Journal article
A Dual-Compartment Scaffolding Role for RACK1 in Hepatic Glucagon Signaling and Gluconeogenesis
Cellular and molecular gastroenterology and hepatology, Vol.20(2), 101666
2025
DOI: 10.1016/j.jcmgh.2025.101666
PMCID: PMC12718467
PMID: 41115526
Abstract
The hepatic glucagon-PKA-CREB signaling axis plays a central role in regulating gluconeogenesis and maintaining glucose homeostasis during fasting. However, the mechanisms that govern the spatial coordination and substrate specificity of this pathway remain incompletely understood. This study determines the role of the scaffolding protein RACK1 (Receptor for Activated C Kinase 1) in orchestrating glucagon signaling to regulate hepatic gluconeogenesis.
RACK1 was acutely deleted in mouse liver and primary hepatocytes. Metabolic phenotypes were assessed by glucose, pyruvate, glucagon and insulin tolerance tests, as well as hepatocyte glucose production assays. Protein interactions were examined by co-immunoprecipitation, GST pulldown, and miniTurbo-ID-mediated proximity labeling. Subcellular localization and signaling events were assessed by Western blotting, confocal microscopy, and cellular fractionation. Functional rescue was achieved by hepatic expression of a constitutively active PKA catalytic subunit (PKAcα
).
Acute hepatic RACK1 deficiency caused fasting hypoglycemia, impaired gluconeogenesis, and improved glucose, pyruvate and glucagon tolerance without affecting insulin signaling. RACK1 directly bound GCGR, PKA regulatory (RIIα) and catalytic (PKAcα) subunits, as well as CREB, functioning as a dual-compartment scaffold assembling GCGR-PKA complexes at the plasma membrane and PKAcα-CREB complexes in the nucleus. Loss of RACK1 impaired PKAcα translocation, CREB phosphorylation, and gluconeogenic gene expression. These defects were rescued by PKAcα
expression. Overexpression of RACK1 WD1-2 and WD3-4 domains, which mediate PKA, GCGR and CREB interactions, similarly disrupted PKA signaling and gluconeogenesis.
RACK1 functions as a dual-compartment scaffold, assembling GCGR-PKA at the plasma membrane and PKAcα-CREB in the nucleus, enabling precise glucagon signaling and gluconeogenesis while sparing insulin pathways, thereby ensuring compartmentalized regulation of hepatic glucose homeostasis.
Details
- Title: Subtitle
- A Dual-Compartment Scaffolding Role for RACK1 in Hepatic Glucagon Signaling and Gluconeogenesis
- Creators
- Cancan Lyu - Departments of Neuroscience and Pharmacology andLing Yang - University of IowaSonghai Chen - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Cellular and molecular gastroenterology and hepatology, Vol.20(2), 101666
- DOI
- 10.1016/j.jcmgh.2025.101666
- PMID
- 41115526
- PMCID
- PMC12718467
- NLM abbreviation
- Cell Mol Gastroenterol Hepatol
- ISSN
- 2352-345X
- eISSN
- 2352-345X
- Publisher
- Elsevier; SAN DIEGO
- Grant note
- National Institutes of Health: R01CA282699 Fraternal Order of Eagle Diabetes Research Center, University of Iowa
This work was supported in part by funding from National Institutes of Health grant R01CA282699 (Songhai Chen) and a pilot grant from Fraternal Order of Eagle Diabetes Research Center, University of Iowa.
- Language
- English
- Electronic publication date
- 10/18/2025
- Date published
- 2025
- Academic Unit
- Molecular Physiology and Biophysics; Anatomy and Cell Biology; Iowa Neuroscience Institute; Fraternal Order of Eagles Diabetes Research Center; Neuroscience and Pharmacology
- Record Identifier
- 9985019040402771
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