ABSTRACT
The actin cytoskeleton is essential for cell adhesion and migration, functions important for tumor invasion. In addition to binding N-WASP/WASP, WIP binds and stabilizes F-actin. WIP−/− fibroblasts were used to test the role of WIP in F-actin function. WIP−/− cells had defective focal adhesion (FA), stress fiber assembly, and adherence to substrates, functions that were restored by transduction of wild-type WIP. Protein and mRNA levels of several FA constituents regulated by the myocardin-related transcription factor (MRTF)–serum response factor (SRF) transcription factor complex were reduced in WIP−/− fibroblasts. The level of G-actin, which sequesters MRTF in the cytoplasm, was increased, and nuclear localization of MRTF-A and SRF was reduced, in WIP−/− fibroblasts. Transfection of an MRTF-A mutant that constitutively translocates to the nucleus or transfection of constitutively active SRF restored FA and stress fiber assembly. Fibroblasts from knock-in mice expressing a WIP mutant that fails to bind actin phenocopied WIP−/− fibroblasts. Thus, WIP is a novel regulator of FA assembly and cell adhesion.
FOOTNOTES
- Received 7 January 2014.
- Returned for modification 14 February 2014.
- Accepted 22 April 2014.
- Accepted manuscript posted online 5 May 2014.
Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00017-14.
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