Receptor-mediated signalings-regulating proliferation, differentiation and neoplastic transformation of hematopoietic cells

C-kit受体酪氨酸激酶(KIT)及其配体干细胞因子(SCF)在造血细胞中传递重要信号。我们发现了两个点突变，即膜旁区域的Val559→Gly(G559)突变和KIT区域的Asp814→Val(V814)突变，导致KIT的结构性和致癌性激活。为了确定在没有SCF的情况下，哪部分突变试剂盒是受体二聚或自结合所必需的，我们构建了一系列KIT的缺失和嵌合突变体，包括胞外区截断型KIT和嵌合型KIT，其中胞外区和跨膜区被src肉豆蔻化信号肽取代。通过使用依赖于IL-3的小鼠BA/F3细胞，我们接受了不同的c-KIT基因的转染，我们发现，在KIT的膜旁和激酶结构域的成分激活突变可能不一定需要它们的胞外和跨膜…除了SCF/KIT系统外，促血小板生成素(TPO)/c-MPL系统在造血过程中也发挥着重要作用。为了阐明TPO诱导F-36p细胞增殖和分化的机制，我们将c-MPL导入人IL-3依赖的F-36p细胞。F-36P-MPL细胞在TPO刺激下增殖分化为成熟巨核细胞。利用显性-阴性(DN)形式的STATs和ras，我们认为TPO诱导的增殖可能是通过激活STAT5和ras介导的，而延长ras的激活可能参与了TPO诱导的巨核细胞分化。此外，我们发现，在造血细胞依赖细胞因子的生长过程中，除了ras信号外，STAT5似乎还介导了细胞周期蛋白D1的转录调控。较少

The c-kit receptor tyrosine kinase (KIT) and its ligand, stem cell factor (SCF) transduce crucial signals in hematopoietic cells. We revealed that two point mutations, Val559→Gly (G559) mutation in the juxtamembrane domain and Asp814→Val (V814) mutation in the kinase domain, lead to constitutive and oncogenic activation of KIT. In order to determine as to which portion of mutant KITs is indispensable for receptor dimerization or self-association in the absence of SCF, we have constructed a series of deletion and chimeric mutants of KIT, including the extracellular domain truncated type KIT and chimeric type KIT in which extracellular and transmembrane domains are replaced by src myristylation signal peptide. By using murine interleukin (IL)-3-dependent Ba/F3 cells that were subjected to transfection of various c-kit genes, we showed that the constituvely activating mutations at both the juxtamembrane and kinase domains of KIT may not necessarily require their extracellular and transmem … More brane domains for their formation of receptor self-association, and that the receptor self-association of mutant KIT may be important for activation of downstream effectors that are required for factor-independent growth and tumorigenicity.In addition to the SCF/KIT system, thrombopoietin (TPO)/c-mpl system also plays a fundamental role in hematopoiesis. In an effort to clarify the mechanisms of TPO-induced proliferation and differentiation, c-mpl was introduced into human IL-3-dependent F-36P cells. F-36P-mpl cells were found to proliferate and differentiate at a high rate into mature megakaryocytes in response to TPO. By using dominant-negative (dn) forms of STATs and ras, it was suggested that TPO-induced proliferation may be mediated through activation of STAT5 and ras, and that prolonged ras activation may be involved in TPO-induced megakaryocytic differentiation. Furthermore, we found that STAT5, in addition to ras signaling, appeared to mediate transcriptional regulation of cyclin D1 during cytokine-dependent growth in hematopoietic cells. Less