| dc.description.abstract | Mycobacterial species contain some of the most dangerous human pathogens described throughout history, responsible for millions of deaths each year. Interestingly, many mycobacteria can infect and replicate in one of our first lines of defense against pathogens, macrophages, whose primary role is finding and killing bacteria.
We infected human THP-1 monocytic cells, a common model for human macrophages, with M. tuberculosis (Mtb), the causative agent of tuberculosis, to better understand the mechanisms that allow pathogenic mycobacteria to survive and replicate within macrophages. We investigated the transcriptional expression profile of human macrophages after infection with Mtb. We found that the EphA (Erythropoietin-producing hepatoma) receptor subfamily member, EphA1, is induced by infection with Mtb and coordinates expression of a broad subset of metabolic, signal transduction and gene regulation pathways. The largest family of eukaryotic receptor tyrosine kinases, Eph receptors, mediate many vital cellular functions, including: tissue organization, cell adhesion, cell migration, immune responses, and granuloma formation in tuberculosis.
Expression of EphA1 and EphA2 receptors and their ligand, EphrinA1, were upregulated in a temporal manner from 15 min to 4 hours post-infection of THP-1-derived macrophages with Mtb. EphA2 expression was greater in Mtb infected EphA1-/- cells than in THP-1 cells, suggesting compensatory expression due to the absence of EphA1. Mtb induces higher levels of EphA1, EphA2, and EphrinA1 gene expression than heat-killed bacilli, suggesting that bacterial viability is involved in optimal expression. Similar to EphA2 KO mice, EphA1-/- THP-1-derived macrophages display increased bacterial killing at later time points than wild type THP-1-derived macrophages.
RNA-Seq studies revealed that an EphA1 KO in THP-1-derived macrophages impacts a wide variety of cellular functions and pathways. EphA1 KO THP-1-derived macrophages differentially regulate metabolic, signal transduction and transcriptional regulation pathways during Mtb infection.
These data indicate that EphA receptors play a key role in modulation of tuberculosis immunity by macrophages and provide a foundation for detailed investigation of the role of Eph genes and their ligands in pathogenesis. | |
