Department of Neurology, University Hospital of Würzburg, Würzburg, 97080 Germany; Institute of Clinical Neurobiology, University Hospital of Würzburg, Würzburg, 97078 Germany.
Institute of Clinical Neurobiology, University Hospital of Würzburg, Würzburg, 97078 Germany; Department of Otorhinolaryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery, University Hospital Würzburg, Germany.
Cell Calcium. 2022 Jan;101:102515. doi: 10.1016/j.ceca.2021.102515. Epub 2021 Dec 3.
How homeostatic ER calcium fluxes shape cellular calcium signals is still poorly understood. Here we used dual-color calcium imaging (ER-cytosol) and transcriptome analysis to link candidates of the calcium toolkit of astrocytes with homeostatic calcium signals. We found molecular and pharmacological evidence that P/Q-type channel Cacna1a contributes to depolarization-dependent calcium entry in astrocytes. For stimulated ER calcium release, the cells express the phospholipase Cb3, IP receptors Itpr1 and Itpr2, but no ryanodine receptors (Ryr1-3). After IP-induced calcium release, Stim1/2 - Orai1/2/3 most likely mediate SOCE. The Serca2 (Atp2a2) is the candidate for refilling of the ER calcium store. The cells highly express adenosine receptor Adora1a for IP-induced calcium release. Accordingly, adenosine induces fast ER calcium release and subsequent ER calcium oscillations. After stimulation, calcium refilling of the ER depends on extracellular calcium. In response to SOCE, astrocytes show calcium-induced calcium release, notably even after ER calcium was depleted by extracellular calcium removal in unstimulated cells. In contrast, spontaneous ER-cytosol calcium oscillations were not fully dependent on extracellular calcium, as ER calcium oscillations could persist over minutes in calcium-free solution. Additionally, cell-autonomous calcium oscillations show a second-long spatial and temporal delay in the signal dynamics of ER and cytosolic calcium. Our data reveal a rather strong contribution of homeostatic calcium fluxes in shaping IP-induced and calcium-induced calcium release as well as spatiotemporal components of intracellular calcium oscillations.
内稳态 ER 钙流如何塑造细胞钙信号仍知之甚少。在这里，我们使用双色钙成像（ER-cytosol）和转录组分析将星形胶质细胞钙工具包的候选物与内稳态钙信号联系起来。我们发现分子和药理学证据表明 P/Q 型通道 Cacna1a 有助于星形胶质细胞的去极化依赖性钙内流。对于刺激的 ER 钙释放，细胞表达磷脂酶 Cb3、IP 受体 Itpr1 和 Itpr2，但没有 Ryanodine 受体（Ryr1-3）。在 IP 诱导的钙释放后，Stim1/2-Orai1/2/3 很可能介导 SOCE。Serca2（Atp2a2）是 ER 钙库再填充的候选物。细胞高度表达 adenosine 受体 Adora1a 以诱导 IP 诱导的钙释放。相应地，腺苷诱导快速 ER 钙释放和随后的 ER 钙振荡。刺激后，ER 钙的再填充取决于细胞外钙。响应 SOCE，星形胶质细胞显示钙诱导的钙释放，特别是在未刺激细胞中通过去除细胞外钙耗尽 ER 钙后。相比之下，自发的 ER-cytosol 钙振荡不完全依赖于细胞外钙，因为 ER 钙振荡在无钙溶液中可以持续数分钟。此外，细胞自主钙振荡显示 ER 和胞质钙信号动力学的第二个长时空延迟。我们的数据揭示了内稳态钙流对内稳态钙流和钙诱导钙释放以及细胞内钙振荡的时空成分有相当大的贡献。
