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KM Hudson, NC Denko, E Schwab, E Oswald, A Weiss and MA Lieberman
Department of Molecular Genetics, Biochemistry, and Microbiology,
University of Cincinnati College of Medicine, OH 45267-0524, USA.
Cytotoxic necrotizing factor (CNF) toxins, isolated from certain
Escherichia coli strains known to cause intestinal and extra intestinal
infections, induce reorganization of the actin cytoskeleton and generate
hyperploidy in adherent cell lines. We have examined the effect of CNF
toxin on one of the few cell types that naturally increase nuclear DNA
content, megakaryocytes. Our studies show that only hematopoietic cells
capable of differentiating along the megakaryocyte lineage responded to the
CNF2 toxin by becoming polyploid and by reorganizing actin. The K562, HEL,
and CHRF-288-11 cell lines can be induced with phorbol ester to
differentiate along the megakaryocyte lineage, and these cells also respond
to the toxin with increased DNA content and actin cytoskeletal
rearrangements. Interestingly, treatment of the K562 and HEL cell lines
with CNF2 does not result in an increase in production of the
megakaryocytic marker glycoprotein IIIa, unlike phorbol ester treatment.
Conversely, two T- cell leukemic cell lines, CEM and Molt4, and the
promyelocytic HL-60 cell line, which do not differentiate along the
megakaryocyte lineage in response to phorbol myristate acetate, do not
respond to CNF2, by increased expression of gpIIIa, increased nuclear DNA
content, or actin reorganization. A potential target of these toxins, RhoA,
is expressed by both megakaryocytic and nonmegakaryocytic cell lines, as
shown by reverse transcription-polymerase chain reaction and Western blot.
Although it is clear that the CNF toxins can affect a wide variety of
adherent nonhematopoietic cell lines, we propose that the response to CNF,
in terms of reorganizing actin structure and increase in DNA content in
hematologic suspension cells, correlates with the capability of these
target cells to differentiate along the megakaryocytic lineage.
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| Copyright © 1996 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||