Phosphatidylinositol 3'-kinase signalling supports cell height in established epithelial monolayers.
Cell-cell interactions influence epithelial morphogenesis through an interplay between cell adhesion, trafficking and the cytoskeleton. These cellular processes are coordinated, often by cell signals found at cell-cell contacts. One such contact-based signal is the phosphatidylinositol 3'-kinase (PI3-kinase; PI3K) pathway. PI3-kinase is best understood for its role in mitogenic signalling, where it regulates cell survival, proliferation and differentiation. Its precise morphogenetic impacts in epithelia are, in contrast, less well-understood. Using phosphoinositide-specific biosensors we confirmed that E-cadherin-based cell-cell contacts are enriched in PIP(3), the principal product of PI3-kinase. We then used pharmacologic inhibitors to assess the morphogenetic impact of PI3-kinase in MDCK and MCF7 monolayers. We found that inhibiting PI3-kinase caused a reduction in epithelial cell height that was reversible upon removal of the drugs. This was not attributable to changes in E-cadherin expression or homophilic adhesion. Nor were there detectable changes in cell polarity. While Myosin II has been implicated in regulating keratinocyte height, we found no effect of PI3-kinase inhibition on apparent Myosin II activity; nor did direct inhibition of Myosin II alter epithelial height. Instead, in pursuing signalling pathways downstream of PI3-kinase we found that blocking Rac signalling, but not mTOR, reduced epithelial cell height, as did PI3-kinase inhibition. Overall, our findings suggest that PI3-kinase exerts a major morphogenetic impact in simple cultured epithelia through preservation of cell height. This is independent of potential effects on adhesion or polarity, but may occur through PI3-kinase-stimulated Rac signaling.
Division of Molecular Cell Biology, Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD 4072, Australia.
Angela
A
Jeanes
Michael
M
Smutny
Joanne M
JM
Leerberg
Alpha S
AS
Yap
D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002450:Cell Communication / Q000187:drug effects; D002460:Cell Line; D016764:Cell Polarity / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D024462:Myosin Type II / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D015820:Cadherins; D047908:Intracellular Signaling Peptides and Proteins; D024462:Myosin Type II; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; D020830:rac1 GTP-Binding Protein; C060974:phosphatidylinositol 3,4,5-triphosphate; C546842:MTOR protein, human