Investigation of the Role of G3BP in Stress Granule Formation in Senescence

Abstract

Senescent cells accumulate with age and are defined as the cells that irreversibly lose their ability to proliferate. They are characterized by an enlarged flat cell phenotype, enlarged nucleus with persistent DNA damage foci, and an increase in senescence-associated β-galactosidase (SA-β-GAL) activity. The accumulation of senescent cells with ageing is associated with physiological decline and age-related diseases.

Cells experience stress and damage from internal or external sources which induce various responses ranging from recovery to cell death. They respond to stress by regulating RNA translation to allow the expression of proteins required for cell viability. During stress, untranslated mRNAs are re-directed from polysomes to cytoplasmic aggregates known as stress granules. The assembly of stress granules is promoted by RNA-binding proteins including G3BP which is the nucleating protein of stress granule assembly.

Mammalian cells have three G3BP proteins: G3BP1, G3BP2a and G3BP2b, encoded by 2 genes G3BP1 and 2. We investigated the formation of stress granules in proliferative, stress induced premature senescent (SIPS) and replicative senescent cells in primary human dermal fibroblast cells and U2OS cell lines. Senescence phenotype, stress granule formation, lipid droplet accumulation and differential proteome-wide expression were investigated in WT U2OS cells and in cells lacking G3BP1/2 as well as in cells that were reconstituted with a single form of G3BP.