scholarly journals Autophagosomal YKT6 is required for fusion with lysosomes independently of syntaxin 17

2018 ◽  
Vol 217 (8) ◽  
pp. 2633-2645 ◽  
Author(s):  
Takahide Matsui ◽  
Peidu Jiang ◽  
Saori Nakano ◽  
Yuriko Sakamaki ◽  
Hayashi Yamamoto ◽  
...  
Keyword(s):  
Hela Cells ◽  
Snare Complex ◽  
Snare Protein ◽  
Wild Type ◽  
Attachment Protein ◽  
Additional Mechanism ◽  
Protein Receptor ◽  
Evolutionarily Conserved ◽  
Sensitive Factor ◽  
Factor Attachment Protein Receptor

Macroautophagy is an evolutionarily conserved catabolic mechanism that delivers intracellular constituents to lysosomes using autophagosomes. To achieve degradation, lysosomes must fuse with closed autophagosomes. We previously reported that the soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) protein syntaxin (STX) 17 translocates to autophagosomes to mediate fusion with lysosomes. In this study, we report an additional mechanism. We found that autophagosome–lysosome fusion is retained to some extent even in STX17 knockout (KO) HeLa cells. By screening other human SNAREs, we identified YKT6 as a novel autophagosomal SNARE protein. Depletion of YKT6 inhibited autophagosome–lysosome fusion partially in wild-type and completely in STX17 KO cells, suggesting that YKT6 and STX17 are independently required for fusion. YKT6 formed a SNARE complex with SNAP29 and lysosomal STX7, both of which are required for autophagosomal fusion. Recruitment of YKT6 to autophagosomes depends on its N-terminal longin domain but not on the C-terminal palmitoylation and farnesylation that are essential for its Golgi localization. These findings suggest that two independent SNARE complexes mediate autophagosome–lysosome fusion.

scholarly journals Endosomal and Phagosomal SNAREs

2018 ◽  
Vol 98 (3) ◽  
pp. 1465-1492 ◽  
Author(s):  
Ilse Dingjan ◽  
Peter T. A. Linders ◽  
Danielle R. J. Verboogen ◽  
Natalia H. Revelo ◽  
Martin ter Beest ◽  
...  
Keyword(s):  
Intracellular Transport ◽  
Snare Proteins ◽  
Intracellular Pathogens ◽  
Snare Protein ◽  
Attachment Protein ◽  
System A ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Organelle Communication ◽  
Factor Attachment Protein Receptor

The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein family is of vital importance for organelle communication. The complexing of cognate SNARE members present in both the donor and target organellar membranes drives the membrane fusion required for intracellular transport. In the endocytic route, SNARE proteins mediate trafficking between endosomes and phagosomes with other endosomes, lysosomes, the Golgi apparatus, the plasma membrane, and the endoplasmic reticulum. The goal of this review is to provide an overview of the SNAREs involved in endosomal and phagosomal trafficking. Of the 38 SNAREs present in humans, 30 have been identified at endosomes and/or phagosomes. Many of these SNAREs are targeted by viruses and intracellular pathogens, which thereby reroute intracellular transport for gaining access to nutrients, preventing their degradation, and avoiding their detection by the immune system. A fascinating picture is emerging of a complex transport network with multiple SNAREs being involved in consecutive trafficking routes.

scholarly journals Complexin splits the membrane-proximal region of a single SNAREpin

2016 ◽  
Vol 473 (14) ◽  
pp. 2219-2224 ◽  
Author(s):  
Linxiang Yin ◽  
Jaewook Kim ◽  
Yeon-Kyun Shin
Keyword(s):  
Neurotransmitter Release ◽  
Proximal Part ◽  
Proximal Region ◽  
Snare Complex ◽  
Spontaneous Release ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Membrane Proximal Region ◽  
Factor Attachment Protein Receptor

Tight regulation of neurotransmitter release by Ca2+ is critical in neurons, which requires suppression of spontaneous release. In the present study, we find that the complexin (Cpx) protein binds to the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex to split the membrane-proximal part, whereby it inhibits spontaneous release.

scholarly journals Characterization of VAMP isoforms in 3T3-L1 adipocytes: implications for GLUT4 trafficking

2015 ◽  
Vol 26 (3) ◽  
pp. 530-536 ◽  
Author(s):  
Jessica B. A. Sadler ◽  
Nia J. Bryant ◽  
Gwyn W. Gould
Keyword(s):  
Plasma Membrane ◽  
Snare Complex ◽  
Cell Type ◽  
Attachment Protein ◽  
Systematic Analysis ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Factor Attachment Protein Receptor

The fusion of GLUT4-containing vesicles with the plasma membrane of adipocytes is a key facet of insulin action. This process is mediated by the formation of functional soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complexes between the plasma membrane t-SNARE complex and the vesicle v-SNARE or VAMP. The t-SNARE complex consists of Syntaxin4 and SNAP23, and whereas many studies identify VAMP2 as the v-SNARE, others suggest that either VAMP3 or VAMP8 may also fulfil this role. Here we characterized the levels of expression, distribution, and association of all the VAMPs expressed in 3T3-L1 adipocytes to provide the first systematic analysis of all members of this protein family for any cell type. Despite our finding that all VAMP isoforms form SDS-resistant SNARE complexes with Syntaxin4/SNAP23 in vitro, a combination of levels of expression (which vary by >30-fold), subcellular distribution, and coimmunoprecipitation analyses lead us to propose that VAMP2 is the major v-SNARE involved in GLUT4 trafficking to the surface of 3T3-L1 adipocytes.

scholarly journals RalA-Exocyst Interaction Mediates GTP-dependent Exocytosis

2004 ◽  
Vol 279 (19) ◽  
pp. 19875-19881 ◽  
Author(s):  
Li Wang ◽  
Gang Li ◽  
Shuzo Sugita
Keyword(s):  
Point Mutations ◽  
Receptor Protein ◽  
Secretory Cells ◽  
Wild Type ◽  
Attachment Protein ◽  
Exocyst Complex ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Dependent Pathway ◽  
Factor Attachment Protein Receptor

Many secretory cells utilize a GTP-dependent pathway, in addition to the well characterized Ca2+-dependent pathway, to trigger exocytotic secretion. However, little is currently known about the mechanism by which this may occur. Here we show the key signaling pathway that mediates GTP-dependent exocytosis. Incubation of permeabilized PC12 cells with soluble RalA GTPase, but not RhoA or Rab3A GTPases, strongly inhibited GTP-dependent exocytosis. A Ral-binding fragment from Sec5, a component of the exocyst complex, showed a similar inhibition. Point mutations in both RalA (RalAE38R) and the Sec5 (Sec5T11A) fragment, which abolish RalA-Sec5 interaction also abolished the inhibition of GTP-dependent exocytosis. Moreover, transfection with wild-type RalA, but not RalAE38R, enhanced GTP-dependent exocytosis. In contrast the RalA and the Sec5 fragment showed no inhibition of Ca2+-dependent exocytosis, but cleavage of a SNARE (solubleN-ethylmaleimide-sensitive factor attachment protein receptor) protein byBotulinumneurotoxin blocked both GTP- and Ca2+-dependent exocytosis. Our results indicate that the interaction between RalA and the exocyst complex (containing Sec5) is essential for GTP-dependent exocytosis. Furthermore, GTP- and Ca2+-dependent exocytosis use different sensors and effectors for triggering exocytosis whereas their final fusion steps are both SNARE-dependent.

scholarly journals Prefused lysosomes cluster on autophagosomes regulated by VAMP8

2021 ◽  
Vol 12 (10) ◽  
Author(s):  
Qixin Chen ◽  
Mingang Hao ◽  
Lei Wang ◽  
Linsen Li ◽  
Yang Chen ◽  
...  
Keyword(s):  
Potential Role ◽  
Autophagic Flux ◽  
Snare Protein ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Fusion Probability ◽  
Autophagosome Maturation ◽  
Factor Attachment Protein Receptor

AbstractLysosome–autophagosome fusion is critical to autophagosome maturation. Although several proteins that regulate this fusion process have been identified, the prefusion architecture and its regulation remain unclear. Herein, we show that upon stimulation, multiple lysosomes form clusters around individual autophagosomes, setting the stage for membrane fusion. The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein on lysosomes—vesicle-associated membrane protein 8 (VAMP8)—plays an important role in forming this prefusion state of lysosomal clusters. To study the potential role of phosphorylation on spontaneous fusion, we investigated the effect of phosphorylation of C-terminal residues of VAMP8. Using a phosphorylation mimic, we observed a decrease of fusion in an ensemble lipid mixing assay and an increase of unfused lysosomes associated with autophagosomes. These results suggest that phosphorylation not only reduces spontaneous fusion for minimizing autophagic flux under normal conditions, but also preassembles multiple lysosomes to increase the fusion probability for resuming autophagy upon stimulation. VAMP8 phosphorylation may thus play an important role in chemotherapy drug resistance by influencing autophagosome maturation.

scholarly journals SNARE zippering

2016 ◽  
Vol 36 (3) ◽  
Author(s):  
Xiaochu Lou ◽  
Yeon-Kyun Shin
Keyword(s):  
Recent Progress ◽  
Snare Complex ◽  
Intracellular Membrane ◽  
Attachment Protein ◽  
Receptor Proteins ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Associated Proteins ◽  
Intracellular Membrane Fusion ◽  
Factor Attachment Protein Receptor

SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins are a highly conserved set of membrane-associated proteins that mediate intracellular membrane fusion. Cognate SNAREs from two separate membranes zipper to facilitate membrane apposition and fusion. Though the stable post-fusion conformation of SNARE complex has been extensively studied with biochemical and biophysical means, the pathway of SNARE zippering has been elusive. In this review, we describe some recent progress in understanding the pathway of SNARE zippering. We particularly focus on the half-zippered intermediate, which is most likely to serve as the main point of regulation by the auxiliary factors.

scholarly journals Identification of Functionally Interacting SNAREs by Using Complementary Substitutions in the Conserved `0' Layer

2005 ◽  
Vol 16 (5) ◽  
pp. 2263-2274 ◽  
Author(s):  
Carmen T. Graf ◽  
Dietmar Riedel ◽  
Hans Dieter Schmitt ◽  
Reinhard Jahn
Keyword(s):  
Snare Complex ◽  
Growth Defect ◽  
Temperature Sensitive ◽  
Central Layer ◽  
Attachment Protein ◽  
Growth Defects ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Factor Attachment Protein Receptor

Soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) complexes form bundles of four parallel α-helices. The central `0' layer of interacting amino acid side chains is highly conserved and contains one arginine and three glutamines, leading to the classification of SNAREs into R, Qa, Qb, and Qc-SNAREs. Replacing one of the glutamines with arginine in the yeast exocytotic SNARE complex is either lethal or causes a conditional growth defect that is compensated by replacing the R-SNARE arginine with glutamine. Using the yeast SNARE complex mediating traffic from the endoplasmic reticulum to the Golgi apparatus, we now show that functionally interacting SNAREs can be mapped by systematically exchanging glutamines and arginines in the `0' layer. The Q→ R replacement in the Qb-SNARE Bos1p has the strongest effect and can be alleviated by an Q→ R replacement in the R-SNARE Sec22p. Four Q residues in the central layer caused growth defects above 30°C that were rescued by Q→ R substitutions in the Qa and Qc SNAREs Sed5p and Bet1p, respectively. The sec22(Q)/sed5(R) mutant is temperature sensitive and is rescued by a compensating R→ Q replacement in the R-SNARE Ykt6p. This rescue is attributed to the involvement of Sed5p and Ykt6p in a different SNARE complex that functions in intra-Golgi trafficking.

scholarly journals A Role for Soluble N-Ethylmaleimide-sensitive Factor Attachment Protein Receptor Complex Dimerization during Neurosecretion

2008 ◽  
Vol 19 (8) ◽  
pp. 3379-3389 ◽  
Author(s):  
Elena Fdez ◽  
Thomas A. Jowitt ◽  
Ming-Chuan Wang ◽  
Manisha Rajebhosale ◽  
Keith Foster ◽  
...  
Keyword(s):  
Dominant Negative ◽  
Neuroendocrine Cells ◽  
Snare Complex ◽  
Membrane Interface ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
The Stability ◽  
Factor Attachment Protein Receptor

The interactions underlying the cooperativity of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes during neurotransmission are not known. Here, we provide a molecular characterization of a dimer formed between the cytoplasmic portions of neuronal SNARE complexes. Dimerization generates a two-winged structure in which the C termini of cytosolic SNARE complexes are in apposition, and it involves residues from the vesicle-associated SNARE synaptobrevin 2 that lie close to the cytosol–membrane interface within the full-length protein. Mutation of these residues reduces stability of dimers formed between SNARE complexes, without affecting the stability of each individual SNARE complex. These mutations also cause a corresponding decrease in the ability of botulinum toxin-resistant synaptobrevin 2 to rescue regulated exocytosis in toxin-treated neuroendocrine cells. Moreover, such synaptobrevin 2 mutants give rise to a dominant-negative inhibition of exocytosis. These data are consistent with an important role for SNARE complex dimers in neurosecretion.

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