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Citation Information: J Clin Invest. 1985;76(1):303-310. https://doi.org/10.1172/JCI111961.
Abstract
Regulation of the cytosolic free calcium concentration is important to neutrophil function. In these studies, an ATP-dependent calcium uptake pump has been identified in human neutrophil lysosomes. This energy-dependent Ca++ uptake pump has a high affinity for Ca++ (Michaelis constant [Km] Ca++ = 107 nM) and a maximum velocity (Vmax) of 5.3 pmol/mg of protein per min. ATP was the only nucleotide that supported Ca++ uptake by lysosomes. The Km for ATP was 177 microM. ATP-dependent Ca++ uptake by neutrophil lysosomes was temperature- and pH-sensitive with optimal Ca++ pump activity at 37 degrees C and pH 7.0-7.5. Mg++ was also essential for ATP-dependent Ca++ uptake by lysosomes. Azide and antimycin A had no effect on the energy-dependent uptake of Ca++ by neutrophil lysosomes. The chemotactic peptide formyl-methionyl-leucyl-phenylalanine inhibited ATP-dependent Ca++ accumulation by isolated lysosomes. Butoxycarbonyl-phenylalanine-leucine-phenylalanine-leucine-phenylalanine , a competitive antagonist of the chemotactic peptide, blocked this inhibitory effect. These studies demonstrate the presence of an ATP-dependent Ca++ uptake pump in human neutrophil lysosomes that functions at physiologic intracellular concentrations of Ca++, ATP, and H+ and may be important to regulating neutrophil function by modulating cytosolic Ca++.
Authors
M S Klemper
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