Uzé G, Di Marco S, Mouchel-Vielh E, Monneron D, Bandu M T, Horisberger M A, Dorques A, Lutfalla G, Mogensen K E
Institut de Génétique Moléculaire, CNRS UMR 9942, Montpellier, France.
J Mol Biol. 1994 Oct 21;243(2):245-57. doi: 10.1006/jmbi.1994.1651.
We describe how constraints on the binding of human interferons (IFNs), alpha1 and alpha2 and alpha8 on mouse cells are partially relieved by the expression of the bovine (Bo) or human (Hu) IFN alpha/beta receptor (IFNAR) component in these cells. We show that, while the binding of all three is substantially increased by the transfection of Bo IFNAR, it is accompanied by an increase in activity only in the case of alpha2 and alpha8 (IFNs that otherwise have little activity on mouse cells). IFN alpha1, which shows some partial activity on mouse cells, responds to the presence of Bo IFNAR by acting, at low concentrations, as a competitive antagonist to IFNs alpha2 and alpha8. A review of published results on IFN hybrid scanning and on the effects of expressing Bo IFNAR in human cells led us to propose that an N-terminal segment of the IFN molecule interacts directly with IFNAR. Applying site-directed mutagenesis to an IFN hybrid; alpha8[60]alpha1[92]alpha8, we show that the point mutations K84 to E84 and Y90 to D90 act synergistically to cause the hybrid to behave as the parental IFN alpha8, switching the preference from Mu to Hu IFNAR in transfected mouse cells. The published structural models for IFN reveal that positions 84 and 90 span the exposed residues of the alpha-helix C of the IFN molecule. We derive a model of IFN-receptor interaction in which the A helix and the C helix of IFN interact with IFNAR and in which a binding phase can be distinguished from a binding/activity phase. We propose that the so-called "hot" domains of the IFN molecule (the AB loop and the D helix) are presented by IFNAR to interact with an additional component of the functional receptor.
我们描述了在小鼠细胞中表达牛（Bo）或人（Hu）干扰素α/β受体（IFNAR）成分如何部分缓解人干扰素（IFN）α1、α2和α8与小鼠细胞结合的限制。我们发现，虽然转染Bo IFNAR后所有三种干扰素的结合都显著增加，但只有α2和α8（原本对小鼠细胞活性很小的干扰素）的活性随之增加。对小鼠细胞有部分活性的IFNα1，在低浓度时作为IFNα2和α8的竞争性拮抗剂，对Bo IFNAR的存在作出反应。对已发表的关于干扰素杂交扫描以及在人细胞中表达Bo IFNAR的影响的结果进行综述后，我们提出干扰素分子的N端片段直接与IFNAR相互作用。对一种干扰素杂交体α8[60]α1[92]α8进行定点诱变，我们发现K84突变为E84以及Y90突变为D90的点突变协同作用，使杂交体表现得如同亲本干扰素α8，在转染的小鼠细胞中改变了对鼠源与人类IFNAR的偏好。已发表的干扰素结构模型表明，84位和90位跨越干扰素分子α螺旋C的暴露残基。我们推导了一个干扰素 - 受体相互作用模型，其中干扰素的A螺旋和C螺旋与IFNAR相互作用，并且可以区分结合阶段和结合/活性阶段。我们提出，干扰素分子所谓的“热点”区域（AB环和D螺旋）由IFNAR呈现，以与功能性受体的另一个成分相互作用。
