Snail mucus from the mantle and foot of two land snails, Lissachatina fulica and Hemiplecta distincta, exhibits different protein profile and biological activity.

OBJECTIVE: Snails secrete different types of mucus that serve several functions, and are increasingly being exploited for medical and cosmetic applications. In this study, we explored the protein pattern and compared the biological properties of the mucus secreted from the mantle collar and foot of two snail species, Lissachatina fulica and Hemiplecta distincta. RESULT: Protein profile showed a different pattern between the two species and between the two secretory parts. The mantle-specific protein bands were further characterized and among them was an antibacterial protein, achacin. Accordingly, the mucus from the mantle exhibited the higher antibacterial activity than that from the foot in both snail species. The mucus from H. distincta, first reported here, also showed antibacterial properties, but with a lower activity compared to that for L. fulica. Snail mucus also exhibited anti-tyrosinase activity and antioxidant activity but with no significant difference between the foot and mantle mucus. These results indicate some different protein compositions and biological activities of snail slime from the mantle and foot, which might be associated with their specific functions in the animal and are useful for medical applications.

Melanization inhibition protein of Penaeus monodon acts as a negative regulator of the prophenoloxidase-activating system.

Melanization mediated by the prophenoloxidase-activating system (proPO) is an important immune response in invertebrates. However, in addition to melanin, the proPO system produces reactive intermediates that are not only harmful to the invading microbes but also to the host cells. Thus, the proPO system must be tightly regulated by several inhibitors. Previously, a melanization inhibition protein from the black tiger shrimp Penaeus monodon, PmMIP, has been identified and preliminarily characterized. In this study, we investigate the function of PmMIP in the regulation of the proPO system in shrimp. When challenged with the bacterium Vibrio harveyi, the expression of PmMIP transcripts in gills was down-regulated dramatically at 24 h but recovered after 48 h post infection (hpi), while the PmMIP protein level in shrimp plasma was decreased at 6 hpi but recovered at 24 hpi. Double-stranded RNA-mediated gene silencing of PmMIP suppressed both PmMIP transcriptional and translational levels and resulted in increased hemolymph phenoloxidase and proteinase activities compared to controls injected with GFP dsRNA or NaCl. Furthermore, the recombinant PmMIP protein successfully expressed in Escherichia coli was able to inhibit hemolymph PO activity by 50%. These results suggested that PmMIP was involved in the proPO system by acting as a negative regulator and interfering with hemolymph proteinase activity.