TIRF Labs, Inc., 106 Grendon Place, Cary, NC, USA.
Cell Calcium. 2013 Sep;54(3):246-56. doi: 10.1016/j.ceca.2013.06.008. Epub 2013 Jul 18.
The assembly of STIM1 protein puncta near endoplasmic reticulum-plasma membrane (ER-PM) junctions is required for optimal activation of store-operated channels (SOC). The mechanisms controlling the translocation of STIM1 puncta to ER-PM junctions remain largely unknown. In the present study, we have explored the role of the microtubule binding protein adenomatous polyposis coli (APC), on STIM1 puncta and store-operated calcium entry (SOCE). APC-depleted cells showed reduced STIM1 puncta near ER-PM junctions, instead puncta is found at the ER surrounding the cell nucleus. Reduced STIM1 puncta near ER-PM junctions in APC-depleted cells correlates with a strong inhibition of SOCE and diminished Orai whole-cell currents. Immunoprecipitation and confocal microscopy co-localization studies indicate that, upon depletion of the ER, STIM1 dissociates from EB1 and associates to APC. Deletion analysis identified an APC-binding domain in the carboxyl terminus of STIM1 (STIM1 650-685). These results together position APC as an important element in facilitating the translocation of STIM1 puncta near ER-PM junctions, which in turn is required for efficient SOCE and Orai activation upon depletion of the ER.
STIM1 蛋白斑点在内质网-质膜（ER-PM）连接处的组装对于最佳激活储存操作通道（SOC）是必需的。控制 STIM1 斑点向 ER-PM 连接处易位的机制在很大程度上尚不清楚。在本研究中，我们探讨了微管结合蛋白腺瘤性结肠息肉病（APC）在 STIM1 斑点和储存操作钙内流（SOCE）中的作用。 APC 耗尽的细胞显示 ER-PM 连接处附近的 STIM1 斑点减少，而斑点则位于围绕细胞核的 ER 周围。 APC 耗尽的细胞中 ER-PM 连接处附近 STIM1 斑点的减少与 SOCE 的强烈抑制和 Orai 全细胞电流的减少密切相关。免疫沉淀和共聚焦显微镜共定位研究表明，在 ER 耗尽时，STIM1 与 EB1 解离并与 APC 结合。删除分析确定了 STIM1 羧基末端的 APC 结合域（STIM1 650-685）。这些结果共同将 APC 定位为促进 ER-PM 连接处附近 STIM1 斑点易位的重要因素，而这对于 ER 耗尽时有效进行 SOCE 和 Orai 激活是必需的。
