Abstract
The P38 mitogen-activated protein kinase (MAPK) signal transduction pathway is widespread in organisms and plays important roles in immune activities. The infection mechanism of environmental gram-negative bacteria on crustaceans is an important scientific problem. In this study, the cDNA full-length sequence ofPortunus trituberculatusP38 (PtP38) was cloned and its structure was analyzed by bioinformatics methods. To study the function of the PtP38 gene after a Gram-negative bacterial infection, we injectedP. trituberculatuswith LPS to activate the immune response instead of directly infecting with Gram-negative bacteria. With LPS stimulation, the expression of the PtP38 gene in different tissues increased significantly. At the same time, the expression of immune-related genes (ALF and crustin) in the hepatopancreas, activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and inducible nitric oxide synthase (iNOS) enzymes], and expression of apoptosis-related genes (caspase2 and caspase3) were increased significantly. To further conform the function of PtP38 in the immune response, we injectedP. trituberculatuswith P38 inhibitor and subsequently injected with LPS. The results showed that the expression of immune-related genes was inhibited, the activity of antioxidant enzymes was decreased, and the expression of apoptosis-related genes were inhibited. Thus, we speculated that PtP38 may increase the immune ability by improving the expression of antimicrobial peptides, increasing the activity of oxidative stress-related enzymes, and promoting cell apoptosis in infectedP. trituberculatus. This study also laid the foundation for further study of the P38 MAPK signaling pathway and immune mechanism ofP. trituberculatus.
Highlights
P38 mitogen-activated protein kinase (MAPK) is one of the important signaling pathways in the body (Seger and Krebs, 1995)
An activated P38 pathway promotes the production of inflammatory factors, such as TNF-a, IL-1, IL-4, IL-6, IL-8, and IL-12 (Guan et al, 1998), increases COX-2, inducible nitric oxide synthase (iNOS), VCAM-1, and other proteins related to inflammation (Badger et al, 1998), promotes the proliferation and differentiation of immune cells (e.g., GM-CSF, EPO, CSF, and CD40) (Da Silva et al, 1997), and plays an important role in the immune mechanism of the organism
The results showed that Portunus trituberculatus P38 (PtP38) has the closest relationship to Scylla paramamosain, followed by Eriocheir sinensis (Figure 3)
Summary
P38 mitogen-activated protein kinase (MAPK) is one of the important signaling pathways in the body (Seger and Krebs, 1995) It is widely present in various eukaryotes from yeast to humans (Lake et al, 2016) and can participate in inflammatory reactions, cell growth, cell differentiation, cell cycle, and cell death (Keshet and Seger, 2010). PtP38 Functions in Portunus trituberculatus conserved TGY (Thr-Gly-Tyr) motif (Ono and Han, 2000) Various extracellular stressors, such as UV, osmotic pressure, radiation, inflammatory cytokines, growth factors, and shock, as well as double phosphorylation of serine and threonine in the TGY motif, through the highly conserved "MAPKKK-MAPKKMAPK" pathway, activate P38 MAPK (Cuenda and Rousseau, 2007; Yokota and Wang, 2016). P38 MAPK–hyaluronan-dependent reprogramming of the tumor microenvironment plays a critical role in driving lung tumorigenesis, while blocking this process could have far-reaching therapeutic implications (Brichkina et al, 2016)
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