Forteza Radia, Figueroa Yolanda, Mashukova Anastasia, Dulam Vipin, Salas Pedro J
Department of Cell Biology, University of Miami Miller School of Medicine, Miami, FL 33136.
Department of Cell Biology, University of Miami Miller School of Medicine, Miami, FL 33136 Department of Physiology, Nova Southeastern University, Ft. Lauderdale, FL 33314.
Mol Biol Cell. 2016 Jul 15;27(14):2186-97. doi: 10.1091/mbc.E16-02-0086. Epub 2016 May 25.
The conserved proteins of the polarity complex made up of atypical PKC (aPKC, isoforms ι and ζ), Par6, and Par3 determine asymmetry in several cell types, from Caenorhabditis elegans oocytes to vertebrate epithelia and neurons. We previously showed that aPKC is down-regulated in intestinal epithelia under inflammatory stimulation. Further, expression of constitutively active PKCι decreases NF-κB activity in an epithelial cell line, the opposite of the effect reported in other cells. Here we tested the hypothesis that aPKC has a dual function in epithelia, inhibiting the NF-κB pathway in addition to having a role in apicobasal polarity. We achieved full aPKC down-regulation in small intestine villi and colon surface epithelium using a conditional epithelium-specific knockout mouse. The results show that aPKC is dispensable for polarity after cell differentiation, except for known targets, including ROCK and ezrin, claudin-4 expression, and barrier permeability. The aPKC defect resulted in increased NF-κB activity, which could be rescued by IKK and ROCK inhibitors. It also increased expression of proinflammatory cytokines. In contrast, expression of anti-inflammatory IL-10 decreased. We conclude that epithelial aPKC acts upstream of multiple mechanisms that participate in the inflammatory response in the intestine, including, but not restricted to, NF-κB.
由非典型蛋白激酶C（aPKC，亚型ι和ζ）、Par6和Par3组成的极性复合体中的保守蛋白，决定了从秀丽隐杆线虫卵母细胞到脊椎动物上皮细胞和神经元等多种细胞类型的不对称性。我们先前发现，在炎症刺激下，肠道上皮细胞中的aPKC表达下调。此外，组成型活性PKCι在一种上皮细胞系中的表达降低了核因子κB（NF-κB）的活性，这与在其他细胞中报道的效应相反。在此，我们验证了一个假说，即aPKC在上皮细胞中具有双重功能，除了在顶基极性中发挥作用外，还抑制NF-κB信号通路。我们利用条件性上皮细胞特异性敲除小鼠，实现了小肠绒毛和结肠表面上皮细胞中aPKC的完全下调。结果表明，除了已知的靶点，包括Rho相关卷曲螺旋形成蛋白激酶（ROCK）和埃兹蛋白、闭合蛋白4的表达以及屏障通透性外，细胞分化后aPKC对于极性形成并非必需。aPKC缺陷导致NF-κB活性增加，而IKK和ROCK抑制剂可挽救这一现象。它还增加了促炎细胞因子的表达。相反，抗炎性白细胞介素-10的表达则下降。我们得出结论，上皮细胞中的aPKC在参与肠道炎症反应的多种机制上游发挥作用，这些机制包括但不限于NF-κB。
