Abstract
Each membrane fusion event along the secretory and endocytic pathways requires a specific set of SNAREs to assemble into a 4-helical coiled-coil, the so-called trans-SNARE complex. Although most SNAREs contribute one helix to the trans-SNARE complex, members of the SNAP-25 family contribute two helixes. We report the characterization of the Drosophila homologue of SNAP-29 (dSNAP-29), which is expressed throughout development. Unlike the other SNAP-25 like proteins in fruit fly (i.e., dSNAP-25 and dSNAP-24), which form SDS-resistant SNARE complexes with their cognate SNAREs, dSNAP-29 does not participate in any SDS-resistant complexes, despite its interaction with dsyntaxin1 and dsyntaxin16 in vitro. Immunofluorescence studies indicated that dSNAP-29 is distributed in various tissues, locating in small intracellular puncta and on the plasma membrane, where it associates with EH domain-containing proteins implicated in the endocytic pathway. Overexpression and RNAi studies suggested that dSNAP-29 mediates an essential process in Drosophila development.
Highlights
Vesicular fusion requires SNAREs (SNAP receptors) located on the transport vesicle (e.g., VAMP/synatobrevin) to interact with cognate SNAREs from the target membrane [1,2]
We report the characterization of the SNAP-29 orthologue in Drosophila, which was initially identified via a yeast 2-hybrid screen using dSNAP as bait. dSNAP-29 is ubiquitously expressed throughout the fly life cycle, interacting with multiple proteins including dSNAP, dsyntaxin1, dsyntaxin 16, dEHD1, and DAP160
DSNAP-29 has a unique N-terminal NPF motif (Fig. 1A), which is involved in the interaction with Eps15 homology (EH) domains, a feature shared by all known SNAP-29 isoforms
Summary
Vesicular fusion requires SNAREs (SNAP receptors) located on the transport vesicle (e.g., VAMP/synatobrevin) to interact with cognate SNAREs from the target membrane (e.g., syntaxin and SNAP-25) [1,2]. Such interaction leads to the formation of a stable 4-helical trans-SNARE complex, whose subsequent disassembly after fusion depends on the actions of an ATPase NSF (N-ethylmaleimide-sensitive factor) and its cofactor SNAP (soluble NSF attachment protein) [3]. Unlike SNAP-25, SNAP-47 is enriched in synaptic vesicle fractions of the neuron rather than in the plasma membrane [6] and is required in postsynaptic rather than presynaptic exocytosis [20]
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