Skoda R C, Seldin D C, Chiang M K, Peichel C L, Vogt T F, Leder P
Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115.
EMBO J. 1993 Jul;12(7):2645-53. doi: 10.1002/j.1460-2075.1993.tb05925.x.
The murine myeloproliferative leukemia virus has previously been shown to contain a fragment of the coding region of the c-mpl gene, a member of the cytokine receptor superfamily. We have isolated cDNA and genomic clones encoding murine c-mpl and localized the c-mpl gene to mouse chromosome 4. Since some members of this superfamily function by transducing a proliferative signal and since the putative ligand of mpl is unknown, we have generated a chimeric receptor to test the functional potential of mpl. The chimera consists of the extracellular domain of the human interleukin-4 receptor and the cytoplasmic domain of mpl. A mouse hematopoietic cell line transfected with this construct proliferates in response to human interleukin-4, thereby demonstrating that the cytoplasmic domain of mpl contains all elements necessary to transmit a growth stimulatory signal. In addition, we show that 25-40% of mpl mRNA found in the spleen corresponds to a novel truncated and potentially soluble isoform of mpl and that both full-length and truncated forms of mpl protein can be immunoprecipitated from lysates of transfected COS cells. Interestingly, however, although the truncated form of the receptor possesses a functional signal sequence and lacks a transmembrane domain, it is not detected in the culture media of transfected cells.
鼠骨髓增殖性白血病病毒先前已被证明含有细胞因子受体超家族成员c-mpl基因编码区的一个片段。我们分离了编码鼠c-mpl的cDNA和基因组克隆，并将c-mpl基因定位到小鼠4号染色体上。由于该超家族的一些成员通过转导增殖信号发挥作用，且mpl的假定配体未知，我们构建了一个嵌合受体来测试mpl的功能潜力。该嵌合体由人白细胞介素-4受体的胞外结构域和mpl的胞质结构域组成。用该构建体转染的小鼠造血细胞系在人白细胞介素-4刺激下增殖，从而证明mpl的胞质结构域包含传递生长刺激信号所需的所有元件。此外，我们发现脾脏中25%-40%的mpl mRNA对应于一种新的截短且可能可溶的mpl异构体，并且全长和截短形式的mpl蛋白都可以从转染的COS细胞裂解物中免疫沉淀出来。然而，有趣的是，尽管受体的截短形式具有功能性信号序列且缺乏跨膜结构域，但在转染细胞的培养基中未检测到它。
