THE CA2+-MOBILIZING ACTIONS OF A JURKAT CELL EXTRACT ON MAMMALIAN-CELLS XENOPUS-LAEVIS OOCYTES

Randriamampita and Tsien (Randriamampita, C., and Tsien, R. Y, (1993) Nature 364, 809-814) suggested that an acid-extracted fraction from a Jurkat cell line contains a messenger responsible for the coupling of calcium entry to the depletion of intracellular stores, i.e. capacitative calcium entry, We found that the extract, prepared as described by Randriamampita and Tsien, caused Ca2+ entry in 1321N1 astrocytoma cells which was not blocked by the D-myo-1,4,5-trisphosphate-receptor antagonist, heparin. In contrast to astrocytoma cells, when applied to mouse lacrimal acinar cells and rat hepatocytes the Jurkat extract always caused the release of intracellular Ca2+, followed by Ca2+ entry across the plasma membrane, This activity of the extract on lacrimal cells was blocked by either intracellular injection of heparin or extracellular atropine, Similarly prepared lacrimal cell extracts gave Ca2+ responses when applied to astrocytoma cells or lacrimal cells which were similar to Obese for Jurkat-derived extract, However, extracts from hepatocytes had no effect, In most Xenopus oocytes, the Jurkat extract had no effect, while in a few oocytes, the extract gave a [Ca2+](i) response similar to that seen in lacrimal cells, that is, release of Ca2+ followed by Ca2+ entry. We conclude that the actions of the Jurkat cell extract are not consistent with its containing the long sought messenger for capacitative calcium entry, It is Likely that this fraction contains a number of factors that mediate Ca2+ response in different cell types, possibly through receptor-mediated mechanisms.