Genetic Analysis of SolubleN-Ethylmaleimide-Sensitive Factor Attachment Protein Function inDrosophilaReveals Positive and Negative Secretory Roles

Abstract

The N-ethylmaleimide-sensitive factor (NSF) and soluble NSF attachment protein (SNAP) are cytosolic factors that promote vesicle fusion with a target membrane in both the constitutive and regulated secretory pathways. NSF and SNAP are thought to function by catalyzing the disassembly of a SNAP receptor (SNARE) complex consisting of membrane proteins of the secretory vesicle and target membrane. Although studies of NSF function have provided strong support for this model, the precise biochemical role of SNAP remains controversial. To further explore the function of SNAP, we have used mutational and transgenic approaches in Drosophila to investigate the effect of altered SNAP dosage on neurotransmitter release and SNARE complex metabolism. Our results indicate that reduced SNAP activity results in diminished neurotransmitter release and accumulation of a neural SNARE complex. Increased SNAP dosage results in defective synapse formation and a variety of tissue morphological defects without detectably altering the abundance of neural SNARE complexes. The SNAP overexpression phenotypes are enhanced by mutations in other secretory components and are at least partially overcome by co-overexpression of NSF, suggesting that these phenotypes derive from a specific perturbation of the secretory pathway. Our results indicate that SNAP promotes neurotransmitter release and SNARE complex disassembly but inhibits secretion when present at high abundance relative to NSF.

Loss of Soluble N-Ethylmaleimide-sensitive Factor Attachment Protein α (αSNAP) Induces Epithelial Cell Apoptosis via Down-regulation of Bcl-2 Expression and Disruption of the Golgi

“…Furthermore, some indirect evidence points to a possible prosurvival role of ␣SNAP in vivo. For example, genetic deletion of its homolog in Drosophila results in embryonic lethality (61). Additionally, ␣SNAP hypomorphic hyh mice (62) are characterized by a significant loss of neuroepithelial cells (63), which can be a consequence of increased apoptosis.…”

Transmission, Development, and Plasticity of Synapses

“…NSF is also required at adult muscle synapses to replenish free t-SNAREs at the AZ for maintaining vesicle fusion during stimulation trains (Kawasaki and Ordway 2009). Mutations in the ⍺-SNAP protein, which is required to tether NSF to the SNARE complex, are embryonic lethal (Babcock et al 2004). Recordings done in hypomorphic ⍺-SNAP mutants have not yet revealed release defects, so further study is required to pinpoint how the disassembly machine is actually working.…”

The syntaxin 31-induced gene, LESION SIMULATING DISEASE1 (LSD1), functions inGlycine maxdefense to the root parasiteHeterodera glycines

“…14,17,18 The roles that these core membrane fusion proteins perform in eukaryotes is extensive, ranging from signaling, cell growth, mitosis, the endocytic cycle, exocytosis, hormonal release, neurotransmission, fertilization, embryogenesis, development, sporulation and cell death. 2,3,[13][14][15][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] A variety of studies show membrane fusion to be important to the defense process that plants have toward pathogens as well as different types of defense responses. 9,11,[34][35][36][37][38][39][40][41][42] While the list of functions that the membrane fusion and vesicle transport proteins have is large, it is less clear whether the proteins also are engaged in other, but related functions.…”