The Journal of Cell Biology, Vol 82, 369-379, Copyright © 1979 by The Rockefeller University Press
Localization of submembranous cations to the leading end of human neutrophils during chemotaxis
EB Cramer and JI Gallin
Potassium pyroantimonate was used to localize sites of bound cations in
human neutrophils under conditions of random migration, stimulated random
migration (chemokinesis), and directed migration (chemotaxis). The cells
were placed in a standard chamber in which 0.45-micron micropore filters
separated the cells from the stimulus (buffer, Escherichia coli
endotoxin-activated serum or the synthetic chemotactic peptide
N-formyl-Met-Leu-Phe). The small pore filters permitted pseudopod formation
but impeded cell imgration through the filter. Cells examined under all
conditions had electron-dense precipitates of antimonate salts in some
granules. However, antimonate deposits were localized in the condensed
chromatin of the nucleus during random migration and associated to a large
extent with the uncondensed nuclear chromatin during chemokinesis and
chemotaxis. Under conditions of chemokinesis deposition of antimonate
procipitates appeared on the cytoplasmic side of the plasma membrane of
neutrophils whereas under conditions of chemotaxis cation deposits beneath
the cell membrane were localized to the pseudopods which were directed
toward the chemoattractant. In addition to endotoxin-activated serum,
concentrations of N-formyl-Met-Leu-Phe which caused neutrophil chemotaxis
(10(-8) M) also caused cation deposition beneath the cell membrane at the
leading end of the cell regardless of whether albumin was present in the
incubation media. However, with higher concentrations of the synthetic
peptide (10(-5) M) which caused granule release and were not chemotactic,
submembranous cation deposition was not seen. EDTA (10 mM) and EGTA (10 mM)
removed nuclear, granular, and submembranous cation deposits from
neutrophils examined under conditions of chemotaxis. X-ray microprobe
analysis of antimonate deposits revealed the possible presence of calcium
but did not detect sodium or magnesium. The data indicate that chemotactic
factors induce submembranous deposition of cations, most likely Ca++, which
localize to the leading edge of cells exposed to a gradient of
chemoattractant.
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