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Aggregatibacter actinomycetemcomitans leukotoxin induces cytosol acidification in LFA‐1 expressing immune cells
Author(s) -
Balashova N.,
Dhingra A.,
BoeszeBattaglia K.,
Lally E.T.
Publication year - 2016
Publication title -
molecular oral microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 77
eISSN - 2041-1014
pISSN - 2041-1006
DOI - 10.1111/omi.12136
Subject(s) - biology , microbiology and biotechnology , k562 cells , cytosol , cytolysis , acridine orange , phagosome , cellular compartment , cell , intracellular , biochemistry , cytotoxicity , apoptosis , in vitro , enzyme
Summary Studies have suggested that Aggregatibacter actinomycetemcomitans leukotoxin (LtxA) kills human lymphocyte function‐associated antigen 1 (LFA‐1; CD11a/CD18)‐bearing immune cells through a lysosomal‐mediated mechanism. Lysosomes are membrane‐bound cellular organelles that contain an array of acid hydrolases that are capable of breaking down biomolecules. The lysosomal membrane bilayer confines the pH‐sensitive enzymes within an optimal acidic (pH 4.8) environment thereby protecting the slightly basic cytosol (pH 6.8–7.5). In the current study, we have probed the effect of LtxA‐induced cytolysis on lysosomal integrity in two different K562 erythroleukemia cell lines. K562‐puro/LFA‐1 cells were stably transfected with CD11a and CD18 cDNA to express LFA‐1 on the cell surface while K562‐puro, which does not express LFA‐1, served as a control. Following treatment with 100 ng ml −1 LtxA cells were analyzed by live cell imaging in conjunction with time‐lapse confocal microscopy and by flow cytometry. Using a pH‐sensitive indicator (pHrodo ® ) we demonstrated that the toxin causes a decrease in the intracellular pH in K562‐puro/LFA‐1 cells that is noticeable within the first 15 min of treatment. This process correlated with the disappearance of lysosomes in the cytosol as determined by both acridine orange and LysoTracker ® Red DND‐99 staining. These changes were not observed in K562‐puro cells or when heat inactivated toxin was added to K562‐puro/LFA‐1. Our results suggest that LtxA induces lysosomal damage, cytosol acidification, which is followed by cell death in K562‐puro/LFA‐1 cells.