Activity-dependent COX-2 proteolysis generates a catalytically inactive fragment that affects aerobic respiration and proliferation

Abstract

Cyclooxygenase-2 (COX-2) catalyzes arachidonic acid (AA) into PGH2, the single source of all prostaglandins (PGs), ligands that activate multiple inflammatory pathways. AA catalysis by COX-2 quickly leads to suicide inactivation, rendering the enzyme catalytically inactive. We show that the catalytic activity is followed by controlled cleavage of COX-2, an event that is differentially regulated by fatty acids and blocked by COX inhibitors. Using mass spectrometry, we identified two adjacent cleavage points within the catalytic domain, which give rise to COX-2 fragments that are catalytically-inactive and localize to different cellular compartments. RNA-seq analysis revealed that one of these fragments significantly alters the expression of genes in the mitochondrial electron transport chain. Subsequent functional assays confirmed that cells expressing this fragment exhibit reduced mitochondrial function and increased lactate production. Our results suggest that in addition to its role in generating PGs, COX-2 has a subsequent, PG-independent function that emanates from its proteolysis.