Antimicrobial and protease inhibitory functions of the human cathelicidin (hCAP18/LL-37) prosequence

J Invest Dermatol. 2003 May;120(5):810-6. doi: 10.1046/j.1523-1747.2003.12132.x.

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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anti-Bacterial Agents
  • Anti-Infective Agents / pharmacology
  • Antimicrobial Cationic Peptides / chemistry*
  • Antimicrobial Cationic Peptides / metabolism*
  • Cathelicidins
  • Drug Resistance
  • Electrophoresis, Polyacrylamide Gel
  • Endopeptidases / chemistry
  • Endopeptidases / metabolism
  • Enzyme Inhibitors / pharmacology
  • Escherichia coli / metabolism
  • Genetic Vectors
  • Humans
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Staphylococcus aureus / metabolism
  • Time Factors

Substances

  • Anti-Bacterial Agents
  • Anti-Infective Agents
  • Antimicrobial Cationic Peptides
  • Cathelicidins
  • Enzyme Inhibitors
  • Recombinant Proteins
  • CAP18 lipopolysaccharide-binding protein
  • Endopeptidases