Affiliation:
1. Department of Biomedical Sciences, Carlson College of Veterinary Medicine, Corvallis, OR, USA
2. Department of Microbiology, College of Sciences, Oregon State University, Corvallis, OR, USA
Abstract
Virulent non-tuberculous Mycobacteria (NTMs) successfully reside and multiply within the phagosomes of phagocytic cells such as monocytes and macrophages. Macrophages play a very important role in the innate clearance of intracellular pathogens including NTMs. Attenuated
Mycobacterium avium
subsp.
hominissuis
100 enters macrophages but is incapable of escaping these cells via canonical mycobacteria escape mechanisms. Alternatively, virulent
Mycobacterium avium
subsp.
hominissuis
104 and
Mycobacterium abscessus
subsp.
abscessus
are able to modify macrophages to suit their growth, survival and ultimately escape from macrophages, while non-virulent
Mycobacterium smegmatis
is readily killed by macrophages. In this study we focused on early infection of macrophages with NTMs to determine the phenotypic response of macrophages, M1 or M2 differentiation, and phosphorylation alterations that can affect cellular response to invading bacteria. Our findings indicate that infection of the macrophage with MAH 100 and
M. smegmatis
favours the development of M1 macrophage, a pro-inflammatory phenotype associated with the killing of intracellular pathogens, while infection of the macrophage with MAH 104 and
M. abscessus
favoured the development of M2 macrophage, an anti-inflammatory phenotype associated with the healing process. Interference with the host post-translational mechanisms, such as protein phosphorylation, is a key strategy used by many intracellular bacterial pathogens to modulate macrophage phenotype and subvert macrophage function. By comparing protein phosphorylation patterns of infected macrophages, we observed that uptake of both MAH 100 and
M. smegmatis
resulted in MARCKS-related protein phosphorylation, which has been associated with macrophage activation. In contrast, in macrophages infected with MAH 104 and
M. abscessus
, methionine adenosyltransferase IIβ, an enzyme that catalyses the biosynthesis of S-adenosylmethionine, a methyl donor for DNA methylation. Inhibition of DNA methylation with 5-aza-2 deoxycytidine, significantly impaired the survival of MAH 104 in macrophages. Our findings suggest that the virulent MAH 104 and
M. abscessus
enhance its survival in the macrophage possibly through interference with the epigenome responses.
Funder
Microbiology Foundation of San Francisco