Scientific Reference
LL-37 (Human Cathelicidin)
Evidence profile: Preclinical, with limited uncontrolled human reports
LL-37 is a 37-residue peptide cleaved from hCAP18, the only human cathelicidin; its name refers to its two leading leucines and its length. It is made by neutrophils and by epithelial cells of the skin, gut and airways, and the gene that encodes it is regulated in part by vitamin D. Laboratory studies have examined its activity against bacteria, fungi and some viruses, and its signalling to host immune and epithelial cells. Its research record runs in two directions: it is studied as a host-defence molecule and also as a contributor to inflammatory skin conditions such as psoriasis and rosacea. Most published work is in vitro or in animals, and interventional human studies are few and small.
Mechanism of Action
In dilute aqueous solution LL-37 is largely disordered; on contact with lipid membranes it has been reported to fold into an amphipathic α-helix. Its side chains give it a net charge of about +6 at neutral pH, which draws it to the negatively charged surfaces of bacterial membranes, and it is thought to permeabilise those membranes. It also binds bacterial lipopolysaccharide. On host cells it has been reported to act through several receptors, among them formyl peptide receptor 2 and the P2X7 purinergic receptor, and to transactivate the epidermal growth factor receptor in keratinocytes. Complexes of LL-37 with self-DNA or RNA have been reported to activate Toll-like receptor signalling in dendritic cells, a pathway examined in psoriasis research.
Molecular Information
- Type: Antimicrobial peptide (cathelicidin)
- Length: 37 amino acids
- Molecular weight: 4493 g/mol
- Molecular formula: C205H340N60O53
- CAS: 154947-66-7