A second SARE role for exocytic SNAP25 in endosome fusion

Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA.
Molecular Biology of the Cell (Impact Factor: 4.47). 06/2006; 17(5):2113-24. DOI: 10.1091/mbc.E06-01-0074
Source: PubMed


Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins play key roles in membrane fusion, but their sorting to specific membranes is poorly understood. Moreover, individual SNARE proteins can function in multiple membrane fusion events dependent upon their trafficking itinerary. Synaptosome-associated protein of 25 kDa (SNAP25) is a plasma membrane Q (containing glutamate)-SNARE essential for Ca2+-dependent secretory vesicle-plasma membrane fusion in neuroendocrine cells. However, a substantial intracellular pool of SNAP25 is maintained by endocytosis. To assess the role of endosomal SNAP25, we expressed botulinum neurotoxin E (BoNT E) light chain in PC12 cells, which specifically cleaves SNAP25. BoNT E expression altered the intracellular distribution of SNAP25, shifting it from a perinuclear recycling endosome to sorting endosomes, which indicates that SNAP25 is required for its own endocytic trafficking. The trafficking of syntaxin 13 and endocytosed cargo was similarly disrupted by BoNT E expression as was an endosomal SNARE complex comprised of SNAP25/syntaxin 13/vesicle-associated membrane protein 2. The small-interfering RNA-mediated down-regulation of SNAP25 exerted effects similar to those of BoNT E expression. Our results indicate that SNAP25 has a second function as an endosomal Q-SNARE in trafficking from the sorting endosome to the recycling endosome and that BoNT E has effects linked to disruption of the endosome recycling pathway.

Download full-text


Available from: Thomas F J Martin, Oct 08, 2015
19 Reads
  • Source
    • "The heavy chain of the toxin has a high affinity for the membrane receptors and, once bound, BTA undergoes endocytosis. The light chain is released within the cell, where it acts as a zinc-dependent endoprotease [16] [17] [18]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: . Botulinum toxin inhibits acetylcholine (ACh) release and probably blocks some nociceptive neurotransmitters. It has been suggested that the development of myofascial trigger points (MTrP) is related to an excess release of ACh to increase the number of sensitized nociceptors. Although the use of botulinum toxin to treat myofascial pain syndrome (MPS) has been investigated in many clinical trials, the results are contradictory. The objective of this paper is to identify sources of variability that could explain these differences in the results. Material and Methods . We performed a content analysis of the clinical trials and systematic reviews of MPS. Results and Discussion . Sources of differences in studies were found in the diagnostic and selection criteria, the muscles injected, the injection technique, the number of trigger points injected, the dosage of botulinum toxin used, treatments for control group, outcome measures, and duration of followup. The contradictory results regarding the efficacy of botulinum toxin A in MPS associated with neck and back pain do not allow this treatment to be recommended or rejected. There is evidence that botulinum toxin could be useful in specific myofascial regions such as piriformis syndrome. It could also be useful in patients with refractory MPS that has not responded to other myofascial injection therapies.
    Evidence-based Complementary and Alternative Medicine 02/2013; 2013(1):381459. DOI:10.1155/2013/381459 · 1.88 Impact Factor
  • Source
    • "If so, then SNAP23CΔ9 would be expected to be a more potent inhibitor of cell motility than other soluble SNARE domains, as was observed. In support of this model, others have reported that a VAMP2-syntaxin13-SNAP25 complex mediates traffic from a sorting endosome to a recycling endosome in neurons [18,36]. In non-neuronal cells, a similar complex, such as the VAMP3-syntaxin13-SNAP23 complex described here, may be involved in an analogous trafficking pathway. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Intracellular membrane traffic is an essential component of the membrane remodeling that supports lamellipodium extension during cell adhesion. The membrane trafficking pathways that contribute to cell adhesion have not been fully elucidated, but recent studies have implicated SNARE proteins. Here, the functions of several SNAREs (SNAP23, VAMP3, VAMP4 and syntaxin13) are characterized during the processes of cell spreading and membrane ruffling. We report the first description of a SNARE complex, containing SNAP23, syntaxin13 and cellubrevin/VAMP3, that is induced by cell adhesion to an extracellular matrix. Impairing the function of the SNAREs in the complex using inhibitory SNARE domains disrupted the recycling endosome, impeded delivery of integrins to the cell surface, and reduced haptotactic cell migration and spreading. Blocking SNAP23 also inhibited the formation of PMA-stimulated, F-actin-rich membrane ruffles; however, membrane ruffle formation was not significantly altered by inhibition of VAMP3 or syntaxin13. In contrast, membrane ruffling, and not cell spreading, was sensitive to inhibition of two SNAREs within the biosynthetic secretory pathway, GS15 and VAMP4. Consistent with this, formation of a complex containing VAMP4 and SNAP23 was enhanced by treatment of cells with PMA. The results reveal a requirement for the function of a SNAP23-syntaxin13-VAMP3 complex in the formation of lamellipodia during cell adhesion and of a VAMP4-SNAP23-containing complex during PMA-induced membrane ruffling. Our findings suggest that different SNARE-mediated trafficking pathways support membrane remodeling during ECM-induced lamellipodium extension and PMA-induced ruffle formation, pointing to important mechanistic differences between these processes.
    BMC Cell Biology 08/2010; 11(1):62. DOI:10.1186/1471-2121-11-62 · 2.34 Impact Factor
  • Source
    • "As GLUT4 molecules appear to be recruited at random it is tempting to speculate that upon low-level insulin stimulation, GLUT4 molecules are mobilized by the action of a downstream insulin effector on a protein or membrane structure that directly regulates GLUT4 retention. The result would be the release of GLUT4 molecules from the GSC into the GLUT4 cell surface recycling pathway or the release of GSVs to allow them to fuse with the plasma membrane (via the formation of the syntaxin 4/ SNAP23/VAMP2 SNARE complex [22]) or perhaps with another compartment of the GLUT4 cell surface recycling pathway (i.e., via a syntaxin 13/SNAP23/VAMP2 complex [23] [24]). In any case, this insulin effector would be the rate-limiting factor in GLUT4 mobilization and affect (a limited amount of) components of the retention mechanism or GSVs at a random fashion. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Glucose transporter 4 (GLUT4) is efficiently retained intracellularly. Here, we investigated the insulin-induced reduction of retention. While increasing insulin concentrations led to gradual increases in both the amount of recycling GLUT4 molecules and cell surface GLUT4 levels, the kinetics of the increase in time was independent of insulin concentration. To determine whether there are GLUT4 subpools that have a distinct insulin sensitivity, adipocytes were consecutively stimulated twice with a low concentration of insulin while recycling GLUT4 molecules were continuously labeled. This revealed that not the same pool of GLUT4 molecules was mobilized twice and thus that upon insulin stimulation, GLUT4 is likely to be recruited at random for insertion within the plasma membrane.
    FEBS letters 12/2009; 584(3):537-42. DOI:10.1016/j.febslet.2009.11.093 · 3.17 Impact Factor
Show more