|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1995 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1994 : ¥1,200,000 (Direct Cost : ¥1,200,000)
CAP18 (cationic antimicrobial protein, 18kDa) is a 142 amino acid protein originally isolated from rabbit granulocytes using agglutination of LPS-coated erythrocytes as an assay. CAP18 is composed of an N-terminal domain of unknown function (CAP18_<1-105>) and a C-terminal LPS-binding domain (CAP18_<106-142>). Synthetic CAP18_<106-142> and CAP18_<106-137>, a 32-amino acid peptide resulting from the truncation of 5 amino acids from the C-terminus of CAP18_<106-142>, inhibited LPS-induced tissue factor generation, nitric oxide production and TNF release by macrophages. Mice treated with CAP18_<106-142> or CAP18_<106-137> were significantly protected from LPS lethality. Although CAP18_<106-142> and CAP18_<106-137> were highly active, other fragments of CAP18_<106-142>, including CAP18_<110-142> with a truncated N-terminus, did not exhibit LPS-binding and LPS-neutralizing activities. Both peptides had broad antimicrobial activity against both gram-negative bacteria such as Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae, Pseudomonas aeruginosa (IC_<50> ; 40-100 nM) and gram-positive bacteria such as Staphylococcus aureus (Methicillin sensitive and resistant strains) and Streptococcus pneumoniae (IC_<50> ; 100-200nM).
We cloned a CAP-18 family protein from human granulocytes. The cloned cDNA encoded 140 amino acid residues. Human CAP18 (CAP18_<1-140>) was highly homologous to that of rabbit. A32-amino-acid C-terminal fragment (CAP18_<104-135>) was shown to bind LPS,inhibit LPS-induced tissue factor generation by murine macrophages, and protect mice from LPS lethality. This peptide exhibited antimicrobial activity against both gram-negative and gram-positive bacteria. We hypothesize that CAP18 and the derived peptides bind to LPS and alter the capacity of LPS to initiate disseminated intravascular coagulation.
In this regard, CAP may act as host defense protein against infectious diseases, and have therapeutic potential for sepsis and endotoxin shock.