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Salivary histatin 5 internalization by translocation, but not endocytosis, is required for fungicidal activity in Candida albicans
Author(s) -
Jang Woong Sik,
Bajwa Jashanjot Singh,
Sun Jianing N.,
Edgerton Mira
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07210.x
Subject(s) - candida albicans , biology , internalization , intracellular , cytosol , endocytosis , extracellular , cell wall , chromosomal translocation , propidium iodide , microbiology and biotechnology , biochemistry , cell membrane , biophysics , cell , programmed cell death , apoptosis , gene , enzyme
Summary Salivary histatin 5 (Hst 5) is a cationic salivary protein with high fungicidal activity against Candida albicans . Binding to the cell wall followed by intracellular translocation is required for killing; however, specific binding components and critical toxic events are not understood. In this study, laminarin (β‐1,3‐glucan) but not sialic acid, mannan or pustulan mediated Hst 5 binding to C. albicans , and was disassociated by 100 mM NaCl. Time‐lapse confocal microscopy revealed a dose‐dependent rate of cytosolic uptake of Hst 5 that invariably preceded propidium iodide (PI) entry, demonstrating that translocation itself does not disrupt membrane integrity. Cell toxicity was manifest by vacuolar expansion followed by PI entrance; however, loss of endocytotic vacuolar trafficking of Hst 5 did not reduce killing. Extracellular NaCl (100 mM), but not sorbitol, prevented vacuolar expansion and PI entry in cells already containing cytosolic Hst 5, thus showing a critical role for ionic balance in Hst 5 toxicity. Hst 5 uptake, but not cell wall binding, was blocked by pretreatment with azide or carbonyl cyanide m‐chlorophenylhydrazone; however, 10% of de‐energized cells had membrane disruption. Thus, Hst 5 is capable of heterogeneous intracellular entry routes, but only direct cytosolic translocation causes cell death as a result of ionic efflux.