Hexokinase 1 Cellular Localization Regulates the Metabolic Fate of Glucose

The product of hexokinase (HK) enzymes, glucose-6-phosphate, can be metabolized through glycolysis or directed to alternative pathways, such as the pentose phosphate pathway (PPP) to generate anabolic intermediates. However, it is not known what determines the fate of G6P. HK1 contains an N-terminal mitochondrial–binding domain, but its physiologic significance remains unclear. We overexpressed full-length and truncated HK1 in tissue culture and generated mice lacking the HK1 mitochondrial-binding domain (ΔE1HK1). Although ΔE1HK1 mice displayed no overt phenotype, HK1 dislocation from the mitochondria increased glucose flux through the PPP, decreased flux below the level of GAPDH, and induced a hyper-inflammatory response to lipopolysaccharide. The mechanism for the increased PPP flux is through glycolytic block at GAPDH, which is mediated by binding of cytosolic HK1 with S100A8/A9 and increased GAPDH nitrosylation through iNOS. Additionally, human and mouse macrophages from conditions of low-grade inflammation, such as aging and diabetes, displayed an increase in cytosolic HK1 and cytokine production, along with reduced GAPDH activity. Our data indicate that HK1 mitochondrial-binding alters glucose metabolism through regulation of GAPDH.