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.

Fibronectin Enhances Soluble N-ethylmaleimide-Sensitive Factor Attachment Protein Receptor Protein Expression in Cultured Human Islets

Pancreas ◽  
2011 ◽  
Vol 40 (7) ◽  
pp. 1153-1155 ◽  
Author(s):  
Rubén D. Fernández-Montes ◽  
Joan Blasi ◽  
Juli Busquets ◽  
Eduard Montanya ◽  
Montserrat Nacher
Keyword(s):  
Protein Expression ◽  
Human Islets ◽  
Receptor Protein ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Factor Attachment Protein Receptor

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 Syntaxin 16 is a master recruitment factor for cytokinesis

2013 ◽  
Vol 24 (23) ◽  
pp. 3663-3674 ◽  
Author(s):  
Hélia Neto ◽  
Alexandra Kaupisch ◽  
Louise L. Collins ◽  
Gwyn W. Gould
Keyword(s):  
Membrane Vesicles ◽  
Attachment Protein ◽  
Recycling Endosome ◽  
Endosomal Sorting ◽  
Escrt Machinery ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Late Telophase ◽  
Intracellular Organelles ◽  
Factor Attachment Protein Receptor

Recently it was shown that both recycling endosome and endosomal sorting complex required for transport (ESCRT) components are required for cytokinesis, in which they are believed to act in a sequential manner to bring about secondary ingression and abscission, respectively. However, it is not clear how either of these complexes is targeted to the midbody and whether their delivery is coordinated. The trafficking of membrane vesicles between different intracellular organelles involves the formation of soluble N-ethylmalei­mide–sensitive factor attachment protein receptor (SNARE) complexes. Although membrane traffic is known to play an important role in cytokinesis, the contribution and identity of intracellular SNAREs to cytokinesis remain unclear. Here we demonstrate that syntaxin 16 is a key regulator of cytokinesis, as it is required for recruitment of both recycling endosome–associated Exocyst and ESCRT machinery during late telophase, and therefore that these two distinct facets of cytokinesis are inextricably linked.

scholarly journals Munc18-1 domain-1 controls vesicle docking and secretion by interacting with syntaxin-1 and chaperoning it to the plasma membrane

2011 ◽  
Vol 22 (21) ◽  
pp. 4134-4149 ◽  
Author(s):  
Gayoung A. Han ◽  
Nancy T. Malintan ◽  
Ner Mu Nar Saw ◽  
Lijun Li ◽  
Liping Han ◽  
...  
Keyword(s):  
Molecular Chaperone ◽  
Dense Core ◽  
Dense Core Vesicle ◽  
Attachment Protein ◽  
Vesicle Docking ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Intracellular Expression ◽  
Factor Attachment Protein Receptor

Munc18-1 plays pleiotropic roles in neurosecretion by acting as 1) a molecular chaperone of syntaxin-1, 2) a mediator of dense-core vesicle docking, and 3) a priming factor for soluble N-ethylmaleimide–sensitive factor attachment protein receptor–mediated membrane fusion. However, how these functions are executed and whether they are correlated remains unclear. Here we analyzed the role of the domain-1 cleft of Munc18-1 by measuring the abilities of various mutants (D34N, D34N/M38V, K46E, E59K, K46E/E59K, K63E, and E66A) to bind and chaperone syntaxin-1 and to restore the docking and secretion of dense-core vesicles in Munc18-1/-2 double-knockdown cells. We identified striking correlations between the abilities of these mutants to bind and chaperone syntaxin-1 with their ability to restore vesicle docking and secretion. These results suggest that the domain-1 cleft of Munc18-1 is essential for binding to syntaxin-1 and thereby critical for its chaperoning, docking, and secretory functions. Our results demonstrate that the effect of the alleged priming mutants (E59K, D34N/M38V) on exocytosis can largely be explained by their reduced syntaxin-1–chaperoning functions. Finally, our data suggest that the intracellular expression and distribution of syntaxin-1 determines the level of dense-core vesicle docking.

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