Lysine acetylation restricts mutant IDH2 activity to optimize transformation in AML cells

Mutant isocitrate dehydrogenase (IDH) 1 and 2 play a pathogenic role in cancers including acute myeloid leukemia (AML) by producing oncometabolite 2- hydroxyglutarate (2-HG) . We recently reported that tyrosine phosphorylation activates IDH1 R132H mutant in AML cells. Here we show that, surprisingly, mutant IDH2 (mIDH2) R140Q commonly has K413-acetylation, which negatively regulates mIDH2 activity in human AML cells by attenuating dimerization and blocking binding of substrate (α-ketoglutarate) and cofactor (NADPH). Mechanistically, K413-acetylation of mitochondrial mIDH2 is achieved through a series of hierarchical phosphorylation events mediated by tyrosine kinase FLT3, which phosphorylates mIDH2 to recruit upstream mitochondrial acetyltransferase ACAT1 and simultaneously activates ACAT1 and inhibits upstream mitochondrial deacetylase SIRT3 through tyrosine- phosphorylation. Moreover, we found that the intrinsic enzyme activity of mIDH2 is much higher than mIDH1, thus the inhibitory K413-acetylation optimizes leukemogenic ability of mIDH2 in AML cells by both producing sufficient 2-HG for transformation and avoiding cytotoxic accumulation of intracellular 2-HG. In order to determine whether increased 2-HG level alone is responsible for the elevated cytotoxicity, we treated FLT3 ITD-expressing MOLM14 AML cells with increasing concentrations (100, 250, 500 and 1,000μM) of cell permeable TFMB-2-HG