Abstract
Ca2+-dependent Cl– secretion in the respiratory tract occurs physiologically or under pathophysiological conditions when inflammatory mediators are released. The mechanism of intracellular Ca2+ release was investigated in the immortalized bronchial epithelial cell line 16HBE14o-. Experiments on both intact and permeabilized cells revealed that only inositol 1,4,5-trisphosphate (InsP 3) receptors and not ryanodine receptors are involved in intracellular Ca2+ release. The expression pattern of the three InsP 3 receptor isoforms was assessed both at the mRNA and at the protein level. The level of expression at the mRNA level was type 3 (92.5%) >> type 2 (5.4%) > type 1 (2.1%) and this rank order was also observed at the protein level. The ATP-induced Ca2+ signals in the intact cell, consisting of abortive Ca2+ spikes or fully developed [Ca2+] rises and intracellular Ca2+ waves, were indicative of positive feedback of Ca2+ on the InsP 3 receptors. Low Ca2+ concentrations stimulated and high Ca2+ concentrations inhibited InsP 3-induced Ca2+ release in permeabilized 16HBE14o- cells. We localized a cytosolic Ca2+-binding site between amino acid residues 2077 and 2101 in the type-2 InsP 3 receptor and between amino acids 2030 and 2050 in the type-3 InsP 3 receptor by expressing the respective parts of these receptors as glutathione S-transferase fusion proteins in bacteria. We conclude that the InsP 3 receptor isoforms expressed in 16HBE14o- cells (mainly type-3 and type-2) are stimulated by Ca2+ and that this phenomenon contributes to the ATP-induced Ca2+ signals in intact 16HBE14o- cells.
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Recieved: 11 September 1997 / Received after revision: 2 January 1998 / Accepted: 21 January 1998
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Sienaert, I., Huyghe, S., Parys, J. et al. ATP-induced Ca2+ signals in bronchial epithelial cells. Pflügers Arch 436, 40–48 (1998). https://doi.org/10.1007/s004240050602
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DOI: https://doi.org/10.1007/s004240050602