Interaction of Penaeus vannamei hemocyanin and α2-macroglobulin modulates the phenoloxidase activity

Prophenoloxidase (proPO)-activating system is a critical innate immune defense in invertebrates. However, the mechanisms involved in regulating the phenoloxidase (PO) activity in shrimp hemolymph remain ill-defined. Our previous studies showed that Penaeus vannamei hemocyanin (HMC) and alpha 2-macroglobulin (alpha 2M), two key regulators of proPO-activating system in plasma, might interact with each other, indicating that this interaction could be implicated in controlling PO activity. Herein, we further confirmed that HMC specifically bind to alpha 2M using Pull down and Far-Western blot analyses. Further studies demonstrated that HMC could directly interact with the receptor binding domain of alpha 2M. In addition, HMC and alpha 2M followed similar expression pattern upon Vibrio parahaemolyticus infection, suggesting the interaction of HMC and alpha 2M might have a role in immune response. Finally, we found that alpha 2M, as a broad-spectrum proteinase inhibitor, suppressed the serum PO activity in vitro, while hemocyanin could partially restore this inhibitory effect. In sum, the present data indicate that HMC interacts with alpha 2M and therefore modulates the PO activity. This finding contributes to better understanding of stable state maintenance of PO activity in shrimp.

Automated summary

This study identified the interaction between hemocyanin and alpha 2-macroglobulin in regulating phenoloxidase activity in shrimp, suggesting a role in immune responses. Hemocyanin can partially restore alpha 2-macroglobulin's inhibitory effect on phenoloxidase activity, contributing to a better understanding of the maintenance of stable immune responses in shrimp.