Bacterial killing mechanism of sheep myeloid antimicrobial peptide-18 (SMAP-18) and its Trp-substituted analog with improved cell selectivity and reduced mammalian cell toxicity.
To develop short antimicrobial peptide with improved cell selectivity and reduced mammalian cell toxicity compared to sheep myeloid antimicrobial peptide-29 (SMAP-29) and elucidate the possible mechanisms responsible for their antimicrobial action, we synthesized a N-terminal 18-residue peptide amide (SMAP-18) from SMAP-29 and its Trp-substituted analog (SMAP-18-W). Due to their reduced hemolytic activity and retained antimicrobial activity, SMAP-18 and SMAP-18-W showed higher cell selectivity than SMAP-29. In addition, SMAP-18 and SMAP-18-W had no cytotoxicity against three different mammalian cells such as RAW 264.7, NIH-3T3 and HeLa cells even at 100 μM. These results suggest that SMAP-18 and SMAP-18-W have potential for future development as novel therapeutic antimicrobial agent. Unlike SMAP-29, SMAP-18 and SMAP-18-W showed relatively weak ability to induce dye leakage from bacterial membrane-mimicking liposomes, N-phenyl-1-napthylamine (NPN) uptake and o-nitrophenyl-β-galactoside (ONPG) hydrolysis. Similar to SMAP-29, SMAP-18-W led to a significant membrane depolarization (> 80%) against Staphylococcus aureus at 2 × MIC. In contrast, SMAP-18 did not cause any membrane depolarization even at 4 × MIC. In confocal laser scanning microscopy, we observed translocation of SMAP-18 across the membrane in a non-membrane disruptive manner. SMAP-29 and SMAP-18-W were unable to translocate the bacterial membrane. Collectively, we propose here that SMAP-29 and SMAP-18-W kill microorganisms by disrupting/perturbing the lipid bilayer and forming pore/ion channels on bacterial cell membranes, respectively. In contrast, SMAP-18 may kill bacteria via intracellular-targeting mechanism.
Department of Bio-Materials, Graduate School and Department of Cellular and Molecular Medicine, School of Medicine, Chosun University, Gwangju, 501-759, Republic of Korea.
Binu
B
Jacob
Yangmee
Y
Kim
Jae-Kyung
JK
Hyun
Il-Seon
IS
Park
Jeong-Kyu
JK
Bang
Song Yub
SY
Shin
D019943:Amino Acid Substitution; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D012756:Sheep; D013211:Staphylococcus aureus
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides