MAP-kinase activity necessary for TGFβ1-stimulated mesangial cell type I collagen expression requires adhesion-dependent phosphorylation of FAK tyrosine 397

Tomoko Hayashida*, Ming Hua Wu, Amy Pierce, Anne Christine Poncelet, John Varga, H. William Schnaper

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

59 Scopus citations

Abstract

The signals mediating transforming growth factor β (TGFβ)-stimulated kidney fibrogenesis are poorly understood. We previously reported TGFβ-stimulated, Smad-mediated collagen production by human kidney mesangial cells, and that ERK MAP kinase activity optimizes collagen expression and enhances phosphorylation of the Smad3 linker region. Furthermore, we showed that disrupting cytoskeletal integrity decreases type I collagen production. Focal adhesion kinase (FAK, PTK2) activity could integrate these findings. Adhesion-dependent FAK Y397 phosphorylation was detected basally, whereas FAK Y925 phosphorylation was TGFβ1-dependent. By immunocytochemistry, TGFβ1 stimulated the merging of phosphorylated FAK with the ends of thickening stress fibers. Cells cultured on poly-L-lysine (pLL) to promote integrin-independent attachment spread less than those on control substrate and failed to demonstrate focal adhesion (FA) engagement with F-actin. FAK Y397 phosphorylation and ERK activity were also decreased under these conditions. In cells with decreased FAK Y397 phosphorylation from either plating on pLL or overexpressing a FAK Y397F point mutant, serine phosphorylation of the Smad linker region, but not of the C-terminus, was reduced. Y397F and Y925F FAK point mutants inhibited TGFβ-induced Elk-Gal activity, but only the Y397F mutant inhibited TGFβ-stimulated collagen-promoter activity. The inhibition by the Y397F mutant or by culture on pLL was prevented by co-transfection of constitutively active ERK MAP kinase kinase (MEK), suggesting that FAK Y397 phosphorylation promotes collagen expression via ERK MAP kinase activity. Finally, Y397 FAK phosphorylation, and both C-terminal and linker-region Smad3 phosphorylation were detected in murine TGFβ-dependent kidney fibrosis. Together, these data demonstrate adhesion-dependent FAK phosphorylation promoting TGFβ-induced responses to regulate collagen production.

Original languageEnglish (US)
Pages (from-to)4230-4240
Number of pages11
JournalJournal of cell science
Volume120
Issue number23
DOIs
StatePublished - Dec 1 2007

Keywords

  • Collagen
  • FAK
  • Sclerosis
  • Smad
  • TGFβ

ASJC Scopus subject areas

  • Cell Biology

Fingerprint Dive into the research topics of 'MAP-kinase activity necessary for TGFβ1-stimulated mesangial cell type I collagen expression requires adhesion-dependent phosphorylation of FAK tyrosine 397'. Together they form a unique fingerprint.

Cite this