Calero-Cuenca Francisco J, Espinosa-Vázquez José Manuel, Reina-Campos Miguel, Díaz-Meco María T, Moscat Jorge, Sotillos Sol
CABD, CSIC/JA/UPO, Campus Universidad Pablo de Olavide, Ctra. De Utrera Km. 1, Seville, 41013, Spain.
Sanford-Burnham Medical Research Institute, La Jolla, CA, 92037, USA.
BMC Biol. 2016 Apr 18;14:32. doi: 10.1186/s12915-016-0253-6.
Cell polarity, essential for cell physiology and tissue coherence, emerges as a consequence of asymmetric localization of protein complexes and directional trafficking of cellular components. Although molecules required in both processes are well known their relationship is still poorly understood.
Here we show a molecular link between Nuclear Fallout (Nuf), an adaptor of Rab11-GTPase to the microtubule motor proteins during Recycling Endosome (RE) trafficking, and aPKC, a pivotal kinase in the regulation of cell polarity. We demonstrate that aPKC phosphorylates Nuf modifying its subcellular distribution. Accordingly, in aPKC mutants Nuf and Rab11 accumulate apically indicating altered RE delivery. We show that aPKC localization in the apico-lateral cortex is dynamic. When we block exocytosis, by means of exocyst-sec mutants, aPKC accumulates inside the cells. Moreover, apical aPKC concentration is reduced in nuf mutants, suggesting aPKC levels are maintained by recycling.
We demonstrate that active aPKC interacts with Nuf, phosphorylating it and, as a result, modifying its subcellular distribution. We propose a regulatory loop by which Nuf promotes aPKC apical recycling until sufficient levels of active aPKC are reached. Thus, we provide a novel link between cell polarity regulation and traffic control in epithelia.
细胞极性对细胞生理和组织连贯性至关重要，它是蛋白质复合物不对称定位和细胞成分定向运输的结果。尽管这两个过程所需的分子已为人熟知，但其关系仍知之甚少。
在此我们展示了核沉降蛋白（Nuf）与非典型蛋白激酶C（aPKC）之间的分子联系，Nuf是循环内体（RE）运输过程中Rab11 - GTP酶与微管运动蛋白的衔接蛋白，而aPKC是细胞极性调控中的关键激酶。我们证明aPKC使Nuf磷酸化，改变其亚细胞分布。相应地，在aPKC突变体中，Nuf和Rab11在顶端积累，表明RE递送发生改变。我们发现aPKC在顶端 - 外侧皮质的定位是动态的。当我们通过外排体 - sec突变体阻断胞吐作用时，aPKC在细胞内积累。此外，在nuf突变体中顶端aPKC浓度降低，表明aPKC水平通过循环得以维持。
我们证明活性aPKC与Nuf相互作用，使其磷酸化，进而改变其亚细胞分布。我们提出一个调节回路，即Nuf促进aPKC顶端循环，直至达到足够水平的活性aPKC。因此，我们揭示了上皮细胞中细胞极性调控与运输控制之间的新联系。
