Seagrave J, Oliver J M
Department of Pathology, University of New Mexico School of Medicine, Albuquerque 87131.
J Cell Physiol. 1990 Jul;144(1):128-36. doi: 10.1002/jcp.1041440117.
In mast cells, basophils, and the RBL-2H3 tumor mast cell model, crosslinking cell surface IgE-receptor complexes by multivalent ligands activates a signal transduction pathway that leads to the secretion of histamine, serotonin, and other inflammatory mediators. Receptor crosslinking in RBL-2H3 cells also changes cell surface morphology and increases F-actin assembly. Previously, Robertson et al. demonstrated that crosslinked IgE-receptor complexes become associated with the Triton X-100-insoluble fraction (the "cytoskeleton") of RBL-2H3 cells and raised the possibility that receptor-cytoskeletal association may be a required step in the stimulation of secretion. The studies reported here confirm by flow cytometry that crosslinking cell surface IgE by antigen induces the association of the crosslinked complexes with the detergent-insoluble fraction. Dose-response studies, also reported here, indicate that the detergent insolubility of the complexes does not correlate with secretion. Thus, secretion increases with antigen concentration to a maximum beyond which more antigen causes less, not more, secretion. There is little residual detergent-insoluble IgE at the concentrations of antigen that promote optimal secretion, whereas the association of IgE with the detergent-insoluble fraction is maximal at the high antigen concentrations that result in reduced secretion. The addition of monovalent hapten to reduce the amount of crosslinking caused by high concentrations of antigen increases secretion and simultaneously reduces the association of IgE with the detergent-insoluble fraction. Dihydrocytochalasin B, an inhibitor of antigen-stimulated actin polymerization, also increases the rate and extent of secretion and simultaneously delays the association of crosslinked IgE-receptor complexes with the detergent-insoluble fraction. From these data, we propose that the association of crosslinked IgE receptors with the detergent-insoluble fraction of RBL-2H3 cells increases with increased receptor crosslinking, is enhanced by antigen-induced actin polymerization, and is more likely related to the termination than the stimulation of secretion. The ligand-induced conversion of receptors to a detergent-insoluble form is not restricted to mast cells but occurs in a variety of cell types. Its general function may be to limit the generation or transmission of transmembrane signals.
在肥大细胞、嗜碱性粒细胞以及RBL - 2H3肿瘤肥大细胞模型中，多价配体交联细胞表面的IgE受体复合物会激活一条信号转导通路，该通路会导致组胺、5 - 羟色胺及其他炎症介质的分泌。RBL - 2H3细胞中的受体交联还会改变细胞表面形态并增加F - 肌动蛋白组装。此前，罗伯逊等人证明交联的IgE受体复合物会与RBL - 2H3细胞的Triton X - 100不溶性组分（“细胞骨架”）相关联，并提出受体 - 细胞骨架关联可能是刺激分泌过程中一个必要步骤的可能性。此处报道的研究通过流式细胞术证实，抗原交联细胞表面IgE会诱导交联复合物与去污剂不溶性组分相关联。此处也报道的剂量反应研究表明，复合物的去污剂不溶性与分泌并无关联。因此，分泌随着抗原浓度增加至最大值，超过该值后更多抗原会导致分泌减少而非增加。在促进最佳分泌的抗原浓度下，几乎没有残留的去污剂不溶性IgE，而在导致分泌减少的高抗原浓度下，IgE与去污剂不溶性组分的关联最大。添加单价半抗原以减少高浓度抗原引起的交联量会增加分泌，同时减少IgE与去污剂不溶性组分的关联。二氢细胞松弛素B，一种抗原刺激的肌动蛋白聚合抑制剂，也会增加分泌的速率和程度，同时延迟交联的IgE受体复合物与去污剂不溶性组分的关联。基于这些数据，我们提出交联的IgE受体与RBL - 2H3细胞去污剂不溶性组分的关联会随着受体交联增加而增加，会因抗原诱导的肌动蛋白聚合而增强，并且更可能与分泌的终止而非刺激相关。配体诱导受体转变为去污剂不溶性形式并不局限于肥大细胞，而是发生在多种细胞类型中。其一般功能可能是限制跨膜信号的产生或传递。
