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Updated: Jun 16, 2025
Sensitive Measurement of Mitophagy by Flow Cytometry Using the pH-dependent Fluorescent Reporter mt-Keima
Published on: August 12, 2018
PKD regulates mitophagy to prevent oxidative stress and mitochondrial dysfunction during mouse oocyte maturation
Ya-Ping Liu1, Bing He1, Wen-Xin Wang1
1College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China.
Abstract:
Mitochondria play dominant roles in various cellular processes such as energy production, apoptosis, calcium homeostasis, and oxidation-reduction balance. Maintaining mitochondrial quality through mitophagy is essential, especially as its impairment leads to the accumulation of dysfunctional mitochondria in aging oocytes. Our previous research revealed that PKD expression decreases in aging oocytes, and its inhibition negatively impacts oocyte quality. Given PKD's role in autophagy mechanisms, this study investigates whether PKD regulates mitophagy to maintain mitochondrial function and support oocyte maturation. When fully grown oocytes were treated with CID755673, a potent PKD inhibitor, we observed meiosis arrest at the metaphase I stage, along with decreased spindle stability. Our results demonstrate an association with mitochondrial dysfunction, including reduced ATP production and fluctuations in Ca2+ homeostasis, which ultimately lead to increased ROS accumulation, stimulating oxidative stress-induced apoptosis and DNA damage. Further research has revealed that these phenomena result from PKD inhibition, which affects the phosphorylation of ULK, thereby reducing autophagy levels. Additionally, PKD inhibition leads to decreased Parkin expression, which directly and negatively affects mitophagy. These defects result in the accumulation of damaged mitochondria in oocytes, which is the primary cause of mitochondrial dysfunction. Taken together, these findings suggest that PKD regulates mitophagy to support mitochondrial function and mouse oocyte maturation, offering insights into potential targets for improving oocyte quality and addressing mitochondrial-related diseases in aging females.
Insights
Protein kinase D (PKD) regulates mitophagy, a process crucial for maintaining mitochondrial quality in aging oocytes. Inhibiting PKD impairs mitophagy, leading to mitochondrial dysfunction and reduced oocyte maturation.
Area of Science:
- Cell Biology
- Reproductive Biology
- Mitochondrial Biology
Background:
- Mitochondria are vital for cellular functions, and their quality control via mitophagy is essential, particularly in aging oocytes where impaired mitophagy causes dysfunction.
- Previous studies showed decreased protein kinase D (PKD) expression in aging oocytes, negatively impacting oocyte quality.
- PKD is implicated in autophagy, prompting an investigation into its role in mitophagy and oocyte maturation.
Purpose of the Study:
- To investigate the role of protein kinase D (PKD) in regulating mitophagy for maintaining mitochondrial function and supporting oocyte maturation.
- To understand the molecular mechanisms by which PKD inhibition affects oocyte quality and mitochondrial health.
Main Methods:
- Treatment of fully grown mouse oocytes with CID755673, a potent PKD inhibitor.
- Assessment of meiotic progression, spindle stability, mitochondrial function (ATP production, Ca2+ homeostasis, ROS levels), and apoptosis.
- Analysis of autophagy-related protein phosphorylation (ULK) and mitophagy-related protein expression (Parkin).
Main Results:
- PKD inhibition caused meiotic arrest at metaphase I and decreased spindle stability.
- Mitochondrial dysfunction was observed, including reduced ATP, altered Ca2+ homeostasis, increased ROS, and enhanced oxidative stress-induced apoptosis and DNA damage.
- PKD inhibition reduced autophagy by affecting ULK phosphorylation and decreased Parkin expression, impairing mitophagy and leading to damaged mitochondria accumulation.
Conclusions:
- Protein kinase D (PKD) plays a critical role in regulating mitophagy to maintain mitochondrial function and support mouse oocyte maturation.
- PKD inhibition disrupts mitophagy, leading to mitochondrial dysfunction and compromised oocyte quality.
- Targeting PKD may offer a strategy for improving oocyte quality and addressing age-related mitochondrial dysfunction in females.
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