Antimicrobial Properties of an Immunomodulator - 15 kDa Human Granulysin.
Granulysin, a cationic protein expressed by human natural killer cells and cytotoxic T lymphocytes, is a mediator for drug-induced Stevens-Johnson syndrome and graft-versus-host disease. Some 15 kDa granulysin are processed into 9 kDa forms and sequestered in cytolytic granules, while others are constitutively secreted into body fluids. Both 9 and 15 kDa granulysin have been shown to be a serum marker for cell-mediated immunity. Furthermore, 15 kDa is able to activate monocyte differentiation. However, its antimicrobial properties have not been clearly addressed. Here, we report a novel method to prepare both the soluble 9 and 15 kDa granulysin and show that the 15 kDa form is more effective than the 9 kDa form in exerting specific antimicrobial activity against Pseudomonas aeruginosa within a range of few micromolars. We also show that the 15 kDa granulysin is able to hyperpolarize the membrane potential and increase membrane permeability of treated bacteria. Interestingly, the bactericidal activity and membrane permeability of the granulysins were markedly reduced at lower pH (pH 5.4) as a result of probable increase in hydrophobicity of the granulysins. Additionally, we've also shown the granulysin to inhibit biofilm formation by P. aeruginosa. These results suggest that the 15 kDa granulysin exhibits a novel mechanism in bacteria killing in a way that's different from most antimicrobial peptides. Our novel granulysin preparation methodology will be useful for further study of action mechanisms of other antimicrobial, cytotoxic and immunomodulating properties in granulysin-mediated diseases.
Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei 112, Taiwan.|Program in Molecular Medicine, National Yang-Ming University and Academia Sinica, Taipei, Taiwan.
Hung-Mu
HM
Wei
Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
Li-Chih
LC
Lin
Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
Chiu-Feng
CF
Wang
Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei 112, Taiwan.
Yi-Jang
YJ
Lee
Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
Yuan-Tsong
YT
Chen
Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.|Program in Molecular Medicine, National Yang-Ming University and Academia Sinica, Taipei, Taiwan.
You-Di
YD
Liao
D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000737:chemistry / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007155:Immunologic Factors / Q000737:chemistry / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000502:physiology*
D000890:Anti-Infective Agents; D000945:Antigens, Differentiation, T-Lymphocyte; C075005:GNLY protein, human; D007155:Immunologic Factors