AMPK and FLCN/FNIP: investigating regulation, interactions and signalling crosstalk
File(s)
Author(s)
Pascual Navarro, Eneko
Type
Thesis
Abstract
Dysregulation of energy metabolism is an important factor underlying many diseases, such as type 2 diabetes, obesity and cancer. AMP-activated protein kinase (AMPK) acts as an ATP sensor, the main energy source in all living cells. AMPK is activated in response to lowered ATP levels, and acts to maintain energy homeostasis by decreasing ATP-utilisation and increasing ATP-generation. Our recent studies revealed that chronic genetic activation of AMPK in mice leads to development of polycystic kidney disease. This phenotype is similar to the renal presentation of Birt-Hogg-Dubé (BHD) syndrome and mice lacking expression of folliculin (FLCN) in the kidney. Mutations in the FLCN gene are causative for BHD. Importantly, loss of FLCN or loss of folliculin interacting proteins (FNIP1 or FNIP2) has been reported to lead to activation of AMPK in both human cells and animal models. The FLCN/FNIP complex has been linked to changes in both mTOR and AMPK pathways. Whilst the function of FLCN/FNIP in mTORC1 signalling has been largely elucidated, its interactions with AMPK are still being explored. In this project the effects of FLCN/FNIP on AMPK activity and energy sensing were explored using human cell lines with FLCN and FNIP1 loss. A number of key findings were made: AMPK activation via FLCN loss was shown to be dependent on nutritional context and changes in mTOR signalling. Lowered ATP/AMP balance and increase of total AMPK protein levels were measured in FLCN KO HEK293T partly explaining greater AMPK activity. FLCN KO was observed to hinder glucose sensing by AMPK. FLCN/FNIP/AMPK association was seen increased with AMPK activation, and FNIP2 specifically interacting with AMPK α2β1γ1. Lastly, FLCN S62 previously reported to be indirectly affected by AMPK was determined to be directly phosphorylated by AMPK and FNIP2 phosphorylation was observed with 3 candidate serine residues: 216, 244 and 667.
Version
Open Access
Date Issued
2023-12
Date Awarded
2024-10
Copyright Statement
Creative Commons Attribution NonCommercial ShareAlike Licence
Advisor
Carling, David
Publisher Department
Institute of Clinical Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)