Association of the crosslinked IgE receptor with the membrane skeleton is independent of the known signaling mechanisms in rat basophilic leukemia cells.

Abstract

Crosslinking of the IgE receptor on the surface of rat basophilic leukemia (RBL) cells by multivalent antigen induces an association of these receptors with the detergent-insoluble membrane skeleton. Detergent insolubility of the receptor can also be induced on purified plasma membranes isolated from RBL cells by the use of either IgE oligomers or IgE monomers plus multivalent antigen. The critical event in initiating this interaction between the receptor and the membrane skeleton is crosslinking of the receptor. This association is rapid, and, when triggered by multivalent antigen, it is quickly reversed by the addition of excess monovalent antigen. The fact that this association occurs with the use of purified plasma membranes indicates that all of the components necessary for this interaction are present in the plasma membrane and that intracellular components are not required.Although crosslinking of the receptor activates phospholipase C and phospholipase A2 leading to the generation of several second messengers, none of these signaling mechanisms appears to be involved in IgE receptor interaction with the membrane skeleton. This interaction cannot be induced by phorbol 12-myristate 13-acetate (PMA), ionomycin, or a combination of these two reagents, although this will result in degranulation. Furthermore, receptor detergent insolubility is temperature independent when triggered by multivalent antigen, thus indicating that enzyme-catalyzed reactions are not important. This was verified by the fact that a variety of inhibitors that block phosphatidylinositol metabolism, arachidonic acid metabolism, Ca2l influx, and protein kinase C (PKC) activation had no effect on antigen-induced association of the receptor with the membrane skeleton. These results indicate that the signaling mechanisms leading to the degranulation response are not involved in the association of the crosslinked receptor with the membrane skeleton.

Interaction of aggregated native and mutant IgE receptors with the cellular skeleton.

“…USA 89 (1992) the P815 cells synthesize endogenously (16). That the aggregated receptors were efficiently insolubilized in these transfectants is consistent with other data that show that the aggregation that leads to insolubilization is independent of, and might even suppress, cellular activation (5,19,28). Our data that aggregated receptors on COS cells are efficiently insolubilized are also confirmatory, since there is no evidence that these cells are activated by transfected FcERI (L. Miller, C. Fewtrell, G.A., C. Jelsema, and H.M., unpublished data).…”

“…Insolubilization shows a lesser dependence on temperature than does internalization (5,19,28) and is relatively insensitive to cytochalasins (20). Furthermore, in the cells we examined, if anything, insolubilization was more prominent in the COS cells (Fig.…”

A transient rise in intracellular Ca2+ is a precursor reaction to the zona pellucida‐induced acrosome reaction in mouse sperm and is blocked by the induced acrosome reaction inhibitor 3‐quinuclidinyl benzilate

“…A similar set of intracellular signal transducing mediators is found in other cells manifesting ligand-induced exocytosis of intracellular granules, in particular, mast cells and basophils, and, in this exocytotic reaction, a transient increase in intracellular Ca2+ is observed (Penner, 1988;Koopman and Jackson, 1990;Benhamou et al, 1990). It is of interest that, in these cells, the signal pathways initiated by ligand-induced receptor aggregation with consequent activation of tyrosine kinase (TK) activity and those activated by Ca2+ influx intersect at effector levels at considerable remove "downstream" from the ligand-induced stimuli (Penner, 1988;Benhamou et al, 1990;Apgar, 1991). Roldan andHarrison (1989, 1990a,b) have reported that Ca2+ influx induced by the ionophore A23187 can trigger polyphosphoinositide breakdown in sperm from ram, boar, mouse, human, and guinea pig and that this reaction occurs under conditions in which acrosomal exocytosis is effected by ionophore treatment.…”