title: Interactions of the human calcitonin fragment 9-32 with phospholipids: a monolayer study.
abstract: 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).
authors.affiliation: Centre de Recherches de Biochimie Macromoléculaire-Centre National de la Recherche Scientifique, Formation de Recherche en Evolution 2593, F-34293 Montpellier Cedex, France.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wagner
authors.forename: Nicole
authors.initials: N
authors.lastname: Van Mau
authors.forename: Sylvie
authors.initials: S
authors.lastname: Boichot
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Kajava
authors.forename: Ulrike
authors.initials: U
authors.lastname: Krauss
authors.forename: Christian
authors.initials: C
authors.lastname: Le Grimellec
authors.forename: Annette
authors.initials: A
authors.lastname: Beck-Sickinger
authors.forename: Frédéric
authors.initials: F
authors.lastname: Heitz
mesh_terms: 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
chemical_list: D010455:Peptides; D010713:Phosphatidylcholines; D010743:Phospholipids; D002116:Calcitonin; C017251:1,2-oleoylphosphatidylcholine