Regulation of Hippo pathway by mitogenic growth factors via phosphoinositide 3-kinase and phosphoinositide-dependent kinase-1.
The Hippo signaling pathway inhibits cell growth and regulates organ size through a kinase cascade that leads to the phosphorylation and nuclear exclusion of the growth-promoting transcriptional coactivator Yes-associated protein (YAP)/Yorkie. It mediates contact inhibition of cell growth downstream of cadherin adhesion molecules and other cell surface proteins. Contact inhibition is often antagonized by mitogenic growth factor signaling. We report an important mechanism for this antagonism, inhibition of Hippo pathway signaling by mitogenic growth factors. EGF treatment of immortalized mammary cells triggers the rapid translocation of YAP into the nucleus along with YAP dephosphorylation, both of which depend on Lats, the terminal kinase in the Hippo pathway. A small-molecule inhibitor screen of downstream effector pathways shows that EGF receptor inhibits the Hippo pathway through activation of PI3-kinase (PI3K) and phosphoinositide-dependent kinase (PDK1), but independent of AKT activity. The PI3K-PDK1 pathway also mediates YAP nuclear translocation downstream of lysophosphatidic acid and serum as a result of constitutive oncogenic activation of PI3K. PDK1 associates with the core Hippo pathway-kinase complex through the scaffold protein Salvador. The entire Hippo core complex dissociates in response to EGF signaling in a PI3K-PDK1-dependent manner, leading to inactivation of Lats, dephosphorylation of YAP, and YAP nuclear accumulation and transcriptional activation of its target gene, CTGF. These findings show that an important activity of mitogenic signaling pathways is to inactivate the growth-inhibitory Hippo pathway and provide a mechanism for antagonism between contact inhibition and growth factor action.
University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
Run
R
Fan
Nam-Gyun
NG
Kim
Barry M
BM
Gumbiner
D064413:3-Phosphoinositide-Dependent Protein Kinases; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000730:Androstadienes; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D003260:Contact Inhibition / Q000235:genetics / Q000502:physiology*; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D046912:Multiprotein Complexes / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors; D000077191:Wortmannin; D000091102:YAP-Signaling Proteins
D064413:3-Phosphoinositide-Dependent Protein Kinases; D048868:Adaptor Proteins, Signal Transducing; D000730:Androstadienes; D015820:Cadherins; D018797:Cell Cycle Proteins; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D020930:MAP Kinase Kinase Kinases; D046912:Multiprotein Complexes; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D014157:Transcription Factors; D000077191:Wortmannin; D000091102:YAP-Signaling Proteins; C415864:SAV1 protein, human; C088374:YAP1 protein, human; C092745:LATS1 protein, human; C578562:PDPK1 protein, human; C093290:MAP3K10 protein, human