Involvement of signaling pathways in the phosphorylation of ZEB1 in epithelial cells

Carlos Paz

Congreso; XLIV Reunión Anual SAIB; 2008

SAIB

The activity of a transcription factor (TF) can be controlled by phosphorylation. ZEB1 (Zinc Finger E‐box Binding Homeobox) is a TF involved in differentiation of mesoderm derived cells and cancer metastasis. ZEB1 exists in two phosphorylated forms (PZEB1). Our goal is to uncover which signaling pathway/s can modify ZEB1 status of phosphorylation and in consequence its function. We showed that the hypophosphorylated ZEB1 binds to target genes stronger than the hyperphosphorylated one. Cell lines expressing one or both P‐ZEB1 were treated with TPA/ionomycin (PKC activators), and the inhibitors CalphostinC (PKC?s), LY294002 (PI3K?s), PD98059 (ERK?s) and SB203580 (p38MAPK?s). EMSAs made with target gene promoters of ZEB1 as probes showed an increased binding capacity to the nuclear extracts (NE) treated with CalC, PD98059, a lower binding with TPA/IO and LY294002 and no change with SB203580. Accordingly, TPA/IO and LY reverted ZEB1 repression of Ecadherin gene in transfection assays. Western blots in NE showed increased ZEB1 expression with TPA/IO which was not due to change in location of ZEB1 as seen by immunofluorescence microscopy and WB but to transcriptional level (cycloheximide reverted effect). Multiple pathways seem to be involved in ZEB1 phosphorylation. They cross‐talk in different models of cell differentiation. In our case PI3K and PKC wouldn?t be part of the same pathway.