Stimulation of Gαq Promotes Stress Granule Formation

During adverse conditions, mammalian cells regulate protein production by sequestering the translational machinery in membrane-less organelles known as stress granules. Here, we found that activation of the G protein subunit Gq promoted the formation of particles that contained stress granule proteins through a mechanism linked to the presence of phospholipase C{beta}1 (PLC{beta}1) in the cytosol. In experiments with PC12 and A10 cells, we showed that under basal conditions, cytosolic PLC{beta}1 bound to stress granule associated proteins, including PABPC1, eIF5A, and Ago2. Knockdown of cytosolic PLC{beta}1 with siRNA or promoting its relocalization to the plasma membrane by activating Gq resulted in the formation of particles containing the stress granule markers, PABPC1, G3BP1, and Ago2. Our studies showed that the composition of these particles resemble those formed under osmotic stress and are distinct from those formed by other stresses. Our results fit a simple thermodynamic model in which cytosolic PLC{beta}1 solubilizes stress granule proteins such that its movement to activated Gq releases these particles to enable the formation of stress granules. Together, our data are suggestive of a link between Gq-coupled signals and protein translation through stress granule formation.