Peptidylarginine deiminase modulates the physiological roles of enolase via citrullination

Abstract

The citrullination of enolase by PAD (peptidylarginine deiminase) has emerged as an important post‐translational modification in human disorders; however, the physiological function of citrullination remains unknown. Here, we report that citrullination diversely regulates the biological functions of ENO1 (α‐enolase) and NSE (neuron‐specific enolase). We developed three mouse IgG1 monoclonal antibodies with specificity to the following: anti‐CE1 (citrullinated enolase 1), anti‐CE1/2, and anti‐CE2. The levels of citrullinated ENO1 and NSE were elevated, and their immunoreactivities were also increased in cortical neuronal cells or around blood vessels in patients with sporadic Creutzfeldt‐Jakob disease and Alzheimer's disease compared with controls. In a time‐ and dose‐dependent manner, PAD negatively regulated enolase activity via citrullination, and enolase in diseased patients was more inactive than in controls. Interestingly, the citrullination of enolase effectively promoted its proteolytic degradation by calpain‐1. Surprisingly, the citrullination of enolase enhanced its plasminogen‐binding affinity, which was blocked by the lysine analogue ε‐aminocaproic acid. These findings suggest that PAD‐mediated citrullination regulates the diverse physiological activities of enolase and that CE may be a candidate diagnostic/prognostic factor for degenerative diseases. [This work was supported by the National Research Foundation of Korea Grant funded by the Korean Government (NRF‐2011–619‐E0001)]