A dual mechanism controlling the localization and function of exocytic v-SNAREs.
SNARE [soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor] proteins are essential for membrane fusion but their regulation is not yet fully understood. We have previously shown that the amino-terminal Longin domain of the v-SNARE TI-VAMP (tetanus neurotoxin-insensitive vesicle-associated membrane protein)/VAMP7 plays an inhibitory role in neurite outgrowth. The goal of this study was to investigate the regulation of TI-VAMP as a model of v-SNARE regulation. We show here that the Longin domain (LD) plays a dual role. First, it negatively regulates the ability of TI-VAMP and of a Longin/Synaptobrevin chimera to participate in SNARE complexes. Second, it interacts with the adaptor complex AP-3 and this interaction targets TI-VAMP to late endosomes. Accordingly, in mocha cells lacking AP-3 delta, TI-VAMP is retained in an early endosomal compartment. Furthermore, TI-VAMPc, an isoform of TI-VAMP lacking part of the LD, does not interact with AP-3, and therefore is not targeted to late endosomes; however, this shorter LD still inhibits SNARE-complex formation. These findings support a mechanism controlling both localization and function of TI-VAMP through the LD and clathrin adaptors. Moreover, they point to the amino-terminal domains of SNARE proteins as multifunctional modules responsible for the fine tuning of SNARE function.
Martinez-Arca
Sonia
S
Membrane Traffic and Neuronal Plasticity, Institut National de la Santé et de la Recherche Médicale U536, Institut du Fer-à-Moulin, 75005 Paris, France.
Rudge
Rachel
R
Vacca
Marcella
M
Raposo
Graça
G
Camonis
Jacques
J
Proux-Gillardeaux
Véronique
V
Daviet
Laurent
L
Formstecher
Etienne
E
Hamburger
Alexandre
A
Filippini
Francesco
F
D'Esposito
Maurizio
M
Galli
Thierry
T
D033963:Adaptor Protein Complex 3; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D004285:Dogs; D005089:Exocytosis; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D013347:Subcellular Fractions / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins
D033963:Adaptor Protein Complex 3; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D014157:Transcription Factors; C121241:VAMP7 protein, human; D033921:Vesicular Transport Proteins