DIFFERENTIAL REGULATION OF MULTIPLE GLUCOSE-TRANSPORTER GENES IN LEISHMANIA-MEXICANA

We have studied the structure and expression of glucose transporter ge nes in the parasitic protozoan Leishmania mexicana. Three distinct glu cose transporter isoforms, LmGT1, LmGT2, and LmGT3, are encoded by sin gle copy genes that are clustered together at a single locus. Quantita tion of Northern blots reveals that LmGT2 mRNA is present at similar t o 15-fold higher level in promastigotes, the insect stage of the paras ite life cycle, compared with amastigotes, the intracellular stage of the life cycle that lives within the mammalian host. In contrast, LmGT 1 and LmGT3 mRNAs are expressed at similar levels in both life cycle s tages. Transcription of the LmGT genes in promastigotes and axenically cultured amastigotes occurs at similar levels, as measured by nuclear run-on transcription. Consequently, the similar to 15-fold up-regulat ion of LmGT2 mRNA levels in promastigotes compared with amastigotes mu st be controlled at the post-transcriptional level. Measurement of LmG T2 RNA decay in promastigotes and axenic amastigotes treated with acti nomycin D suggests that differential mRNA stability may play a role in regulating glucose transporter mRNA levels in the two life cycle stag es.