Intraphagosomal Mycobacterium tuberculosis Acquires Iron from Both Extracellular Transferrin and Intracellular Iron Pools

doi:10.1074/jbc.M209768200

Intraphagosomal Mycobacterium tuberculosis Acquires Iron from Both Extracellular Transferrin and Intracellular Iron Pools

IMPACT OF INTERFERON-γ AND HEMOCHROMATOSIS*

From the ^‡Department of Internal Medicine and Research Service, Veteran Affairs Medical Center-Iowa City, Iowa City, Iowa 52246 and the Departments of ^§Internal Medicine and ^¶Microbiology, the ^‖Interdisciplinary Program in Immunology, and the ^**Free Radical and Radiation Biology Program, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242

Abstract

Mycobacterium tuberculosis multiplies within the macrophage phagosome and requires iron for growth. We examined the route(s) by which intracellular M. tuberculosis acquires iron. During intracellular growth of the virulent Erdman M. tuberculosis strain in human monocyte-derived macrophages (MDM), M. tuberculosisacquisition of ⁵⁹Fe from transferrin (TF) provided extracellularly (exogenous source) was compared with acquisition when MDM were loaded with ⁵⁹Fe from TF prior to M. tuberculosis infection (endogenous sources). M. tuberculosis ⁵⁹Fe acquisition required viable bacteria and was similar from exogenous and endogenous sources at 24 h and greater from exogenous iron at 48 h. Interferon-γ treatment of MDM reduced ⁵⁹Fe uptake from TF 51% and TF receptor expression by 34%. Despite this, intraphagosomal M. tuberculosis iron acquisition in IFN-γ-treated cells was decreased by only 30%. Macrophages from hereditary hemochromatosis patients have altered iron metabolism. Intracellular M. tuberculosis acquired markedly less iron in MDM from these individuals than in MDM from healthy donors, regardless of the iron source (exogenous and endogenous): 36 ± 3.8% and 17 ± 9.6% of control, respectively. Thus, intraphagosomal M. tuberculosis can acquire iron from both extracellular TF and endogenous macrophage sources. Acquisition of iron from macrophage cytoplasmic iron pools may be critical for the intracellular growth ofM. tuberculosis. This acquisition is altered by IFN-γ treatment to a small extent, but is markedly reduced in macrophages from hemochromatosis patients.

Footnotes

↵* This work was supported in part by Veteran Affairs Merit Review Grants (to B. E. B. and L. S. S.) and National Institutes of Health Grants AI24954 (to B. E. B.), AI33004 (to L. S. S.), and AI43870 (to L. S. S.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ To whom correspondence should be addressed: University of Iowa Hospitals and Clinics, Dept. of Internal Medicine, Division of Infectious Diseases, SW54, GH, Iowa City, IA 52242. Fax: 319-356-4600; E-mail: bradley-britigan@uiowa.edu.
↵§§ Present address: Division of Infectious Diseases, Dept. of Medicine, Ohio State University, 4715 Cramblett Hall, 456 W. 10th Ave., Columbus, OH 43210. Fax: 614-293-5240; E-mail: schlesinger-2@medctr.osu.edu.
Published, JBC Papers in Press, October 23, 2002, DOI 10.1074/jbc.M209768200
Abbreviations:

TF

transferrin

IFN-γ

interferon-γ

MDM

monocyte-derived macrophages

MOI

multiplicity of infection

NTA

nitrilotriacetic acid

PD

phosphate buffer

TFR

TF receptor

mAb

monoclonal antibody

ELISA

enzyme-linked immunosorbent assay

DMT

divalent metal transporter
- Received September 23, 2002.
- Revision received October 23, 2002.
The American Society for Biochemistry and Molecular Biology, Inc.