Hammacher A, Richardson R T, Layton J E, Smith D K, Angus L J, Hilton D J, Nicola N A, Wijdenes J, Simpson R J
Joint Protein Structure Laboratory, Ludwig Institute for Cancer Research (Melbourne Tumour Biology Branch) and The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.
J Biol Chem. 1998 Aug 28;273(35):22701-7. doi: 10.1074/jbc.273.35.22701.
The transmembrane protein gp130 is a shared component of the receptor complexes for the interleukin-6 (IL-6)-type cytokines, which include IL-6, leukemia inhibitory factor (LIF) and oncostatin M (OSM). In addition to its role in the generation of high affinity receptors, gp130 is required for signal transduction by these cytokines. In the present study we have examined the role of the N-terminal located, extracellular immunoglobulin (Ig)-like module of gp130 in signal transduction by IL-6 and LIF. We have expressed wild-type human gp130 or three mutants in murine myeloid M1-UR21 cells that lack functional endogenous gp130 but express the IL-6 receptor (IL-6R) and the LIF receptor (LIFR). By measuring cellular responses, such as morphological changes upon differentiation, soft agar colony formation, and induction of tyrosine phosphorylation of the signal transducer and activator of transcription, STAT3, we show that signaling by IL-6, but not LIF, is significantly reduced by mutations in the Ig-like module of gp130. However, the binding of 125I-labeled IL-6 or LIF is not affected by these mutations. We also present evidence that the Ig-like module forms part of the epitope of an anti-gp130 monoclonal antibody that neutralizes the bioactivity of IL-6, but not of LIF or OSM. The data suggest that gp130-activation by IL-6 and LIF requires different regions of gp130, that the Ig-like module of gp130 may be required for IL-6-induced gp130 dimerization, and that the stoichiometry of the high affinity IL-6 receptor-complex differs from those of the receptor-complexes for LIF and OSM.
跨膜蛋白gp130是白细胞介素-6（IL-6）型细胞因子受体复合物的共同组成部分，这些细胞因子包括IL-6、白血病抑制因子（LIF）和抑瘤素M（OSM）。除了在高亲和力受体生成中的作用外，gp130也是这些细胞因子信号转导所必需的。在本研究中，我们研究了gp130位于N端的细胞外免疫球蛋白（Ig）样模块在IL-6和LIF信号转导中的作用。我们在缺乏功能性内源性gp130但表达IL-6受体（IL-6R）和LIF受体（LIFR）的小鼠髓样M1-UR21细胞中表达了野生型人gp130或三种突变体。通过测量细胞反应，如分化时的形态变化、软琼脂集落形成以及信号转导和转录激活因子STAT3的酪氨酸磷酸化诱导，我们发现gp130的Ig样模块中的突变会显著降低IL-6而非LIF的信号转导。然而，这些突变并不影响125I标记的IL-6或LIF的结合。我们还提供证据表明，Ig样模块构成了一种抗gp130单克隆抗体表位的一部分，该抗体可中和IL-6的生物活性，但不能中和LIF或OSM的生物活性。数据表明，IL-6和LIF激活gp130需要gp130的不同区域，gp130的Ig样模块可能是IL-6诱导gp130二聚化所必需的，并且高亲和力IL-6受体复合物的化学计量与LIF和OSM的受体复合物不同。
