Updated project metadata. The phosphorylation state of human HA-tagged-SIK2, adenovirally introduced in murine hepatocytes (C57/BL/6 strain) was analysed in unstimulated and in response to glucagon- or insulin- treated conditions. Background:- LKB1 is a master kinase that regulates metabolism and growth through AMPK and 12 other closely-related kinases. Liver-specific ablation of LKB1 causes increased glucose production in hepatocytes in vitro and hyperglycaemia in fasting mice in vivo. The salt-inducible kinases (SIK1, 2 and 3), members of the AMPK-related kinase family, play a key role as gluconeogenic suppressor downstream of LKB1 in the liver. A selective SIK inhibitor (HG-9-91-01) promotes dephosphorylation of transcriptional co-activators CRTC2/3 resulting in enhanced gluconeogenic gene expression and glucose production in hepatocytes, an effect that is abolished when an HG-9-91-01-insensitive-mutant-SIK is introduced or LKB1 is ablated. Although SIK2 was proposed as a key regulator of insulin-mediated suppression of gluconeogenesis, we provide genetic evidence that liver-specific ablation of SIK2 alone has no effect on gluconeogenesis and insulin does not modulate SIK2 phosphorylation/activity. Collectively, we demonstrate that the LKB1-SIK pathway functions as a key gluconeogenic gatekeeper in the liver.