ACTIVATED MUTANTS AS PROBES OF GM-CSF RECEPTOR FUNCTION

本研究旨在探讨粒细胞巨噬细胞集落刺激因子(GM-CSF)、白介素3(IL-3)和白介素5(IL-5)受体的功能。这些因子对髓系造血细胞有很强的增殖和分化作用。此外，自分泌GM-CSF的产生与一些白血病有关，IL-5与许多过敏反应有关，包括哮喘。GM-CSF、IL-3和IL-5的细胞表面受体是细胞因子受体家族的成员，由两个不同的亚基组成，即α和β。α亚基对每个因子都是独一无二的，而β亚基(Hbetac)则由三个因子共享。具体地说，建议利用hbetac的一组独特的成分活性突变体来检测功能性受体复合体的结构、组装、组成和活性。这些研究将测试一个模型，该模型预测hbetac可以形成具有不同性质的中间功能受体复合体。这项研究将通过以下方式进行：(I)检查活化的hbetac络合物的组成和结构，特别是那些包含hbetac的构成突变体的络合物。(Ii)确定阿尔法亚单位在受体激活中的作用。(Iii)研究与受体复合体相关的分子在激活和信号传递中的作用(Iv)研究EPOR的交叉激活的性质和作用(V)研究hbetac的脂质修饰及其对膜定位的影响。此外，还提出了新试剂(如：可产生与hbetac关键区域相互作用的单抗)，并可在没有细胞因子的情况下触发信号活动。

This project aims to investigate the function of the receptors for granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-3 (IL-3) and interleukin-5 (IL-5). These factors exert strong proliferative and differentiative effects on myeloid haemopoietic cells. Moreover, autocrine GM-CSF production has been implicated in some leukemias and IL-5 is involved in many allergic reactions, including asthma. The cell-surface receptors for GM-CSF, IL-3 and IL-5 are members of the cytokine receptor family and are comprised of two different subunits, alpha and beta. The alpha-subunit is unique to each factor while the beta- subunit (hbetac) is shared by the three factors. Specifically, it is proposed to utilise a unique set of constitutively active mutants of hbetac to examine the structure, assembly, composition and activity of the functional receptor complexes. These studies will test a model that predicts that hbetac can form intermediate, functional receptor complexes with distinct properties. This studies will be carried out by: (i) Examination of the composition and structure of activated hbetac complexes, in particular those comprising constitutive mutants of hbetac. (ii) Establishing the role of the alpha-subunit in receptor activation. (iii) Examination of the role, in activation and signalling, of molecules associated with the receptor complexes (iv) Examination of the nature and role of cross-activation of EpoR (v) Examination of lipid modification of hbetac and its effects on membrane localisation. In addition, it is proposed that novel reagents (eg. monoclonal antibodies) can be generated which interact with critical regions of hbetac and can trigger signalling activity in the absence of cytokine.