Identifying the function of LvPI3K during the pathogenic infection of Litopenaeus vannamei by Vibrio alginolyticus

Abstract

It is well known that PI3K regulates various processes in mammalian cells by generating a secondary messenger that later activates AKT. However, its innate immune function in crustaceans remains unclear. We report the characterization of Litopenaeus vannamei PI3K (LvPI3K) for investigating how PI3K participates in the innate immunity of crustaceans. Full-length LvPI3K cDNA was 3357 bp long, with a 3222 bp open reading frame (ORF) that encodes a putative protein of 1292 amino acids. The PI3K catalytic domain (PI3Kc) of LvPI3K was found to be rather conserved when the PI3Ks from other species were analyzed. The LvPI3K protein was shown to be localized to the cytoplasm of Drosophila S2 cells, while LvPI3K mRNA was ubiquitously expressed in healthy L. vannamei, with the highest expression found in hemolymph. A dual luciferase reporter gene assay demonstrated that LvPI3K overexpression activated the promoter of antibacterial peptide LvPEN4 in a dose-dependent manner. However, the addition of PDTC, a specific inhibitor of NF-κB, suppressed the LvPI3K-induced LvPEN4 promoter activation. Moreover, Vibrio alginolyticus challenge induced a rapid up-regulation of LvPI3K expression. Further experiments showed that LvPI3K silencing in shrimp challenged with V. alginolyticus significantly increased Vibrio number, ROS production and DNA damage in the hemolymph, as well as significantly decreased total hemocyte count. The mRNA levels of certain molecules related to LvPI3K signaling, such as LvAKT and LvPEN4, also decreased following LvPI3K silencing. Taken together, these results suggest that LvPI3K regulates the downstream signal component LvPEN4 and functions in V. alginolyticus resistance.

Andrographolide promote the growth and immunity of Litopenaeus vannamei, and protects shrimps against Vibrio alginolyticus by regulating inflammation and apoptosis via a ROS-JNK dependent pathway

“…In line with the previous findings, dietary Andr enhanced the THC and phagocytosis of shrimps hemocytes. Like hemocytes, hepatopancreas are also important immune organs in crustaceans, which play a very important role in the immune response against pathogen invasion (22). Results obtained in the present study showed that dietary Andr significantly upregulated the expression of immune-related genes, antimicrobial peptide genes, antioxidant genes and enzyme activity in both hemocytes and hepatopancreas.…”

“…V. alginolyticus is one of the major pathogens causing mass mortality of shrimps worldwide, affecting energy metabolism, immune response and development of shrimps (52)(53)(54). Our previous studies have shown that the infection of V. alginolyticus can affect the survival, growth and metabolism of shrimp, induce the production of ROS, apoptosis and autophagy, reduce immune function, and cause DNA damage (22,(55)(56)(57). Therefore, it is necessary to find a drug that can protect shrimp from V. alginolyticus.…”

“…If homeostasis is disrupted, uncontrolled ROS production will result in oxidative stress, excessive inflammatory responses, tissue damage, apoptosis (20) and necrosis, thus detrimental to host defense (21). Our previous study found that the ROS production and DNA damage accumulation in hemocytes increased after V. alginolyticus infected L. vannamei for 6 h, leading to a decrease in THC (22). In addition, studies have found that ROS formation was accelerated during V. alginolyticus WT infection, promoting hemocyte apoptosis in the oyster and fish (14,23).…”

Identification of Single Nucleotide Polymorphisms Related to the Resistance Against Acute Hepatopancreatic Necrosis Disease in the Pacific White Shrimp Litopenaeus vannamei by Target Sequencing Approach

“…Several key molecules in this pathway have been reported to be associated with the invasion of some viruses in shrimp (Su et al, 2014; Zhang et al, 2016). Previous studies have reported that V. alginolyticus challenge induced an up-regulation of LvPI3K expression (Kong et al, 2018), which illustrated that LvPI3K might play an important role in Vibrio infection.…”

Molecular Characterization and Expression Analysis of a Novel Glutaredoxin 3 Gene in Pacific White Shrimp (Litopenaeus vannamei)

“…First, the synthetic dsRNA was dissolved in a protective buffer (10 mM Tris-HCl and 400 mM NaCl, pH 7.5) to make a final concentration of 2.5 µg µl −1 . Then, the shrimps were split into two groups and injected with LvGrx 3 (2.5 µg g −1 shrimp) or GFP dsRNA (2.5 µg g −1 shrimp) into each shrimp at the lateral area of the fourth abdominal segment (Kong et al, 2018). The hepatopancreas samples in three shrimps from the test or control group were collected at 0, 12, 24, and 48 h after injection.…”