SNAP-25a and SNAP-25b differently mediate interactions with Munc18-1 and G beta gamma subunits

作者：Daraio Teresa; Valladolid Acebes Ismael; Brismar Kerstin; Bark Christina^*

来源：Neuroscience Letters, 2018, 674: 75-80.

DOI：10.1016/j.neulet.2018.03.024

• SNARE
• Hippocampus
• Protein interactions
• Presynaptic inhibition
• GPCR

SNAP-25 is a protein involved in regulated membrane fusion and part of the SNARE complex. It exists as two splicing variants, SNAP-25a and SNAP-25b, which differ in 9 out of 206 amino acids. SNAP-25 together with Syntaxin 1 and VAMP-2 forms the ternary SNARE complex essential for mediating activity-dependent release of hormones and neurotransmitters. The functional difference between SNAP-25a and SNAP-25b is poorly understood as both can participate in SNARE complexes and mediate membrane fusion. However, we recently demonstrated that SNAP-25b-deficiency results in metabolic disease and increased insulin secretion. Here we investigated if SNAP-25a and SNAP-25b differently affect interactions with other SNAREs and SNARE-interacting proteins in mouse hippocampus. Adult mice almost exclusively express the SNAP-25b protein in hippocampus whereas SNAP-25b-deficient mice only express SNAP-25a. Immunoprecipitation studies showed no significant differences in amount of Syntaxin 1 and VAMP-2 co-precipitated with the different SNAP-25 isoforms. In contrast, Munc18-1, that preferentially interacts with SNAP-25 via Syntaxin 1 and/or the trimeric SNARE complex, demonstrated an increased ability to bind protein-complexes containing SNAP-25b. Moreover, we found that both SNAP-25 isoforms co-precipitated the G beta gamma subunits of the heterotrimeric G proteins, an interaction known to play a role in presynaptic inhibition. We have identified G beta(1) and G beta(2) as the interacting partners of both SNAP-25 isoforms in mouse hippocampus, but G beta(2) was less efficiently captured by SNAP-25a. These results implicate that the two SNAP-25 isoforms could differently mediate protein interactions outside the ternary SNARE core complex and thereby contribute to modulate neurotransmission.

• 出版日期2018-5-1