scholarly journals A presynaptic endosomal trafficking pathway controls synaptic growth signaling

2011 ◽  
Vol 193 (1) ◽  
pp. 201-217 ◽  
Author(s):  
Avital A. Rodal ◽  
Aline D. Blunk ◽  
Yulia Akbergenova ◽  
Ramon A. Jorquera ◽  
Lauren K. Buhl ◽  
...  
Keyword(s):  
Endocytic Pathway ◽  
Physical Interaction ◽  
Endosomal Trafficking ◽  
Synaptic Growth ◽  
Recycling Endosomes ◽  
Sorting Nexin ◽  
Trafficking Pathway ◽  
Early Endosomes ◽  
Protein Receptors ◽  
Escrt Complex

Structural remodeling of synapses in response to growth signals leads to long-lasting alterations in neuronal function in many systems. Synaptic growth factor receptors alter their signaling properties during transit through the endocytic pathway, but the mechanisms controlling cargo traffic between endocytic compartments remain unclear. Nwk (Nervous Wreck) is a presynaptic F-BAR/SH3 protein that regulates synaptic growth signaling in Drosophila melanogaster. In this paper, we show that Nwk acts through a physical interaction with sorting nexin 16 (SNX16). SNX16 promotes synaptic growth signaling by activated bone morphogenic protein receptors, and live imaging in neurons reveals that SNX16-positive early endosomes undergo transient interactions with Nwk-containing recycling endosomes. We identify an alternative signal termination pathway in the absence of Snx16 that is controlled by endosomal sorting complex required for transport (ESCRT)–mediated internalization of receptors into the endosomal lumen. Our results define a presynaptic trafficking pathway mediated by SNX16, NWK, and the ESCRT complex that functions to control synaptic growth signaling at the interface between endosomal compartments.

scholarly journals Higher-order assembly of Sorting Nexin 16 controls tubulation and distribution of neuronal endosomes

2019 ◽  
Vol 218 (8) ◽  
pp. 2600-2618 ◽  
Author(s):  
ShiYu Wang ◽  
Zechuan Zhao ◽  
Avital A. Rodal
Keyword(s):  
Cell Body ◽  
Motor Neurons ◽  
Coiled Coil ◽  
Higher Order ◽  
Synaptic Growth ◽  
Sorting Nexin ◽  
Protein Receptors ◽  
Self Association ◽  
Signaling Receptors

The activities of neuronal signaling receptors depend heavily on the maturation state of the endosomal compartments in which they reside. However, it remains unclear how the distribution of these compartments within the uniquely complex morphology of neurons is regulated and how this distribution itself affects signaling. Here, we identified mechanisms by which Sorting Nexin 16 (SNX16) controls neuronal endosomal maturation and distribution. We found that higher-order assembly of SNX16 via its coiled-coil (CC) domain drives membrane tubulation in vitro and endosome association in cells. In Drosophila melanogaster motor neurons, activation of Rab5 and CC-dependent self-association of SNX16 lead to its endosomal enrichment, accumulation in Rab5- and Rab7-positive tubulated compartments in the cell body, and concomitant depletion of SNX16-positive endosomes from the synapse. This results in accumulation of synaptic growth–promoting bone morphogenetic protein receptors in the cell body and correlates with increased synaptic growth. Our results indicate that Rab regulation of SNX16 assembly controls the endosomal distribution and signaling activities of receptors in neurons.

scholarly journals Clathrin Hub Expression Affects Early Endosome Distribution with Minimal Impact on Receptor Sorting and Recycling

2001 ◽  
Vol 12 (9) ◽  
pp. 2790-2799 ◽  
Author(s):  
Elizabeth M. Bennett ◽  
Sharron X. Lin ◽  
Mhairi C. Towler ◽  
Frederick R. Maxfield ◽  
Frances M. Brodsky
Keyword(s):  
Plasma Membrane ◽  
Early Endosome ◽  
Dominant Negative ◽  
Endocytic Pathway ◽  
Endocytic Trafficking ◽  
Minimal Impact ◽  
Recycling Endosomes ◽  
Receptor Mediated Endocytosis ◽  
Early Endosomes ◽  
Endosomal Membranes

Clathrin-coated vesicles execute receptor-mediated endocytosis at the plasma membrane. However, a role for clathrin in later endocytic trafficking processes, such as receptor sorting and recycling or maintaining the organization of the endocytic pathway, has not been thoroughly characterized. The existence of clathrin-coated buds on endosomes suggests that clathrin might mediate later endocytic trafficking events. To investigate the function of clathrin-coated buds on endosomal membranes, endosome function and distribution were analyzed in a HeLa cell line that expresses the dominant-negative clathrin inhibitor Hub in an inducible manner. As expected, Hub expression reduced receptor-mediated endocytosis at the plasma membrane. Hub expression also induced a perinuclear aggregation of early endosome antigen 1-positive early endosomes, such that sorting and recycling endosomes were found tightly concentrated in the perinuclear region. Despite the dramatic redistribution of endosomes, Hub expression did not affect the overall kinetics of receptor sorting or recycling. These data show that clathrin function is necessary to maintain proper cellular distribution of early endosomes but does not play a prominent role in sorting and recycling events. Thus, clathrin's role on endosomal membranes is to influence organelle localization and is distinct from its role in trafficking pathways at the plasma membrane and trans-Golgi network.

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 MARCH-II Is a Syntaxin-6–binding Protein Involved in Endosomal Trafficking

2005 ◽  
Vol 16 (4) ◽  
pp. 1696-1710 ◽  
Author(s):  
Nobuhiro Nakamura ◽  
Hidekazu Fukuda ◽  
Akira Kato ◽  
Shigehisa Hirose
Keyword(s):  
Transmembrane Domain ◽  
Retrograde Transport ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Immune Recognition ◽  
Endosomal Trafficking ◽  
Binding Studies ◽  
Recycling Endosomes ◽  
Protein Receptors

Membrane-associated RING-CH (MARCH) is a recently identified member of the mammalian E3 ubiquitin ligase family, some members of which down-regulate the expression of immune recognition molecules. Here, we have identified MARCH-II, which is ubiquitously expressed and localized to endosomal vesicles and the plasma membrane. Immunoprecipitation and in vitro binding studies established that MARCH-II directly associates with syntaxin 6. Overexpression of MARCH-II resulted in redistribution of syntaxin 6 as well as some syntaxin-6–interacting soluble N-ethylmaleimide–sensitive factor attachment protein receptors (SNAREs) into the MARCH-II–positive vesicles. In addition, the retrograde transport of TGN38 and a chimeric version of furin to trans-Golgi network (TGN) was perturbed—without affecting the endocytic degradative and biosynthetic secretory pathways—similar to effects caused by a syntaxin 6 mutant lacking the transmembrane domain. MARCH-II overexpression markedly reduced the cell surface expression of transferrin (Tf) receptor and Tf uptake and interfered with delivery of internalized Tf to perinuclear recycling endosomes. Depletion of MARCH-II by small interfering RNA perturbed the TGN localization of syntaxin 6 and TGN38/46. MARCH-II is thus likely a regulator of trafficking between the TGN and endosomes, which is a novel function for the MARCH family.

scholarly journals Control of Ste6 Recycling by Ubiquitination in the Early Endocytic Pathway in Yeast

2005 ◽  
Vol 16 (6) ◽  
pp. 2809-2821 ◽  
Author(s):  
Tamara Krsmanović ◽  
Agnes Pawelec ◽  
Tobias Sydor ◽  
Ralf Kölling
Keyword(s):  
Endocytic Pathway ◽  
Wild Type ◽  
Endocytic Recycling ◽  
Sorting Nexin ◽  
Class D ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Internal Structures ◽  
Vacuolar Protein ◽  
Polar Distribution

We present evidence that ubiquitination controls sorting of the ABC-transporter Ste6 in the early endocytic pathway. The intracellular distribution of Ste6 variants with reduced ubiquitination was examined. In contrast to wild-type Ste6, which was mainly localized to internal structures, these variants accumulated at the cell surface in a polar manner. When endocytic recycling was blocked by Ypt6 inactivation, the ubiquitination deficient variants were trapped inside the cell. This indicates that the polar distribution is maintained dynamically through endocytic recycling and localized exocytosis (“kinetic polarization”). Ste6 does not appear to recycle through late endosomes, because recycling was not blocked in class E vps (vacuolar protein sorting) mutants (Δvps4, Δvps27), which are affected in late endosome function and in the retromer mutant Δvps35. Instead, recycling was partially affected in the sorting nexin mutant Δsnx4, which serves as an indication that Ste6 recycles through early endosomes. Enhanced recycling of wild-type Ste6 was observed in class D vps mutants (Δpep12, Δvps8, and Δvps21). The identification of putative recycling signals in Ste6 suggests that recycling is a signal-mediated process. Endocytic recycling and localized exocytosis could be important for Ste6 polarization during the mating process.

scholarly journals RAB-10 Is Required for Endocytic Recycling in the Caenorhabditis elegans Intestine

2006 ◽  
Vol 17 (3) ◽  
pp. 1286-1297 ◽  
Author(s):  
Carlos Chih-Hsiung Chen ◽  
Peter J. Schweinsberg ◽  
Shilpa Vashist ◽  
Darren P. Mareiniss ◽  
Eric J. Lambie ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Endocytic Pathway ◽  
Intestinal Cells ◽  
Reporter Protein ◽  
Transport Pathway ◽  
Endocytic Recycling ◽  
Direct Role ◽  
Recycling Endosomes ◽  
Early Endosomes ◽  
Fluid Membranes

The endocytic pathway of eukaryotes is essential for the internalization and trafficking of macromolecules, fluid, membranes, and membrane proteins. One of the most enigmatic aspects of this process is endocytic recycling, the return of macromolecules (often receptors) and fluid from endosomes to the plasma membrane. We have previously shown that the EH-domain protein RME-1 is a critical regulator of endocytic recycling in worms and mammals. Here we identify the RAB-10 protein as a key regulator of endocytic recycling upstream of RME-1 in polarized epithelial cells of the Caenorhabditis elegans intestine. rab-10 null mutant intestinal cells accumulate abnormally abundant RAB-5-positive early endosomes, some of which are enlarged by more than 10-fold. Conversely most RME-1-positive recycling endosomes are lost in rab-10 mutants. The abnormal early endosomes in rab-10 mutants accumulate basolaterally recycling transmembrane cargo molecules and basolaterally recycling fluid, consistent with a block in basolateral transport. These results indicate a role for RAB-10 in basolateral recycling upstream of RME-1. We found that a functional GFP-RAB-10 reporter protein is localized to endosomes and Golgi in wild-type intestinal cells consistent with a direct role for RAB-10 in this transport pathway.

scholarly journals Differential Roles of Syntaxin 7 and Syntaxin 8 in Endosomal Trafficking

1999 ◽  
Vol 10 (11) ◽  
pp. 3891-3908 ◽  
Author(s):  
Rytis Prekeris ◽  
Bin Yang ◽  
Viola Oorschot ◽  
Judith Klumperman ◽  
Richard H. Scheller
Keyword(s):  
Membrane Fusion ◽  
Protein Trafficking ◽  
Molecular Mechanisms ◽  
Protein Transport ◽  
Growth Factor Receptor ◽  
Endosomal Trafficking ◽  
Attachment Protein ◽  
Early Endosomes ◽  
Protein Receptors ◽  
And Function

To understand molecular mechanisms that regulate the intricate and dynamic organization of the endosomal compartment, it is important to establish the morphology, molecular composition, and functions of the different organelles involved in endosomal trafficking. Syntaxins and vesicle-associated membrane protein (VAMP) families, also known as soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptors (SNAREs), have been implicated in mediating membrane fusion and may play a role in determining the specificity of vesicular trafficking. Although several SNAREs, including VAMP3/cellubrevin, VAMP8/endobrevin, syntaxin 13, and syntaxin 7, have been localized to the endosomal membranes, their precise localization, biochemical interactions, and function remain unclear. Furthermore, little is known about SNAREs involved in lysosomal trafficking. So far, only one SNARE, VAMP7, has been localized to late endosomes (LEs), where it is proposed to mediate trafficking of epidermal growth factor receptor to LEs and lysosomes. Here we characterize the localization and function of two additional endosomal syntaxins, syntaxins 7 and 8, and propose that they mediate distinct steps of endosomal protein trafficking. Both syntaxins are found in SNARE complexes that are dissociated by α-soluble NSF attachment protein and NSF. Syntaxin 7 is mainly localized to vacuolar early endosomes (EEs) and may be involved in protein trafficking from the plasma membrane to the EE as well as in homotypic fusion of endocytic organelles. In contrast, syntaxin 8 is likely to function in clathrin-independent vesicular transport and membrane fusion events necessary for protein transport from EEs to LEs.

scholarly journals The Recycling Endosome of Madin-Darby Canine Kidney Cells Is a Mildly Acidic Compartment Rich in Raft Components

2000 ◽  
Vol 11 (8) ◽  
pp. 2775-2791 ◽  
Author(s):  
Raluca Gagescu ◽  
Nicolas Demaurex ◽  
Robert G. Parton ◽  
Walter Hunziker ◽  
Lukas A. Huber ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Membrane Dynamics ◽  
Endocytic Pathway ◽  
Madin Darby Canine Kidney ◽  
Recycling Endosome ◽  
Recycling Endosomes ◽  
Early Endosomes ◽  
Recycling Pathway ◽  
Darby Canine Kidney ◽  
Canine Kidney

We present a biochemical and morphological characterization of recycling endosomes containing the transferrin receptor in the epithelial Madin-Darby canine kidney cell line. We find that recycling endosomes are enriched in molecules known to regulate transferrin recycling but lack proteins involved in early endosome membrane dynamics, indicating that recycling endosomes are distinct from conventional early endosomes. We also find that recycling endosomes are less acidic than early endosomes because they lack a functional vacuolar ATPase. Furthermore, we show that recycling endosomes can be reached by apically internalized tracers, confirming that the apical endocytic pathway intersects the transferrin pathway. Strikingly, recycling endosomes are enriched in the raft lipids sphingomyelin and cholesterol as well as in the raft-associated proteins caveolin-1 and flotillin-1. These observations may suggest that a lipid-based sorting mechanism operates along the Madin-Darby canine kidney recycling pathway, contributing to the maintenance of cell polarity. Altogether, our data indicate that recycling endosomes and early endosomes differ functionally and biochemically and thus that different molecular mechanisms regulate protein sorting and membrane traffic at each step of the receptor recycling pathway.

scholarly journals Endocytosis and the Src family of non-receptor tyrosine kinases

2014 ◽  
Vol 5 (2) ◽  
pp. 143-155 ◽  
Author(s):  
James Reinecke ◽  
Steve Caplan
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Tyrosine Kinases ◽  
Intracellular Transport ◽  
Intracellular Localization ◽  
Endocytic Pathway ◽  
Recycling Endosomes ◽  
Related Family ◽  
Spatiotemporal Regulation ◽  
Early Endosomes

AbstractThe regulated intracellular transport of nutrient, adhesion, and growth factor receptors is crucial for maintaining cell and tissue homeostasis. Endocytosis, or endocytic membrane trafficking, involves the steps of intracellular transport that include, but are not limited to, internalization from the plasma membrane, sorting in early endosomes, transport to late endosomes/lysosomes followed by degradation, and/or recycling back to the plasma membrane through tubular recycling endosomes. In addition to regulating the localization of transmembrane receptor proteins, the endocytic pathway also controls the localization of non-receptor molecules. The non-receptor tyrosine kinase c-Src (Src) and its closely related family members Yes and Fyn represent three proteins whose localization and signaling activities are tightly regulated by endocytic trafficking. Here, we provide a brief overview of endocytosis, Src function and its biochemical regulation. We will then concentrate on recent advances in understanding how Src intracellular localization is regulated and how its subcellular localization ultimately dictates downstream functioning. As Src kinases are hyperactive in many cancers, it is essential to decipher the spatiotemporal regulation of this important family of tyrosine kinases.

scholarly journals Identification and Characterization of Small Molecules That Inhibit Intracellular Toxin Transport

2007 ◽  
Vol 75 (9) ◽  
pp. 4552-4561 ◽  
Author(s):  
Jose B. Saenz ◽  
Teresa A. Doggett ◽  
David B. Haslam
Keyword(s):  
Golgi Apparatus ◽  
Small Molecule ◽  
Therapeutic Potential ◽  
Early Stage ◽  
Endocytic Pathway ◽  
Plant Toxin ◽  
Chemical Library ◽  
Transport Pathway ◽  
Recycling Endosomes ◽  
Early Endosomes

ABSTRACT Shiga toxin (Stx), cholera toxin (Ctx), and the plant toxin ricin are among several toxins that reach their intracellular destinations via a complex route. Following endocytosis, these toxins travel in a retrograde direction through the endosomal system to the trans-Golgi network, Golgi apparatus, and endoplasmic reticulum (ER). There the toxins are transported across the ER membrane to the cytosol, where they carry out their toxic effects. Transport via the ER from the cell surface to the cytosol is apparently unique to pathogenic toxins, raising the possibility that various stages in the transport pathway can be therapeutically targeted. We have applied a luciferase-based high-throughput screen to a chemical library of small-molecule compounds in order to identify inhibitors of Stx. We report two novel compounds that protect against Stx and ricin inhibition of protein synthesis, and we demonstrate that these compounds reversibly inhibit bacterial transport at various stages in the endocytic pathway. One compound (compound 75) inhibited transport at an early stage of Stx and Ctx transport and also provided protection against diphtheria toxin, which enters the cytosol from early endosomes. In contrast, compound 134 inhibited transport from recycling endosomes through the Golgi apparatus and protected only against toxins that access the ER. Small-molecule compounds such as these will provide insight into the mechanism of toxin transport and lead to the identification of compounds with therapeutic potential against toxins routed through the ER.

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