<em>Litopenaeus vannamei</em> Sterile-Alpha and Armadillo Motif Containing Protein (LvSARM) Is Involved in Regulation of <em>Penaeidins</em> and <em>antilipopolysaccharide factors</em>

<div><p>The Toll-like receptor (TLR)-mediated NF-κB pathway is tightly controlled because overactivation may result in severe damage to the host, such as in the case of chronic inflammatory diseases and cancer. In mammals, sterile-alpha and armadillo motif-containing protein (SARM) plays an important role in negatively regulating this pathway. While <em>Caenorhabditis elegans</em> SARM is crucial for an efficient immune response against bacterial and fungal infections, it is still unknown whether <em>Drosophila</em> SARM participates in immune responses. Here, <em>Litopenaeus vannamei</em> SARM (LvSARM) was cloned and functionally characterized. LvSARM shared signature domains with and exhibited significant similarities to mammalian SARM. Real-time quantitative PCR analysis indicated that the expression of <em>LvSARM</em> was responsive to <em>Vibrio alginolyticus</em> and white spot syndrome virus (WSSV) infections in the hemocyte, gill, hepatopancreas and intestine. In <em>Drosophila</em> S2 cells, LvSARM was widely distributed in the cytoplasm and could significantly inhibit the promoters of the NF-κB pathway-controlled antimicrobial peptide genes (AMPs). Silencing of <em>LvSARM</em> using dsRNA-mediated RNA interference increased the expression levels of <em>Penaeidins</em> and <em>antilipopolysaccharide factors</em>, which are <em>L.vannamei</em> AMPs, and increased the mortality rate after <em>V. alginolyticus</em> infection. Taken together, our results reveal that LvSARM may be a novel component of the shrimp Toll pathway that negatively regulates shrimp AMPs, particularly <em>Penaeidins</em> and <em>antilipopolysaccharide factors</em>.</p>