Interactions of the human calcitonin fragment 9-32 with phospholipids: a monolayer study.
Human calcitonin and its C-terminal fragment 9-32 (hCT(9-32)) administered in a spray translocate into respiratory nasal epithelium with an effect similar to intravenous injection. hCT(9-32) is an efficient carrier to transfer the green fluorescent protein into excised bovine nasal mucosa. To understand the translocation of hCT(9-32) across plasma membranes, we investigated its interactions with phospholipids and its interfacial structure using model lipid monolayers. A combination of physicochemical methods was applied including surface tension measurements on adsorbed and spread monolayers at the air-water interface, Fourier transform infrared, circular dichroism, and atomic force microscopy on Langmuir-Blodgett monolayers. The results disclose that hCT(9-32) preferentially interacts with negatively charged phospholipids and does not insert spontaneously into lipid monolayers. This supports a nonreceptor-mediated endocytic internalization pathway as previously suggested. Structural studies revealed a random coil conformation of hCT(9-32) in solution, transforming to alpha-helices when the peptide is localized at lipid-free or lipid-containing air-water interfaces. Atomic force microscopy studies of monolayers of the peptide alone or mixed with dioleoylphosphatidylcholine revealed that hCT(9-32) forms filaments rolled into spirals. In contrast, when interacting with dioleoylphosphatidylglycerol, hCT(9-32) does not adopt filamentous structures. A molecular model and packing is proposed for the spiral-forming hCT(9-32).
Wagner
Kerstin
K
Centre de Recherches de Biochimie Macromoléculaire-Centre National de la Recherche Scientifique, Formation de Recherche en Evolution 2593, F-34293 Montpellier Cedex, France.
Van Mau
Nicole
N
Boichot
Sylvie
S
Kajava
Andrey V
AV
Krauss
Ulrike
U
Le Grimellec
Christian
C
Beck-Sickinger
Annette
A
Heitz
Frédéric
F
D002116:Calcitonin / Q000737:chemistry*; D006801:Humans; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
D010455:Peptides; D010713:Phosphatidylcholines; D010743:Phospholipids; D002116:Calcitonin; C017251:1,2-oleoylphosphatidylcholine