Zyxin Interacts with the SH3 Domains of the Cytoskeletal Proteins LIM-nebulette and Lasp-1

Abstract

Focal adhesions are essential cellular structures of metazoan organisms that link the extracellular matrix to the cytoskeleton. The controlled assembly and disassembly of focal adhesions is critical for a diversity of biological functions, including cell adhesion, motility, and spreading. Typically, focal adhesions are found at sites where a number of proteins from different signaling pathways converge to respond to extracellular signals (1). Thus far, more than 50 different focal adhesion proteins have been identified (2). Among them are several adapter proteins with protein-protein interaction motifs that play an important role in the dynamic assembly of focal adhesions.One of these adapter proteins is zyxin. Zyxin was originally identified in chicken fibroblasts as a protein associated with stress fibers and focal adhesions (3). The mammalian homologue of avian zyxin was subsequently cloned from a subtracted cDNA library enriched with clones that are down-regulated in transformed fibroblasts (4). At the same time, human zyxin was also cloned from umbilical vein endothelial cells by crosshybridization (5). Analysis of the protein sequence revealed the typical structure of a multidomain protein. At the C terminus, zyxin contains three LIM domains arranged in tandem. LIM domains are cysteine-rich motifs with two zinc finger-like structures that mediate specific protein-protein interactions. Three different binding partners for the LIM domains of zyxin have been identified, namely, the cysteine-rich protein CRP, the adapter protein p130cas, and the tumor suppressor protein H-warts/LATS1 (6 -8). At the N terminus, zyxin features an extended, proline-rich domain, which contains a nuclear export signal and several proline clusters. By virtue of these proline clusters, zyxin binds to proteins of the Ena/VASP family, which control the assembly and disassembly of actin filaments (9). The proline clusters also serve as docking sites for the oncoprotein Vav, a nucleotide exchange factor for the Rho family of GTPases (10). Moreover, the extended N-terminal domain is responsible for the interaction of zyxin with the actin-bundling protein ␣-actinin (11). We have recently demonstrated that a linear sequence motif found at the extreme N terminus of zyxin is essential for this interaction (12, 13). Our observation is supported by the fact that LPP (lipoma preferred partner), another member of the zyxin family containing the same linear motif, binds to ␣-actinin, too (14).Several pieces of evidence from different lines of investigation suggest that zyxin might play an important role in the organization of the actin cytoskeleton. Zyxin induces the polymerization of actin on the surface of mitochondria when artificially targeted to these ectopic sites (15,16). Actin polymerization and the resulting tension appear to be crucial for the dynamic assembly of focal adhesions (1). On the other hand, zyxin is one of the first molecules that dissociate from dissolving focal adhesions (17). This observation raises the intriguing possibil...

Overexpression of LASP-1 mediates migration and proliferation of human ovarian cancer cells and influences zyxin localisation

“…LASP-1 has previously been shown to localise to sites of cell adhesion and to interact with zyxin and actin (Chew et al, 2002;Li et al, 2004). To assess whether silencing of LASP-1 affects these binding partners, siRNA-treated SKOV-3 cells were stained with phalloidin green against actin or mouse anti-zyxin hybridoma supernatant.…”

“…Along with zyxin (Li et al, 2004) and actin (Schreiber et al, 1998), LASP-1 interacts with Krp1 (Spence et al, 2006), palladin (Rachlin and Otey 2006), lipoma-preferred partner (LPP) and VASP (Keicher et al, 2004), which all can influence actin filament dynamics and pseudopodial elongation. In the case of palladin, LPP and zyxin, the binding occurs between the C-terminal SH3 domain of LASP-1 and the N-terminal proline-rich domains of these proteins, whereas in the case of Krp1, binding is observed between the nebulin-like repeats of LASP-1 and the N-terminal BTB/POZ domain of Krp1.…”

“…The SH3 domain at the C-terminus is involved in proteinprotein interactions through binding to proline-rich sequences, specifically with zyxin, pallidin, lipoma preferred partner (LPP) and vasodilator-stimulated phosphoprotein (VASP) (Keicher et al, 2004;Li et al, 2004;Rachlin and Otey, 2006).…”

Nuclear localisation of LASP-1 correlates with poor long-term survival in female breast cancer

“…As LPP and Zyxin are known binding partners of LASP-1 (Keicher et al, 2004;Li et al, 2004) and are discussed as possible shuttle proteins to transfer LASP-1 into the nucleus we also controlled their distribution during cell cycle phases. Consistently, like LASP-1, both proteins showed a cell phase-dependent nuclear increase in G2/M ( Figure 5B) without changes in absolute protein concentration.…”

Nebulin: A Study of Protein Repeat Evolution

“…Although it is predominantly found in cardiac muscle, where it is probably involved in myofibril assembly, 14 Nebulette also has a ubiquitously expressed splice form with the same domain structure as LASP. 15,16 Recently, the first invertebrate Nebulin protein was discovered in the amphioxus cephalocordate Branchiostoma floridae. 17 The gene structure of this newly discovered invertebrate protein, whose relatives generally are found in skeletal muscle, is vastly different from the structures of vertebrate genes.…”