Albumin-Like Proteins Are Critical Regulators of Vascular Redox Signaling

This laboratory previously identified an albumin-like protein (denoted as p70) as a component of the macromolecular complex assembled within the 5′-regulatory region of redox-sensitive genes in vascular smooth muscle cells (vSMCs). Here we show that p70 is present in the cytosolic and nuclear compartments of vSMCs and dynamically responsive to redox status. Intense cytoplasmic and perinuclear staining, coupled with enhanced nuclear localization, was observed in vSMCs, but not HepG2 cells, treated with benzo(a)pyrene (BaP), H(2)O(2), or N-acetylcysteine, agents known to modulate redox status. 3′ RACE indicated that p70 is not generated as a product of endogenous gene expression, but rather taken up from the extracellular compartment. While p70 was undetectable in cells grown for 24 hours under serum-free conditions, cell-associated, acid-resistant albumin was detected 30 min after the addition of exogenous albumin. vSMCs incubated at 4°C with 100 μg/mL unlabeled BSA and 10 μg/mL FITC-BSA for 60 minutes and switched to 37°C to examine temperature-sensitive label uptake showed punctate structures throughout the cell consistent with albumin internalization at the higher temperature. Albumin was found to influence redox-signaling, as evidenced by modulation of cyp1a1 gsta1 and Ha-ras gene inducibility. Together, these results implicate albumin and albumin-like proteins as critical regulators of vascular redox signaling.