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Down-regulation of MARCKS-related protein (MRP) in macrophages infected with Leishmania
S Corradin1, J Mauël, A Ransijn
1Institute of Biochemistry, University of Lausanne, 1066 Epalinges, Switzerland. Sally.CorradinBetz@ib.unil.ch
Abstract:
Leishmania, a protozoan parasite of macrophages, has been shown to interfere with host cell signal transduction pathways including protein kinase C (PKC)-dependent signaling. Myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP, MacMARCKS) are PKC substrates in diverse cell types. MARCKS and MRP are thought to regulate the actin network and thereby participate in cellular responses involving cytoskeletal rearrangement. Because MRP is a major PKC substrate in macrophages, we examined its expression in response to infection by Leishmania. Activation of murine macrophages by cytokines increased MRP expression as determined by Western blot analysis. Infection with Leishmania promastigotes at the time of activation or up to 48 h postactivation strongly decreased MRP levels. Leishmania-dependent MRP depletion was confirmed by [3H]myristate labeling and by immunofluorescence microscopy. All species or strains of Leishmania parasites tested, including lipophosphoglycan-deficient Leishmania major L119, decreased MRP levels. MRP depletion was not obtained with other phagocytic stimuli including zymosan, latex beads, or heat-killed Streptococcus mitis, a Gram-positive bacterium. Experiments with [3H]myristate labeled proteins revealed the appearance of lower molecular weight fragments in Leishmania-infected cells suggesting that MRP depletion may be due to proteolytic degradation.
Insights
Leishmania parasites deplete Myristoylated alanine-rich C kinase substrate (MARCKS)-related protein (MRP) in macrophages. This depletion, potentially due to proteolysis, suggests a novel parasite mechanism impacting host cell signaling.
Area of Science:
- Immunology
- Cell Biology
- Parasitology
Background:
- Leishmania parasites disrupt host cell signaling, particularly protein kinase C (PKC) pathways.
- Myristoylated alanine-rich C kinase substrate (MARCKS)-related protein (MRP) is a key PKC substrate involved in cytoskeletal regulation.
Purpose of the Study:
- To investigate the effect of Leishmania infection on MRP expression in macrophages.
- To understand the mechanism behind Leishmania-induced changes in MRP levels.
Main Methods:
- Murine macrophages were activated with cytokines and subsequently infected with Leishmania.
- MRP expression was analyzed using Western blot, [3H]myristate labeling, and immunofluorescence microscopy.
- Control experiments used other phagocytic stimuli like zymosan and latex beads.
Main Results:
- Cytokine activation increased MRP expression in macrophages.
- Leishmania infection significantly decreased MRP levels, irrespective of parasite strain or lipophosphoglycan presence.
- MRP depletion was specific to Leishmania infection and not observed with other phagocytic stimuli.
- Evidence suggests proteolytic degradation of MRP in infected cells.
Conclusions:
- Leishmania infection actively downregulates MRP expression in macrophages.
- This depletion is a specific host-parasite interaction, potentially mediated by proteolysis.
- Understanding this mechanism may reveal new insights into Leishmania pathogenesis and host cell manipulation.