Interactions of the human cathelicidin peptide LL-37 with DNA by biophysical methods.

Psosriasis, an auto-immune skin disease, not only causes damage to the physical appearance of the patient, but may also cause emotional trauma too. Currently, there is no complete cure for psoriasis. The binding of LL-37, the only cathelicidin found in humans, to self DNA leads to the uptake of this LL-37/self-DNA complex by plasmacytoid dendritic cells (pDCs). The production of interferon-α is stimulated, mainly due to binding of the complex by Toll-like receptors in enodosomal compartments. Excess interferon-α (IFN- α) stimulates auto-reactive T-cells, which in turn induce keratinocytes to differentiate aberrantly, a major characteristic of psoriasis. Thus, by inhibiting LL-37 from binding to self-DNA, psoriasis may be prevented. A first step to achieving this would be to characterize this binding with biophysical methods. We have found out that LL-37 binds to DNA via both electrostatic and hydrophobic interactions. Specifically, LL-37 binds to the major groove of DNA and its structure is essential for binding to DNA. Once LL-37 binds to DNA, it probably condenses DNA and confers upon it a compact structure resembling that of DNA from bacteriophages. Plasmacytoid dendritic cells mistake this as foreign DNA, uptake it possibly via non-clathrin mediated endocytosis and stimulate the production of IFN-α.Bachelor of Science in Biological Science