Burchmore R J, Landfear S M
Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, Portland, Oregon 97201, USA.
J Biol Chem. 1998 Oct 30;273(44):29118-26. doi: 10.1074/jbc.273.44.29118.
We have studied the structure and expression of glucose transporter genes in the parasitic protozoan Leishmania mexicana. Three distinct glucose transporter isoforms, LmGT1, LmGT2, and LmGT3, are encoded by single copy genes that are clustered together at a single locus. Quantitation of Northern blots reveals that LmGT2 mRNA is present at approximately 15-fold higher level in promastigotes, the insect stage of the parasite life cycle, compared with amastigotes, the intracellular stage of the life cycle that lives within the mammalian host. In contrast, LmGT1 and LmGT3 mRNAs are expressed at similar levels in both life cycle stages. Transcription of the LmGT genes in promastigotes and axenically cultured amastigotes occurs at similar levels, as measured by nuclear run-on transcription. Consequently, the approximately 15-fold up-regulation of LmGT2 mRNA levels in promastigotes compared with amastigotes must be controlled at the post-transcriptional level. Measurement of LmGT2 RNA decay in promastigotes and axenic amastigotes treated with actinomycin D suggests that differential mRNA stability may play a role in regulating glucose transporter mRNA levels in the two life cycle stages.
我们研究了寄生原生动物墨西哥利什曼原虫中葡萄糖转运蛋白基因的结构和表达。三种不同的葡萄糖转运蛋白异构体，即LmGT1、LmGT2和LmGT3，由单拷贝基因编码，这些基因在单个位点聚集在一起。Northern印迹定量分析表明，与无鞭毛体（寄生虫生命周期的细胞内阶段，存在于哺乳动物宿主内）相比，LmGT2 mRNA在前鞭毛体（寄生虫生命周期的昆虫阶段）中的含量大约高15倍。相比之下，LmGT1和LmGT3 mRNA在两个生命周期阶段的表达水平相似。通过核延伸转录测量，前鞭毛体和体外培养的无鞭毛体中LmGT基因的转录水平相似。因此，与无鞭毛体相比，前鞭毛体中LmGT2 mRNA水平大约15倍的上调必定是在转录后水平受到调控。用放线菌素D处理前鞭毛体和体外培养的无鞭毛体后对LmGT2 RNA降解的测量表明，mRNA稳定性差异可能在调节两个生命周期阶段的葡萄糖转运蛋白mRNA水平中发挥作用。
