Piau J P, Wakasugi H, Bertoglio J, Tursz T, Fradelizi D, Gacon G
Unité de Recherche en Pathologie Moléculaire, U15 INSERM, Paris, France.
Eur J Biochem. 1989 Nov 6;185(2):455-9. doi: 10.1111/j.1432-1033.1989.tb15136.x.
Interleukin 2 is a growth factor secreted by T lymphocytes upon antigenic stimulation and inducing the proliferation of T cells bearing at their surface the heterodimeric high-affinity form of its receptor. No enzymatic function has so far been demonstrated in the receptor subunits. In an attempt to elucidate the biochemical pathway of signal transduction, we investigated the capacity of interleukin 2 to modulate tyrosine phosphorylation in T cell membranes. Membrane-rich fractions from T cells were tested for their ability to phosphorylate tyrosine in the presence or absence of added recombinant interleukin 2. Using as substrate a synthetic polymer of glutamic acid and tyrosine, we demonstrated a 3-4-fold stimulation of tyrosine phosphorylation in the presence of interleukin 2; this stimulating effect appeared to be well correlated with interleukin 2 function since (a) it was not observed in insensitive cells, (b) it required the presence of the high-affinity form of the receptor and (c) it was dose-dependent. Confirmatory results were obtained by phosphorylating membrane-rich fractions with [gamma-32P]ATP and by analysing the resulting phosphoproteins: only in fractions from cells with the high-affinity form of the receptor were several membrane proteins specifically phosphorylated on tyrosine residues in response to interleukin 2. At least two proteins of 115 and 58 kDa were consistently hyperphosphorylated on tyrosine in an interleukin-2-dependent manner. This stimulation was strongly dependent on the presence of the protein tyrosine phosphatase inhibitor, sodium orthovanadate. Thus, we propose that interleukin 2 enhances tyrosine phosphorylation by stimulating a tyrosine kinase activity. The nature of the enzyme involved remains to be determined.
白细胞介素2是一种由T淋巴细胞在抗原刺激下分泌的生长因子，可诱导其表面带有异二聚体高亲和力形式受体的T细胞增殖。迄今为止，在受体亚基中尚未证明有酶促功能。为了阐明信号转导的生化途径，我们研究了白细胞介素2调节T细胞膜中酪氨酸磷酸化的能力。测试了来自T细胞的富含膜的组分在添加或不添加重组白细胞介素2的情况下磷酸化酪氨酸的能力。使用谷氨酸和酪氨酸的合成聚合物作为底物，我们证明在白细胞介素2存在下酪氨酸磷酸化有3至4倍的刺激作用；这种刺激作用似乎与白细胞介素2的功能密切相关，因为（a）在不敏感细胞中未观察到，（b）它需要高亲和力形式的受体存在，并且（c）它是剂量依赖性的。通过用[γ-32P]ATP使富含膜的组分磷酸化并分析所得的磷蛋白获得了证实性结果：只有来自具有高亲和力形式受体的细胞的组分中，几种膜蛋白才会响应白细胞介素2在酪氨酸残基上特异性磷酸化。至少有两种115 kDa和58 kDa的蛋白质始终以白细胞介素2依赖性方式在酪氨酸上过度磷酸化。这种刺激强烈依赖于蛋白质酪氨酸磷酸酶抑制剂原钒酸钠的存在。因此，我们提出白细胞介素2通过刺激酪氨酸激酶活性来增强酪氨酸磷酸化。所涉及的酶的性质仍有待确定。
