Conformational analysis of the frog skin peptide, plasticin-L1, and its effects on production of proinflammatory cytokines by macrophages.
Plasticin-L1 (GLVNGLLSSVLGGGQGGGGLLGGIL) is a conformationally flexible glycine/leucine-rich peptide originally isolated from norepinephrine-stimulated skin secretions of the South-American Santa Fe frog Leptodactylus laticeps (Leptodactylidae). A nuclear magnetic resonance/molecular dynamics characterization of plasticin-L1 in the presence of dodecylphosphocholine (DPC) and DPC/sodium dodecylsulphate micelles as membrane-mimetic models showed that the peptide has affinity for both neutral and anionic membranes. The peptide adopts a stable helical conformation at the N-terminal region and a more disordered helix at the C-terminal region, separated by an unstructured loop wherein the highest number of glycines is localized. In both micelle environments, plasticin-L1 slowly inserts between the detergent head groups but always remains localized at the micelle/water interface. Plasticin-L1 lacks direct antimicrobial activity but stimulates cytokine production by macrophages. Incubation with plasticin-L1 (20 μg/mL) significantly (P < 0.05) increased the production of the proinflammatory cytokines IL-1β, IL-12, IL-23, and TNF-α from unstimulated peritoneal macrophages from both C57BL/6 and BALB/C mice. The peptide also increased IL-6 production by unstimulated (P < 0.01) and lipopolysaccharide-stimulated (P < 0.01) macrophages, whereas the effects on production of the anti-inflammatory cytokine IL-10 were not significant. These findings suggest that plasticin-L1 may play an immunomodulatory role in vivo by stimulating cytokine production from frog skin macrophages in response to microbial pathogens. This peptide may represent a template for the design of peptides with therapeutic applications as immunostimulatory agents.
Department of Chemical and Geological Sciences, University of Cagliari , Monserrato, Cagliari I-09042, Italy.
Mariano A
MA
Scorciapino
Giorgia
G
Manzo
Andrea C
AC
Rinaldi
Roberta
R
Sanna
Mariano
M
Casu
Jelena M
JM
Pantic
Miodrag L
ML
Lukic
J Michael
JM
Conlon
D029845:Amphibian Proteins / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001001:Anura / Q000378:metabolism*; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology*; D005136:Eye Proteins; D007700:Kinetics; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000276:immunology*; D008279:Magnetic Resonance Imaging; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D015394:Molecular Structure; D009419:Nerve Tissue Proteins; D012867:Skin / Q000737:chemistry / Q000378:metabolism*
D029845:Amphibian Proteins; D016207:Cytokines; D005136:Eye Proteins; D009419:Nerve Tissue Proteins; C585162:plasticin-L1 peptide, Leptodactylus laticeps; C076104:plasticin