Phosphorylation of the rat Ins(1,4,5)P₃ receptor at T930 within the coupling domain decreases its affinity to Ins(1,4,5)P₃

Abstract

The Ins(1,4,5)P₃ receptor acts as a central hub for Ca²⁺ signaling by integrating multiple signaling modalities into Ca²⁺ release from intracellular stores downstream of G-protein and tyrosine kinase-coupled receptor stimulation. As such, the Ins(1,4,5)P₃ receptor plays fundamental roles in cellular physiology. The regulation of the Ins(1,4,5)P₃ receptor is complex and involves protein-protein interactions, post-translational modifications, allosteric modulation, and regulation of its sub-cellular distribution. Phosphorylation has been implicated in the sensitization of Ins(1,4,5)P₃-dependent Ca²⁺ release observed during oocyte maturation. Here we investigate the role of phosphorylation at T-930, a residue phosphorylated specifically during meiosis. We show that a phosphomimetic mutation at T-930 of the rat Ins(1,4,5)P₃ receptor results in decreased Ins(1,4,5)P₃-dependent Ca²⁺ release and lowers the Ins(1,4,5)P₃ binding affinity of the receptor. These data, coupled to the sensitization of Ins(1,4,5)P₃-dependent Ca²⁺ release during meiosis, argue that phosphorylation within the coupling domain of the Ins(1,4,5)P₃ receptor acts in a combinatorial fashion to regulate Ins(1,4,5)P₃ receptor function.

Keywords: :

• Ca²⁺ signaling
• IP₃ receptor
• phosphorylation
• affinity
• phosphomimetic

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

This work was supported by a grant from the National Institutes of Health, GM61829, and by a grant from the Qatar National Research Fund (QNRF), NPRP 08-395-3-088. R01-DK054568 to D.I.Y. The statements made herein are solely the responsibility of the authors. Additional support for the authors comes from Biomedical Research Program funds at Weill Cornell Medical College in Qatar, a program funded by Qatar Foundation.