title: Multiple functions of the SNARE protein Snap29 in autophagy, endocytic, and exocytic trafficking during epithelial formation in Drosophila.
abstract: How autophagic degradation is linked to endosomal trafficking routes is little known. Here we screened a collection of uncharacterized Drosophila mutants affecting membrane transport to identify new genes that also have a role in autophagy. We isolated a loss of function mutant in Snap29 (Synaptosomal-associated protein 29 kDa), the gene encoding the Drosophila homolog of the human protein SNAP29 and have characterized its function in vivo. Snap29 contains 2 soluble NSF attachment protein receptor (SNARE) domains and a asparagine-proline-phenylalanine (NPF motif) at its N terminus and rescue experiments indicate that both SNARE domains are required for function, whereas the NPF motif is in part dispensable. We find that Snap29 interacts with SNARE proteins, localizes to multiple trafficking organelles, and is required for protein trafficking and for proper Golgi apparatus morphology. Developing tissue lacking Snap29 displays distinctive epithelial architecture defects and accumulates large amounts of autophagosomes, highlighting a major role of Snap29 in autophagy and secretion. Mutants for autophagy genes do not display epithelial architecture or secretion defects, suggesting that the these alterations of the Snap29 mutant are unlikely to be caused by the impairment of autophagy. In contrast, we find evidence of elevated levels of hop-Stat92E (hopscotch-signal transducer and activator of transcription protein at 92E) ligand, receptor, and associated signaling, which might underlie the epithelial defects. In summary, our findings support a role of Snap29 at key steps of membrane trafficking, and predict that signaling defects may contribute to the pathogenesis of cerebral dysgenesis, neuropathy, ichthyosis, and palmoplantar keratoderma (CEDNIK), a human congenital syndrome due to loss of Snap29.
authors.affiliation: a IFOM - The FIRC Institute of Molecular Oncology ; Milan , Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Morelli
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Ginefra
authors.forename: Valeria
authors.initials: V
authors.lastname: Mastrodonato
authors.forename: Galina V
authors.initials: GV
authors.lastname: Beznoussenko
authors.forename: Tor Erik
authors.initials: TE
authors.lastname: Rusten
authors.forename: David
authors.initials: D
authors.lastname: Bilder
authors.forename: Harald
authors.initials: H
authors.lastname: Stenmark
authors.forename: Alexandre A
authors.initials: AA
authors.lastname: Mironov
authors.forename: Thomas
authors.initials: T
authors.lastname: Vaccari
mesh_terms: D000818:Animals; D001343:Autophagy / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D055354:Exosomes / Q000378:metabolism; D006801:Humans; D010588:Phagosomes / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D050766:Qb-SNARE Proteins / Q000378:metabolism*; D050767:Qc-SNARE Proteins / Q000378:metabolism*; D050600:SNARE Proteins / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; C432420:SNAP29 protein, human; D050600:SNARE Proteins; C582206:Snap29 protein, Drosophila; D033921:Vesicular Transport Proteins
keywords: Atg, autophagy-related; CEDNIK, cerebral dysgenesis, neuropathy, ichthyosis, and palmoplantar keratoderma; CFP, cyan fluorescent protein; E(spl)mβ-HLH, enhancer of split mβ, helix-loop-helix; EM, electron microscopy; ESCRT, endosomal sorting complex required for transport; FE, follicular epithelium; GFP, green fluorescent protein; MENE, mutant eye no eclosion; MVB, multivesicular body; N, Notch; NECD, N extracellular domain; NPF, asparagine-proline-phenylalanine; Notch; SNARE; SNARE, soluble NSF attachment protein receptor; Snap29; Snap29, synaptosomal-associated protein 29 kDa; Socs36E, suppressor of cytokine signaling at 36E; Syb, Synaptobrevin; Syx, syntaxin; V-ATPase, vacuolar H+-ATPase; Vamp, vesicle-associated membrane protein; Vps25, vacuolar protein sorting 25; WT, wild type; autophagy; dome; dome, domeless; histone H3, His3; hop-Stat92E, hopscotch-signal transducer and activator of transcription protein at 92E; os, outstretched; ref(2)P, refractory to sigma P; trafficking; usnp