Abstract 466: Redox Regulation of 14-3-3zeta Controls Monocyte Migration
Cofilin regulates actin turnover and is inactivated by phosphorylation at Ser-3 by LIM kinase (LIMK) and reactivated by the cofilin-phosphatase Slingshot-1L (SSH1L). We recently reported that protein-S-glutathionylation induced by metabolic disorders enhances monocyte recruitment into vascular lesions. Because monocyte priming and accelerated migration involves increases actin turnover, we tested the hypothesis that these regulators of actin assembly/disassembly are redox-regulated. Metabolic priming was induced in human THP-1 monocytes by exposing the cells to diabetic conditions, i.e. human native LDL plus high glucose concentrations (LDL+HG). Phosphorylation of cofilin in response to MCP-1 was completely blocked in metabolically primed monocytes, suggesting that hyperactivation of cofilin may contribute to the enhanced chemotactic activity of primed monocytes. Yet, neither LIMK1 nor SSH1L levels were affected by metabolic stress. However, metabolic priming resulted in a 3.8-fold increase the S-glutathionylation of 14-3-3zeta, a SSH1L binding protein which maintains the cofilin phosphatase in an inactive state. S-glutathionylation of 14-3-3zeta resulted in its caspase-dependent degradation and a 35% reduction in 14-3-3zeta protein levels. Overexpression of glutaredoxin 1 in monocytes inhibited both LDL+HG-induced S-glutathionylation and degradation of 14-3-3zeta, and normalized cofilin phosphorylation in response to MCP-1. The C25S mutant of 14-3-3zeta was resistant to S-glutathionylation and degradation induced by LDL+HG, and restored MCP-1-induced cofilin phosphorylation in metabolically primed monocytes. 14-3-3zeta S-glutathionylation did not affect binding of 14-3-3zeta to SSH1L, suggesting that loss of 14-3-3zeta increases the pool of free SSH1L phosphatase, thus preventing the phosphorylation and deactivation of cofilin in response to chemokine activation. In conclusion, we identified a novel redox-sensitive mechanism for the regulation of monocyte migration that links (thiol) oxidative stress induced by metabolic disorders to monocyte dysfunction and the conversion of blood monocytes into a hypermigratory, proinflammatory and proatherogenic phenotype.
- © 2013 by American Heart Association, Inc.