Biology subjects

Subkhangulova, A.

Publications and source records attributed to Subkhangulova, A..

2 recordsLinked to original sources

bioRxiv2023

Tomosyns attenuate SNARE assembly and synaptic depression by binding to VAMP2-containing template complexes

Tomosyns are soluble SNARE proteins proposed to attenuate membrane fusion by competing with synaptobrevin-2/VAMP2 for SNARE-complex assembly. Here, we present evidence against this scenario using a novel mouse model, energy barrier recordings, and single-molecule force measurements. Tomosyn-1/2 deficiency drastically enhanced the probability that synaptic vesicles fuse at synapses, resulting in stronger synapses with faster depression and slower recovery. While wildtype tomosyn-1m rescued these phenotypes, substitution of its SNARE motif with that of synaptobrevin-2/VAMP2 did not. Force measurements revealed that tomosyns SNARE motif cannot substitute synaptobrevin-2/VAMP2 to form template complexes with Munc18-1 and syntaxin-1, an essential intermediate for SNARE assembly. Instead, tomosyns bind synaptobrevin-2/VAMP2-containing template complexes and prevent SNAP-25 association. Structure-function analyses indicate that regions outside the SNARE motif contribute to tomosyns inhibitory function. These results reveal that tomosyns regulate synaptic transmission by preventing SNAP-25 binding to template complexes, increasing the energy barrier for synaptic vesicle fusion, and limiting synaptic depression.

neuroscience↗

bioRxiv2022

SNARE protein tomosyn regulates dense core vesicle composition but not exocytosis in mammalian neurons

Tomosyn is a large, non-canonical SNARE protein proposed to act as a competitive inhibitor of SNARE complex formation in vesicle exocytosis. In the brain, tomosyn inhibits fusion of synaptic vesicles (SVs), whereas its role in the fusion of neuropeptide-containing dense core vesicles (DCVs) is unknown. Here, we addressed this question using a new mouse model allowing conditional deletion of tomosyn (Stxbp5) and its paralogue tomosyn-2 (Stxbp5l), and an assay that detects DCV exocytosis with single vesicle resolution in primary hippocampal neurons. Surprisingly, loss of both tomosyns did not affect DCV exocytosis but resulted in a strong reduction of intracellular levels of many DCV cargos, most prominently brain-derived neurotrophic factor (BDNF), granin VGF and prohormone convertase PCSK1. Reduced levels of DCV cargos were paralleled by decreased DCV size and impaired mRNA expression of the corresponding genes. We conclude that tomosyns regulate neuropeptide and neurotrophin secretion via control of DCV cargo production, and not at the step of cargo release. Our findings suggest a differential effect of tomosyn on the two main secretory pathways in mammalian neurons and argues against a conserved role of tomosyn as competitive inhibitor of SNARE complex formation.

neuroscience↗