Abstract：
Complex organ development depends on single lumen formation and its expansion during tubulogenesis. This can be achieved by correct mitotic spindle orientation during cell division, combined with luminal fluid filling that generates hydrostatic pressure. Using a human 3D cell culture model, we have identified two regulators of these processes. We find that pleckstrin homology leucine-rich repeat protein phosphatase (PHLPP) 2 regulates mitotic spindle orientation, and thereby midbody positioning and maintenance of a single lumen. Silencing the sole PHLPP family phosphatase in Drosophila melanogaster, phlpp, resulted in defective spindle orientation in Drosophila neuroblasts. Importantly, cystic fibrosis transmembrane conductance regulator (CFTR) is the main channel regulating fluid transport in this system, stimulated by phosphorylation by protein kinase A and inhibited by the AMP-activated protein kinase AMPK. During lumen expansion, CFTR remains open through the action of PHLPP1, which stops activated AMPK from inhibiting ion transport through CFTR. In the absence of PHLPP1, the restraint on AMPK activity is lost and this tips the balance in the favour of channel closing, resulting in the lack of lumen expansion and accumulation of mucus.
摘要：
复杂器官的发育取决于单腔形成及其在肾小管发生过程中的扩张。这可以通过在细胞分裂过程中正确的有丝分裂纺锤体取向来实现，结合腔内流体填充，产生静水压力。使用人类3D细胞培养模型，我们已经确定了这些过程的两个监管机构。我们发现pleckstrin同源富含亮氨酸的重复蛋白磷酸酶（PHLPP）2调节有丝分裂纺锤体的取向，从而对单个管腔进行中体定位和维持。沉默果蝇中唯一的PHLPP家族磷酸酶，phlpp,导致果蝇神经母细胞的纺锤体取向缺陷。重要的是,囊性纤维化跨膜传导调节因子(CFTR)是该系统中调节液体运输的主要通道,由蛋白激酶A磷酸化刺激，并由AMP激活的蛋白激酶AMPK抑制。在管腔扩张过程中,CFTR通过PHLPP1的作用保持开放,这阻止了活化的AMPK抑制通过CFTR的离子传输。在没有PHLPP1的情况下，对AMPK活性的抑制作用丧失，这提示了有利于通道关闭的平衡，导致缺乏管腔扩张和粘液积聚。
