Department of Biochemistry, University of Western Ontario, London, ON, Canada.
Institute of Biochemistry, Carleton University, Ottawa, ON, Canada.
Mol Cell Endocrinol. 2021 Oct 1;536:111400. doi: 10.1016/j.mce.2021.111400. Epub 2021 Jul 24.
Fetal growth restriction (FGR) is associated with decreased nutrient availability and reduced insulin-line growth factor (IGF)-I bioavailability via increased IGF binding protein (IGFBP)-1 phosphorylation. While protein kinase C (PKC) is implicated in IGFBP-1 hyperphosphorylation in nutrient deprivation, the mechanisms remain unclear. We hypothesised that the interaction of PKCα with protein kinase CK2β and activation of PKCα under leucine deprivation (L0) mediate fetal hepatic IGFBP-1 hyperphosphorylation. Parallel Reaction Monitoring Mass Spectrometry (PRM-MS) followed by PKCα knockdown demonstrated the PKCα isoform interacts with IGFBP-1 and CK2β under L0. Pharmacological PKCα activation with phorbol 12-myristate 13-acetate (PMA) increased whereas inhibition with bisindolylmaleimide II (Bis II) decreased IGFBP-1 phosphorylation (Ser101/119/169, Ser98 + 101 and Ser169 + 174), respectively. Furthermore, PMA mimicked L0-induced PKCα translocation and IGFBP-1 expression. PKCα expression was increased in baboon fetal liver in FGR, providing biological relevance in vivo. In summary, we report a novel nutrient-sensitive mechanism for PKCα in mediating IGFBP-1 hyperphosphorylation in FGR.
胎儿生长受限（FGR）与营养物质供应减少以及胰岛素样生长因子（IGF）-I 生物利用度降低有关，其机制与 IGF 结合蛋白（IGFBP）-1 磷酸化增加有关。虽然蛋白激酶 C（PKC）在营养剥夺时参与 IGFBP-1 的过度磷酸化，但具体机制尚不清楚。我们假设 PKCα 与蛋白激酶 CK2β 的相互作用以及亮氨酸剥夺（L0）下 PKCα 的激活介导胎儿肝脏 IGFBP-1 的过度磷酸化。平行反应监测质谱（PRM-MS）和 PKCα 敲低实验表明，PKCα 同工型在 L0 条件下与 IGFBP-1 和 CK2β 相互作用。佛波醇 12-肉豆蔻酸 13-乙酸酯（PMA）可激活 PKCα，增加 IGFBP-1 磷酸化（Ser101/119/169、Ser98+101 和 Ser169+174），而双吲哚基马来酰亚胺 II（Bis II）抑制 PKCα 则降低 IGFBP-1 磷酸化。此外，PMA 模拟了 L0 诱导的 PKCα 易位和 IGFBP-1 的表达。FGR 中狒狒胎儿肝脏中 PKCα 的表达增加，为体内生物学相关性提供了证据。总之，我们报告了一种新的与营养有关的 PKCα 介导胎儿生长受限中 IGFBP-1 过度磷酸化的机制。
