A Role for the ATP7A Copper-transporting ATPase in Macrophage Bactericidal Activity

Carine White,Jaekwon Lee,Taiho Kambe,Kevin Fritsche,Michael J Petris

doi:10.1074/jbc.m109.070201

Abstract

Copper is an essential micronutrient that is necessary for healthy immune function. This requirement is underscored by an increased susceptibility to bacterial infection in copper-deficient animals; however, a molecular understanding of its importance in immune defense is unknown. In this study, we investigated the effect of proinflammatory agents on copper homeostasis in RAW264.7 macrophages. Interferon-gamma was found to increase expression of the high affinity copper importer, CTR1, and stimulate copper uptake. This was accompanied by copper-stimulated trafficking of the ATP7A copper exporter from the Golgi to vesicles that partially overlapped with phagosomal compartments. Silencing of ATP7A expression attenuated bacterial killing, suggesting a role for ATP7A-dependent copper transport in the bactericidal activity of macrophages. Significantly, a copper-sensitive mutant of Escherichia coli lacking the CopA copper-transporting ATPase was hypersensitive to killing by RAW264.7 macrophages, and this phenotype was dependent on ATP7A expression. Collectively, these data suggest that copper-transporting ATPases, CopA and ATP7A, in both bacteria and macrophage are unique determinants of bacteria survival and identify an unexpected role for copper at the host-pathogen interface.

Highlights

Copper is an essential nutrient for aerobic organisms
Consistent with this role, a copper-sensitive mutant of E. coli with a defect in copper export was significantly more sensitive to macrophage-mediated killing than wild type cells, and this sensitivity was dependent on ATP7A expression
Copper Enhances the Bactericidal Activity of Macrophages— We began this study by testing whether copper supplementation to the growth medium of the murine macrophage cell line, 33950 JOURNAL OF BIOLOGICAL CHEMISTRY

Summary

Introduction

Copper is an essential nutrient for aerobic organisms. Its ability to exchange electrons as it cycles between cuprous and cupric states has been harnessed by enzymes that catalyze a wide variety of biochemical processes [1]. Silencing of ATP7A expression attenuated bacterial killing, suggesting a role for ATP7A-dependent copper transport in the bactericidal activity of macrophages. Consistent with this role, a copper-sensitive mutant of E. coli with a defect in copper export was significantly more sensitive to macrophage-mediated killing than wild type cells, and this sensitivity was dependent on ATP7A expression.

Results

Conclusion