Investigating the role and regulation of the AMPK-related kinase NUAK1

Abstract

AMP-activated protein kinase (AMPK) is a well characterised central regulator of energy homeostasis with many downstream substrates and potential therapeutic targets. Recently several kinases related to AMPK have been identified which are activated by the same upstream kinase, LKB1, and share significant sequence homology with the catalytic α subunit of AMPK. Previous studies have implicated NUAK1, one of these related kinases, in cell cycle regulation and other studies have identified various partner proteins but as yet there is no consensus model of its regulation or physiological role. This aim of this study was to investigate the regulation and interactions of NUAK1 using an in vitro system and also use an in vivo tissue specific mouse knockout system to investigate its function in two different tissues. The results of these studies reveal new insights into the regulation of NUAK1 in vitro and suggest that the kinase is capable of activation by autophosphorylation, in the absence of LKB1. NUAK1 is shown to interact with 14-3-3 proteins and evidence that this interaction may be important for the function of the kinase is presented. Cell based studies in mouse embryonic fibroblasts (MEFs) lacking NUAK1 show that it is involved in proliferation and there are suggestions of pathways involved in regulating this effect. NUAK1 liver-specific knockout mice were generated and extensive metabolic phenotyping analyses were carried out. In young animals deletion of NUAK1 in liver did not lead to any obvious changes in whole body metabolism. However, preliminary studies revealed a possible role for NUAK1 in metabolic regulation in older mice and in response to liver damage. Mice with heart-specific deletion of NUAK1 were generated and these mice were found to have a cardiac hypertrophy phenotype in response to angiotensin II treatment. Potential signalling pathways downstream of NUAK1 in the heart were then investigated in this model.