Abstract 17485: Antioxidant-1 in Tissue Resident Cells Mediates Neointimal Formation via Cu Transporter ATP7A-IQGAP1-Rac1-dependent Vascular Migration
Migration of vascular smooth muscle cells (VSMCs) via PDGF and copper (Cu) contributes to vascular remodeling in response to vascular injury. We previously demonstrated that Cu chaperone protein antioxidant-1 (Atox1) knockout (KO) mice show impaired neointimal formation in wire-injured femoral arteries. However, underlying mechanisms as well as role of Atox1 in tissue resident cells and bone marrow (BM) cells in this response remain unknown. Here we show that transplantation of either wild type (WT)- or Atox1 KO-BM into irradiated Atox1 KO mice shows inhibition of neointimal formation (I/M ratio: 44%) and infiltration of α-SMA (+) VSMCs within neointima (62% inhibition) at day 21 after wire injury, vs. WT mice transplanted with Atox1 KO or WT BM. These results suggest that Atox1 in tissue resident cells including VSMCs, but not BM cells, is involved in increasing VSMC content within neointima in injured vessels. Mechanistically, in cultured VSMCs, Atox1 binds to Rac1-binding scaffold protein IQGAP1 in basal state. PDGF stimulation rapidly promotes recruitment of Cu transporter ATP7A which obtains Cu from Atox1 to the Atox1/IQGAP1/Rac1 complex within 5 min. Functionally, knockdown of endogenous Atox1 or IQGAP1 with siRNAs inhibits PDGF-induced association of ATP7A with Rac1 as well as their translocation to the leading edge in a Cu-dependent manner, thereby inhibiting VSMC migration. Moreover, co-transfection experiments in HEK293 cells reveal that IQGAP1 directly binds to ATP7A in addition to Rac1, suggesting that IQGAP1 functions as a scaffold to mediate association of Cu transporter Atox1/ATP7A complex with Rac1 to promote Cu-dependent VSMC migration. Functional significance of ATP7A and IQGAP1, which are downstream of Atox1, is demonstrated that neoinitimal formation after vascular injury is significantly inhibited in ATP7A mutant mice with reduced Cu transporter function as well as IQGAP1 KO mice. In summary, Atox1 in tissue resident cells plays a critical role in neointimal formation following vascular injury through promoting Cu-ATP7A-IQGAP1-Rac1-dependent PDGF-induced VSMC migration. Thus, Cu transport system Atox1-ATP7A pathway and its regulators are potential therapeutic targets for VSMC migration-related vascular diseases.
- © 2013 by American Heart Association, Inc.