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PAK1 Is Involved in the Spindle Assembly during the First Meiotic Division in Porcine Oocytes
Lei Peng1, Yijing He1, Weihan Wang1
1MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
Abstract:
P21-activated kinase 1 (PAK1), as a member of the PAK family, has been implicated in various functions during somatic mitosis; however, less is known about its role during oocyte meiosis. Herein, we highlight the indispensable role of PAK1 in regulating spindle assembly and cell cycle progression during the first meiotic division of porcine oocytes. First, we found that the activated PAK1 expressed dynamically, and its subcellular localization was tightly associated with the spindle dynamics during meiosis in porcine oocytes. Specific inhibition of PAK1 activity by inhibitor targeting PAK1 activation-3 (IPA-3) led to impaired extrusion of the first polar body (PB1); with most of the IPA-3-treated oocytes arrested at germinal vesicle breakdown (GVBD) and subjected to failure of bipolar spindle formation. However, the adverse effects caused by IPA-3 on oocytes could be restored by reducing disulfide bonds between PAK1 and IPA-3 with dithiothreitol (DTT) treatment. Furthermore, the co-immunoprecipitation assay revealed that PAK1 interacted directly with Aurora A and transforming acidic coiled coil 3 (TACC3), providing an additional explanation for the similar localization of Aurora A and activated PAK1. Additionally, inhibiting the activity of PAK1 decreased the expression of p-Aurora A and p-TACC3; however, the reduced activity of Aurora A and TACC3 could be restored by DTT. In conclusion, PAK1 plays a crucial role in the proper assembly of the spindle during the first meiotic division of porcine oocytes, and the regulation of PAK1 is associated with its effects on p-Aurora A and p-TACC3 expression.
Insights
P21-activated kinase 1 (PAK1) is essential for spindle assembly and cell cycle progression during porcine oocyte meiosis. Inhibiting PAK1 disrupts first polar body extrusion and bipolar spindle formation, but effects are reversible.
Area of Science:
- Reproductive biology
- Cell biology
- Molecular biology
Background:
- P21-activated kinase 1 (PAK1) is known for its role in somatic cell mitosis.
- Its function in oocyte meiosis remains largely unexplored.
- Understanding PAK1's role is crucial for reproductive science.
Purpose of the Study:
- To investigate the role of PAK1 in regulating spindle assembly and cell cycle progression during porcine oocyte meiosis.
- To elucidate the molecular mechanisms underlying PAK1's function in oocyte maturation.
Main Methods:
- Dynamic expression and localization analysis of activated PAK1 in porcine oocytes.
- Inhibition of PAK1 activity using IPA-3 and assessment of meiotic progression.
- Restoration of oocyte function using dithiothreitol (DTT).
- Co-immunoprecipitation assays to identify PAK1 interacting partners.
Main Results:
- Activated PAK1 expression and localization correlate with spindle dynamics during meiosis.
- PAK1 inhibition by IPA-3 leads to meiotic arrest at germinal vesicle breakdown (GVBD), impaired first polar body (PB1) extrusion, and failure of bipolar spindle formation.
- IPA-3's adverse effects are reversible with DTT treatment.
- PAK1 directly interacts with Aurora A and transforming acidic coiled coil 3 (TACC3).
- PAK1 inhibition decreases p-Aurora A and p-TACC3 levels, which are restored by DTT.
Conclusions:
- PAK1 is indispensable for proper spindle assembly during the first meiotic division of porcine oocytes.
- PAK1 regulates spindle formation through its effects on Aurora A and TACC3 phosphorylation.
- PAK1's role in oocyte meiosis is critical for successful cell cycle progression.
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