S-nitrosylated glyceraldehyde-3-phosphate dehydrogenase initiates apoptotic cell death by nuclear translocation following Siah1 binding

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a classical glycolytic protein known for its pivotal role in energy production. Recent evidence demonstrates that mammalian GAPDH displays a number of diverse activities unrelated to its glycolytic function, including its possible role in apoptosis. Our laboratory has found that GAPDH translocates to the nucleus following a wide range of apoptotic stimuli1. Antisense oligonucleotides targeted to GAPDH decrease nuclear GAPDH and prevent cell death. This thesis attempts to study a mechanism underlying this nuclear translocation and cytotoxicity. GAPDH, which lacks a nuclear localization signal (NLS), bind to the NLS-containing protein Siahl (an E3-ubiquitin-ligase), which mediates GAPDH's nuclear translocation. Nitric oxide (NO) generation following apoptotic stimulation elicits S-nitrosylation of GAPDH, which augments its binding to Siahl. GAPDH stabilizes Siahl facilitating its degradation of nuclear proteins. Activation of macrophages by endotoxin and of neurons by glutamate elicits GAPDH-Siahl binding, nuclear translocation and apoptosis, which are prevented by NO deletion. The NO-S-nitrosylation-GAPDH-Siahl cascade may represent a major molecular mechanism of cytotoxicity.