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. 2018 Nov 28;9:5041. doi: 10.1038/s41467-018-07464-8

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© The Author(s) 2018

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 10 — Model of PIP rearrangements during lumen formation. Shortly after plating into 3D, single MDCK cells undergo morphogenesis to form a cell doublet with initially inverted polarity a, whereby the apical surface marked by Podxl abuts the ECM. At this stage, a PI(4)P>PI(4,5)P₂ > PIP₃ cascade defines the cell–cell contact, while PI(3,4)P₂ is inverted. b To reorient polarity, peripheral Podxl internalizes into vesicles which are initially PI(3)P and/or PI(4)P positive, before progressively enriching to become PI(3,4)P₂/Rab11a-positive. These vesicles target to the apical membrane initiation site (AMIS). The PI(3,4)P₂-promoting Class-II PI3Ks PIK3C2A/B promote, whereas the PI(3,4)P₂-degrading phosphatases INPP4A/B inhibit, this process. Concomitantly, the AMIS is formed by two PIP phosphatases, PTEN and SHIP1, which focally convert PIP₃ into, PI(4,5)P₂ or PI(3,4)P₂, respectively to form this zone for apical vesicle delivery. c Upon delivery of transcytosing Podxl, de novo lumen formation is completed, leaving cortical PI(4)P and PI(4,5)P₂, basolateral PIP₃, and apical and recycling endosome PI(3,4)P₂