Progesterone-induced Warburg Effect is Regulated by Cell-type-specific Interaction of Progesterone Receptor Membrane Component 1 and Hexokinases
Background: Progesterone receptor membrane component 1 (PGRMC1) is a non-canonical progesterone (P4) binding protein. PGRMC1 is elevated in a variety of cancers and its phosphorylation state associated with hormone responsiveness in breast cancer. Metabolic reprogramming is a key factor for tumor growth during malignancies. Recently, we reported that the P4-inducedWarburg effectinHEK293cells is associated with altered post-translational modifications (PTMs) of PGRMC1, including phosphorylation,
... ng phosphorylation, SUMOylation, and ubiquitination, which were linked to rapid proteasomal degradation of the protein. The previous study also identified hexokinase (HK) as a potential novel interacting partner of PGRMC1. HKs catalyze the first essential step of glucose metabolism and directly couple glycolysis to mitochondrial respiration. Therefore, in the present study, P4's effects on glycolysis and PTMs of PGRMC1 as well as its interaction with HKs were compared between HEK293 and HepG2 cells to unravel the signaling pathways that mediate cell-type-specific metabolic reprogramming.Methods: P4-induced glucose metabolism in wild-type and PGRMC1-deficient cells wasassessed using the Seahorse flux analyzer, while PTMs of PGRMC1/HKs and protein-protein interaction were studied using immunoprecipitation, isoelectric focussing, phosphomimetics, and mass spectrometry.Translocation of HKs to different subcellular organelles were studied using subcellular fractionation, and the cell-type-specific effect of PGRMC1-deficiency on endoplasmic reticulum (ER) and mitochondria; ultrastructure were examined by electron microscopy. Results:P4 treatment caused a rapid increase in glycolysis in HEK293 cells, whereas it decreased glycolysis in HepG2 cells. In addition, PGRMC1 was not degraded in HepG2 cells which is in contrast to HEK293 cells where rapid proteasomal degradation of PGRMC1 occurredfollowing P4 treatment. Besides, PGRMC1 half-life and PTMs under basal condition were found cell-type-specific and the P4-induced PTMsdiffered between the two cell types. Furthermore, we observed cell-type-specific interaction of HKs with PGRMC1, and differential translocation of HK1/2 to the ER, mitochondria and nuclear compartments following P4 treatment. PGRMC1 deficiency altered ER structure in HepG2 cells. Thus, multiple factors underlying the cell-type-specific P4-PGRMC1-mediated metabolic reprogrammingwere identified. Conclusions: These findings provide a hitherto unknown novel P4-induced cell-type-specific PGRMC1-HK signaling mechanism that contributes to the molecular basis of P4-induced metabolic reprogramming, with important applications for hormone responsiveness in cancer.