Membrane-delimited coupling between sigma receptors and K+ channels in rat neurohypophysial terminals requires neither G-protein nor ATP
Membrane-delimited coupling between sigma receptors and K+ channels in rat neurohypophysial terminals requires neither G-protein nor ATP
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DOI：
10.1111/j.1469-7793.2000.00527.x
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发表时间：
2000-08-01
影响因子：
5.5
通讯作者：
Jackson, MB
中科院分区：
文献类型：
--
作者：
Lupardus, PJ;Wilke, RA;Jackson, MB
1.受体介导的离子通道调节通常涉及G蛋白、磷酸化或两者的组合。调节电压门控K+通道的σ受体是一种新的蛋白质，与已知调节离子通道的其他受体没有同源性。本研究采用膜片钳技术和光标记技术研究了sigma受体对肽能神经末梢钾通道的调节机制.σ受体光探针碘代叠氮可卡因标记的蛋白质具有与通过克隆鉴定的σ受体蛋白质相同的分子量（26 kDa）。σ受体配体喷他佐辛和SKF10047调节K+通道，尽管用不含GTP的溶液、G i蛋白抑制剂（GDP β S）、G蛋白激活剂（GTP γ S）或不可水解的ATP类似物（AMPPcP）进行终末内灌注。通道切出外向补丁调制配体，表明不需要可溶性细胞质因子。与此相反，通道内的细胞附着的补丁不调制的配体补丁外，表明受体和通道必须在功能相互作用的紧密接近。在没有受体的卵母细胞中表达的通道对σ受体激动剂无反应，排除了通过与通道的直接药物相互作用的抑制。这些实验表明，σ受体介导的信号转导是膜界定的，既不需要G蛋白活化，也不需要蛋白磷酸化。这种新的转导机制是由膜蛋白介导的密切联系，可能通过受体和通道之间的直接相互作用。这将允许比其他离子通道调节机制更快速的信号转导，在神经垂体神经末梢的本情况下，这将导致神经肽释放的增强。
1. Receptor-mediated modulation of ion channels generally involves G-proteins, phosphorylation, or both in combination. The sigma receptor, which modulates voltage-gated K+ channels, is a novel protein with no homology to other receptors known to modulate ion channels. In the present study patch clamp and photolabelling techniques were used to investigate the mechanism by which sigma receptors modulate K+ channels in peptidergic nerve terminals.2. The sigma receptor photoprobe iodoazidococaine labelled a protein with the same molecular mass (26 kDa) as the sigma receptor protein identified by cloning.3. The sigma receptor ligands pentazocine and SKF10047 modulated K+ channels, despite intra-terminal perfusion with GTP-free solutions, a Gi-protein inhibitor (GDP beta S), a G-protein activator (GTP gamma S) or a non-hydrolysable ATP analogue (AMPPcP).4. Channels in excised outside-out patches were modulated by ligand, indicating that soluble cytoplasmic factors are not required. In contrast, channels within cell-attached patches were not modulated by ligand outside a patch, indicating that receptors and channels must be in close proximity for functional interactions. Channels expressed in oocytes without receptors were unresponsive to sigma receptor agonists, ruling out inhibition through a direct drug interaction with channels.5. These experiments indicate that sigma receptor-mediated signal transduction is membrane delimited, and requires neither G-protein activation nor protein phosphorylation. This novel transduction mechanism is mediated by membrane proteins in close proximity, possibly through direct interactions between the receptor and channel. This would allow for more rapid signal transduction than other ion channel modulation mechanisms, which in the present case of neurohypophysial nerve terminals would lead to the enhancement of neuropeptide release.