Sugamura K, Takeshita T, Asao H, Kumaki S, Ohbo K, Ohtani K, Nakamura M
Department of Microbiology, Tohoku University School of Medicine, Sendai, Japan.
Lymphokine Res. 1990 Winter;9(4):539-42.
We previously established a monoclonal antibody, TU11 mAb, which is specific for human IL-2 receptor (IL-2R) beta chain (p75) and does not inhibit IL-2-binding to IL-2R beta. Using TU11 mAb, we first demonstrated the existence of a third component, p64, of IL-2R, tentatively named the gamma chain of IL-2R. TU11 mAb precipitated not only the beta chain but also the alpha and gamma chains in the lysates of cells bearing the high-affinity IL-2R in the presence of IL-2 without any chemical crosslinker. The gamma chain was also detected in lymphoid MOLT alpha beta and MOLT beta cells, which were stably transfected with both alpha and beta cDNA, and with beta cDNA alone, respectively, but not in fibroblastoid COS alpha beta and COS beta cells, which were stably transfected with both alpha and beta cDNA, and with beta cDNA alone, respectively. Furthermore, IL-2-mediated growth signals were transduced in the lymphoid transfectant cells but not in the fibroblastoid transfectant cells, suggesting the possibility that the gamma chain along with the beta chain has an essential role in the transduction of IL-2-mediated growth signals. Using TU11 mAb, we secondly demonstrated that IL-2 rapidly induces tyrosine phosphorylation of both the beta and gamma chains in an IL-2-dose-dependent manner. The tyrosine phosphorylation of beta and gamma chains were also detected in the lymphoid transfectant cells but not in the fibroblastoid transfectant cells, indicating the correlation between tyrosine kinase activation and IL-2-mediated growth signaling. The beta chain was phosphorylated in in vitro on serine, threonine and tyrosine residues, but the gamma chain was phosphorylated in in vitro predominantly on tyrosine residues, suggesting the possibility that the gamma chain itself is a tyrosine kinase molecule.
我们先前制备了一种单克隆抗体TU11 mAb，它对人白细胞介素2受体（IL-2R）β链（p75）具有特异性，且不抑制IL-2与IL-2Rβ的结合。利用TU11 mAb，我们首次证实了IL-2R存在第三种成分p64，暂命名为IL-2R的γ链。在没有任何化学交联剂的情况下，TU11 mAb在有IL-2存在时，能沉淀出携带高亲和力IL-2R的细胞裂解物中的β链，以及α链和γ链。在分别稳定转染了α和β cDNA以及仅转染了β cDNA的淋巴样MOLTαβ和MOLTβ细胞中也检测到了γ链，但在分别稳定转染了α和β cDNA以及仅转染了β cDNA的成纤维细胞样COSαβ和COSβ细胞中未检测到。此外，IL-2介导的生长信号在淋巴样转染细胞中得以转导，但在成纤维细胞样转染细胞中未转导，这表明γ链与β链一起在IL-2介导的生长信号转导中可能起着重要作用。利用TU11 mAb，我们其次证明了IL-2以IL-2剂量依赖性方式快速诱导β链和γ链的酪氨酸磷酸化。在淋巴样转染细胞中也检测到了β链和γ链的酪氨酸磷酸化，但在成纤维细胞样转染细胞中未检测到，这表明酪氨酸激酶激活与IL-2介导的生长信号传导之间存在相关性。β链在体外丝氨酸、苏氨酸和酪氨酸残基上发生磷酸化，但γ链在体外主要在酪氨酸残基上发生磷酸化，这表明γ链本身可能是一种酪氨酸激酶分子。
