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Zusammenfassung:
PI(3,4,5)P-3 is a low-abundance lipid thought to play a role in the regulation of synaptic activity; however, the mechanism remains obscure. We have constructed novel split Venus-based probes and used superresolution imaging to localize PI(3,4,5)P-3 at Drosophila larval neuromuscular synapses. We find the lipid in membrane domains at neurotransmitter release sites, where it concentrates with Syntaxin1A, a protein essential for vesicle fusion. Reducing PI(3,4,5)P-3 availability disperses Syntaxin1A clusters and increasing PI(3,4,5)P-3 levels rescues this defect. In artificial giant unilamellar vesicles, PI(3,4,5)P-3 also induces Syntaxin1A domain formation and this clustering, in vitro and in vivo, is dependent on positively charged residues in the Syntaxin1A-juxtannembrane domain. Functionally, reduced PI(3,4,5)P-3 causes temperature-sensitive paralysis and reduced neurotransmitter release, a phenotype also seen in animals expressing a Syntaxin1A with a mutated juxtamembrane domain. Thus, our data indicate that PI(3,4,5)P-3, based on electrostatic interactions, clusters Syntaxin1A at release sites to regulate neurotransmitter release.
