LRRC8A channels support TNFα-induced superoxide production by Nox1 which is required for receptor endocytosis.

Choi H, Ettinger N, Rohrbough J, Dikalova A, Nguyen HN, Lamb FS
Free Radic Biol Med. 2016 101: 413-423

PMID: 27838438 · PMCID: PMC5206799 · DOI:10.1016/j.freeradbiomed.2016.11.003

Leucine Rich Repeat Containing 8A (LRRC8A) is a required component of volume-regulated anion channels (VRACs). In vascular smooth muscle cells, tumor necrosis factor-α (TNFα) activates VRAC via type 1 TNFα receptors (TNFR1), and this requires superoxide (O) production by NADPH oxidase 1 (Nox1). VRAC inhibitors suppress the inflammatory response to TNFα by an unknown mechanism. We hypothesized that LRRC8A directly supports Nox1 activity, providing a link between VRAC current and inflammatory signaling. VRAC inhibition by 4-(2-butyl-6,7-dichlor-2-cyclopentylindan-1-on-5-yl) oxobutyric acid (DCPIB) impaired NF-κB activation by TNFα. LRRC8A siRNA reduced the magnitude of VRAC and inhibited TNFα-induced NF-κB activation, iNOS and VCAM expression, and proliferation of VSMCs. Signaling steps disrupted by both siLRRC8A and DCPIB included; extracellular O production by Nox1, c-Jun N-terminal kinase (JNK) phosphorylation and endocytosis of TNFR1. Extracellular superoxide dismutase, but not catalase, selectively inhibited TNFR1 endocytosis and JNK phosphorylation. Thus, O is the critical extracellular oxidant for TNFR signal transduction. Reducing JNK expression (siJNK) increased extracellular O suggesting that JNK provides important negative feedback regulation to Nox1 at the plasma membrane. LRRC8A co-localized by immunostaining, and co-immunoprecipitated with, both Nox1 and its p22phox subunit. LRRC8A is a component of the Nox1 signaling complex. It is required for extracellular O production, which is in turn essential for TNFR1 endocytosis. These data are the first to provide a molecular mechanism for the potent anti-proliferative and anti-inflammatory effects of VRAC inhibition.

Copyright © 2016 Elsevier Inc. All rights reserved.

MeSH Terms (21)

Cell Line Cyclopentanes Endocytosis Gene Expression Regulation HEK293 Cells Humans Indans JNK Mitogen-Activated Protein Kinases Membrane Proteins Myocytes, Smooth Muscle NADPH Oxidase 1 NF-kappa B Phosphorylation Protein Subunits Receptors, Tumor Necrosis Factor, Type I RNA, Small Interfering Signal Transduction Superoxide Dismutase Superoxides Tumor Necrosis Factor-alpha Vascular Cell Adhesion Molecule-1

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