Expression of a heat-inducible gene of the HSP70 family in human
myelomonocytic cells: regulation by bacterial products and cytokines
G Fincato, N Polentarutti, A Sica, A Mantovani and F Colotta
Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
In this study we have examined the expression of a heat-shock protein (HSP)
70 gene in normal human peripheral blood leukocytes. Northern blot analysis
showed that appreciable levels of hsp70 mRNA are present in monocytes and
granulocytes, whereas transcript levels were barely detectable or absent in
lymphocytes. Monocytes functionally activated by bacterial
lipopolysaccharide (LPS) showed an early (15 minutes) increase of hsp70
transcripts that was shown, by actinomycin D blocking and nuclear run-off
experiments, to be dependent on transcriptional activation of the gene. LPS
did not appreciably affect the hsp70 mRNA half-life. Monocytes exposed to
inactivated streptococci, phorbol-12- myristate-13-acetate, and tumor
necrosis factor showed augmented levels of hsp70 transcripts, whereas
interferon-gamma and monocyte, granulocyte, and granulocyte-monocyte
colony-stimulating factors had no effect. Adherence to plastic augmented
hsp70 expression in monocytes. S1 protection analysis indicated that the
gene expressed in monocytes is indeed a heat-inducible member of the hsp70
gene family rather than a constitutively expressed heat-shock cognate gene.
Western blot analysis showed that a heat-inducible HSP72 was present in
monocytes and, at augmented levels, in LPS-treated monocytes. LPS-activated
monocytes were more resistant to heat shock than unstimulated cells. These
data indicate that a heat-inducible hsp70 gene can be efficiently expressed
in myelomonocytic cells at physiologic temperatures. Expression of hsp70
genes in monocytes suggests a possible role of heat- inducible genes in the
differentiation and/or functional activation of terminally differentiated
nonproliferating elements of the myelomonocytic lineage.
Volume 77,
Issue 3,
pp. 579-586,
02/01/1991
Copyright © 1991 by The American Society of Hematology
