cAMP-dependent Protein Kinase Phosphorylation of EVL, a Mena/VASP Relative, Regulates Its Interaction with Actin and SH3 Domains

Abstract

Proteins of the Ena/VASP family are implicated in processes that require dynamic actin remodeling such as axon guidance and platelet activation. In this work, we explored some of the pathways that likely regulate actin dynamics in part via EVL (Ena/VASP-like protein). Two isoforms, EVL and EVL-I, were highly expressed in hematopoietic cells of thymus and spleen. In CD3-activated T-cells, EVL was found in F-actin-rich patches and at the distal tips of the microspikes that formed on the activated side of the T-cells. Like the other family members, EVL localized to focal adhesions and the leading edge of lamellipodia when expressed in fibroblasts. EVL was a substrate for the cAMP-dependent protein kinase, and this phosphorylation regulated several of the interactions between EVL and its ligands. Unlike VASP, EVL nucleated actin polymerization under physiological conditions, whereas phosphorylation of both EVL and VASP decreased their nucleating activity. EVL bound directly to the Abl, Lyn, and nSrc SH3 domains; the FE65 WW domain; and profilin, likely via its proline-rich core. Binding of Abl and nSrc SH3 domains, but not profilin or other SH3 domains, was abolished by cAMP-dependent protein kinase phosphorylation of EVL. We show strong cooperative binding of two profilin dimers on the polyproline sequence of EVL. Additionally, profilin competed with the SH3 domains for binding to partially overlapping binding sites. These data suggest that the function of EVL could be modulated in a complex manner by its interactions with multiple ligands and through phosphorylation by cyclic nucleotide dependent kinases.To respond properly to environmental cues, cells possess multiple complex signal transduction networks. Many pathways lead to dynamic changes of the actin cytoskeleton that form the basis for cell movement in a wide variety of biological phenomena. In recent years, many proteins participating in one or more signal transduction pathways have been identified. One group of multifunctional proteins, involved in actin-based motility, is the Ena/VASP family of proteins that include Drosophila Ena (Enabled), Mena (mammalian Ena), VASP (vasodilator-stimulated phosphoprotein), and EVL (Ena/VASP-like protein) (1). Ena was identified through genetic interactions with the Drosophila Abl homologue (2, 3), whereas VASP was identified as a prominent target for cAMP (PKA) 1 -and cGMPdependent protein kinases in platelets (4). Mena and EVL were identified by similarity to Ena (1). Ena, Mena, and VASP are important in processes that require highly dynamic actin reorganization, including axon guidance (5), platelet aggregation (6, 7), and fibroblast motility (8). The proteins are concentrated in regions of the cell associated with movement and adhesion, including the leading edge of lamellipodia, focal adhesions, and adherens junctions (1, 9, 10).The Ena/VASP proteins share a common domain structure that consists of an amino-terminal Ena/VASP homology (EVH) 1 domain, a carboxyl-terminal EVH2 domain, and a central proline-rich domain...

Direct cAMP Signaling through G-Protein-Coupled Receptors Mediates Growth Cone Attraction Induced by Pituitary Adenylate Cyclase-Activating Polypeptide

“…Other candidate PKA targets likely to be regulated during axon guidance include members of the Enabled (Ena)/ Vasodilator-stimulated phosphoprotein (VASP) family, which have been implicated in the regulation of actin-based motility. In particular, the Ena/VASP-like protein binds its ligands in a manner that depends on PKA phosphorylation (Lambrechts et al, 2000). It remains to be determined whether any members of the Rho GTPases and Ena/VASP are the direct targets of protein kinase A during PACAP-induced attraction.…”

Involvement of vasodilator-stimulated phosphoprotein in UDP-induced microglial actin aggregation via PKC- and Rho-dependent pathways

“…The phosphorylation of VASP negatively regulates actin nucleation/G-actin binding and interaction with F-actin and some cell adhesion regulators [48][49][50]. On the other hand, VASP binding to focal adhesion protein and profilin, a regulator of actin polymerization, are independent of the VASP phosphorylation status [48,51].…”

Nitric oxide/cyclic guanosine monophosphate inducers sodium nitroprusside and L-arginine inhibit the proliferation of gastric cancer cells via the activation of type II cyclic guanosine monophosphate-dependent protein kinase

“…The effect of SNP and L-arginine on PKG II activity was confirmed by detecting the phosphorylation of VASP, the serine/threonine residues of which are substrates for the PKA and PKG (24). There are three phosphorylation sites of VASP, namely Ser157, Ser239 and Tyr278 (13,(25)(26)(27). Tao et al (13) reported that Ser239 was a key phosphorylation site of VASP for PKG II activation.…”