Abstract 13647: Copper Transport Protein Antioxidant-1 Plays an Important Role in Neointmal Formation in Response to Vascular Injury by Regulating Vascular Smooth Muscle Cell Migration
Platelet-derived growth factor (PDGF) stimulates vascular smooth muscle cell (VSMC) migration and activates secretory copper (Cu) enzyme lysyl oxidase (LOX), thereby promoting vascular remodeling. Cu chelation inhibits neointimal formation in response to injury. We demonstrated that Cu chaperone antioxidant-1 (Atox1) is involved in Cu-induced cell growth and that Cu transporter ATP7A which obtains Cu from Atox1 is involved in VSMC migration. We thus examined the role of Atox1 in neointimal formation in vivo and VSMC migration. Here we show that Atox1 expression is markedly upregulated at neointimal VSMC after wire-induced femoral artery injury in WT mice. Atox1 KO mice show significant inhibition of neointimal formation (I/M ratio: 53%) and fibrosis (34%) at day 21. In cultured VSMCs, Atox1 depletion with siRNA inhibits VSMC migration induced by PDGF (77%) or wound scratch (63%). PDGF rapidly promotes Atox1 binding to ATP7A within 5 min via Cu dependent manner, which recruits Rac1 and its binding partner, scaffold protein IQGAP1 to the Atox1/ATP7A complex. Functional significance of this multiple Atox1-bound ATP7A/IQGAP1/Rac1 complex is demonstrated that Atox1 siRNA inhibits PDGF-induced ATP7A and Rac1 translocation to the leading edge without affecting IQGAP1, thereby inhibiting lamellipodia formation. We next examined a role of IQGAP1 in Atox1-mediated VSMC migration. IQGAP1 siRNA inhibits formation of the Atox1-ATP7A-Rac1 complex, thereby inhibiting ATP7A translocation to the leading edge and VSMC migration. Further, overexpression of IQGAP1 promotes ATP7A translocation to the leading edge and VSMC migration. In IQGAP1/Rac1-independent manner, Atox1 KO cells show reduced PDGF-induced LOX specific activity (53%), which is regulated by Cu loading to its catalytic site via ATP7A. These suggest that Cu-dependent Atox1/ATP7A complex couples to two parallel pathways including IQGAP1/Rac1-dependent lamellipodia formation and IQGAP1-independent LOX activity, thereby promoting PDGF-induced VSMC migration. In summary, Atox1 plays an important role in IQGAP1-dependent lamellipodia formation and IQGAP1-independent LOX activation via ATP7A, thereby promoting VSMC migration and fibrosis, which may contribute to vascular remodeling.
- © 2011 by American Heart Association, Inc.