USP9X and Miyoshi myopathy: Although WP1130 probably inhibits several deubiquitinases including USP5, USP9X, and others,14 when USP5 was knocked down, the effects of WP1130 on MM cell death was markedly decreased, which suggested that USP5 is critical for WP1130 action in modulation of c-Maf stability and MM cell apoptosis.