G‐Protein‐Coupled Receptor Kinase 2 Inhibition Induces Meiotic Arrest by Disturbing Ca2+ Release in Porcine Oocytes

Abstract

ABSTRACTG‐protein‐coupled receptor kinase 2 (GRK2) interacts with Gβγ and Gαq, subunits of G‐protein alpha, to regulate cell signalling. The second messenger inositol trisphosphate, produced by activated Gαq, promotes calcium release from the endoplasmic reticulum (ER) and regulates maturation‐promoting factor (MPF) activity. This study aimed to investigate the role of GRK2 in MPF activity during the meiotic maturation of porcine oocytes. A specific inhibitor of GRK2 (βi) was used in this study. The present study showed that GRK2 inhibition increased the percentage of oocyte arrest at the metaphase I (MI) stage (control: 13.84 ± 0.95%; βi: 31.30 ± 4.18%), which resulted in the reduction of the maturation rate (control: 80.36 ± 1.94%; βi: 65.40 ± 1.14%). The level of phospho‐GRK2 decreased in the treated group, suggesting that GRK2 activity was reduced upon GRK2 inhibition. Furthermore, the addition of βi decreased Ca2+ release from the ER. The protein levels of cyclin B and cyclin‐dependent kinase 1 were higher in the treatment group than those in the control group, indicating that GRK2 inhibition prevented a decrease in MPF activity. Collectively, GRK2 inhibition induced meiotic arrest at the MI stage in porcine oocytes by preventing a decrease in MPF activity, suggesting that GRK2 is essential for oocyte meiotic maturation in pigs.