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).

Specific labeling with potent radiolabels alters the uptake of cell‐penetrating peptides

“…This finding is in agreement with previously reported data about the parent unbranched hCT(9-32) peptide. 22 Interestingly, 6 is still unstructured in TFE solution pointing again to the formation of random coil structure with a minimum at 198 nm. We then compared the influence of the Ga-DOTA modification with the influence of the NBD label to the CD spectra of the branched peptides (for hCT(9-32)-br, data not shown).…”

Cell-penetrating peptides: tools for intracellular delivery of therapeutics

“…Physicochemical investigations have also confirmed that peptide concentration is a key factor in determining the internalization process. Indeed, low peptide concentrations do not disturb membrane organization [108] ( fig. 2), while high concentrationsi.e.…”

Amyloid – Membrane Interactions: Experimental Approaches and Techniques

“…Wagner et al presented an elegant study in which atomic force microscopy was applied for studying mixed monolayers comprising phospholipids and a fragment of human calcitonin (hCT) [81]. The AFM screening demonstrated formation of distinct fibrillar structures of the calcitonin fragment, which morphologies were highly dependent upon the headgroup of the lipid forming the monolayer.…”