Post-translational protein deimination in cod (Gadus morhua L.) ontogeny novel roles in tissue remodelling and mucosal immune defences?

Peptidylarginine deiminases (PADs) are calcium dependent enzymes with physiological and pathophysiologicalroles conserved throughout phylogeny. PADs promote post-translational deimination of protein arginine to ci-trulline, altering the structure and function of target proteins. Deiminated proteins were detected in the earlydevelopmental stages of cod from 11 days post fertilisation to 70 days post hatching. Deiminated proteins werepresent in mucosal surfaces and in liver, pancreas, spleen, gut, muscle, brain and eye during early cod larvaldevelopment. Deiminated protein targets identified in skin mucosa included nuclear histones; cytoskeletalproteins such as tubulin and beta-actin; metabolic and immune related proteins such as galectin, mannan-binding lectin, toll-like receptor, kininogen, Beta2-microglobulin, aldehyde dehydrogenase, bloodthirsty andpreproapolipoprotein A-I. Deiminated histone H3, a marker for anti-pathogenic neutrophil extracellular traps,was particularly elevated in mucosal tissues in immunostimulated cod larvae. PAD-mediated protein deimina-tion may facilitate protein moonlighting, allowing the same protein to exhibit a range of biological functions, intissue remodelling and mucosal immune defences in teleost ontogeny.