Nox4-Derived H2O2 Mediates Endoplasmic Reticulum Signaling through Local Ras Activation

• DOI: 10.1128/mcb.01445-09
• Publication Date: 2010-05-11T04:10:13Z
• Authors: Ru-Feng Wu; Zhenyi Ma; Zhe Liu; Lance S. Terada
• Keywords: Tunicamycin; Thapsigargin; NOX4

The unfolded-protein response (UPR) of the endoplasmic reticulum (ER) has been linked to oxidant production, although molecular details and functional significance this linkage are poorly understood. Using a ratiometric H(2)O(2) sensor targeted different subcellular compartments, we demonstrate specific production by ER in stressors tunicamycin HIV-1 Tat, but not thapsigargin or dithiothreitol. Knockdown oxidase Nox4, expressed on endomembranes, expression ER-targeted catalase blocked Tat prevented UPR following exposure these two agonists, also triggered Nox4-dependent, sustained activation Ras leading ERK, phosphatidylinositol 3-kinase (PI3K)/mTOR, pathway activation. Cell fractionation studies green fluorescent protein (GFP) fusions GTPase effector binding domains confirmed selective endogenous RhoA surface, with ER-associated K-Ras acting upstream downstream Nox4. Notably, Nox4/Ras/ERK induced autophagy, suppression autophagy unmasked cell death differentiation endothelial cells 3-dimensional matrix. We conclude that surface provides platform spatially organize agonist-specific Nox4-dependent oxidative signaling events, homeostatic protective mechanisms rather than stress.