Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska, United States of America.
PLoS One. 2012;7(10):e47572. doi: 10.1371/journal.pone.0047572. Epub 2012 Oct 15.
Platelet-derived growth factor-CC (PDGF-CC) is the third member of the PDGF family, and has been implicated both in embryogenesis and development of the CNS. The biological function of this isoform however, remains largely unexplored in the context of HIV-associated dementia (HAD). In the present study, we demonstrate that exposure of human neuroblastoma cells SH-SY5Y to HIV transactivator protein Tat resulted in decreased intrinsic expression of PDGF-CC as evidenced by RT-PCR and western blot assays. Reciprocally, pretreatment of SH-SY5Y cells with PDGF-CC abrogated Tat-mediated neurotoxicity by mitigating apoptosis and neurite & MAP-2 loss. Using pharmacological and loss of function approaches we identified the role of phosphatidylinositol 3-kinase (PI3K)/Akt signaling in PDGF-CC-mediated neuroprotection. We report herein a novel role about the involvement of transient receptor potential canonical (TRPC) channel 1 in modulation of calcium transients in PDGF-CC-mediated neuroprotection. Furthermore we also demonstrated PDGF-CC-mediated inactivation of the downstream mediator--glycogen synthase kinase 3β (GSK3β) evidenced by its phosphorylation at Ser-9. This was further validated by gain and loss of function studies using cells transfected with either the wild type or mutant GSK3β constructs. Intriguingly, pretreatment of cells with either the PI3K inhibitor or TRPC blocker resulted in failure of PDGF-CC to inactivate GSK3β, thereby suggesting the intersection of PI3K and TRPC signaling at GSK3β. Taken together our findings lead to the suggestion that PDGF-CC could be developed as a therapeutic target to reverse Tat-mediated neurotoxicity with implications for HAD.
血小板衍生生长因子-CC（PDGF-CC）是 PDGF 家族的第三个成员，它与胚胎发生和中枢神经系统的发育都有关。然而，在 HIV 相关痴呆症（HAD）的背景下，这种同工型的生物学功能在很大程度上仍未得到探索。在本研究中，我们证明了人类神经母细胞瘤细胞 SH-SY5Y 暴露于 HIV 转录激活蛋白 Tat 会导致 PDGF-CC 的内在表达减少，这可以通过 RT-PCR 和 Western blot 检测证实。相反，SH-SY5Y 细胞用 PDGF-CC 预处理可以通过减轻细胞凋亡和轴突及 MAP-2 丢失来阻断 Tat 介导的神经毒性。我们通过药理学和功能丧失方法确定了磷脂酰肌醇 3-激酶（PI3K）/Akt 信号通路在 PDGF-CC 介导的神经保护中的作用。我们在此报告了瞬时受体电位经典通道（TRPC）1 参与调节 PDGF-CC 介导的神经保护中钙瞬变的新作用。此外，我们还证明了 PDGF-CC 介导的下游介质——糖原合酶激酶 3β（GSK3β）失活，这可以通过其在丝氨酸 9 位的磷酸化来证明。这通过用野生型或突变 GSK3β 构建体转染的细胞进行的增益和失能研究得到了进一步验证。有趣的是，细胞用 PI3K 抑制剂或 TRPC 阻断剂预处理会导致 PDGF-CC 无法使 GSK3β失活，这表明 PI3K 和 TRPC 信号在 GSK3β 处相交。总之，我们的研究结果表明，PDGF-CC 可以作为一种治疗靶点，逆转 Tat 介导的神经毒性，这对 HAD 具有重要意义。
