Chronic stress disrupts the network among stress granules, P-bodies, and motor proteins

Stress granules (SGs) are dynamic RNA granules that rapidly form in response to various stresses concurrent with mRNA translation shutdown, contributing to cellular adaptation and disease pathogenesis. While SG assembly and disassembly under acute stress have been extensively characterized, how SGs behave under chronic stress remains poorly understood. We previously reported that chronic stress preconditioning inhibits the earliest steps of SG assembly via translation-dependent mechanisms. In contrast, the regulation of SG maturation under chronic stress has not yet been investigated. Here, we show that chronic stress decreases SG size by disrupting the MYH9-dependent myosin crosstalk with core SG nucleator G3BP1. This defect leads to impaired SG and processing body (PB) docking as well, limiting the biogenesis of early SGs. Furthermore, chronic stress reduces expression of the SG nucleator UBAP2L, required for SG-PB docking, thus exacerbating these deficiences. In summary, chronic stress disrupts the myosin-SG-PB network and inhibits SG maturation in a translation-independent manner. Summary Chronic stress disrupts the MYH9 network with G3BP1, which inhibits stress granule (SG) assembly. It also decreases UBAP2L levels, which inhibits SG and processing body docking. Disrupted MYH9 network further inhibits this docking, thus blocking maturation of SGs.