AI Insight
This study demonstrates that Leishmania parasites secrete small RNA fragments derived from transfer RNAs (tRFs) through exosomes that enter host macrophages and alter their protein expression. Using quantitative proteomics, researchers found that two specific tRFs (Ld-tRF-Asp and Ld-tRF-Leu) modulate approximately 20 and 18 macrophage proteins respectively, with about one-third of these changes potentially favoring parasite survival. The fragments appear to work by hijacking the host cell's Argonaute protein machinery, particularly Ago1, to target and regulate host genes.
Why it matters
Understanding how Leishmania parasites manipulate host immune cells through exosomal RNA fragments could lead to new therapeutic approaches for leishmaniasis, a disease affecting millions worldwide. These findings reveal a novel mechanism of host-pathogen interaction that may be targetable for intervention, potentially offering new treatment strategies beyond conventional antiparasitic drugs.
Understand the Science
by Harsimran Kaur Brar, Atieh Moradimotlagh, Dilraj Kaur Longowal, Kyung-Mee Moon, Leonard J. Foster, Alice L-F Mui, Neil Reiner, Devki Nandan
Protozoan parasites of the genus Leishmania, the causative agents of human leishmaniasis, have evolved mechanisms to manipulate host cell functions to their advantage. Recently, small non-coding RNAs have been identified as contributors to the pathogenesis of Leishmania infection. An increasing number of studies have demonstrated that Leishmania tRNA-derived small non-coding RNAs, also known as Leishmania tRNA-derived fragments (Ld-tRFs), can be delivered to host cells via exosomes, thereby influencing host cell function. Here, we investigated the potential effects of Leishmania exosomal Ld-tRF-Asp and Ld-tRF-Leu in THP-1-derived host macrophages. SILAC (Stable Isotope Labelling by Amino acids in Cell culture) based quantitative proteomics was used to investigate the effects of synthetic Ld-tRF-Asp and Ld-tRF-Leu by analyzing how these Ld-tRFs affect the macrophage proteome. Ld-tRF-Asp modulated 20 proteins, whereas Ld-tRF-Leu affected 18 proteins in macrophages. Interestingly, 7 of the Ld-tRF-Asp-modulated proteins and 7 of the Ld-tRF-Leu-modulated proteins showed potential pro-Leishmania effects. Biochemical isolation of Argonaute (Ago) protein complexes by “Ago proteins Affinity Purification by Peptide,” followed by identification of interacting small non-coding RNAs, revealed the selective presence of both tRFs in Leishmania-infected macrophages. This striking finding suggested that Ld-tRFs engage macrophage Ago proteins for their effects. In addition, an in vivo biotin-RNA pull-down assay showed that Ld-tRF-Leu selectively interacted with Ago 1, suggesting that Ago 1 is the preferred Ago guiding Ld-tRFs to target host genes. Taken together, this study shows, for the first time, that Leishmania exosomal tRFs significantly alter the host macrophage proteome in favour of Leishmania survival. This may offer new insights into the mechanisms of leishmaniasis and may provide future therapeutic interventions targeting these regulatory molecules.