Binding of the WASP/N-WASP-Interacting Protein WIP to Actin Regulates Focal Adhesion Assembly and Adhesion

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.

UNC-45A Is a Nonmuscle Myosin IIA Chaperone Required for NK Cell Cytotoxicity via Control of Lytic Granule Secretion

“…Mutations in WAS (encoding WASp) on the other side are associated with reduced perforin granule polarization at the NKIS due to inefficient F-actin branching (5, 30–33). Furthermore, loss of WASp-interacting protein functions causes defects in NK cell–mediated killing via increased proteasome-mediated WASp degradation and its mislocalization (32, 34–37). Lastly, inefficient tethering of lytic granules to the plasma membrane in NK cells carrying mutations in the UNC13D gene is associated with a complete loss of NK cell–mediated cytotoxicity (11, 38–41).…”

WIP-1 and DBN-1 promote scission of endocytic vesicles by bridging actin and Dynamin-1 in theC. elegansintestine

“…WASP-interacting protein (WIP, also known as WIPF1) is a WASP-binding partner (de la Fuente et al, 2007) that regulates WASP/N-WASP activity (Martinez-Quiles et al, 2001). Cumulative evidence has indicated that WIP may facilitate efficient actin polymerization independently of WASP via direct binding to actin (Martinez-Quiles et al, 2001;Anton et al, 2003;Ramesh et al, 2014) or via interaction with multiple actin regulators, such as Nck, profilin, cortactin and Abp1 (also known as Dbnl; DBN-1 in Caenorhabditis elegans) (Fried et al, 2014;Cortesio et al, 2010). A WASP-independent regulation of actin by WIP is involved in several cellular processes, including fibroblast focal adhesion assembly, T cell chemotaxis and migration, and membrane protrusion (Ramesh et al, 2014;Massaad et al, 2014).…”

NKG2D–DAP10 signaling recruits EVL to the cytotoxic synapse to generate F-actin and promote NK cell cytotoxicity

“…CRKL has been previously shown to be active in adhesion of NK cells to target cells (Nolz et al, 2008;Segovis et al, 2009), as well as in the localization of WASP to the T cell immunological synapse (Sasahara et al, 2002), though its impact on WASP localization in NK cells has not been investigated. In this context, it is interesting to note that both EVL (Lambrechts et al, 2000) and WASP-interacting protein (WIP, also known as WIPF1) (Sasahara et al, 2002) have been shown to bind to the SH3 domains of CRKL, without any requirement for the WIP domains that bind WASP (Ramesh et al, 1997;Ramesh et al, 2014;Volkman et al, 2002;Fried et al, 2014). This leaves interesting possibilities as to the interactions between EVL-and CRKL-mediated WASP localization pathways, and the possible conservation of CRKL-mediated WASP localization in NK cells.…”