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Ca2+-induced exocytosis in individual human neutrophils: high- and low-affinity granule populations and submaximal responses

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Published in EMBO Journal. 1998, vol. 17, no. 5, p. 1279-1288
Abstract We have investigated Ca2+-induced exocytosis from human neutrophils using the whole cell patch-clamp capacitance technique. Microperfusion of Ca2+ buffer solutions (<30 nM to 5 mM free Ca2+) through the patch-clamp pipette revealed a biphasic activation of exocytosis by Ca2+. The first phase was characterized by high affinity (1.5-5 microM) and low apparent cooperativity (<=2) for Ca2+, and the second phase by low affinity (approximately 100 microM) and high cooperativity (>6). Only the second phase was accompanied by loss of myeloperoxidase, suggesting that the low-affinity exocytosis reflected release of peroxidase-positive (primary) granules, while the high-affinity exocytosis reflected release of peroxidase-negative (secondary and tertiary) granules. At submaximal Ca2+ concentrations, only a fraction of a given granule population was released. This submaximal release cannot simply be explained by Ca2+ modulation of the rate of exocytosis, and it suggests that the secretory response of individual cells is adjusted to the strength of the stimulus. The Ca2+ dependence of the high- and low-affinity phases of neutrophil exocytosis bears a resemblance to endocrine and neuronal exocytosis, respectively. The occurrence of such high- and low-affinity exocytosis in the same cell is novel, and suggests that the Ca2+ sensitivity of secretion is granule-, rather than cell-specific.
Keywords Calcium/analysis/ physiologyCells, CulturedCytoplasmic Granules/ secretionExocytosis/ physiologyHumansNeutrophils/ cytologyPatch-Clamp TechniquesPeroxidase/analysis
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PMID: 9482725
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NUSSE, Olivier et al. Ca2+-induced exocytosis in individual human neutrophils: high- and low-affinity granule populations and submaximal responses. In: EMBO Journal, 1998, vol. 17, n° 5, p. 1279-1288. https://archive-ouverte.unige.ch/unige:7450

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Deposited on : 2010-06-21

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