Biochem. J. (2005) 388
(689–695) (Printed in Great Britain)
Candidacidal effects of two antimicrobial peptides: histatin 5 causes small membrane defects, but LL-37 causes massive disruption of the cell membrane
Alice L. DEN HERTOG*1, Jan VAN MARLE†, Henk A. VAN VEEN†, Wim VAN'T HOF*, Jan G. M. BOLSCHER*, Enno C. I. VEERMAN* and Arie V. NIEUW AMERONGEN*
*Department of Oral Biochemistry, Academic Centre for Dentistry Amsterdam (ACTA), Vrije Universiteit and Universiteit van Amsterdam, Van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands, and †Department of Cell Biology & Histology/CMO, Academic Medical Centre (AMC), Meibergdreef 1, 1100 DD, Amsterdam, The Netherlands
The effects of antimicrobial peptides on artificial membranes have been well-documented; however, reports on the ultrastructural effects on the membranes of micro-organisms are relatively scarce. We compared the effects of histatin 5 and LL-37, two antimicrobial peptides present in human saliva, on the functional and morphological properties of the Candida albicans cell membrane. Fluorescence microscopy and immunogold transmission electron microscopy revealed that LL-37 remained associated with the cell wall and cell membrane, whereas histatin 5 transmigrated over the membrane and accumulated intracellularly. Freeze-fracture electron microscopy revealed that LL-37 severely affected the membrane morphology, resulting in the disintegration of the membrane bilayer into discrete vesicles, and an instantaneous efflux of small molecules such as ATP as well as larger molecules such as proteins with molecular masses up to 40 kDa. The effects of histatin 5 on the membrane morphology were less pronounced, but still resulted in the efflux of nucleotides. As the morphological defects induced by histatin 5 are much smaller than those induced by LL-37, but the efflux of nucleotides is similar at comparable candidacidal concentrations, we suggest that the loss of nucleotides plays an important role in the killing process.
Key words: antimicrobial peptide, Candida albicans, electron microscopy, freeze fracture, histatin 5, LL-37.
Abbreviations used: CFU, colony forming units; CZE, capillary zone electrophoresis; Fmoc, fluoren-9-ylmethoxycarbonyl; IMP, intramembranous particle; PI, propidium iodide; PPB, potassium phosphate buffer.
1To whom correspondence should be addressed (email al.denhertog@vumc.nl).
Received 17 December 2004/11 February 2005; accepted 14 February 2005
Published as BJ Immediate Publication 14 February 2005, DOI 10.1042/BJ20042099
The Biochemical Society, London ©2005
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