PI(4,5)P2 produced by the PI4P5K SKTL controls apical size by tethering PAR-3 in Drosophila epithelial cells.
BACKGROUND
The control of apical-basal polarity in epithelial layers is a fundamental event in many processes, ranging from embryonic development to tumor formation. A key feature of polarized epithelial cells is their ability to maintain an asymmetric distribution of specific molecular complexes, including the phosphoinositides PI(4,5)P2 and PI(3,4,5)P3. The spatiotemporal regulation of these phosphoinositides is controlled by the concerted action of phosphoinositide kinases and phosphatases.


RESULTS
Using the Drosophila follicular epithelium as a model system in vivo, we show here that PI(4,5)P2 is crucial to maintain apical-basal polarity. PI(4,5)P2 is essentially regulated by the PI4P5 kinase Skittles (SKTL), whereas neither the phosphatase PTEN nor the PI(4,5)P3 kinase DP110 lead to loss of apical-basal polarity. By inactivating SKTL and thereby strongly reducing PI(4,5)P2 levels in a single cell of the epithelium, we observe the disassembly of adherens junctions, actin cytoskeleton reorganization, and apical constriction leading to delamination, a process similar to that observed during epithelial-mesenchymal transition. We provide evidence that PI(4,5)P2 controls the apical targeting of PAR-3/Bazooka to the plasma membrane and that the loss of this polarized distribution is sufficient to induce a similar cell shape change. Finally, we show that PI(4,5)P2 is excluded from the cell apex and that PAR-3 diffuses laterally just prior to the apical constriction in a context of endogenous invagination.


CONCLUSIONS
All together, these results indicate that the PIP5 kinase SKTL, by controlling PI(4,5)P2 polarity, regulates PAR-3 localization and thus the size of the apical domain.
Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris, France. Electronic address: claret.sandra@ijm.univ-paris-diderot.fr.
Sandra
S
Claret
Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris, France.
Julie
J
Jouette
Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris, France.
Béatrice
B
Benoit
Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris, France.
Kevin
K
Legent
Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris, France. Electronic address: guichet.antoine@ijm.univ-paris-diderot.fr.
Antoine
A
Guichet
D000199:Actins / Q000378:metabolism; D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D003599:Cytoskeleton / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D004847:Epithelial Cells / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D009024:Morphogenesis; D010716:Phosphatidylinositols / Q000378:metabolism*
D000199:Actins; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010716:Phosphatidylinositols; C400774:baz protein, Drosophila