title: Antimicrobial and protease inhibitory functions of the human cathelicidin (hCAP18/LL-37) prosequence.
abstract: Cathelicidins are a class of small cationic peptide antibiotics that are expressed in skin and in other epithelial cells and are an active component of mammalian innate immunity. Human cathelicidin (hCAP18/LL-37) consists of a conserved prosequence called the cathelin-like domain and a C-terminal peptide named LL-37. To date, our understanding of the cathelin-like domain was very limited. To bring insight into the function of this evolutionarily conserved prosequence, we produced recombinant human cathelin-like protein and full-length hCAP18/LL-37 in Escherichia coli. As the cathelin-like protein shares homology with the cystatin family of cysteine protease inhibitors, we first analyzed the effect of the cathelin-like recombinant protein on the cysteine protease cathepsin L. We found that the cathelin-like protein inhibited protease activity. Next, we tested the cathelin-like protein for antimicrobial activity using solid phase radial diffusion and liquid phase killing assays. The cathelin-like prosequence, but not full-length hCAP18/LL-37, killed human pathogens including E. coli and methicillin-resistant Staphylococcus aureus at concentrations ranging from 16 to 32 microM. Together these findings suggest that after proteolytic cleavage the cathelin-like domain can contribute to innate host defense through inhibition of bacterial growth and limitation of cysteine-proteinase-mediated tissue damage. As these dual functions are complementary to the LL-37 peptide released from the C-terminus of full-length hCAP18/LL-37, human cathelicidin represents an elegant multifunctional effector molecule for innate immune defense of the skin.
authors.affiliation: Department of Medicine and Pediatrics, Division of Dermatology, University of California at San Diego and VA San Diego Healthcare System, 92161, USA.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Zaiou
authors.forename: Victor
authors.initials: V
authors.lastname: Nizet
authors.forename: Richard L
authors.initials: RL
authors.lastname: Gallo
mesh_terms: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000378:metabolism*; D054804:Cathelicidins; D004351:Drug Resistance; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000737:chemistry / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism; D005822:Genetic Vectors; D006801:Humans; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013211:Staphylococcus aureus / Q000378:metabolism; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D054804:Cathelicidins; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D010450:Endopeptidases