Involvement of tetraspanin 8 in the innate immune response of the giant prawn, Macrobrachium rosenbergii.

The tetraspanins, representing a conserved superfamily of four-span membrane proteins, are highly involved in viral and bacterial infections. Thus far, the function of the tetraspanins in crustaceans remains largely unknown. In this study, we report the cloning and expression analysis of a tetraspanin 8 from the giant freshwater prawn, Macrobrachium rosenbergii (named as MrTspan8). MrTspan8 contains a 720-bp open reading frame encoding a 239-amino acids protein, which exhibits four transmembrane domains and two extracellular loops that are typical for tetraspanins. MrTspan8 was found to be widely expressed in a variety of prawn tissues including heart, gill, muscle, gut, and hepatopancreas. Additionally, MrTspan8 expression was significantly increased in the hepatopancreas and gill of the prawns challenged by the bacterial pathogen Aeromonas hydrophila. Moreover, we show that pre-incubation of the peptides from the large extracellular loop of MrTSPAN8 protein reduced the cell death caused by A. hydrophila infection in prawn tissue, suggesting that MrTSPAN8 could be a mediator for bacterial infection to prawn.

Wntless, a conserved Wnt-transport protein, is involved in the innate immune response of Macrobrachium rosenbergii.

Wnt signaling plays important roles in a variety of developmental and pathological processes. Here we show that Wntless, the main regulator for Wnt secretion, is involved in the innate immune response of the giant freshwater prawn, Macrobrachium rosenbergii. The full-length cDNA of the prawn Wntless (named MrWntless) is 2173 bp in length and contains a 1602-bp open reading frame (ORF), which is conceptually translated into a 533-amino acids sequence. MrWntless protein contains a highly conserved Wnt-binding domain which is required for secretion of Wnt ligands, and exhibits 57-67% identity with known Wntless proteins of other animals. MrWntless was found to be expressed in a variety of prawn tissues including heart, gill, muscle, gut, hepatopancreas and ovary. Moreover, MrWntless expression was significantly increased in the hepatopancreas and gill of the prawns challenged by the bacterial pathogen Aeromonas hydrophila and Vibrio parahaemolyticus. Knockdown of MrWntless by RNA interference in prawns led to dramatically decreased MrWntless expression of approximately 70%. Furthermore, the cumulative mortality rate of the prawn injected with MrWntless dsRNA was greatly increased in response to A. hydrophila challenge compared with the control prawns. Taken together, we provide evidence that prawn Wntless is important for their innate immune response against bacterial pathogens.

Molecular cloning and expression analysis of a prawn (Macrobrachium rosenbergii) juvenile hormone esterase-like carboxylesterase following immune challenge.

Methyl farnesoate (MF), the crustacean juvenile hormone (JH), plays critical roles in various physiological processes in crustaceans. The titer of MF is precisely regulated by specific carboxylesterase. Here, we report for the first time that the cloning and expression analysis of a JH esterase-like carboxylesterase from the prawn Macrobrachium rosenbergii (named as MrCXE). MrCXE contained a 1935-bp open reading frame (ORF) conceptually translated into a 644-amino acids protein. MrCXE protein shared the highest identity (36%) with JH esterase-like carboxylesterase from the swimming crab, Portunus trituberculatus and exhibited the typical motifs of JH esterase-like carboxylesterases. MrCXE was most abundantly expressed in hepatopancreas, the major tissue for MF metabolism. MrCXE was expressed at a low level in gut and was not detected in other tissues. Additionally, MrCXE expression was upregulated in hepatopancreas by eyestalk ablation to increase MF level. Furthermore, the mRNA level of MrCXE was significantly increased in the hepatopancreas when challenged by the bacterial pathogens Aeromonas hydrophila and Vibrio parahaemolyticus. To our knowledge, this is the first report that the JH esterase-like carboxylesterase is involved in the innate immune response of the crustaceans.