To avoid conflicting and deleterious outcomes, eukaryotic cells often confine second messengers to spatially restricted subcompartments. The smallest signaling unit is the Ca²⁺ nanodomain, which forms when Ca²⁺ channels open. Ca²⁺ nanodomains arising from store-operated Orai1 Ca²⁺ channels stimulate the protein phosphatase calcineurin to activate the transcription factor nuclear factor of activated T cells (NFAT). Here, we show that NFAT1 tethered directly to the scaffolding protein AKAP79 (A-kinase anchoring protein 79) is activated by local Ca²⁺ entry, providing a mechanism to selectively recruit a transcription factor. We identify the region on the N terminus of Orai1 that interacts with AKAP79 and demonstrate that this site is essential for physiological excitation–transcription coupling. NMR structural analysis of the AKAP binding domain reveals a compact shape with several proline-driven turns. Orai2 and Orai3, isoforms of Orai1, lack this region and therefore are less able to engage AKAP79 and activate NFAT. A shorter, naturally occurring Orai1 protein that arises from alternative translation initiation also lacks the AKAP79-interaction site and fails to activate NFAT1. Interfering with Orai1–AKAP79 interaction suppresses cytokine production, leaving other Ca²⁺ channel functions intact. Our results reveal the mechanistic basis for how a subtype of a widely expressed Ca²⁺ channel is able to activate a vital transcription pathway and identify an approach for generation of immunosuppressant drugs.

为了避免冲突和有害的结果，真核细胞通常将第二信使限制在空间受限的子区室中。最小的信号传导单元是 Ca ²⁺纳米域，它在 Ca ²⁺通道打开时形成。由存储操纵的 Orai1 Ca ²⁺通道产生的 Ca ²⁺纳米结构域刺激蛋白磷酸酶钙调神经磷酸酶，激活活化 T 细胞的转录因子核因子 (NFAT)。在这里，我们发现直接与支架蛋白 AKAP79（A-激酶锚定蛋白 79）连接的 NFAT1 被局部 Ca ²⁺进入激活，提供了一种选择性招募转录因子的机制。我们确定了 Orai1 N 末端与 AKAP79 相互作用的区域，并证明该位点对于生理兴奋转录耦合至关重要。 AKAP 结合域的 NMR 结构分析揭示了具有多个脯氨酸驱动转角的紧凑形状。 Orai2 和 Orai3 是 Orai1 的亚型，缺少该区域，因此不太能够参与 AKAP79 并激活 NFAT。由替代翻译起始产生的较短的天然存在的 Orai1 蛋白也缺乏 AKAP79 相互作用位点，并且无法激活 NFAT1。干扰 Orai1-AKAP79 相互作用会抑制细胞因子的产生，使其他 Ca ²⁺通道功能完好无损。我们的结果揭示了广泛表达的 Ca ²⁺通道的亚型如何能够激活重要的转录途径并确定产生免疫抑制药物的方法的机制基础。