The roles of the CaVbeta2 subunit and the synaptic protein interaction site in determining Ca2+ channel function in neuroendocrine secretion

CaVbeta2亚基和突触蛋白相互作用位点在神经内分泌分泌中Ca2通道功能中的作用

• 批准号: RGPIN-2015-05536
• 负责人: Fisher, Thomas
• 金额: $ 2.19万
• 依托单位: University of Saskatchewan
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=683677
• 关键词: roles; CaVbeta2; subunit; synaptic; protein

The flow of Ca2+ into neurons through voltage-gated Ca2+ (CaV) channels triggers the release of neurotransmitters and hormones and the intracellular targeting of these channels is therefore of fundamental importance for intercellular communication. CaV channels are composed of a CaValpha1 subunit and one of four CaVbeta subunits, which may help transport channels to axon terminals. The two types of Ca2+ channels most important in synaptic release (CaV2.1 and CaV2.2) contain a peptide sequence that allows them to interact with synaptic proteins and is thus called the "synprint" site.****We propose to study the roles of the CaVbeta2 subunit and the synprint site in central neurons called the magnocellular neurosecretory cells (MNCs), which secrete the hormones oxytocin and vasopressin. Release occurs from both MNC cell bodies and terminals and increases as plasma osmolality increases. We found that the CaVbeta2 is enriched in MNC terminals, suggesting that it might play a role in CaV transport. We have also shown that MNCs express a variant of CaV2.1 that lacks the synprint site, but do not express an equivalent variant of CaV2.2. These data may explain the observation that CaV2.2, but not CaV2.1, triggers release of oxytocin from the MNC cell bodies.****We propose to test 1) whether the CaVbeta2 subunit plays a role in axonal targeting of CaV channels and 2) whether the interaction between the synprint site of CaV2.2 and synaptic proteins plays a role in triggering release of oxytocin from MNC cell bodies.****We will compare CaV expression in the MNC terminals of transgenic mice that lack the CaVbeta2 subunit in the brain to that of control littermates and predict that the expression will be lower. We further predict that these mice will fail to release vasopressin properly. We will test this by measuring vasopressin levels and plasma osmolality of control and knockout mice exposed to osmotic stress. We will test the role of the synprint site in facilitating neuropeptide secretion in MNC somata and terminals by interfering with the interaction between Ca2+ channels and synaptic proteins and measuring oxytocin release from MNC cell bodies. We predict that the disruption of this interaction will inhibit the ability of influx through CaV2.2 to trigger release, which would support a role for this interaction in hormone release. These studies will therefore help elucidate the mechanisms that allow neurons to regulate the release of hormones and neurotransmitters.***

Ca2+通过电压门控Ca2+（CaV）通道流入神经元，触发神经递质和激素的释放，因此这些通道的细胞内靶向对于细胞间通讯至关重要。 CaV通道由CaValpha1亚基和四个CaV β亚基之一组成，这可能有助于将通道运输到轴突末端。 在突触释放中最重要的两种类型的Ca 2+通道（CaV2.1和CaV2.2）包含一个肽序列，使它们能够与突触蛋白相互作用，因此被称为“突触印记”位点。我们建议研究CaV β 2亚基和synprint网站在中央神经元称为大细胞神经分泌细胞（MNCs），分泌激素催产素和加压素的作用。 从MNC细胞体和终末释放，并随着血浆渗透压的增加而增加。 我们发现CaV β 2在MNC末端富集，这表明它可能在CaV运输中发挥作用。 我们还表明，MNCs表达的CaV2.1的变体，缺乏synprint网站，但不表达CaV2.2的等效变体。 这些数据可以解释CaV2.2而不是CaV2.1触发MNC细胞体释放催产素的观察结果。*我们建议测试1）CaV β 2亚基是否在CaV通道的轴突靶向中起作用，以及2）CaV 2.2的synprint位点和突触蛋白之间的相互作用是否在触发MNC细胞体释放催产素中起作用。我们将比较CaV在转基因小鼠的MNC末端的表达，缺乏CaV β 2亚单位在大脑中的控制同窝出生的，并预测表达将较低。 我们进一步预测，这些小鼠将无法正常释放加压素。 我们将通过测量暴露于渗透应激的对照和基因敲除小鼠的血管加压素水平和血浆渗透压来测试这一点。我们将测试的synprint网站在促进MNC胞体和终端的神经肽分泌的作用，通过干扰Ca 2+通道和突触蛋白之间的相互作用，并测量从MNC细胞体的催产素释放。 我们预测这种相互作用的破坏将抑制通过CaV2.2的流入触发释放的能力，这将支持这种相互作用在激素释放中的作用。 因此，这些研究将有助于阐明允许神经元调节激素和神经递质释放的机制。