New endogenous
antimicrobial peptides (AMPs) derived from
chromogranin A (CgA) are secreted by nervous, endocrine and immune cells during stress. They display antimicrobial activities by lytic effects at micromolar range using a pore-forming mechanism against Gram-positive bacteria, filamentous fungi and yeasts. These AMPs can also penetrate quickly into neutrophils (without lytic effects), where, similarly to "
cell penetrating peptides", they interact with cytoplasmic
calmodulin, and induce
calcium influx via Store Operated Channels therefore triggering neutrophils activation. Staphylococcus aureus and Salmonella
enteritis are bacteria responsible for severe
infections. We investigated here the effects of S. aureus and S.
enteritis bacterial
proteases on CgA-derived
peptides and evaluated their antimicrobial activities. We showed that the
Glu-C protease produced by S. aureus V8 induces the loss of the AMPs antibacterial activities and produces new antifungal
peptides. In addition, four antimicrobial CGA-derived
peptides (
chromofungin, procatestatin, human/bovine
catestatin) are degraded when treated with bacterial supernatants from S. aureus and S.
enteritis, whereas,
cateslytin, the short active form of
catestatin, resists to this degradation. Finally, we demonstrate that several antimicrobial CgA-derived
peptides are able to act synergistically with
antibiotics against bacteria and fungi indicating their roles in innate defense.