WNT3a stimulates proliferation of NIH3T3 cells via activation of the extracellular signal-regulated kinase (ERK) pathway. The RAF-1→MEK→ERK cascade was immediately increased by WNT3a treatment, however, the upstream event triggering ERK pathway activation by WNT3a is not clear. WNT3a activated RAS and WNT3a-induced ERK activation was blocked by dominant-negative RAS, indicating that WNT3a might act upstream of RAS. WNT3a-induced ERK pathway activations were blocked by AG1478, the epidermal growth factor receptor (EGFR) inhibitor, and EGFR siRNA. The WNT3a-induced ERK pathway activation was not observed in fibroblasts retaining defective EGFR, but the WNT3a effect was restored by EGFR reconstitution. These results indicate involvement of EGFR in the WNT3a-induced ERK pathway activation. WNT3a-induced motility and cytoskeletal rearrangement as well as proliferation of NIH3T3 cells were blocked by AG1478 and EGFR siRNA or abolished in EGFR knock-out fibroblasts, indicating involvement of EGFR in those cellular processes. WNT3a-induced ERK pathway activation was not affected by Dickkoff-1 (DKK-1), although WNT3a-induced activations of the WNT/β-catenin pathway and proliferation were reduced by DKK-1. EGFR is involved in WNT3a-induced proliferation via both routes dependent on and independent of the WNT/β-catenin pathway. These results indicate that WNT3a stimulates proliferation and motility of NIH3T3 fibroblasts via EGFR-mediated ERK pathway activation.
Bibliographical noteFunding Information:
The authors thank Drs. Tony Burgers and Francesca Walker for providing Wa-2, Wa-2-FR, and EGFR−/− cell lines. This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MOST) (No. 2005–01564; 2006–02681; R112000078010020). S.E. Kim was supported by a BK21 studentship from the ministry of education and human resources development.
All Science Journal Classification (ASJC) codes
- Cell Biology