A G-Protein Subunit Translocation Embedded Network Motif Underlies GPCR Regulation of Calcium Oscillations
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G-protein beta gamma subunits translocate reversibly from the plasma membrane to internal membranes on receptor activation. Translocation rates differ depending on the gamma subunit type. There is limited understanding of the role of the differential rates of G(beta gamma) translocation in modulating signaling dynamics in a cell. Bifurcation analysis of the calcium oscillatory network structure predicts that the translocation rate of a signaling protein can regulate the damping of system oscillation. Here, we examined whether the G(beta gamma) translocation rate regulates calcium oscillations induced by G-protein-coupled receptor activation. Oscillations in HeLa cells expressing gamma subunit types with different translocation rates were imaged and quantitated. The results show that differential G(beta gamma) translocation rates can underlie the diversity in damping characteristics of calcium oscillations among cells. Mathematical modeling shows that a translocation embedded motif regulates damping of G-protein-mediated calcium oscillations consistent with experimental data. The current study indicates that such a motif may act as a tuning mechanism to design oscillations with varying damping patterns by using intracellular translocation of a signaling component.
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