title: Reciprocal intramolecular interactions of tomosyn control its inhibitory activity on SNARE complex formation.
abstract: Neurotransmitter release from presynaptic nerve terminals is regulated by SNARE complex-mediated synaptic vesicle fusion. Tomosyn, a negative regulator of neurotransmitter release, which is composed of N-terminal WD40 repeats, a tail domain, and a C-terminal VAMP-like domain, is known to inhibit SNARE complex formation by sequestering target SNAREs (t-SNAREs) upon interaction of its C-terminal VAMP-like domain with t-SNAREs. However, it remains unclear how the inhibitory activity of tomosyn is regulated. Here we show that the tail domain functions as a regulator of the inhibitory activity of tomosyn through intramolecular interactions. The binding of the tail domain to the C-terminal VAMP-like domain interfered with the interaction of the C-terminal VAMP-like domain with t-SNAREs, and thereby repressed the inhibitory activity of tomosyn on the SNARE complex formation. The repressed inhibitory activity of tomosyn was restored by the binding of the tail domain to the N-terminal WD40 repeats. These results indicate that the probable conformational change of tomosyn mediated by the intramolecular interactions of the tail domain controls its inhibitory activity on the SNARE complex formation, leading to a regulated inhibition of neurotransmitter release.
authors.affiliation: Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Sumiko
authors.initials: S
authors.lastname: Mochida
authors.forename: Takao
authors.initials: T
authors.lastname: Kurooka
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sakisaka
mesh_terms: D000818:Animals; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D050683:R-SNARE Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D050600:SNARE Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000235:genetics / Q000378:metabolism*
chemical_list: D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D050683:R-SNARE Proteins; D050600:SNARE Proteins; C484769:Stxbp5 protein, rat