Posted by Kasra Hassani
In this paper, Silverman et al. have pointed to two interesting subjects: first, what proteins are generally secreted from Leishmania, and second, how are these proteins secreted. In an extensive proteomic analysis, they have pointed out 151 proteins that they believe are being actively secreted out of stationary promastigotes of Leishmania donovani. These proteins belong to a wide variety of groups, such as proteases, antioxidants, nucleases etc. and each might play roles in survival of the parasite within its hosts and modulation of the immune response. Identification of these proteins opens up many opportunities for further studies that promote understanding their function and possible therapeutic targets in continuing studies.
Another interesting finding of Silverman et al. was that among these secreted proteins only 2 contain a classical amino-terminal secretion signal, which means that Leishmania largely might benefit from non-classical secretion pathways such as exosomes. Exosomes have been studied previously in human B cells and dendritic cells and it is actually interesting to point out that there is striking correspondence between the proteome content of these exosomes and Leishmania’s secretome (except for the proteins for which Leishmania does not have an ortholog). The authors have proposed the release of exosomes from the surface of the cell and especially from the flagellar pocket to be an important pathway of protein secretion by Leishmania and they have observed vesicular budding from the parasite surface by STM.