Wagner K, Kafert-Kasting S, Heil G, Ganser A, Eder M
Department of Hematology and Oncology, Hannover Medical School, and the Center for Cell Therapy/Cytonet, Hannover, Germany.
Blood. 2001 Nov 1;98(9):2689-96. doi: 10.1182/blood.v98.9.2689.
The receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 are composed of a ligand-specific alpha-chain (eg, alpha-GM-CSF receptor [alpha-GMR]) and a common beta-subunit (beta-GMR). Ligand binding is believed to induce assembly or conformational changes in preformed complexes containing more than one alpha- and beta-subunit in the activated receptor complex. To analyze the function of a splice variant of beta-GMR with a truncation in the intracellular domain (beta-GMR(IT)), BaF-3 cells expressing human alpha-GMR plus beta-GMR were transfected with beta-GMR(IT). In these cells, coexpression of beta-GMR(IT) inhibits GM-CSF-mediated survival and proliferation in a GM-CSF concentration-dependent manner. To analyze the effect of cytoplasmic assembly of truncated and full-length intracellular beta-GMR sequences, beta-GMR and beta-GMR(IT) were coexpressed with different chimeric alpha/beta-GMR constructs. Whereas both beta-GMR and beta-GMR(IT) generate high-affinity GMR complexes in the presence of alpha/beta-GMR, beta-GMR(IT) inhibits while beta-GMR supports proliferation and cell survival mediated by alpha/beta-GMR. Correspondingly, beta-GMR, but not beta-GMR(IT), generates functional GMR complexes when coexpressed with a defective alpha/beta-GMR construct. These data indicate that beta-GMR(IT) can inhibit survival and mitogenic signaling of the wild-type GMR and demonstrate that recruitment of alternatively spliced receptor subunits may regulate the function of heteromeric cytokine receptors.
人粒细胞-巨噬细胞集落刺激因子（GM-CSF）、白细胞介素-3（IL-3）和IL-5的受体由配体特异性α链（如α-GM-CSF受体[α-GMR]）和共同的β亚基（β-GMR）组成。据信配体结合会诱导活化受体复合物中包含多个α和β亚基的预形成复合物发生组装或构象变化。为了分析细胞内结构域截短的β-GMR剪接变体（β-GMR(IT)）的功能，将表达人α-GMR加β-GMR的BaF-3细胞用β-GMR(IT)转染。在这些细胞中，β-GMR(IT)的共表达以GM-CSF浓度依赖的方式抑制GM-CSF介导的存活和增殖。为了分析截短的和全长细胞内β-GMR序列的细胞质组装的影响，将β-GMR和β-GMR(IT)与不同的嵌合α/β-GMR构建体共表达。虽然在存在α/β-GMR的情况下，β-GMR和β-GMR(IT)都能产生高亲和力的GMR复合物，但β-GMR(IT)抑制而β-GMR支持由α/β-GMR介导的增殖和细胞存活。相应地，当与有缺陷的α/β-GMR构建体共表达时，β-GMR能产生功能性GMR复合物，而β-GMR(IT)则不能。这些数据表明β-GMR(IT)可以抑制野生型GMR的存活和促有丝分裂信号，并证明选择性剪接受体亚基的募集可能调节异源细胞因子受体的功能。
