A second SNARE role for exocytic SNAP25 in endosome fusion.

Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA.
Molecular Biology of the Cell (Impact Factor: 4.55). 06/2006; 17(5):2113-24. DOI: 10.1091/mbc.E06-01-0074
Source: PubMed

ABSTRACT 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, Jul 30, 2015
  • 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: Introduction. 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; 2013:381459. DOI:10.1155/2013/381459 · 1.88 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 · 3.34 Impact Factor
  • Source
    • "We also generated soluble mutant forms of VAMP3 and syntaxin-13. VAMP3 was targeted because of its observed colocalization with MMP2 and MMP9 (Fig. 1); syntaxin-13 (also known as syntaxin-12) was targeted because it is known to interact with SNAP23 (Tang et al., 1998) and with SNAP25, a neuronal homolog of SNAP 23 (Aikawa et al., 2006). We generated mutant forms of these SNAREs lacking transmembrane domains (VAMP3cyto and Syn13cyto). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cellular remodeling of the extracellular matrix (ECM), an essential component of many physiological and pathological processes, is dependent on the trafficking and secretion of matrix metalloproteinases (MMPs). Soluble NSF attachment protein receptor (SNARE)-mediated membrane traffic has documented roles in cell-ECM interactions and the present study specifically examines SNARE function in the trafficking of MMPs during ECM degradation. Using the invasive human fibrosarcoma cell line HT-1080, we demonstrate that a plasma membrane SNARE, SNAP23, and an endosomal v-SNARE, VAMP3 (also known as cellubrevin), partly colocalize with MMP2 and MMP9, and that inhibition of these SNAREs using dominant-negative SNARE mutants impaired secretion of the MMPs. Inhibition of VAMP3, SNAP23 or syntaxin-13 using dominant-negative SNARES, RNA interference or tetanus toxin impaired trafficking of membrane type 1 MMP to the cell surface. Consistent with these observations, we found that blocking the function of these SNAREs reduced the ability of HT-1080 cells to degrade a gelatin substrate in situ and impaired invasion of HT-1080 cells in vitro. The results reveal the importance of VAMP3, syntaxin-13 and SNAP23 in the trafficking of MMP during degradation of ECM substrates and subsequent cellular invasion.
    Journal of Cell Science 11/2009; 122(Pt 22):4089-98. DOI:10.1242/jcs.052761 · 5.33 Impact Factor
Show more