TGFβ₁activates c-Jun and Erk1 via α_Vβ₆integrin

Abstract

Abstract Transforming growth factor β (TGFβ) plays an important role in animal development and many cellular processes. A variety of cellular functions that are required for tumor metastasis are controlled by integrins, a family of cell adhesion receptors. Overexpression of αVβ6 integrin is associated with lymph node metastasis of gastric carcinomas. It has been demonstrated that a full TGFβ1 signal requires both αVβ6 integrin and SMAD pathway. TGFβ1 binds to αVβ6 via the DLXXL motif, a freely accessible amino acid sequence in the mature form of TGFβ1. Binding of mature TGFβ1 to αVβ6 leads to immobilization and tyrosine phosphorylation of proteins, which are associated with focal adhesions, a hallmark of integrin-mediated signal transduction. Here, we show that binding of mature TGFβ1 recruits the mitogen-activated protein kinase kinase kinase 1 (MEKK1), a mediator of c-Jun activation, and the extracellular signaling-regulated kinase-1 (Erk1) to focal adhesions. In addition, the p21-activated kinase 1 (PAK1) is associated with focal adhesions and differentially phosphorylated upon TGFβ1 stimulation. We conclude that TGFβ1 activates c-Jun via the MEKK1/p38 MAP kinase pathway and influences cytoskeletal organization. These finding may provide a link between TGFβ1 and the metastatic behavior of cancers.

Keywords

• α_Vβ₆
• c-Jun
• MEKK1
• TGFβ₁
• Erk1
• focal adhesion
• cytoskeleton