Identification of Mycobacterium avium subsp. hominissuis secreted proteins using an in vitro system mimicking the phagosomal environment.
Mycobacterium avium subsp. hominissuis is a common intracellular pathogen that infects patients with HIV/AIDS and cause lung infection in patients with underlying lung pathology. M.avium preferably infects macrophages and uses diverse mechanisms to alter phagosome maturation. Once in the macrophage, the pathogen can alter the host cellular defenses by secreting proteins into the cytosol of host cells, but despite considerable research, only a few secreted effector proteins have been identified. We hypothesized that the environmental cues inside the phagosome can trigger bacterial protein secretion. To identify M. avium secretome within the phagosome, we utilized a previously established in vitro system that mimics the metal ion concentrations and pH of the M. avium phagosome.



M. avium was exposed to phagosome metal concentrations for different time points and exported proteins were profiled and analyzed against bacterial proteins secreted in the culture medium. Mass spectrometric analysis of the secreted proteome identified several proteins, of which 46 were unique to bacteria incubated in the metal mixture. Ten of potential effectors were selected and secretion of these proteins was monitored within M. avium infected mononuclear phagocytic cells using the beta-lactamase FRET-based reporter system. In addition, pull-down assay was performed for secreted calmodulin-like protein MAV_1356 protein to evaluate for eukaryotic target. All examined M. avium proteins were secreted into the macrophage cytosol, and gene expression analysis suggested that the metal environment likely stimulates secretion of pre-made proteins. Further investigation of bacterial secreted MAV_1356 protein, lead to the observation that the MAV_1356 interacts with the host proteins Annexin A1 and Protein S100-A8.



We established an in vitro system for the study if proteins secreted intracellularly, and revealed that the metal mixture mimicking the concentration of metals in the phagosome environment, triggers protein secretion.
Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.|Department of Microbiology, College of Science, Oregon State University, Corvallis, OR, USA.
Jessica J
JJ
Chinison
Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.
Lia
L
Danelishvili
Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.
Rashmi
R
Gupta
Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.|Department of Microbiology, College of Science, Oregon State University, Corvallis, OR, USA.
Sasha J
SJ
Rose
Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.|Department of Microbiology, College of Science, Oregon State University, Corvallis, OR, USA.
Lmar M
LM
Babrak
Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA. luiz.bermudez@oregonstate.edu.|Department of Microbiology, College of Science, Oregon State University, Corvallis, OR, USA. luiz.bermudez@oregonstate.edu.
Luiz E
LE
Bermudez
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D002412:Cations / Q000378:metabolism; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D054884:Host-Pathogen Interactions; D006801:Humans; D008264:Macrophages / Q000382:microbiology; D008670:Metals / Q000378:metabolism / Q000494:pharmacology; D009000:Monocytes / Q000382:microbiology; D009162:Mycobacterium avium / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism*; D020543:Proteome / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics; D001618:beta-Lactamases / Q000378:metabolism
D001426:Bacterial Proteins; D002147:Calmodulin; D002412:Cations; D004269:DNA, Bacterial; D008670:Metals; D020543:Proteome; D012329:RNA, Bacterial; D001618:beta-Lactamases
Cytoplasm; Macrophages; Mycobacterium avium; Phagosome metal concentrations; Proteins; Secretion