A novel non-catalytic scaffolding activity of Hexokinase 2 contributes to EMT and metastasis

Hexokinase 2 (HK2), a glycolytic enzyme that catalyzes the first committed step in glucose metabolism, is markedly induced in cancer cells. HK2s role in tumorigenesis has been attributed to its glucose kinase activity. However, we uncovered a novel kinase-independent HK2 activity, which promotes metastasis. We found that HK2 binds and sequesters glycogen kinase 3 (GSK3) and acts as a scaffold forming a ternary complex with the regulatory subunit of protein kinase A (PRKAR1a) and GSK3b to facilitate GSK3b phosphorylation by PKA, and to inhibit its activity. Thus, HK2 functions as an A-kinase anchoring protein (AKAP). GSK3b is known to phosphorylate proteins, which in turn are targeted for degradation. Consistently, HK2 increased the level and stability of the GSK3 targets, MCL1, NRF2, and SNAIL. In a mouse model of breast cancer metastasis, systemic HK2 deletion after tumor onset inhibited metastasis, which is determined by the effect of HK2 on GSK3b and SNAIL. We concluded that HK2 promotes SNAIL stability and breast cancer metastasis via two mechanisms: direct modulation of GSK3-activity and SNAIL-glycosylation that decreases susceptibility to phosphorylation by GSK3.