Glucose modulates transcription factor dimerization to enable tissue differentiation
Glucose is a universal energy currency for living organisms, however, its non-energetic functions in processes such as differentiation are undefined. In epidermis, differentiating cells exhibit dynamic changes in gene expression1-4 driven by specific transcription factors (TFs)5-9. The interplay between such TFs and biomolecules that also change in this process is not understood. Metabolomic analyses revealed that increased intracellular glucose accompanies differentiation of epidermal keratinocytes. This elevation also occurred in differentiating cells from other tissues and was verified in epidermal tissue engineered with glucose sensors, which detected a glucose gradient that peaked in the outermost differentiated layers. Free glucose accumulation, unaccompanied by its increased metabolism, was essential for epidermal differentiation and required GLUT1, GLUT3, and SGLT1 transporters. Glucose affinity chromatography and azido-glucose click chemistry uncovered glucose binding to diverse regulatory proteins, including the IRF6 TF, whose epidermal knockout confirmed its requirement in glucose-dependent differentiation. Direct glucose binding enabled IRF6 dimerization, DNA binding, genomic localization, and induction of IRF6 target genes, including essential pro-differentiation TFs GRHL1, GRHL3, HOPX and PRDM1. The IRF6R84C mutant found in undifferentiated cancers was unable to bind glucose. These data identify a new role for glucose as a gradient morphogen that modulates protein multimerization in cellular differentiation.