽  
pp. 5488-5499 ◽  
Author(s):  
Audrey Chong ◽  
Tara D. Wehrly ◽  
Vinod Nair ◽  
Elizabeth R. Fischer ◽  
Jeffrey R. Barker ◽  
...  
Keyword(s):  
Protein Expression ◽  
Francisella Tularensis ◽  
Pathogenicity Island ◽  
Endocytic Pathway ◽  
Atpase Inhibitor ◽  
Murine Bone Marrow ◽  
Concanamycin A ◽  
Late Endosomes ◽  
Endosomal Acidification ◽  
Schu S4

ABSTRACT Francisella tularensis is an intracellular pathogen that can survive and replicate within macrophages. Following phagocytosis and transient interactions with the endocytic pathway, F. tularensis rapidly escapes from its original phagosome into the macrophage cytoplasm, where it eventually replicates. To examine the importance of the nascent phagosome for the Francisella intracellular cycle, we have characterized early trafficking events of the F. tularensis subsp. tularensis strain Schu S4 in a murine bone marrow-derived macrophage model. Here we show that early phagosomes containing Schu S4 transiently interact with early and late endosomes and become acidified before the onset of phagosomal disruption. Inhibition of endosomal acidification with the vacuolar ATPase inhibitor bafilomycin A1 or concanamycin A prior to infection significantly delayed but did not block phagosomal escape and cytosolic replication, indicating that maturation of the early Francisella-containing phagosome (FCP) is important for optimal phagosomal escape and subsequent intracellular growth. Further, Francisella pathogenicity island (FPI) protein expression was induced during early intracellular trafficking events. Although inhibition of endosomal acidification mimicked the early phagosomal escape defects caused by mutation of the FPI-encoded IglCD proteins, it did not inhibit the intracellular induction of FPI proteins, demonstrating that this response is independent of phagosomal pH. Altogether, these results demonstrate that early phagosomal maturation is required for optimal phagosomal escape and that the early FCP provides cues other than intravacuolar pH that determine intracellular induction of FPI proteins.

scholarly journals A Selective Transport Route from Golgi to Late Endosomes That Requires the Yeast Gga Proteins

2000 ◽  
Vol 151 (3) ◽  
pp. 587-600 ◽  
Author(s):  
Michael W. Black ◽  
Hugh R.B. Pelham
Keyword(s):  
Fluorescent Protein ◽  
Transmembrane Domain ◽  
Endocytic Pathway ◽  
Coat Proteins ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Mutant Strains ◽  
Direct Delivery ◽  
Green Fluorescent ◽  
Exocytic Pathway

Pep12p is a yeast syntaxin located primarily in late endosomes. Using mutagenesis of a green fluorescent protein chimera we have identified a sorting signal FSDSPEF, which is required for transport of Pep12p from the exocytic pathway to late endosomes, from which it can, when overexpressed, reach the vacuole. When this signal is mutated, Pep12p instead passes to early endosomes, a step that is determined by its transmembrane domain. Surprisingly, Pep12p is then specifically retained in early endosomes and does not go on to late endosomes. By testing appropriate chimeras in mutant strains, we found that FSDSPEF-dependent sorting was abolished in strains lacking Gga1p and Gga2p, Golgi-associated coat proteins with homology to gamma adaptin. In the gga1 gga2 double mutant endogenous Pep12p cofractionated with the early endosome marker Tlg1p, and recycling of Snc1p through early endosomes was defective. Pep12p sorting was also defective in cells lacking the clathrin heavy or light chain. We suggest that specific and direct delivery of proteins to early and late endosomes is required to maintain the functional heterogeneity of the endocytic pathway and that the GGA proteins, probably in association with clathrin, help create vesicles destined for late endosomes.

scholarly journals Phosphatidylinositol 3-Kinase/Akt and MEK/ERK Signaling Pathways Facilitate Sapovirus Trafficking and Late Endosomal Acidification for Viral Uncoating in LLC-PK Cells

2018 ◽  
Vol 92 (24) ◽  
Author(s):  
Mahmoud Soliman ◽  
Deok-Song Kim ◽  
Jun-Gyu Park ◽  
Ji-Yun Kim ◽  
Mia Madel Alfajaro ◽  
...  
Keyword(s):  
Cell Surface ◽  
Signaling Pathways ◽  
Early Stage ◽  
Erk Signaling ◽  
Porcine Sapovirus ◽  
Early Activation ◽  
Cell Surface Carbohydrate ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Endosomal Acidification

ABSTRACTSapovirus, an important cause of acute gastroenteritis in humans and animals, travels from the early to the late endosomes and requires late endosomal acidification for viral uncoating. However, the signaling pathways responsible for these viral entry processes remain unknown. Here we demonstrate the receptor-mediated early activation of phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein extracellular signal-regulated kinase/extracellular signal-regulated kinase (MEK/ERK) signaling pathways involved in sapovirus entry processes. Both signaling pathways were activated during the early stage of porcine sapovirus (PSaV) infection. However, depletion of the cell surface carbohydrate receptors by pretreatment with sodium periodate or neuraminidase reduced the PSaV-induced early activation of these signaling pathways, indicating that PSaV binding to the cell surface carbohydrate receptors triggered these cascades. Addition of bile acid, known to be essential for PSaV escape from late endosomes, was also found to exert a stiffening effect to stimulate both pathways. Inhibition of these signaling pathways by use of inhibitors specific for PI3K or MEK or small interfering RNAs (siRNAs) against PI3K or MEK resulted in entrapment of PSaV particles in early endosomes and prevented their trafficking to late endosomes. Moreover, phosphorylated PI3K and ERK coimmunoprecipitated subunit E of the V-ATPase proton pump that is important for endosomal acidification. Based on our data, we conclude that receptor binding of PSaV activates both PI3K/Akt and MEK/ERK signaling pathways, which in turn promote PSaV trafficking from early to late endosomes and acidification of late endosomes for PSaV uncoating. These signaling cascades may provide a target for potent therapeutics against infections by PSaV and other caliciviruses.IMPORTANCESapoviruses cause acute gastroenteritis in both humans and animals. However, the host signaling pathway(s) that facilitates host cell entry by sapoviruses remains largely unknown. Here we demonstrate that porcine sapovirus (PSaV) activates both PI3K/Akt and MEK/ERK cascades at an early stage of infection. Removal of cell surface receptors decreased PSaV-induced early activation of both cascades. Moreover, blocking of PI3K/Akt and MEK/ERK cascades entrapped PSaV particles in early endosomes and prevented their trafficking to the late endosomes. PSaV-induced early activation of PI3K and ERK molecules further mediated V-ATPase-dependent late endosomal acidification for PSaV uncoating. This work unravels a new mechanism by which receptor-mediated early activation of both cascades may facilitate PSaV trafficking from early to late endosomes and late endosomal acidification for PSaV uncoating, which in turn can be a new target for treatment of sapovirus infection.

scholarly journals Relationship between invariant chain expression and major histocompatibility complex class II transport into early and late endocytic compartments.

1993 ◽  
Vol 177 (3) ◽  
pp. 583-596 ◽  
Author(s):  
P Romagnoli ◽  
C Layet ◽  
J Yewdell ◽  
O Bakke ◽  
R N Germain
Keyword(s):  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Class Ii ◽  
Endocytic Pathway ◽  
Invariant Chain ◽  
Major Histocompatibility ◽  
Histocompatibility Complex ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Endocytic Compartments

Invariant chain (Ii), which associates with major histocompatibility complex (MHC) class II molecules in the endoplasmic reticulum, contains a targeting signal for transport to intracellular vesicles in the endocytic pathway. The characteristics of the target vesicles and the relationship between Ii structure and class II localization in distinct endosomal subcompartments have not been well defined. We demonstrate here that in transiently transfected COS cells expressing high levels of the p31 or p41 forms of Ii, uncleaved Ii is transported to and accumulates in transferrin-accessible (early) endosomes. Coexpressed MHC class II is also found in this same compartment. These early endosomes show altered morphology and a slower rate of content movement to later parts of the endocytic pathway. At more moderate levels of Ii expression, or after removal of a highly conserved region in the cytoplasmic tail of Ii, coexpressed class II molecules are found primarily in vesicles with the characteristics of late endosomes/prelysosomes. The Ii chains in these late endocytic vesicles have undergone proteolytic cleavage in the lumenal region postulated to control MHC class II peptide binding. These data indicate that the association of class II with Ii results in initial movement to early endosomes. At high levels of Ii expression, egress to later endocytic compartments is delayed and class II-Ii complexes accumulate together with endocytosed material. At lower levels of Ii expression, class II-Ii complexes are found primarily in late endosomes/prelysosomes. These data provide evidence that the route of class II transport to the site of antigen processing and loading involves movement through early endosomes to late endosomes/prelysosomes. Our results also reveal an unexpected ability of intact Ii to modify the structure and function of the early endosomal compartment, which may play a role in regulating this processing pathway.

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.

Characterization of Endocytic Pathways by Quantitative Fluorescence Microscopy

1998 ◽  
Vol 4 (S2) ◽  
pp. 1024-1025
Author(s):  
Frederick R. Maxfield ◽  
Richik N. Ghosh ◽  
William G. Mallet ◽  
Thwe Thwe Soe ◽  
Philip L. Leopold ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Surface ◽  
Light And Electron Microscopy ◽  
Endocytic Pathway ◽  
Early Endosomes ◽  
Pass Through ◽  
Golgi Network ◽  
Quantitative Fluorescence ◽  
Endocytic Pathways

We have used light and electron microscopy to analyze endocytic trafficking pathways. In one set of studies, we have used fluorescently labeled antibodies to trace an endocytic pathway from the cell surface to the trans- Golgi network (TGN). Cells were transfected with a construct consisting of the transmembrane and cytoplasmic domains of TGN38 and the extracellular domain of Tac. TGN38 is predominantly in the TGN, but a small fraction is found on the cell surface. We used FITC-labeled anti-Tac monoclonal IgG to analyze the pathway from the surface to the TGN. We compared the distribution of internalized Tac-TGN38 to internalized transferrin. We found that most Tac-TGN38 enters the same early endosomes as transferrin. Furthermore, most Tac-TGN38 returns to the cell surface from the endocytic recycling compartment (ERC) at the same rate as transferrin. However, on each pass through the cell approximately 18% of Tac-TGN is retained, and this Tac-TGN38 is delivered to the TGN.

scholarly journals Syntaxin 7 and VAMP-7 are SolubleN-Ethylmaleimide–sensitive Factor Attachment Protein Receptors Required for Late Endosome–Lysosome and Homotypic Lysosome Fusion in Alveolar Macrophages

2000 ◽  
Vol 11 (7) ◽  
pp. 2327-2333 ◽  
Author(s):  
Diane McVey Ward ◽  
Jonathan Pevsner ◽  
Matthew A. Scullion ◽  
Michael Vaughn ◽  
Jerry Kaplan
Keyword(s):  
Alveolar Macrophages ◽  
Transmembrane Domain ◽  
Late Endosome ◽  
Endocytic Pathway ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Early Endosomes ◽  
Sensitive Factor ◽  
Protein Receptors

Endocytosis in alveolar macrophages can be reversibly inhibited, permitting the isolation of endocytic vesicles at defined stages of maturation. Using an in vitro fusion assay, we determined that each isolated endosome population was capable of homotypic fusion. All vesicle populations were also capable of heterotypic fusion in a temporally specific manner; early endosomes, isolated 4 min after internalization, could fuse with endosomes isolated 8 min after internalization but not with 12-min endosomes or lysosomes. Lysosomes fuse with 12-min endosomes but not with earlier endosomes. Using homogenous populations of endosomes, we have identified Syntaxin 7 as a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) required for late endosome–lysosome and homotypic lysosome fusion in vitro. A bacterially expressed human Syntaxin 7 lacking the transmembrane domain inhibited homotypic late endosome and lysosome fusion as well as heterotypic late endosome–lysosome fusion. Affinity-purified antibodies directed against Syntaxin 7 also inhibited lysosome fusion in vitro but had no affect on homotypic early endosome fusion. Previous work suggested that human VAMP-7 (vesicle-associated membrane protein-7) was a SNARE required for late endosome–lysosome fusion. A bacterially expressed human VAMP-7 lacking the transmembrane domain inhibited both late endosome–lysosome fusion and homotypic lysosome fusion in vitro. These studies indicate that: 1) fusion along the endocytic pathway is a highly regulated process, and 2) two SNARE molecules, Syntaxin 7 and human VAMP-7, are involved in fusion of vesicles in the late endocytic pathway in alveolar macrophages.

scholarly journals Identification of a membrane glycoprotein found primarily in the prelysosomal endosome compartment.

1991 ◽  
Vol 112 (2) ◽  
pp. 245-255 ◽  
Author(s):  
J E Park ◽  
J M Lopez ◽  
E B Cluett ◽  
W J Brown
Keyword(s):  
Lysosomal Enzymes ◽  
Endocytic Pathway ◽  
Membrane Glycoprotein ◽  
Cell Fractionation ◽  
Density Fractions ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Acidic Compartment ◽  
Intracellular Vesicles ◽  
Secondary Lysosomes

Cells contain an intracellular compartment that serves as both the "prelysosomal" delivery site for newly synthesized lysosomal enzymes by the mannose 6-phosphate (Man6P) receptor and as a station along the endocytic pathway to lysosomes. We have obtained mAbs to a approximately 57-kD membrane glycoprotein, (called here plgp57), found predominantly in this prelysosomal endosome compartment. This conclusion is supported by the following results: (a) plgp57 was primarily found in a population of late endosomes that were located just distal to the 20 degrees C block site in the endocytic pathway to lysosomes (approximately 83% of the prelysosomes were positive for plgp57 but less than 5% of the early endosomes had detectable amounts of this marker); (b) plgp57 and the cation-independent (CI) Man6P receptor were located in many of the same intracellular vesicles; (c) plgp57 was found in the membranes of an acidic compartment; (d) immunoelectron microscopy showed that plgp57 was located in characteristic multilamellar- and multivesicular-type vacuoles believed to be prelysosomal endosomes; and (e) cell fractionation studies demonstrated that plgp57 was predominantly found in low density organelles which comigrated with late endosomes and CI Man6P receptors, and only approximately 10-15% of the antigen was found in high density fractions containing the majority of secondary lysosomes. These results indicate that plgp57 is a novel marker for a unique prelysosomal endosome compartment that is the site of confluence of the endocytic and biosynthetic pathways to lysosomes.

scholarly journals Fusion of sequentially internalized vesicles in alveolar macrophages.

1990 ◽  
Vol 110 (4) ◽  
pp. 1013-1022 ◽  
Author(s):  
D M Ward ◽  
D P Hackenyos ◽  
J Kaplan
Keyword(s):  
Endocytic Pathway ◽  
Receptor Complexes ◽  
Intracellular Vesicle ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Changing Patterns ◽  
Intracellular Vesicle Transport ◽  
Shift Technique ◽  
Ligand Addition ◽  
Density Shift

Previously we reported that internalized ligand-receptor complexes are transported within the alveolar macrophage at a rate that is independent of the ligand and/or receptor but is dependent on the endocytic apparatus (Ward, D. M., R. S. Ajioka, and J. Kaplan. 1989. J. Biol. Chem. 264:8164-8170). To probe the mechanism of intracellular vesicle transport, we examined the ability of vesicles internalized at different times to fuse. The mixing of ligands internalized at different times was studied using the 3,3'-diaminobenzidine/horseradish peroxidase density shift technique. The ability of internalized vesicles to fuse was dependent upon their location in the endocytic pathway. When ligands were administered as tandem pulses a significant amount of mixing (20-40%) of vesicular contents was observed. The pattern of mixing was independent of the ligands employed (transferrin, mannosylated BSA, or alpha macroglobulin), the order of ligand addition, and temperature (37 degrees C or 28 degrees C). Fusion was restricted to a brief period immediately after internalization. The amount of fusion in early endosomes did not increase when cells, given tandem pulses, were chased such that the ligands further traversed the early endocytic pathway. Little fusion, also, was seen when a chase was interposed between the two ligand pulses. The temporal segregation of vesicle contents seen in early endosomes was lost within late endosomes. Extensive mixing of vesicle contents was observed in the later portion of the endocytic pathway. This portion of the pathway is defined by the absence of internalized transferrin and is composed of ligands en route to lysosomes. Incubation of cells in iso-osmotic medium in which Na+ was replaced by K+ inhibited movement of internalized ligands to the lysosome, resulting in ligand accumulation within the late endocytic pathway. The accumulation of ligand was correlated with extensive mixing of sequentially internalized ligands. Although significant amounts of ligand degradation were observed, this compartment was devoid of conventional lysosomal markers such as acid glycosidases. These results indicate changing patterns of vesicle fusion within the endocytic pathway, with a complete loss of temporal ligand segregation in a prelysosomal compartment.

scholarly journals Rapid Transport of Internalized P-Selectin to Late Endosomes and the Tgn

2000 ◽  
Vol 151 (1) ◽  
pp. 107-116 ◽  
Author(s):  
Kimberly S. Straley ◽  
Samuel A. Green
Keyword(s):  
Cell Surface ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Cell Surface Receptors ◽  
Surface Receptors ◽  
Endosomal Sorting ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Granule Membrane

Prior studies on receptor recycling through late endosomes and the TGN have suggested that such traffic may be largely limited to specialized proteins that reside in these organelles. We present evidence that efficient recycling along this pathway is functionally important for nonresident proteins. P-selectin, a transmembrane cell adhesion protein involved in inflammation, is sorted from recycling cell surface receptors (e.g., low density lipoprotein [LDL] receptor) in endosomes, and is transported from the cell surface to the TGN with a half-time of 20–25 min, six to seven times faster than LDL receptor. Native P-selectin colocalizes with LDL, which is efficiently transported to lysosomes, for 20 min after internalization, but a deletion mutant deficient in endosomal sorting activity rapidly separates from the LDL pathway. Thus, P-selectin is sorted from LDL receptor in early endosomes, driving P-selectin rapidly into late endosomes. P-selectin then recycles to the TGN as efficiently as other receptors. Thus, the primary effect of early endosomal sorting of P-selectin is its rapid delivery to the TGN, with rapid turnover in lysosomes a secondary effect of frequent passage through late endosomes. This endosomal sorting event provides a mechanism for efficiently recycling secretory granule membrane proteins and, more generally, for downregulating cell surface receptors.

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