ChREBP regulates the expression of numerous genes involved in lipid and carbohydrate homeostasis. The activity of ChREBP can be modulated by AMPKmediated phosphorylation. A defect in which of the following enzymes would most likely be apparent if ChREBP was found to be constitutively phosphorylated and inhibited?

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Protein phosphatase 2Aδ is responsible for dephosphorylating ChREBP, allowing it to become active. If ChREBP is constitutively phosphorylated and inhibited, it suggests a defect in the enzyme responsible for its dephosphorylation, which is protein phosphatase 2Aδ.  Under conditions of low (basal) glucose concentration, ChREBP is phosphorylated and resides in the cytosol. When glucose levels rise, protein phosphatase 2Aδ (PP2Aδ) is activated by xylulose 5-phosphate which is generated in the pentose phosphate pathway. PP2Aδ dephosphorylates ChREBP allowing it to migrate into the nucleus. In the nucleus PP2Aδ carries out a second dephosphorylation which allows ChREBP to bind to specific sequence elements (ChoREs) in target genes. Therefore, a defect in the activity of PP2Ad would lead to constitutive phosphorylation and inhibition of ChREBP

ChREBP Regulates the Expression of Numerous Genes Involved in Lipid