Prominin-1-Radixin Axis controls hepatic gluconeogenesis by regulating PKA activity

Prominin-1 (Prom1) is a major cell surface marker of cancer stem cells, but its physiological functions in the liver have not been elucidated. We analyzed the levels of mRNA transcripts in serum-starved primary Prom1 +/+ and Prom1 -/- mouse hepatocytes using RNA-sequencing (RNA-seq) data, and found that CREB target genes were down-regulated. This initial observation led us to determine that the Prom1 deficiency inhibited cAMP response element binding protein (CREB) activation and gluconeogenesis, but not cyclic AMP (cAMP) accumulation, in glucagon-, epinephrine-, or forskolin-treated liver tissues and primary hepatocytes, and mitigated glucagon-induced hyperglycemia. Because Prom1 interacted with radixin, the Prom1 deficiency prevented radixin from localizing to the plasma membrane. Moreover, systemic adenoviral knockdown of radixin inhibited CREB activation and gluconeogenesis in glucagon-treated liver tissues and primary hepatocytes, and mitigated glucagon-elicited hyperglycemia. Based on these results, we conclude that Prom1 regulates hepatic PKA signaling via radixin functioning as an A kinase-anchored protein (AKAP). * AKAP : A kinase-anchored protein AC : adenylyl cyclase cAMP : cyclic adenosine monophosphate PKA : protein kinase A CREB : cAMP response element binding protein pck : phosphoenol pyruvate carboxykinase g6p : glucose-6-phosphatase G6pc : g6p catalytic subunit PI3K : phosphatidylinositide 3-kinases Fbp1 : fructose 1,6-bisphosphatase 1 GPCR : G protein– coupled receptor PDE : phosphodiesterase IBMX : 3-isobutyl-1-methylxanthine 8-Br-cAMP : 8-Bromo-cAMP DIO : diet-induced obese shRNA : short hairpin RNA FERM : F for 4.1 protein, E for ezrin, R for radixin and M for moesin CFTR : fibrosis transmembrane conductance regulator NHE3 : Na+-H+ exchanger 3 Cx43 : connexin 43 EPAC : exchange protein directrly activated by cAMP