Alpha-2-macroglobulin is a modulator of prophenoloxidase system in pacific white shrimp Litopenaeus vannamai

• Published in: Fish & shellfish immunology 2017-03, Vol.62, p.68-74
• Main Authors: Ponprateep, Sirikwan, Vatanavicharn, Tipachai, Lo, Chu Fang, Tassanakajon, Anchalee, Rimphanitchayakit, Vichien
• Format: Article
• Language: English
• Subjects: Alpha-2-macroglobulin; alpha-Macroglobulins - genetics; alpha-Macroglobulins - metabolism; Animals; Arthropod Proteins - genetics; Arthropod Proteins - metabolism; Catechol Oxidase - genetics; Catechol Oxidase - metabolism; Enzyme Precursors - genetics; Enzyme Precursors - metabolism; Gene Expression; Gene Knockdown Techniques; Immunity, Innate; Litopenaeus vannamei; Penaeidae - genetics; Penaeidae - immunology; Penaeidae - microbiology; Prophenoloxidase system; Proteinase inhibitor; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Serine Proteases - genetics; Serine Proteases - metabolism; Vibrio parahaemolyticus - physiology; Vibrio parahaemolyticus AHPND
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2016.12.028

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. •The rLvA2M strongly and specifically inhibits trypsin.•The rLvA2M inhibits the PO activity in shrimp plasma in a dose-dependent manner.•Silencing of LvA2M leads to an increase in PO activity in shrimp plasma.•Upon bacterial infection, the LvA2M activity is decreased while the PO activity is increased.•The proPO-activating system is regulated by the LvA2M.