ACTIVATED MUTANTS AS PROBES OF GM-CSF RECEPTOR FUNCTION

本课题旨在研究粒细胞-巨噬细胞集落刺激因子（GM-CSF）、白细胞介素-3（IL-3）和白细胞介素-5（IL-5）受体的功能。 这些因子对髓系造血细胞产生强烈的增殖和分化作用。 此外，自分泌GM-CSF的产生与某些白血病有关，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，并且由两个不同的亚基α和β组成。 α-亚基对于每个因子是独特的，而β-亚基（hbetac）由三个因子共享。 具体而言，建议利用一组独特的hbetac组成型活性突变体来检查功能性受体复合物的结构、组装、组成和活性。 这些研究将测试一个模型，该模型预测hbetac可以形成具有不同特性的中间功能受体复合物。 （i）检查活化的hbetac复合物的组成和结构，特别是包含hbetac的组成型突变体的那些。(ii)确定α-亚基在受体活化中的作用。(iii)检查与受体复合物相关的分子在激活和信号传导中的作用（iv）检查EpoR交叉激活的性质和作用（v）检查hbetac的脂质修饰及其对膜定位的影响。此外，还提出了新的试剂（例如，单克隆抗体），其可与HBetac的关键区域相互作用，并可在细胞因子不存在的情况下触发信号传导活性。

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.