Figure 5. Proteolysis of COX2 by 2OAA.

A. Bar diagram showing the upregulation of COX2 mRNA in differentiated U937 cells challenged with LPS (62 ng/ml). 2OAA (120×10⁻⁶ M; 6 h) failed to downregulate COX2 mRNA levels despite its inhibitory effect on COX2 protein. B. Representative immunoblot showing COX2 protein in the presence or absence of the general protein synthesis inhibitor CHX (50×10⁻⁶ M), the chemical blocker of the COX2 active site NS-398 (20×10⁻⁶ M), and the 26S proteasome inhibitor MG132 (20×10⁻⁶ M) plus 2OAA (120×10⁻⁶ M). Constitutive COX1 protein expression is shown as a Western blot loading control.