Extracellular signal-regulated kinase activated by epidermal growth factor and cell adhesion interacts with and phosphorylates vinexin

Abstract

Extracellular signal-regulated kinase 1/2 (ERK1/2) is activated by various extracellular stimuli including growth factors and cytokines and plays a pivotal role in regulating cell proliferation and differentiation by phosphorylating nuclear transcription factors. Recently, it was reported that activated ERK1/2 also concentrates at adhesion sites and regulates cell spreading and migration. Vinexin is a focal adhesion protein regulating both cell spreading and growth factor signaling. We show here that vinexin was directly phosphorylated by ERK1/2 upon stimulation with growth factors. ERK1/2 phosphorylated the linker region of vinexin between the second and third SH3 domains. Site-directed mutagenesis revealed that ERK2 mainly phosphorylated the serine 189 residue of vinexin β. Furthermore, vinexin β interacted with ERK1/2 both in vitro and in vivo. Vinexin interacted with the active but not inactive form of ERK1/2. A putative DEF (docking for ERK FXFP) domain located in the linker region of vinexin was required for the interaction with ERK1/2 and efficient phosphorylation of vinexin β by ERK2. Finally, we showed that cell adhesion to fibronectin also induced the association of vinexin β with ERK2 and the phosphorylation of vinexin β. Furthermore, vinexin and ERK were co-localized to the periphery of cells during cell spreading on fibronectin. Together, these results suggest that vinexin is a novel substrate of ERK2 and may play roles in ERK-dependent cell regulation during cell spreading as well as in growth factor-induced responses.