MAV_4644 Interaction with the Host Cathepsin Z Protects Mycobacterium avium subsp. hominissuis from Rapid Macrophage Killing

Matthew S Lewis,Sasha J Rose,Lia Danelishvili,Luiz E Bermudez

doi:10.3390/microorganisms7050144

Matthew S Lewis, Sasha J Rose + Show 2 more

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https://doi.org/10.3390/microorganisms7050144

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Journal: Microorganisms	Publication Date: May 21, 2019
Citations: 5	License type: CC BY 4.0

Affiliation: Oregon State University

Abstract

Mycobacterium avium subspecies hominissuis (MAH) is an opportunistic pathogen that is ubiquitous in the environment and often isolated from faucets and showerheads. MAH mostly infects humans with an underlying disease, such as chronic pulmonary disorder, cystic fibrosis, or individuals that are immunocompromised. In recent years, MAH infections in patients without concurrent disease are increasing in prevalence as well. This pathogen is resistant to many antibiotics due to the impermeability of its envelope and due to the phenotypic resistance established within the host macrophages, making difficult to treat MAH infections. By screening a MAH transposon library for mutants that are susceptible to killing by reactive nitrogen intermediaries, we identified the MAV_4644 (MAV_4644:Tn) gene knockout clone that was also significantly attenuated in growth within the host macrophages. Complementation of the mutant restored the wild-type phenotype. The MAV_4644 gene encodes a dual-function protein with a putative pore-forming function and ADP-ribosyltransferase activity. Protein binding assay suggests that MAV_4644 interacts with the host lysosomal peptidase cathepsin Z (CTSZ), a key regulator of the cell signaling and inflammation. Pathogenic mycobacteria have been shown to suppress the action of many cathepsins to establish their intracellular niche. Our results demonstrate that knocking-down the cathepsin Z in human macrophages rescues the attenuated phenotype of MAV_4644:Tn clone. Although, the purified cathepsin Z by itself does not have any killing effect on MAH, it contributes to bacterial killing in the presence of the nitric oxide (NO). Our data suggest that the cathepsin Z is involved in early macrophage killing of MAH, and the virulence factor MAV_4644 protects the pathogen from this process.

Highlights

Mycobacterium avium subspecies hominissuis (MAH) is a ubiquitous environmental saprophyte capable of infecting a broad host range of animals, including humans [1]
While we found that 250–5000 μmol spermine NONOate inhibited the bacterial growth during 48 h of incubation, 100 μmol concentration was near the threshold of sensitivity and, this concentration was used in the tranMsicprooosrgoannislmibsr2a0r1y9, 7s,cxreen to isolate nitric oxide sensitive mutants
The mycobacterial response to nitric oxide within the host macrophage plays an important role in the survival and replication of these intracellular pathogens

Summary

Introduction

Mycobacterium avium subspecies hominissuis (MAH) is a ubiquitous environmental saprophyte capable of infecting a broad host range of animals, including humans [1]. The gut is a route of MAH entry, and the increasing prevalence of MAH is apparent in both respiratory and gastrointestinal infections [5,6,7]. Patients with MAH infections are typically given a combination therapy with two or three antimicrobial agents for one year, increasing chances of development of drug-resistance. Among many factors including the bacterial intrinsic resistance makes MAH infection difficult to treat [8]. This intrinsic resistance in part is attributed to the impermeability of the mycobacterial envelope, which is rich in hydrophobic mycolic acids [9]. MAH resides and replicates within the host macrophages, further isolating the bacteria from effective levels of circulating antibiotic [10]

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