Identification of variants of the basophilic leukemia (RBL-2H3) cells that have defective phosphoinositide responses to antigen and stimulants of guanosine 5'-triphosphate-regulatory proteins.

Antigen immunoglobulin E-mediated secretion of histamine from RBL-2H3 cells is associated with substantial hydrolysis of membrane inositol phospholipids and a rise in the concentration of cytosol Ca2+ (calcium signal). Such responses differed among cloned variant lines of the RBL-2H3 cell line from undetectable (1A3 bromodeoxyuridine-resistant (BUDRR), 2B1 BUDRR, and 1B3 BUDRR lines) to about 80% of those in the parent RBL-2H3 cells. In all but one line (1B3 thioguanine-resistant (TgR)), the intensities of the phosphoinositide response and of the calcium signal were correlated with the secretory response. The 1B3 TgR line had no detectable calcium signal (as measured by quin 2 fluorescence or uptake of 45Ca2+) but paradoxically showed modest rates of hydrolysis of inositol phospholipids and of secretion. The responses of the 1B3 TgR line were, however, dependent on the presence of external Ca2+ ions. The induction of secretion with antigen, therefore, was invariably associated with the hydrolysis of inositol phospholipids, but it was not necessarily associated with a change in concentration of cytosol Ca2+. All antigen unresponsive clones could secrete when synergistic signals were induced by exposure to the Ca2+ -ionophore, A23187 and the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate. These lines, otherwise, had immunoglobulin E receptors and had no obvious defect in their capacity to synthesize the inositol phospholipids or in their phenotypic expression of phospholipase C as measured in cell extracts. One finding of possible relevance to the role of guanosine 5'-triphosphate-regulatory proteins in the activation of phospholipase C was the inability of one antigen-nonresponsive line to respond to NaF (in intact cells) or to guanosine 5'-(3-O-thio)triphosphate (in electrically permeabilized cells).