Antimicrobial peptides (AMPs) are key components of host immune defense of vertebrates against microbial invasions. Here, we report a new AMP (esculentin-1GN) characterized from the skin of the frog Hylarana guentheri. Esculentin-1GN (GLFSKKGGKGGKSWIKGV-FKGIKGIGKEVGGDVIRTGIEIAACKIKGEC) with high amphipathic αhelical structure in membrane-mimetic environments has the microbialkilling activity by destruction of the cell membrane. Moreover, esculentin-1GN inhibits LPS-induced expression of proinflammatory nitric oxide, interleukin-1β, interleukin-6, and tumor necrosis factor while it enhances expression of interleukin-10. Furthermore, esculentin-1GN can bind to D-(+)-galacturonic acid and LPS. Meanwhile, esculentin-1GN suppresses the activation of inflammatory response pathway induced by LPS. In addition, esculentin-1GN significantly reduces acute inflammation in carrageenaninduced mice paw. Taken together, the novel LPS-binding esculentin-1GN with antimicrobial and anti-inflammatory activities will be an excellent temple for designing new antibiotic formulations.

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Edited by Mike ShipstonThe voltage-gated potassium (Kv) 1.3 channel plays a crucial role in the immune responsiveness of T-lymphocytes and macrophages, presenting a potential target for treatment of immune-and inflammation related-diseases. FS48, a protein from the rodent flea Xenopsylla cheopis, shares the three disulfide bond feature of scorpion toxins. However, its threedimensional structure and biological function are still unclear. In the present study, the structure of FS48 was evaluated by circular dichroism and homology modeling. We also described its in vitro ion channel activity using patch clamp recording and investigated its anti-inflammatory activity in LPS-induced Raw 264.7 macrophage cells and carrageenaninduced paw edema in mice. FS48 was found to adopt a common αββ structure and contain an atypical dyad motif. It dose-dependently exhibited the Kv1.3 channel in Raw 264.7 and HEK 293T cells, and its ability to block the channel pore was demonstrated by the kinetics of activation and competition binding with tetraethylammonium. FS48 also downregulated the secretion of proinflammatory molecules NO, IL-1β, TNF-α, and IL-6 by Raw 264.7 cells in a manner dependent on Kv1.3 channel blockage and the subsequent inactivation of the MAPK/NF-κB pathways. Finally, we observed that FS48 inhibited the paw edema formation, tissue myeloperoxidase activity, and inflammatory cell infiltrations in carrageenantreated mice. We therefore conclude that FS48 identified from the flea saliva is a novel potassium channel inhibitor displaying anti-inflammatory activity. This discovery will promote understanding of the bloodsucking mechanism of the flea and provide a new template molecule for the design of Kv1.3 channel blockers.Voltage-gated potassium (Kv) channels play an important role in Ca 2+ signaling, action potential repolarization, cellular proliferation, migration and secretion, and cell volume

Background: Integrins are crucial anti-cancer therapy targets. We previously showed that tablysin-15 is an integrin antagonist with its Arg-Gly-Asp motif in a novel structural context. Objective: Here we investigated the anti-cancer effects and mechanisms of action of tablysin-15 in melanoma cells. Methods: Cell adhesion, competitive binding, cell viability, and ATP chemiluminescence assays were used to analyze the binding of tablysin-15 to αvβ3 integrin and its phenotypic effects. Wound healing, transwells, and zymography were performed to detect motility and matrix metalloproteinase- 2/-9 activities. PARP and caspase-3 cleavage were used as apoptosis assays, while LDH release and flow cytometry were used for necrosis and cell cycle analysis. The expression of mRNAs and proteins of target molecules was measured by qRT-PCR and western blotting, respectively. Results: Tablysin-15 dose-dependently inhibited the proliferation, migration, and invasion of M21 cells through integrin αvβ3. The proliferation inhibition caused by tablysin-15 was attributable to G0/G1 phase arrest rather than apoptosis or necrosis. Furthermore, tablysin-15 suppressed MMP-2/- 9 activities and the mRNA expression of MMP-2/-9 and COX-2 but was upregulated TIMP-1 in M21 cells. Meanwhile, tablysin-15 suppressed the expression of cyclin D1/E and CDK 2/6, the phosphorylation of FAK, Akt, and ERK, and nuclear translocation of NF-κB, while increasing the expression of the CDK inhibitor p21waf1/C1. Taken together, tablysin-15 might inhibit melanoma cell metastasis and proliferation by competing with αvβ3 integrin, thereby blocking FAK-associated signaling pathways and nuclear translocation of NF-κB. Conclusions: Tablysin-15 has reliable anti-cancer effects against M21 melanoma cells, suggesting tablysin-15 is a promising anti-tumor drug.