SNAP-25a and SNAP-25b differently mediate interactions with Munc18-1 and Gβγ subunits
SNAP-25a and SNAP-25b differently mediate interactions with Munc18-1 and Gβγ subunits
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DOI：
10.1016/j.neulet.2018.03.024
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发表时间：
2018-05-01
影响因子：
2.5
通讯作者：
Bark, Christina
中科院分区：
文献类型：
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作者：
Daraio, Teresa;Valladolid-Acebes, Ismael;Bark, Christina
SNAP-25是一种参与调节膜融合的蛋白质，也是SNARE复合体的一部分。它以两个剪接变体SNAP-25a和SNAP-25b的形式存在，在206个氨基酸中有9个不同。SNAP-25与Syntaxin 1和VAMP-2形成三元SNARE复合物，对调节激素和神经递质的活性依赖性释放至关重要。SNAP-25a和SNAP-25b之间的功能差异尚不清楚，因为两者都可以参与SNARE复合物并介导膜融合。然而，我们最近证明snap -25b缺乏导致代谢性疾病和胰岛素分泌增加。在这里，我们研究了SNAP-25a和SNAP-25b是否不同地影响小鼠海马中其他SNAREs和snare相互作用蛋白的相互作用。成年小鼠海马区几乎完全表达SNAP-25b蛋白，而SNAP-25b缺陷小鼠仅表达SNAP-25a。免疫沉淀研究显示，不同SNAP-25亚型共沉淀Syntaxin 1和VAMP-2的数量无显著差异。相比之下，Munc18-1优先通过Syntaxin 1和/或三聚体SNARE复合物与SNAP-25相互作用，显示出结合含有SNAP-25b的蛋白质复合物的能力增强。此外，我们发现两种SNAP-25亚型共同沉淀了异源三聚体G蛋白的G β γ亚基，这种相互作用已知在突触前抑制中发挥作用。我们已经确定G β(1)和G β(2)是小鼠海马中SNAP-25同种异构体的相互作用伙伴，但G β(2)被SNAP-25a捕获的效率较低。这些结果表明，两种SNAP-25异构体可以不同地介导三元SNARE核心复合物外的蛋白质相互作用，从而有助于调节神经传递。
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.