Division of Biochemistry, Chungbuk National University, City of Cheongju, 361-763, Korea.
Department of Pediatrics, College of Medicine, Chungbuk National University, City of Cheongju, 361-763, Korea.
Exp Mol Med. 2018 May 21;50(5):1-10. doi: 10.1038/s12276-018-0093-2.
Calcium mobilization is necessary for cell movement during embryonic development, lymphocyte synapse formation, wound healing, and cancer cell metastasis. Depletion of calcium in the lumen of the endoplasmic reticulum using inositol triphosphate (IP3) or thapsigargin (TG) is known to induce oligomerization and cytoskeleton-mediated translocation of stromal interaction molecule 1 (STIM1) to the plasma membrane, where it interacts with the calcium release-activated calcium channel Orai1 to mediate calcium influx; this process is referred to as store-operated calcium entry (SOCE). Furthermore, aberrant STIM1 or SOCE regulation is associated with cancer cell motility and metastasis. The p21-activated kinases (PAKs), which are downstream effectors of GTPases, reportedly regulate cytoskeletal organization, protrusive activity, and cell migration. Although cytoskeletal remodeling apparently contributes to calcium mobilization via SOCE, and vice versa, the mechanisms by which they regulate each other remain unclear. In this study, we aimed to characterize whether PAK1 modulates calcium mobilization and STIM1 localization. Our data demonstrate that PAK1 interacts with STIM1 in vitro and that this interaction was enhanced by treatment with a nascent adhesion inducer, such as phorbol 12,13-dibutyrate (PDBu). Under basal conditions, both proteins appeared to primarily colocalize in the cytosol, whereas treatment with PDBu induced their colocalization to vinculin-positive peripheral adhesions. Downregulation of PAK1 activity via chemical inhibitors or by PAK1 shDNA expression impaired STIM1-mediated calcium mobilization via SOCE. Based on these findings, we propose that PAK1 interacts with STIM1 to regulate calcium mobilization and the formation of cellular adhesions.
钙动员对于胚胎发育、淋巴细胞突触形成、伤口愈合和癌细胞转移过程中的细胞运动是必要的。已知使用三磷酸肌醇 (IP3) 或 thapsigargin (TG) 耗尽内质网腔中的钙会诱导基质相互作用分子 1 (STIM1) 寡聚化和细胞骨架介导的向质膜易位，在质膜上，它与钙释放激活钙通道 Orai1 相互作用介导钙内流；这个过程被称为储存操作的钙进入 (SOCE)。此外，异常的 STIM1 或 SOCE 调节与癌细胞的运动性和转移有关。p21 激活激酶 (PAKs) 是 GTPases 的下游效应物，据报道可调节细胞骨架组织、突起活性和细胞迁移。尽管细胞骨架重塑显然通过 SOCE 有助于钙动员，反之亦然，但它们相互调节的机制尚不清楚。在这项研究中，我们旨在表征 PAK1 是否调节钙动员和 STIM1 定位。我们的数据表明 PAK1 在体外与 STIM1 相互作用，并且这种相互作用通过处理新生粘附诱导剂（如佛波醇 12,13-二丁酸酯 (PDBu)）而增强。在基础条件下，两种蛋白质似乎主要在细胞质中共定位，而用 PDBu 处理会诱导它们共定位到 vinculin 阳性周围附着。通过化学抑制剂或 PAK1 shDNA 表达下调 PAK1 活性会损害 STIM1 通过 SOCE 介导的钙动员。基于这些发现，我们提出 PAK1 与 STIM1 相互作用以调节钙动员和细胞粘附的形成。
