Development, characterization, and subcellular location of DNAse activity
in HL-60 cells and monocytes
PJ Roberts
Department of Clinical Haematology, University College, London, England.
The digestion of DNA from intact bacteria by human phagocytic cells was
measured by the release of solubilized radiolabeled DNA. Two subclones from
the human promyelocytic HL-60 cell line were unable to digest bacterial DNA
unless they were previously induced to mature by incubation for several
days with 1.25% dimethylsulfoxide (DMSO). The maximal capacity of
DMSO-induced HL-60 cells to digest DNA was similar to that of monocytes
purified from peripheral blood (PB) and much greater than that of
neutrophils. The increasing capacity to digest DNA during maturation was
associated with the development of acid DNAse activity, measured in a
cell-free system, and slightly preceded development of 12-O-tetradecanoyl
phorbol 13-acetate-stimulated respiratory burst activity. The acid DNAse
had a pH optimum of 5.0 and did not require the presence of calcium or
2-mercaptoethanol (2-ME). A third subclone of HL-60 cells was able to
digest DNA from intact bacteria without previous maturation, however, and
this was associated with the presence of an alkaline DNAse which had a pH
optimum between 7.0 and 8.0 and showed a dependence on calcium and 2-ME for
maximal activity. The subcellular location of acid DNAse in DMSO-induced
HL-60 cells was similar to that of monocytes in having a bimodal
distribution on fractionated sucrose density gradients. The dense peak
(mean density 1.195 g/mL) was located in the same region of the gradient as
primary granule enzymes but the light peak (mean density 1.137 g/mL) did
not codistribute with either plasma membrane, endoplasmic reticulum, or
mitochondria, suggesting accumulation in a different organelle.
Volume 75,
Issue 4,
pp. 976-983,
02/15/1990
Copyright © 1990 by The American Society of Hematology
