Both Ca2+ and Zn2+ are essential for S100A12 protein oligomerization and function
Authors: Moroz, Olga V.; Burkitt, Will; Wittkowski, Helmut; He, Wei; Ianoul, Anatoli; Novitskaya, Vera; Xie, Jingjing; Polyakova, Oxana; Lednev, Igor K.; Shekhtman, Alexander; Derrick, Peter J.; Bjoerk, Per; Foell, Dirk; Bronstein, Igor B.
Background: Human S100A12 is a member of the S100 family of EF-hand calcium-modulated proteins that are associated with many diseases including cancer, chronic inflammation and neurological disorders. S100A12 is an important factor in host/parasite defenses and in the inflammatory response. Like several other S100 proteins, it binds zinc and copper in addition to calcium. Mechanisms of zinc regulation have been proposed for a number of S100 proteins e. g. S100B, S100A2, S100A7, S100A8/9. The interaction of S100 proteins with their targets is strongly dependent on cellular microenvironment. Results: The aim of the study was to explore the factors that influence S100A12 oligomerization and target interaction. A comprehensive series of biochemical and biophysical experiments indicated that changes in the concentration of calcium and zinc led to changes in the oligomeric state of S100A12. Surface plasmon resonance confirmed that the presence of both calcium and zinc is essential for the interaction of S100A12 with one of its extracellular targets, RAGE - the Receptor for Advanced Glycation End products. By using a single-molecule approach we have shown that the presence of zinc in tissue culture medium favors both the oligomerization of exogenous S100A12 protein and its interaction with targets on the cell surface. Conclusion: We have shown that oligomerization and target recognition by S100A12 is regulated by both zinc and calcium. Our present work highlighted the potential role of calcium-binding S100 proteins in zinc metabolism and, in particular, the role of S100A12 in the cross talk between zinc and calcium in cell signaling.
Inhibition of dermatophytes by the antimicrobial peptides human beta-defensin-2, ribonuclease 7 and psoriasin
Authors: Fritz, Peter; Beck-Jendroschek, Vera; Brasch, Jochen
Previous studies have described some antibacterial effects of antimicrobial peptides (AMPs) expressed in human skin, but little is known about their possible activity against dermatophytes. Therefore we have tested the effects of human beta-defensin 2 (hBD-2), ribonuclease 7 (RNase 7) and psoriasin on the in vitro growth of four dermatophyte species. Germinating conidia of Trichophyton rubrum, T. mentagrophytes, Microsporum canis and Epidermophyton floccosum were exposed in vitro to hBD-2, RNase 7, psoriasin and fluconazole. Subsequent fungal growth was measured photometrically over 168 hours. All AMPs significantly inhibited fungal growth, with the degree of inhibition dependent on the dermatophyte species and the specific AMP. E. floccosum was found to be the most susceptible species in that it was markedly suppressed by all AMPs, whereas M. canis was inhibited only by psoriasin. Overall, psoriasin was the most effective AMP and had even stronger inhibitory effects on some dermatophytes than fluconazole. Our findings show that AMPs expressed in human skin can, in principal, inhibit the growth of dermatophytes in vitro. Therefore the question whether AMPs are relevant for human protection against tineas is justified and should be addressed by investigating their role in vivo