The effect of tunicamycin on Leishmania brasiliensis. Glycosylation and the cell surface components

Culture conditions of Leishmania cells were developed to allow the study of the effect of tunicamycin (TM) on glycosylation and on the cell surface components. Leishmania incorporate [14C]-mannose and [35S]-methionine in vitro. The incorporation of [14C]-mannose is linear for 150 min and is inhibited by TM (2 micrograms/ml) in a time dependent effect which reaches a plateau of 45% inhibition at 36 h. Under the same experimental conditions [35S]-methionine incorporation into protein is slightly affected. This is reflected by an almost identical polypeptide pattern for TM treated and non-treated cells when analyzed on SDS-PAGE. On the contrary, strong differences were detected on the labeled compounds analyzed on SDS-PAGE followed by autoradiography when the precursor used was [14C]-mannose. A shift in the electrophoretic mobility of most of the glycopeptides synthesized in the presence of TM was observed, which is also reflected in the structure of the main Leishmania cell surface components. The findings are discussed in the light of biological implications.