Involvement of a novel protein kinase C (nPKC) in immunocompetence in hemocytes of white shrimp, Litopenaeus vannamei

Complementary (c)DNA encoding novel protein kinase C (PKC) messenger (m)RNA of the white shrimp Litopenaeus vannamei, consisted of 2454-bp cDNA containing an open reading frame (ORF) of 2232 bp, belonging to the novel (n)PKC family of proteins characterized by their containing two phorbol ester/diacylglycerolbinding domains (Cl domain), a C2 domain, and a catalytic domain of the serine/threonine kinase, designated LvnPKC. A comparison of amino acid sequences showed that LvnPKC was closely related to arthropod nPKC. LvnPKC cDNA was detected in all tested tissues with a real-time PCR including the hepatopancreas, gills, muscles, subcuticular epithelium, abdominal nerve, thoracic nerve, brain, the stomach, heart, and especially in hemocytes and the intestines. Moreover, significantly upregulated LvnPKC expression was only observed in the eyestalk, brain, and hepatopancreas of shrimp transferred from 28 degrees C to 18 degrees C for 30 min. Induction of LvnPKC expression in hemocytes of L. vannarnei injected with Vibrio alginolyticus at 10(5) cfu shrimp(-1) was detected earlier than in those injected with 10(3) cfu shrimp(-1). Shrimp received LvnPKC-dsRNA for 1 days specifically depleted the expression of LvnPKC mRNA in hemocytes compared those of diethylpyrocarbonate water treatment. After that, significantly decreased expressions of lipopolysaccharide - and beta-1,3-glucan-binding protein, prophenoloxidase-activating enzyme, peroxinectin, prophenoloxidase I, and prophenoloxidase II in the prophenoloxidaseactivating system; lysozyme and cytosolic manganese superoxide dismutase and mitochondrial manganese superoxide dismutase in the antioxidant system were observed. We therefore concluded that LvnPKC is involved in immune defense of L. vannamei exposed to hypothermal stress or infected with V. alginolyticus.