Differing roles of pyruvate dehydrogenase kinases during mouse oocyte maturation

Abstract

Pyruvate dehydrogenase kinases (PDKs) modulate energy homeostasis in multiple tissues and cell types, under various nutrient conditions, through phosphorylation of the α subunit (PDHE1α, also known as PDHA1) of the pyruvate dehydrogenase (PDH) complex. However, the roles of PDKs in meiotic maturation are currently unknown. Here, by undertaking knockdown and overexpression analysis of PDK paralogs (PDK1-PDK4) in mouse oocytes, we established the site-specificity of PDKs towards the phosphorylation of three serine residues (Ser232, Ser293 and Ser300) on PDHE1α. We found that PDK3-mediated phosphorylation of Ser293-PDHE1α results in disruption of meiotic spindle morphology and chromosome alignment and decreased total ATP levels, probably through inhibition of PDH activity. Unexpectedly, we discovered that PDK1 and PDK2 promote meiotic maturation, as their knockdown disturbs the assembly of the meiotic apparatus, without significantly altering ATP content. Moreover, phosphorylation of Ser232-PDHE1α was demonstrated to mediate PDK1 and PDK2 action in meiotic maturation, possibly through a mechanism that is distinct from PDH inactivation. These findings reveal that there are divergent roles of PDKs during oocyte maturation and indicate a new mechanism controlling meiotic structure.

SIRT4 is essential for metabolic control and meiotic structure during mouse oocyte maturation

“…Of note, ectopic expression of SIRT4 results in the very similar phenotypes as we observed in oocytes overexpressing pyruvate dehydrogenase kinase 3 (PDK3) (Hou et al., 2015). Moreover, it has been reported that PDKs expression was altered in multiple cell types with SIRT4 depletion (Nasrin et al., 2010; Tao, Zhang, Ling, McCall, & Liu, 2018).…”

“…PDH is able to modulate tricarboxylic acid (TCA) cycle in cells, producing ATP and many biosynthetic intermediates in mammalian oocytes. We have discovered that the phosphorylation status of PDHE1α subunit is associated with metabolic control and meiotic apparatus in mouse oocytes (Hou et al., 2015). We therefore asked whether the PDHE1α phosphorylation, at least in part, mediates the effects of SIRT4 on oocyte maturation.…”

“…Toward this goal, we first examined the phosphorylation status of two serine residues (Ser232 and Ser293) on PDHE1α in control and SIRT4‐OE oocytes. pSer232‐PDHE1α accumulated on the spindle region and its poles of metaphase oocytes (Figure 6A,B) as we reported previously (Hou et al., 2015). However, neither SIRT4 knockdown nor overexpression showed an apparent effect on the pSer232‐PDHE1α signal intensity.…”

“…PDH is able to convert pyruvate into acetyl coenzyme A and thereupon modulates the entry of glucose‐derived carbons into TCA cycle (Hou et al., 2015). Pdha1‐deficient mouse oocytes experience inadequate ATP levels along with chromatin and microtubular abnormalities (Johnson et al., 2007).…”

“…Pdha1‐deficient mouse oocytes experience inadequate ATP levels along with chromatin and microtubular abnormalities (Johnson et al., 2007). We have demonstrated that phosphorylation of Ser293‐PDHE1α results in disruption of meiotic spindle morphology and chromosome movement and lowered total ATP content, probably through inhibition of PDH activity (Hou et al., 2015). It is note that, SIRT4 was recently found to decrease the activity of the PDH complex in human cell lines and mouse models (Mathias et al., 2014).…”