Immunoproteasome content was upregulated in cultures of WT murine RPE following exposure to (A) chronic, low levels of hydrogen peroxide (0.5 mM), (B) TNFα (1 ng/ml) to mimic the inflammatory response, and (C) tunicamycin (5 μg/ml) to induce ER stress. Blots show antibody reaction to immunoproteasome subunits LMP2 and LMP7. Total proteasome content was estimated from reactions of alpha subunits (α6, α7), which are present in all proteasome subtypes. (A, B) Graph and numbers below blots indicate the densitometry of immune reactions relative to untreated controls. (C) Graph shows the dose-dependent response of RPE cell viability for WT and cells lacking the LMP7 and MECL-1 (L7M1) immunoproteasome subunits. Unpublished data.