Department of Biology, University of Osnabrück, Barbarastr. 11, 49076 Osnabrück, Germany.
Howard Hughes Medical Institute, Stanford University School of Medicine, 279 Campus Drive, Stanford, California 94305-5345, USA.
Nat Commun. 2017 Jul 14;8:15976. doi: 10.1038/ncomms15976.
The spatiotemporal organization of cytokine receptors in the plasma membrane is still debated with models ranging from ligand-independent receptor pre-dimerization to ligand-induced receptor dimerization occurring only after receptor uptake into endosomes. Here, we explore the molecular and cellular determinants governing the assembly of the type II interleukin-4 receptor, taking advantage of various agonists binding the receptor subunits with different affinities and rate constants. Quantitative kinetic studies using artificial membranes confirm that receptor dimerization is governed by the two-dimensional ligand-receptor interactions and identify a critical role of the transmembrane domain in receptor dimerization. Single molecule localization microscopy at physiological cell surface expression levels, however, reveals efficient ligand-induced receptor dimerization by all ligands, largely independent of receptor binding affinities, in line with the similar STAT6 activation potencies observed for all IL-4 variants. Detailed spatiotemporal analyses suggest that kinetic trapping of receptor dimers in actin-dependent microcompartments sustains robust receptor dimerization and signalling.
细胞因子受体在质膜中的时空组织仍存在争议，模型范围从配体非依赖性受体预二聚化到配体诱导的受体二聚化，仅发生在受体被内吞体摄取之后。在这里，我们利用各种与受体亚基结合具有不同亲和力和速率常数的激动剂，探索了控制 II 型白细胞介素-4 受体组装的分子和细胞决定因素。使用人工膜进行的定量动力学研究证实，受体二聚化受二维配体-受体相互作用的控制，并确定跨膜结构域在受体二聚化中的关键作用。然而，在生理细胞表面表达水平的单分子定位显微镜下，所有配体都能有效地诱导受体二聚化，这在很大程度上与所有 IL-4 变体观察到的相似 STAT6 激活效力一致，而不依赖于受体结合亲和力。详细的时空分析表明，肌动蛋白依赖性微区中受体二聚体的动力学捕获维持了强大的受体二聚化和信号转导。
