SKAP2, a novel target of HSF4b, associates with NCK2/F-actin at membrane ruffles and regulates actin reorganization in lens cell

J Cell Mol Med. 2011 Apr;15(4):783-95. doi: 10.1111/j.1582-4934.2010.01048.x.


In addition to roles in stress response, heat shock factors (HSFs) play crucial roles in differentiation and development. Heat shock transcription factor 4 (HSF4) deficiency leads to defect in lens epithelial cell (LEC) differentiation and cataract formation. However, the mechanism remains obscure. Here, we identified Src kinase-associated phosphoprotein 2 (SKAP2) as a downstream target of HSF4b and it was highly expressed at the anterior tip of lens elongating fibre cells in vivo. The HSF4-deficient lenses showed reduced SKAP2 expression and defects in actin reorganization. The disassembly of stress fibres and formation of cortical actin fibres are critical for the initiation of LEC differentiation. SKAP2 localized at actin-rich ruffles in human LECs (SRA01/04 cells) and knockdown SKAP2 using RNA interference impaired the disassembly of cellular stress fibres in response to fibroblast growth factor (FGF)-b. Overexpression of SKAP2, but not the N-terminal deletion mutant of SKAP2, induced the actin remodelling. We further found that SKAP2 interacted with the SH2 domain of non-catalytic region of tyrosine kinase adaptor protein 2 (NCK2) via its N-terminus. The complex of SKAP2-NCK2-F-actin accumulated at the leading edge of the lamellipodium, where FGF receptors and focal adhesion were also recruited. These results revealed an essential role for HSF4-mediated SKAP2 expression in the regulation of actin reorganization during lens differentiation, likely through a mechanism that SKAP2 anchors the complex of NCK2/focal adhesion to FGF receptors at the lamellipodium in lens epithelial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Sequence
  • Animals
  • Cell Differentiation
  • Cell Line
  • Cell Surface Extensions / metabolism*
  • DNA-Binding Proteins / metabolism*
  • Down-Regulation / genetics
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism
  • Focal Adhesion Protein-Tyrosine Kinases / metabolism
  • Heat Shock Transcription Factors
  • Humans
  • Intracellular Signaling Peptides and Proteins / chemistry
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Lens, Crystalline / cytology*
  • Lens, Crystalline / metabolism*
  • Mice
  • Models, Biological
  • Molecular Sequence Data
  • Oncogene Proteins / metabolism*
  • Protein Binding
  • Pseudopodia / enzymology
  • Receptors, Fibroblast Growth Factor / metabolism
  • Stress Fibers / metabolism
  • Transcription Factors / metabolism*


  • Actins
  • Adaptor Proteins, Signal Transducing
  • DNA-Binding Proteins
  • Heat Shock Transcription Factors
  • Hsf4 protein, mouse
  • Intracellular Signaling Peptides and Proteins
  • Nck2 protein, mouse
  • Oncogene Proteins
  • Receptors, Fibroblast Growth Factor
  • Transcription Factors
  • src kinase associated phosphoprotein 2
  • Focal Adhesion Protein-Tyrosine Kinases