Alpha-2-macroglobulin is a modulator of prophenoloxidase system in pacific white shrimp Litopenaeus vannamai
Sirikwan Ponprateep1, Tipachai Vatanavicharn2, Chu Fang Lo3
1Department of Chemistry, Faculty of Science, Srinakharinwirot University, 114 Sukhumvit 23 Road, Bangkok 10110, Thailand.
Abstract:
The shrimp multifunctional protein alpha-2-macroglobulin (A2M) is abundantly expressed in plasma, highly up-regulated upon microbial infection and involved in several immune pathways such as blood clotting system, phagocytosis and melanization. Herein, the function of LvA2M from Litopenaeus vannamei on the prophenoloxidase (proPO) system is reported. The recombinant (r)LvA2M produced strongly and specifically inhibited trypsin and the PO activity in shrimp plasma in a dose-dependent manner. Silencing of LvA2M led to an increase in the PO activity in shrimp plasma although the expression of proPO-associated genes, proPO-activating enzyme (PPAE) and prophenoloxidase (proPO) but not the proPO-activating factor (PPAF) was down-regulated. In Vibrio parahaemolyticus AHPND-infected shrimp, the LvA2M activity was suppressed in an early phase of infection while the PO activity was increased. Thus, the proPO-activating system was regulated by the LvA2M.
Insights
Shrimp alpha-2-macroglobulin (A2M) regulates the prophenoloxidase (proPO) system. LvA2M inhibits trypsin and PO activity, impacting shrimp immunity during infection.
Area of Science:
- Marine Biology
- Immunology
- Biochemistry
Background:
- Alpha-2-macroglobulin (A2M) is a key immune protein in shrimp (Litopenaeus vannamei), involved in pathways like clotting and melanization.
- A2M is upregulated during microbial infections, suggesting a critical role in shrimp innate immunity.
Purpose of the Study:
- To investigate the function of Litopenaeus vannamei alpha-2-macroglobulin (LvA2M) in regulating the prophenoloxidase (proPO) system.
- To determine the inhibitory effects of LvA2M on trypsin and phenoloxidase (PO) activity.
Main Methods:
- Produced recombinant LvA2M (rLvA2M) and tested its inhibitory effects on trypsin and shrimp plasma PO activity.
- Utilized gene silencing techniques to assess the impact of LvA2M on proPO-associated gene expression and PO activity.
- Analyzed LvA2M and PO activity in shrimp infected with Vibrio parahaemolyticus causing AHPND.
Main Results:
- Recombinant LvA2M demonstrated potent and specific inhibition of trypsin and PO activity in a dose-dependent manner.
- Silencing LvA2M resulted in increased PO activity, despite downregulation of proPO-activating enzyme (PPAE) and prophenoloxidase (proPO) gene expression.
- During early AHPND infection, LvA2M activity was suppressed, coinciding with elevated PO activity, indicating LvA2M's regulatory role.
Conclusions:
- LvA2M plays a significant role in regulating the shrimp proPO-activating system.
- The interaction between LvA2M and the proPO system is crucial for shrimp immune response against microbial infections.
