Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon 24252, Korea.
Int J Mol Sci. 2020 Sep 4;21(18):6476. doi: 10.3390/ijms21186476.
Recently, we have reported that blockade/deletion of P2X7 receptor (P2X7R), an ATP-gated ion channel, exacerbates heat shock protein 25 (HSP25)-mediated astroglial autophagy (clasmatodendrosis) following kainic acid (KA) injection. In P2X7R knockout (KO) mice, prolonged astroglial HSP25 induction exerts 5' adenosine monophosphate-activated protein kinase/unc-51 like autophagy activating kinase 1-mediated autophagic pathway independent of mammalian target of rapamycin (mTOR) activity following KA injection. Sustained HSP25 expression also enhances AKT-serine (S) 473 phosphorylation leading to astroglial autophagy via glycogen synthase kinase-3β/bax interacting factor 1 signaling pathway. However, it is unanswered how P2X7R deletion induces AKT-S473 hyperphosphorylation during autophagic process in astrocytes. In the present study, we found that AKT-S473 phosphorylation was increased by enhancing activity of focal adhesion kinase (FAK), independent of mTOR complex (mTORC) 1 and 2 activities in isolated astrocytes of P2X7R knockout (KO) mice following KA injection. In addition, HSP25 overexpression in P2X7R KO mice acted as a chaperone of AKT, which retained AKT-S473 phosphorylation by inhibiting the pleckstrin homology domain and leucine-rich repeat protein phosphatase (PHLPP) 1- and 2-binding to AKT. Therefore, our findings suggest that P2X7R may be a fine-tuner of AKT-S473 activity during astroglial autophagy by regulating FAK phosphorylation and HSP25-mediated inhibition of PHLPP1/2-AKT binding following KA treatment.
最近，我们报道了 P2X7 受体（P2X7R）的阻断/缺失会加剧红藻氨酸（KA）注射后热休克蛋白 25（HSP25）介导的星形胶质细胞自噬（clasmatodendrosis），P2X7R 是一种 ATP 门控离子通道。在 P2X7R 敲除（KO）小鼠中，KA 注射后，持续的星形胶质细胞 HSP25 诱导会通过 5' 腺苷一磷酸激活蛋白激酶/非典型丝氨酸/苏氨酸蛋白激酶 1（UNC-51 样自噬激活激酶 1）介导的自噬途径发挥作用，而不依赖于哺乳动物雷帕霉素靶蛋白（mTOR）活性。持续的 HSP25 表达也会增强 AKT 丝氨酸（S）473 磷酸化，通过糖原合酶激酶-3β/ bax 相互作用因子 1 信号通路导致星形胶质细胞自噬。然而，P2X7R 缺失如何在星形胶质细胞自噬过程中诱导 AKT-S473 过度磷酸化仍未得到解答。在本研究中，我们发现 KA 注射后，P2X7R 敲除（KO）小鼠分离的星形胶质细胞中，粘着斑激酶（FAK）活性增强导致 AKT-S473 磷酸化增加，而不依赖于 mTOR 复合物（mTORC）1 和 2 的活性。此外，在 P2X7R KO 小鼠中过表达 HSP25 充当 AKT 的伴侣，通过抑制 PH 结构域和富含亮氨酸重复蛋白磷酸酶（PHLPP）1 和 2 与 AKT 的结合，保留 AKT-S473 磷酸化。因此，我们的研究结果表明，P2X7R 可能通过调节 FAK 磷酸化和 HSP25 介导的 PHLPP1/2-AKT 结合抑制，在 KA 处理后调节 AKT-S473 活性，从而成为星形胶质细胞自噬过程中 AKT-S473 活性的精细调节剂。
