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Updated: Jul 8, 2026
Investigating the Phagocytosis of Leishmania using Confocal Microscopy
Published on: July 29, 2021
Fibronectin binding and proteolytic degradation by Leishmania and effects on macrophage activation
Manjusha M Kulkarni1, Eric A Jones, W Robert McMaster
1Division of Infectious Diseases and Center for Microbial Interface Biology, The Ohio State University, Columbus, OH 43210, USA.
Abstract:
Infection by vector-borne protozoa of the genus Leishmania occurs by the deposition of parasites within the skin of the mammalian host, where they eventually bind to and are phagocytized by Mphis. Our previous work supported the idea that parasites can interact with extracellular matrix and basement membrane proteins, such as fibronectin (FN), within the skin, leading to enhanced invasion. In this report, we extend these findings and show that both promastigotes and amastigotes of Leishmania species can bind directly to soluble FN and laminin (LM) and that promastigotes express a distinct surface protein of approximately 60 kDa that binds both FN and LM. Promastigotes of multiple Leishmania species can rapidly degrade FN by using surface-localized and secreted metalloprotease (leishmanolysin). FN degradation at the surfaces of amastigotes is leishmanolysin dependent, whereas both secreted leishmanolysin and cysteine protease B contribute to extracellular FN degradation. Leishmania-degraded FN decreased the production of reactive oxygen intermediates by parasite-infected macrophages and affected the accumulation of intracellular parasites. These findings show that both parasite stages of Leishmania species bind to and proteolytically degrade FN at the parasite surface and distantly through secreted proteases and that degraded forms of FN can influence the activation state of parasite-infected macrophages.
Insights
Leishmania parasites bind to and degrade fibronectin (FN), a skin protein, using proteases. This degradation impacts macrophage responses and parasite infection within macrophages.
Area of Science:
- Parasitology
- Immunology
- Molecular Biology
Background:
- Leishmania parasites infect mammalian hosts via skin deposition.
- Parasite interaction with extracellular matrix proteins like fibronectin (FN) may enhance invasion.
- Previous studies suggested a role for FN in Leishmania invasion.
Purpose of the Study:
- To investigate the direct binding of Leishmania parasites to FN and laminin (LM).
- To identify parasite surface proteins involved in FN and LM binding.
- To determine the role of parasite proteases in FN degradation and its impact on host cells.
Main Methods:
- Binding assays using soluble FN and LM with Leishmania promastigotes and amastigotes.
- Identification of parasite surface proteins via Western blot and immunoprecipitation.
- Protease activity assays to assess FN degradation by leishmanolysin and cysteine protease B.
- Measurement of reactive oxygen intermediates (ROIs) in infected macrophages.
Main Results:
- Both Leishmania promastigotes and amastigotes bind directly to soluble FN and LM.
- Promastigotes possess a ~60 kDa surface protein that binds FN and LM.
- Leishmania promastigotes degrade FN using surface and secreted metalloprotease (leishmanolysin).
- Leishmanolysin and cysteine protease B contribute to extracellular FN degradation.
- Degraded FN reduced ROI production by infected macrophages and affected parasite accumulation.
Conclusions:
- Leishmania parasites, in both life stages, bind to and proteolytically degrade FN.
- Degradation occurs both at the parasite surface and extracellularly via secreted proteases.
- Degraded FN influences the activation state of parasite-infected macrophages, potentially aiding parasite survival.
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