SCP4 Promotes Gluconeogenesis Through FoxO1/3a Dephosphorylation

Area of Science:

• Cellular Biology
• Metabolism
• Molecular Endocrinology

Background:

• FoxO1 and FoxO3a (FoxO1/3a) proteins are crucial regulators of hepatic gluconeogenesis.
• Akt-mediated phosphorylation causes cytoplasmic retention of FoxO1/3a, inhibiting its activity.
• The nuclear phosphatase directly regulating FoxO1/3a activity remained unidentified.

Purpose of the Study:

• To identify the nuclear phosphatase responsible for regulating FoxO1/3a activity.
• To investigate the role of this phosphatase in hepatic gluconeogenesis.
• To explore its potential as a therapeutic target for metabolic disorders.

Main Methods:

• Identification and characterization of a novel nuclear phosphatase, SCP4/CTDSPL2 (SCP4).
• Assays to determine SCP4's effect on FoxO1/3a dephosphorylation and transcriptional activity.
• In vitro and in vivo studies using gene manipulation (ectopic expression, knockdown, ablation) to assess glucose production and metabolic phenotypes.
• Analysis of SCP4 expression under various physiological and pathophysiological conditions.

Main Results:

• SCP4 was identified as a nuclear phosphatase that dephosphorylates FoxO1/3a.
• SCP4 enhances the transcription of gluconeogenic genes PEPCK1 and G6PC.
• SCP4 overexpression increases, while knockdown inhibits, hepatic glucose production.
• SCP4 gene ablation results in hypoglycemia in neonatal mice.
• SCP4 expression is induced by glucose deprivation and elevated in obese mice.

Conclusions:

• SCP4 is a key regulator of hepatic gluconeogenesis by dephosphorylating and activating FoxO1/3a.
• SCP4 plays a critical role in maintaining glucose homeostasis.
• SCP4 represents a potential therapeutic target for conditions like diet-induced glucose intolerance and type 2 diabetes.