Dephosphorylation at Ser548 regulates hemocyanin-derived antibacterial peptides and immune defense in Penaeus vannamei

Phosphorylation plays a critical role in regulating immune responses in invertebrates. In <i>Penaeus vannamei</i>, hemocyanin, a multifunctional immune protein, is cleaved to produce antimicrobial peptides (AMPs) essential for pathogen defense. This study identifies Ser548 phosphorylation of the hemocyanin small subunit (<i>Pv</i>HMCs) as a key regulator of trypsin-mediated hemocyanin degradation and antimicrobial peptides production. Dephosphorylation of Ser548, controlled by <i>Pv</i>CK2α kinase and <i>Pv</i>PP2AC phosphatase, enhances cleavage, generating peptides with strong antibacterial activity against <i>Vibrio parahaemolyticus</i> and <i>Streptococcus iniae</i>. Phosphorylation inhibits this process, reducing peptide production and immune efficacy. <i>In vivo</i>, Ser548 dephosphorylation improves bacterial clearance and enhances shrimp survival. These findings reveal a critical molecular mechanism underlying shrimp immunity and suggest targeting hemocyanin phosphorylation to boost disease resistance in aquaculture.