SMURF2 inhibits autophagic control of Mycobacterium tuberculosis in macrophages
Priscila C. Campos, Kathryn C. Rahlwes, Victoria A. Ektnitphong, Beatriz R.S. Dias, Kubra F. Naqvi, Samuel Alvarez-Arguedas, Michael U. Shiloh
Priscila C. Campos, Kathryn C. Rahlwes, Victoria A. Ektnitphong, Beatriz R.S. Dias, Kubra F. Naqvi, Samuel Alvarez-Arguedas, Michael U. Shiloh
View: Text | PDF
Research Article Immunology Infectious disease Microbiology

SMURF2 inhibits autophagic control of Mycobacterium tuberculosis in macrophages

Abstract

Autophagy is a critical host defense mechanism that restricts intracellular pathogens such as Mycobacterium tuberculosis. A key step in this process is the ubiquitination of M. tuberculosis or M. tuberculosis–associated structures. The E3 ligase Smad-specific E3 ubiquitin protein ligase 1 (SMURF1) catalyzes K48-linked ubiquitination, promoting bacterial clearance. However, the function of its homolog, SMURF2, in host defense remains undefined. Here, we demonstrate that Smurf2 deletion in murine macrophages increases SMURF1 levels, enhances LC3B lipidation, augments K48 ubiquitination of M. tuberculosis–associated structures, and reduces intracellular M. tuberculosis replication. These effects are reversed by Smurf1 deletion, supporting a role for SMURF1 in SMURF2-dependent control of M. tuberculosis. Mice with myeloid-specific Smurf2 deletion exhibit modestly prolonged survival after aerosol M. tuberculosis infection. In human macrophages, SMURF2 knockdown or its pharmacological inhibition with the HECT E3-ligase inhibitor Heclin reduces M. tuberculosis replication. Together, our findings identify SMURF2 as a negative regulator of macrophage control of M. tuberculosis and support further investigation of SMURF2 as a potential target for host-directed therapy in tuberculosis.

Authors

Priscila C. Campos, Kathryn C. Rahlwes, Victoria A. Ektnitphong, Beatriz R.S. Dias, Kubra F. Naqvi, Samuel Alvarez-Arguedas, Michael U. Shiloh

×

Figure 5

Smurf2 complementation reduces K48 ubiquitin and LC3B colocalization with M. tuberculosis in murine macrophages.

Options: View larger image (or click on image) Download as PowerPoint
Smurf2 complementation reduces K48 ubiquitin and LC3B colocalization wi...
(A) Representative immunofluorescence images of M. tuberculosis–mCherry (red) with K48 ubiquitin (green) in BV2-WT and Smurf2-KO cells, transduced with either an EV or the constructs shown in Figure 4A. Cells were stained with an anti-K48 antibody 17 hours after infection. (B) Quantification of M. tuberculosis–mCherry colocalization with K48 as shown in A (mean ± SD of 3 independent experiments, performed in triplicate, ns, nonsignificant, *P ≤ 0.05 and **P ≤ 0.01; unpaired t test). (C) Representative immunofluorescence images of mCherry-expressing M. tuberculosis (red) with LC3B (green) under the same conditions as in A, using an anti-LC3B antibody. (D) Quantification of M. tuberculosis–mCherry colocalization with LC3B as shown in C (mean ± SD of 3 independent experiments, performed in triplicate, ns, nonsignificant, *P ≤ 0.05; unpaired t test). Scale bar: 5 μm.