Negative regulation of the EGFR-MAPK cascade by actin-MAL-mediated Mig6/Errfi-1 induction.

We analyzed the G-actin-regulated transcriptome by gene expression analysis using previously characterized actin-binding drugs. We found many known MAL/MRTF-dependent target genes of serum response factor (SRF), as well as additional directly regulated genes. Surprisingly, several putative antiproliferative target genes were identified, including mig6/errfi-1, a negative regulator of the EGFR family. Mig6 induction occurred through actin-MAL-SRF signaling, and MAL was inducibly recruited to and activated a mig6 promoter element. Upregulation of Mig6 by lipid agonists such as LPA and S1P or actin drugs involved MAL and correlated with decreased activation of EGFR, MAPK/Erk, and c-fos. Mig6 depletion restored EGFR signaling and provided a proliferative advantage. Overexpression of MAL exhibited strong antiproliferative effects requiring the domains for SRF binding and transactivation, which supports antagonistic functions of MAL on growth-promoting signals. Our results show the existence of negatively acting transcriptional networks between pro- and antiproliferative signaling pathways toward SRF.