Background/Purpose: Th17 cells are key players in SLE. Because Th17 cells use mainly glycolysis, blocking glycolysis can inhibit Th17 cell differentiation and treatment of lupus-prone mice with a combination of glycolysis and mitochondrial metabolism inhibitors reverses disease manifestations. In Th17 cells, pyruvate dehydrogenase (PDH), the enzyme which converts pyruvate to acetyl coenzyme A, is decreased. PDH kinase (PDHK) inactivates PDH whereas PDH phosphatase (PDP) activates PDH. Although previous reports showed PDHK was increased in Th17 and inhibition of PDHK suppressed Th17 differentiation, the underlying molecular mechanisms have not been elucidated yet. cAMP response element modulator (CREM) modulates the transcription of c-AMP responsible genes. We have shown that the inducible cAMP early repressor (ICER) isoform of CREM promotes Th17 cell differentiation and ICER/CREM deficient mice have less autoimmune disease and CD4⁺ T cells from the patients with SLE have more ICER/CREM expression than those from health donors¹. Because many genes associated with cell metabolism have cAMP response element (CRE) sites, to which ICER/CREM binds, we sought to identify metabolic enzymes controlled directly by ICER/CREM in Th17 cells.

Methods: Naïve CD4⁺ T cells from ICER/CREM sufficient or deficient mice were cultured under Th17 conditions. Glycolysis and glycolytic capacity were analyzed by extracellular flux analyzer. PDHK and PDP catalytic subunit 2 (PDP2) expression were measured by qPCR and Western blotting. These experiments were repeated after ICERγ overexpression. Then the effect of ICER to Pdp2 promoter was assessed by luciferase reporter and chromatin immunoprecipitation assays. We also analyzed the effect of PDP2 overexpression on glycolysis and Th17 cell differentiation in vitro. Finally, CD4⁺CD45RA^–CCR6⁺CCR4⁺ cells (memory Th17 cells) were sorted from patients with SLE or healthy donors and Pdp2 gene expression was assessed by qPCR.

Results: ICER/CREM deficiency decreased glycolysis and glycolytic capacity in Th17 polarized cells and this was reversed by ICERγ overexpression. PDP2 expression increased in ICER/CREM-deficient Th17 polarized cells compared to that recorded in ICER/CREM-sufficient counterparts. ICERγ overexpression corrected the increased levels of PDP2 in ICER/CREM-deficient Th17 cells. On the other hand, decreased PDHK was observed in ICER/CREM-deficient Th17 cells, however, ICERγ overexpression did not restore its expression. Furthermore, Pdp2 promoter reporter assay revealed that Pdp2 activity was increased by site-direct mutation of putative ICER binding site. ICER accumulation at those CRE sites was confirmed by chromatin immunoprecipitation assays. PDP2 overexpression reduced glycolysis and Th17 differentiation. Pdp2 gene expression in memory Th17 cells tended to be decreased in lupus compared to healthy donors.

Conclusion: ICER increases glycolysis and promotes Th17 differentiation by inhibiting directly the expression of PDP2. Because PDP2 overexpression reduces Th17 cell differentiation, PDP2 might be a new therapeutic target.

Reference

1. Nobuya Y et. al. Nature Commun. 2016 29;7:12993

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/inducible-camp-early-repressor-promotes-glycolysis-by-inhibiting-the-pyruvate-dehydrogenase-phosphatase-catalytic-subunit-2-in-th17-cells/