A G-Protein Subunit Translocation Embedded Network Motif Underlies GPCR Regulation of Calcium Oscillations

Abstract

G-protein βγ subunits translocate reversibly from the plasma membrane to internal membranes on receptor activation. Translocation rates differ depending on the γ subunit type. There is limited understanding of the role of the differential rates of Gβγ 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 Gβγ translocation rate regulates calcium oscillations induced by G-protein-coupled receptor activation. Oscillations in HeLa cells expressing γ subunit types with different translocation rates were imaged and quantitated. The results show that differential Gβγ 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.

Band-pass processing in a GPCR signaling pathway selects for NFAT transcription factor activation

“…Most calcium mathematical models exhibit continuous oscillations without decay in frequency or amplitude when subjected to step ligand stimulation, in contrast to our own experimental observations and literature data 29–31 . One model that does offer an explanation for frequency and amplitude decay 32 doesn’t explain the phase locking behavior we observe. Building upon Jovic et al 33 , we incorporated receptor phosphorylation and receptor internalization followed by receptor recycling or degradation to reproduce our observed calcium response at various frequencies and concentrations of stimulation (Text S2, ESI†).…”

When trafficking and signaling mix: How subcellular location shapes G protein‐coupled receptor activation of heterotrimeric G proteins

“…If GPCRs activate G proteins at the endosome, a next important question is whether relevant effectors and cofactors are present in sufficiently close physical proximity to mediate downstream signaling. There is evidence indicating that some G protein‐dependent effector proteins are indeed present in the endosome limiting membrane but much remains unknown, and there is also evidence that heterotrimeric G proteins have the potential to traffic or translocate between membranes separately from GPCRs . Moreover, considering that plasma membrane and endosome membranes differ broadly in protein and lipid compositions, it is conceivable that there exist numerous mediators or regulators of compartment‐specific GPCR signaling and trafficking that are presently unknown.…”

Optogenetic approaches for dissecting neuromodulation and GPCR signaling in neural circuits

“…Localization of signaling is now at the forefront of GPCR research. Gautam et al demonstrated that Gβγ subunits not only translocate to intracellular membranes upon GPCR activation, but regulate cytoplasmic calcium concentrations [30,31]. Additionally, there is recent and increasing evidence for the sustain propagation of G-protein-mediated signaling within endosomes [32,33].…”