Work

Caveosomal Oxidative Stress Causes Src-p21 Activation and Lysine 63 TRAF6 Protein Polyubiquitination in Iron-induced M1 Hepatic Macrophage Activation

Year: 2012

Type: article

Abstract: Proinflammatory M1 activation of hepatic macrophages (HM) is critical in pathogenesis of hepatitis, but its mechanisms are still elusive. Our earlier work demonstrates the role of ferrous iron (Fe(2+)) as a pathogen-associated molecular pattern-independent agonist for activation of IκB kinase (IKK) and NF-κB in HM via activation and interaction of p21(ras), transforming growth factor β-activated kinase-1 (TAK1), and phosphatidylinositol 3-kinase (PI3K) in caveosomes. However, iron-induced signaling upstream of these kinases is not known. Here we show that Fe(2+) induces generation of superoxide anion (O(2)()) in endosomes, reduces protein-tyrosine phosphatase (PTP) activity, and activates Src at 2∼10 min of Fe(2+) addition to rat primary HM culture. Superoxide dismutase (SOD) blocks O(2)() generation, PTP inhibition, and Src activation. Fe(2+)-induced p21(ras) activity is abrogated with the Src inhibitor PP2 and SOD. Fe(2+) stimulates Lys(63)-linked polyubiquitination (polyUb) of TRAF6 in caveosomes, and a dominant negative K63R mutant of ubiquitin or SOD prevents iron-induced TRAF6 polyUb and TAK1 activation. These results demonstrate that Fe(2+)-generated O(2)() mediates p21(ras) and TAK1 activation via PTP inhibition and Lys(63)-polyUb of TRAF6 in caveosomes for proinflammatory M1 activation in HM.

Source: Journal of Biological Chemistry

DOI: 10.1074/jbc.m112.377358

Authors: Shuping Zhong, Jun Xu, Peggy Li, Hidekazu Tsukamoto

Institutions: University of Southern California, VA Greater Los Angeles Healthcare System

Language: English

Topic: NF-κB Signaling Pathways

Subfield: Cancer Research

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $3,430