Nuclear localization of pyruvate dehydrogenase complex-E2 (PDC-E2), a mitochondrial enzyme, and its role in signal transducer and activator of transcription 5 (STAT5)-dependent gene transcription

Abstract

STAT (signal transducer and activator of transcription) proteins play a critical role in cellular response to a wide variety of cytokines and growth factors by regulating specific nuclear genes. STAT-dependent gene transcription can be finely tuned through the association with cofactors in the nucleus. We showed previously that STAT5 (including 5a and 5b) specifically interacts with a mitochondrial enzyme PDC-E2 (E2 subunit of pyruvate dehydrogenase complex) in both leukemic T cells and cytokine-stimulated cells. However, the functional significance of this novel association remains largely unknown. Here we report that PDC-E2 may function as a co-activator in STAT5-dependent nuclear gene expression. Subcellular fractionation analysis revealed that a substantial amount of PDC-E2 was constitutively present in the nucleus of BaF3, an interleukin-3 (IL-3)-dependent cell line. IL-3-induced tyrosine-phosphorylated STAT5 associated with nuclear PDC-E2 in co-immunoprecipitation analysis. These findings were confirmed by confocal immunofluorescence microscopy showing constant nuclear localization of PDC-E2 and its co-localization with STAT5 after IL-3 stimulation. Similar to mitochondrial PDC-E2, nuclear PDC-E2 was lipoylated and associated with PDC-E1. Overexpression of PDC-E2 in BaF3 cells augmented IL-3-induced STAT5 activity as measured by reporter assay with consensus STAT5-binding sites. Consistent with the reporter data, PDC-E2 overexpression in BaF3 cells led to elevated mRNA levels of endogenous SOCS3 (suppressor of cytokine signaling 3) gene, a known STAT5 target. We further identified two functional STAT5-binding sites in the SOCS3 gene promoter important for its IL-3-inducibility. The observation that both cis-acting elements were essential to detect the stimulatory effect by PDC-E2 strongly supports the role of PDC-E2 in up-regulating the transactivating ability of STAT5. All together, our results reveal a novel function of PDC-E2 in the nucleus. It also raises the possibility of nuclear-mitochondrial crosstalk through the interaction between STAT5 and PDC-E2.

Metabolic Enzymes Moonlighting in the Nucleus: Metabolic Regulation of Gene Transcription

“…The nuclear complex of PDC, PKM2, and p300, as discussed earlier, acetylates a specific histone, resulting in the activation of the transcription of a specific gene (arylhydrocarbon receptor) [6] (Figure 2). Similarly, the PDCE2 subunit has been found to form complexes with the transcription factor STAT5 [73]. These data support the existence of mechanisms that regulate localized acetylation in the nucleus by the strategic delivery of an ACPE in sub-nuclear domains.…”

Nuclear Localization of Mitochondrial TCA Cycle Enzymes as a Critical Step in Mammalian Zygotic Genome Activation

“…Nevertheless, following the four steps elaborated above for PCB, we found that a fraction of the CS enzyme also localizes to the nucleus (Figures 4D–4F) in a pyruvate-dependent manner (Figures 4F–4F″). While nuclear localization of PDH has been reported in other systems (Chueh et al, 2011; Sutendra et al, 2014), nuclear localization of a TCA cycle enzyme such as citrate synthase is an unexpected finding and led us to investigate the 2-cell embryo localization status of all TCA cycle enzyme isoforms that normally function in the mitochondrion. Beyond CS, the next TCA cycle step uses the mitochondrial enzyme aconitase 2 (ACO2) to metabolize citrate to iso-citrate.…”

“…Published literature provides precedence for extra-mitochondrial localization of PDH (Chueh et al, 2011; Mitra et al, 2005; Sutendra et al, 2014). Similar to our results in the pre-implantation embryo, all three subunits of PDH can be detected during the S phase of the cell cycle in the nucleus of lung cancer cell lines (Sutendra et al, 2014).…”

STAT3 Undergoes Acetylation-dependent Mitochondrial Translocation to Regulate Pyruvate Metabolism

“…However, GRIM19 largely inhibits STAT3 transcription by disrupting STAT3-DNA binding activity and further inhibits STAT3-mediated cell proliferation50. Pyruvate dehydrogenase complex-E2 (PDC-E2) has previously been reported to interact with STAT family members in a cytokine stimulation-dependent manner52. CBP-acetylated STAT3 translocates into mitochondria where STAT3 associates with PDC E1 and promotes pyruvate oxidation.…”