Institute of Biology and Molecular Genetics (IBGM), University of Valladolid and Spanish National Research Council (CSIC), Valladolid, Spain.
The Signal Transduction Laboratory, National Institute of Environmental Health Sciences (NIEHS/NIH), Triangle Research Park, NC, USA.
Biochim Biophys Acta Mol Cell Res. 2019 Jul;1866(7):1124-1136. doi: 10.1016/j.bbamcr.2018.11.006. Epub 2018 Nov 17.
Store operated Ca entry (SOCE) is the most important Ca entry pathway in non-excitable cells. However, SOCE can also play a pivotal role in excitable cells such as anterior pituitary (AP) cells. The AP gland contains five different cell types that release six major AP hormones controlling most of the entire endocrine system. AP hormone release is modulated by Ca signals induced by different hypothalamic releasing hormones (HRHs) acting on specific receptors in AP cells. TRH and LHRH both induce Ca release and Ca entry in responsive cells while GHRH and CRH only induce Ca entry. SOCE has been shown to contribute to Ca responses induced by TRH and LHRH but no molecular evidence has been provided. Accordingly, we used AP cells isolated from mice devoid of Orai1 channels (noted as Orai1-/- or Orai1 KO mice) and mice lacking expression of all seven canonical TRP channels (TRPC) from TRPC1 to TRPC7 (noted as heptaTRPC KO mice) to investigate contribution of these putative channel proteins to SOCE and intracellular Ca responses induced by HRHs. We found that thapsigargin-evoked SOCE is lost in AP cells from Orai1-/- mice but unaffected in cells from heptaTRPC KO mice. Conversely, while spontaneous intracellular Ca-oscillations related to electrical activity were not affected in the Orai1-/- mice, these responses were significantly reduced in heptaTRPC KO mice. We also found that Ca entry induced by TRH and LHRH is decreased in AP cells isolated from Orai1-/-. In addition, Ca responses to several HRHs, particularly TRH and GHRH, are decreased in the heptaTRPC KO mice. These results indicate that expression of Orai1, and not TRPC channel proteins, is necessary for thapsigargin-evoked SOCE and is required to support Ca entry induced by TRH and LHRH in mouse AP cells. In contrast, TRPC channel proteins appear to contribute to spontaneous Ca-oscillations and Ca responses induced by TRH and GHRH. We conclude that expression of Orai1 and TRPC channels proteins may play differential and significant roles in AP physiology and endocrine control.
钙库操纵性钙内流（SOCE）是无兴奋细胞中最重要的钙内流途径。然而，SOCE 也可以在前垂体（AP）细胞等兴奋细胞中发挥关键作用。AP 腺含有五种不同的细胞类型，它们释放六种主要的 AP 激素，控制着整个内分泌系统的大部分功能。AP 激素的释放受到不同下丘脑释放激素（HRH）作用于 AP 细胞上特定受体所诱导的钙信号的调节。TRH 和 LHRH 均可诱导反应性细胞中的钙释放和钙内流，而 GHRH 和 CRH 仅诱导钙内流。已经表明 SOCE 有助于 TRH 和 LHRH 诱导的钙反应，但没有提供分子证据。因此，我们使用从小鼠中分离出的缺乏 Orai1 通道（称为 Orai1-/-或 Orai1 KO 小鼠）和缺乏从 TRPC1 到 TRPC7 的所有七种经典 TRP 通道（TRPC）表达的小鼠（称为 heptaTRPC KO 小鼠）来研究这些假定的通道蛋白对 HRH 诱导的 SOCE 和细胞内钙反应的贡献。我们发现，在 Orai1-/-小鼠的 AP 细胞中，毒胡萝卜素诱导的 SOCE 丧失，但在 heptaTRPC KO 小鼠的细胞中不受影响。相反，虽然 Orai1-/-小鼠的电活动相关的自发细胞内钙振荡不受影响，但这些反应在 heptaTRPC KO 小鼠中显著减少。我们还发现，TRH 和 LHRH 诱导的钙内流在 Orai1-/-AP 细胞中减少。此外，heptaTRPC KO 小鼠中几种 HRH 的钙反应，特别是 TRH 和 GHRH 的钙反应减少。这些结果表明，Orai1 的表达而不是 TRPC 通道蛋白对于毒胡萝卜素诱导的 SOCE 是必需的，并且对于支持 TRH 和 LHRH 诱导的小鼠 AP 细胞中的钙内流是必需的。相比之下，TRPC 通道蛋白似乎有助于自发钙振荡和 TRH 和 GHRH 诱导的钙反应。我们得出结论，Orai1 和 TRPC 通道蛋白的表达可能在 AP 生理学和内分泌控制中发挥不同且重要的作用。
