Changes in the Membrane-Associated Proteins of Exosomes Released from Human Macrophages after Mycobacterium tuberculosis Infection

Abstract

Tuberculosis (TB) is the deadliest infectious disease worldwide. One obstacle hindering the elimination of TB is our lack of understanding of host-pathogen interactions. Exosomes, naturally loaded with microbial molecules, are circulating markers of TB. Changes in the host protein composition of exosomes from Mycobacterium tuberculosis (Mtb)-infected cells have not been described, can contribute to our understanding of the disease process, and serve as a direct source of biomarkers or as capture targets to enrich for exosomes containing microbial molecules. Here, the protein composition of exosomes from Mtb-infected and uninfected THP-1-derived macrophages was evaluated by tandem-mass-spectrometry and differences in protein abundances were assessed. Our results show that infection with Mtb leads to significant changes in the protein composition of exosomes. Specifically, 41 proteins were significantly more abundant in exosomes from Mtb-infected cells; 63% of these were predicted to be membrane associated. Thus, we used a novel biotinylation strategy to verify protein localization, and confirmed the localization of some of these proteins in the exosomal membrane. Our findings reveal another important scenario where Mtb could be influencing changes in host cells that unveil new features of the host-pathogen interaction and may also be exploited as a source of biomarkers for TB.

Discovery and Validation of a Six-Marker Serum Protein Signature for the Diagnosis of Active Pulmonary Tuberculosis

“…Upregulation of SYWC in the host leads to restriction of free tryptophan, and tryptophan depletion is lethal to M. tuberculosis ( 35 ). SYWC has very recently been found upregulated in human THP-1 cells infected with M. tuberculosis ( 36 ). In a separate mechanism during TB infection, tryptophan often becomes limiting due to its conversion to kynurenine by indoleamine 2,3-dioxygenase ( 37 ).…”

Characterization of exosomes derived from <em>Toxoplasma gondii</em> and their functions in modulating immune responses

“…Increasing evidence has indicated that exosomes and their cargo can be transferred from one cell to another, resulting in the cell-to-cell communication via various functional biomolecules including proteins, bioactive lipids, and RNA, which can alter recipient cell functions. [23][24][25] For instance, exosome-like vesicles from T. gondii-infected HFF cells could attach and deliver their contents to uninfected cells, thereby leading to altered functions in the uninfected cell. 20 In addition, exosomes secreted by T. gondii-infected L6 cells could change the host cell proliferation and alter the host cell cycle.…”

Message in a vesicle – trans-kingdom intercommunication at the vector–host interface

“…Extracellular vesicles are involved in immune activation and antigen presentation during Mycobacterium tuberculosis infection. M. tuberculosis manipulates the secretion of extracellular vesicles in mammalian cells by increasing the abundance of immune-related proteins (Diaz et al, 2016), and packaging bacterial molecules within host-derived exosomes (Giri et al, 2010;Kruh-Garcia et al, 2014). M. tuberculosis proteins within these exosomes activate the host immune response in the recipient cell (Giri et al, 2010) ( Fig.…”