Characterization of secretory mechanisms in α-toxin-permeabilized rat basophilic leukemia (RBL-2H3) cells

• Published in: Japanese Journal of Pharmacology 1992, Vol.58 (suppl.1), p.327-327
• Main Authors: Tomoyuki Uekusa, Youichi Fukuda, Hisao Ikeya, Masaatsu K. Uchida, Kazuhiko Oishi
• Format: Article
• Language: Japanese
• ISSN: 0021-5198

RBL-2H3 cells secrete inflammatory mediators such as histamine by aggregation of IgE receptors. The cells prelabeled with 「^^14 C」-serotonin and sensitized with anti-DNP IgE were permeabilized by Staphylococcal α-toxin, which forms small pores of 2-3 nm in plasma membrane. Cross-linking IgE receptors with DNP-HSA induced 「^^14 C」-serotonin release from the permeabilized cells in a Ca^2+ -dependent manner. Ca^2+ and/or GTPγS did not cause secretion without cross-linking IgE receptors, indicating that the stimulation of IgE receptors is essential for the receptor-coupled secretion in the α-toxin-permeabilized cells. Next, the cells were permeabilized by streptolysin-Ο, which forms large pores of 10 nm in plasma membrane. In this case, GTPγS induced 「^^14 C」-serotonin release in a Ca^2+ -dependent manner, although Ca^2+ alone had no effect. These results suggest that the mechanisms, which block the stimulus-secretion coupling unless IgE receptors are stimulated, exist in α-toxin-permeabilized RBL-2H3 cells. The leaked proteins from streptolysin-Ο-formed pores were concentrated and subjected to gel filtration. The activities to inhibit GTPγS-induced release from the streptolysin-Ο-permeabilized cells were found in the fractions which were eluted through Superose 12 column. The cytosolic proteins which leak out through the streptolysin-Ο-formed pores are possibly contributed to the inhibitory mechanisms.