A Hydride Transfer Complex Reprograms NAD Metabolism Preventing Senescence

Abstract

Metabolic rewiring and redox balance play pivotal roles in cancer. Cellular senescence is a barrier for tumorigenesis circumvented in cancer cells by poorly understood mechanisms. We report a novel multi-enzymatic complex that reprograms NAD metabolism by transferring reducing equivalents from NADH to NADP +. This hydride transfer complex (HTC) is assembled by Malate Dehydrogenase-1, Malic Enzyme-1 and cytosolic Pyruvate Carboxylase. HTC enzymes are found in phase-separated bodies in the cytosol of cancer cells and can be assembled in vitro from purified proteins. They are repressed in senescent cells but induced by p53 inactivation. HTC enzymes are highly expressed in mouse and human prostate cancer models and their inactivation triggers senescence. Exogenous expression of HTC is sufficient to bypass senescence, rescue cells from complex I inhibitors and cooperate with oncogenic RAS to transform primary cells. We provide evidence for a new multi-enzymatic complex that reprograms metabolism and prevents cellular senescence.

Keywords: NAD, NADPH, cellular senescence, mitochondrial dysfunction, MDH1, ME1, PC, metabolon