Stimulation of phospholipase Cβ1 by Gα _q promotes the assembly of stress granule proteins

Abstract

Stimulation of Gα q -coupled GPCRs releases PLCβ1 from stress granule–associated proteins, enabling their aggregation.

Activation of Gαq sequesters specific transcripts into Ago2 particles

“…As expected, we find a significant increase in the cumulative number and size of particles relative to control for all three stress conditions, consistent with stress granule formation 15 . The trends seen for eGFP-G3BP1 mirror previous studies 4 of Ago2 under stress conditions. Removing the stress and viewing the cells 30 min after recovery show little disassembly of the stress granules (Fig.…”

“…Previous studies followed the formation of stress granules associated with Ago2 and PABPC1 by Gαq activation in undifferentiated PC12 cells as well as two other cell lines 4 , and here we extended these studies to differentiated PC12 cells. We first followed the assembly of the stress granule marker, eGFP-G3BP1, whose dimerization initiates stress granule formation 15 .…”

“…These studies used time-lapse fluorescence imaging and assessed the number of fluorophores associated with a diffusing particle called Number and Brightness (N&B) 16 analysis. We find that the amount of eGFP-G3BP1 fluorescence intensity associated with diffusing particles increases with the loss of cytosolic PLCβ1 either by down-regulation, by relocalization to the membrane upon Gαq activation, or by osmotic stress which also reduces cytosolic PLCβ1 levels 4 (Fig. 1 A–D).…”

“…Our recent study showed that reducing the cytosolic PLCβ1 population increases the number and size of particles containing Ago2 as well as the stress granule markers PABPC1 and G3BP1 4 , 12 . Binding between PLCβ1 and stress granule proteins helps keep them disperse, while activation of Gαq promotes relocalization of cytosolic PLCβ1 to the plasma membrane, promoting release of bound proteins and the formation of stress granules.…”

“…Gαq, in turn, activates phospholipase Cβ, which catalyzes the hydrolysis of the signaling lipid phosphoinositide 4,5 bisphosphate leading to an increase in intracellular calcium 2 . Along with this important membrane function, PLCβ1 has been shown to have a cytosolic population that binds to the Promoter of RNA-induced silencing, C3PO, as well as several proteins involved in stress granules formation 3 , 4 . Stress granules are halted ribosomal complexes that protect mRNAs under stress conditions such as arsenite treatment, heat/cold shock and osmotic stress 5 – 7 .…”