Department of Pharmacology, Yamaguchi University Graduate School of Medicine, 1-1-1, Minamikogushi, Ube, Yamaguchi 755-8505, Japan.
Department of Clinical Immuno Oncology, Showa University Clinical Research Institute for Clinical Pharmacology and Therapeutics, 6-11-11, Kitakarasuyama, Setagaya-ku, Tokyo 157-8577, Japan.
Cell Signal. 2021 Jul;83:109973. doi: 10.1016/j.cellsig.2021.109973. Epub 2021 Mar 6.
Histamine induces chemotaxis of mast cells through the histamine H receptor. This involves the activation of small GTPases, Rac1 and Rac2, downstream of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). Activation of the H receptor also results in phospholipase C (PLC)-mediated calcium mobilization; however, it is unclear whether the PLC‑calcium pathway interacts with the PI3K-Rac pathway. Here, we demonstrated that calcium mobilization regulates the PI3K-dependent activation of Rac GTPases through calmodulin. A PLC inhibitor (U73122) and an intracellular calcium chelator (BAPTA-AM) suppressed the histamine-induced activation of Rac, whereas the calcium ionophore ionomycin increased the active Rac GTPases, suggesting that intracellular calcium regulates the activation of Rac. The calmodulin antagonist (W-7) inhibited the histamine-induced activation of Rac and migration of mast cells, indicating that calmodulin mediates the effect of calcium. Inhibition of calcium/calmodulin signaling suppressed histamine-induced phosphorylation of Akt. The Akt inhibitor MK-2206 attenuated histamine-induced migration of mast cells. However, it did not suppress the activation of Rac GTPases. These results suggest that Rac GTPases and Akt play independent roles in the histamine-induced chemotaxis of mast cells. Our findings enable further elucidation of the molecular mechanism of histamine-induced chemotaxis of mast cells and help identify therapeutic targets for allergic and inflammatory conditions involving mast cell accumulation.
组胺通过组胺 H 受体诱导肥大细胞的趋化作用。这涉及到磷脂酰肌醇-4,5-二磷酸 3-激酶 (PI3K) 下游的小 GTP 酶 Rac1 和 Rac2 的激活。H 受体的激活还导致磷脂酶 C (PLC) 介导的钙动员;然而，尚不清楚 PLC-钙途径是否与 PI3K-Rac 途径相互作用。在这里，我们证明钙动员通过钙调蛋白调节 PI3K 依赖性 Rac GTPase 的激活。PLC 抑制剂 (U73122) 和细胞内钙螯合剂 (BAPTA-AM) 抑制组胺诱导的 Rac 激活，而钙离子载体离子霉素增加活性 Rac GTPases，表明细胞内钙调节 Rac 的激活。钙调蛋白拮抗剂 (W-7) 抑制组胺诱导的 Rac 激活和肥大细胞迁移，表明钙调蛋白介导钙的作用。钙/钙调蛋白信号的抑制抑制 Akt 的组胺诱导磷酸化。Akt 抑制剂 MK-2206 减弱了组胺诱导的肥大细胞迁移。然而，它并没有抑制 Rac GTPase 的激活。这些结果表明 Rac GTPases 和 Akt 在组胺诱导的肥大细胞趋化作用中发挥独立的作用。我们的发现使进一步阐明组胺诱导的肥大细胞趋化作用的分子机制成为可能，并有助于确定涉及肥大细胞积累的过敏和炎症状态的治疗靶点。
