Department of Cell Biology, University of Miami Miller School of Medicine, Miami, FL 33136.
Department of Medical Education, Dr. Kiran C. Patel College of Allopathic Medicine, Nova Southeastern University, Fort Lauderdale, FL 33314.
Mol Biol Cell. 2021 Apr 15;32(8):690-702. doi: 10.1091/mbc.E20-10-0646. Epub 2021 Feb 17.
Par1b/MARK2 is a Ser/Thr kinase with pleiotropic effects that participates in the generation of apico-basal polarity in . It is phosphorylated by atypical PKC(ι/λ) in Thr595 and inhibited. Because previous work showed a decrease in atypical protein kinase C (aPKC) activity under proinflammatory conditions, we analyzed the hypothesis that the resulting decrease in Thr595-MARK2 with increased kinase activity may also participate in innate immunity. We confirmed that pT595-MARK2 was decreased under inflammatory stimulation. The increase in MARK2 activity was verified by Par3 delocalization and rescue with a specific inhibitor. MARK2 overexpression significantly enhanced the transcriptional activity of NF-kB for a subset of transcripts. It also resulted in phosphorylation of a single band (∼Mr 80,000) coimmunoprecipitating with RelA, identified as Med17. In vitro phosphorylation showed direct phosphorylation of Med17 in Ser152 by recombinant MARK2. Expression of S152D-Med17 mimicked the effect of MARK2 activation on downstream transcriptional regulation, which was antagonized by S152A-Med17. The decrease in pThr595 phosphorylation was validated in aPKC-deficient mouse jejunal mucosae. The transcriptional effects were confirmed in transcriptome analysis and transcript enrichment determinations in cells expressing S152D-Med17. We conclude that theMARK2-Med17 axis represents a novel form of cross-talk between polarity signaling and transcriptional regulation including, but not restricted to, innate immunity responses.
Par1b/MARK2 是一种丝氨酸/苏氨酸激酶，具有多种效应，参与了 . 的顶底极性的产生。它在 Thr595 被非典型蛋白激酶 C（aPKC）（ι/λ）磷酸化并被抑制。由于先前的工作表明在促炎条件下非典型蛋白激酶 C（aPKC）活性降低，我们分析了假设，即 Thr595-MARK2 的减少伴随着激酶活性的增加，也可能参与先天免疫。我们证实了在炎症刺激下 pT595-MARK2 减少。通过 Par3 定位和特异性抑制剂的挽救来验证 MARK2 活性的增加。MARK2 的过表达显著增强了 NF-kB 对一组转录物的转录活性。它还导致与 RelA 共免疫沉淀的单个条带（∼Mr80000）的磷酸化，该条带被鉴定为 Med17。体外磷酸化显示重组 MARK2 直接在 Ser152 处磷酸化 Med17。S152D-Med17 的表达模拟了 MARK2 激活对下游转录调控的影响，而 S152A-Med17 则拮抗了这种影响。在 aPKC 缺陷型小鼠空肠黏膜中验证了 pThr595 磷酸化的减少。在表达 S152D-Med17 的细胞中转录组分析和转录本富集测定中证实了转录效应。我们得出结论，MARK2-Med17 轴代表了极性信号和转录调控之间的一种新的串扰形式，包括但不限于先天免疫反应。
