A novel form of NF-kappaB is induced by Leishmania infection: involvement in macrophage gene expression

Area of Science:

• Immunology
• Molecular Biology
• Parasitology

Background:

• Leishmania parasites are obligate intracellular pathogens residing within macrophage phagolysosomes.
• Pathogen manipulation of host cell signaling and gene expression is crucial for Leishmania survival and disease.
• Understanding these interactions is key to developing effective treatments.

Purpose of the Study:

• To investigate the impact of Leishmania infection on host cell signaling pathways, specifically NF-kappaB.
• To identify the mechanism by which Leishmania alters NF-kappaB activity.
• To determine the functional consequences of Leishmania-induced NF-kappaB modification.

Main Methods:

• In vitro infection of macrophages with Leishmania promastigotes.
• Analysis of NF-kappaB p65 RelA subunit cleavage using biochemical assays.
• Identification of the responsible Leishmania protease (gp63).
• Investigation of nuclear translocation and DNA binding of cleaved NF-kappaB fragments.
• Assessment of chemokine gene expression induction.

Main Results:

• Leishmania infection specifically cleaves the NF-kappaB p65 RelA subunit in the cytoplasm.
• The Leishmania protease gp63 mediates this cleavage, generating a p35 RelA fragment.
• The p35 RelA fragment translocates to the nucleus and forms functional heterodimers with NF-kappaB p50.
• These dimers activate transcription of key chemokine genes (MIP-2, MCP-1, MIP-1alpha, MIP-1beta).
• Cleavage occurs with pathogenic Leishmania species but not non-pathogenic strains or IFN-gamma treatment.

Conclusions:

• Leishmania employs a novel mechanism to subvert macrophage regulatory pathways by cleaving NF-kappaB p65 RelA.
• The resulting p35 RelA/p50 complex activates chemokine gene expression, potentially contributing to Leishmania pathogenesis.
• This study reveals a new strategy used by pathogens to manipulate host immunity for their survival.