Biology subjects

Sontag, E. M.

Publications and source records attributed to Sontag, E. M..

4 recordsLinked to original sources

bioRxiv2026

Spatial protein quality control requires a functional GET pathway to prevent proteotoxicity

The proper management of misfolded proteins is an essential biological process that is required for the survival of all organisms. Previous work has demonstrated that misfolded proteins can be spatially sequestered into membrane-less compartments to facilitate their degradation. Soluble cytoplasmic misfolded proteins are sequestered in the juxtanuclear quality control compartment (JUNQ), and insoluble cytoplasmic misfolded proteins are sequestered into the insoluble protein deposit (IPOD). It is still unknown if there are upstream targeting pathways necessary for regulating JUNQ and IPOD formation. Here we investigated the role of ER targeting on JUNQ and IPOD formation. We find that the GET pathway is necessary for JUNQ formation. Inefficiencies in the GET pathway contribute to premature IPOD formation, and a defective GET pathway inhibits JUNQ formation altogether. Notably, we find the role of the GET pathway in JUNQ formation is required for cell survival and loss of GET pathway function is only toxic under proteotoxic stress. Overall, we identify a new role for the GET pathway in regulating spatial PQC and demonstrate that spatial quality control is essential for cell health and survival.

cell biology↗

bioRxiv2025

Stress granules and protein aggregates reveal intracellular resource competition

Stress granules are biomolecular condensates that form in response to environmental stress and disassemble once normal conditions are restored. However, when disassembly fails, stress granules can persist and solidify. While stress granule solidification has been well documented, the cellular mechanisms underlying the transition from reversible to persistent stress granules remain unclear. Persistent stress granules can seed the formation of pathological aggregates, such as TDP-43 in amyotrophic lateral sclerosis1, 2. Although amyloid and tau aggregates are hallmarks of Alzheimers disease, a subset of patients also develop TDP-43 deposits, suggesting a possible role for stress granule solidification in Alzheimers disease progression3-5. Despite theoretical models explaining why persistence and ensuing solidification occurs, strong in vivo evidence is lacking6. Here we show that competition for limited chaperone resources drive stress granule persistence. In the presence of TDP-43 aggregates or yeast amyloid proteins called prions, stress granule disassembly is slowed or halted disassembly. Using yeast prions as a model, we show that the addition of chaperones, specifically the AAA+ ATPase molecular chaperone, Hsp104, resulted in resumption of stress granule disassembly. Our results demonstrate that the competition for shared resources, such as molecular chaperones, can limit stress granule disassembly. We suspect that the presence of pathological aggregates results in resource competition within the aging brain, contributing to the persistence of stress granules and their subsequent solidification and aggregation.

cell biology↗

bioRxiv2022

An ESCRT-dependent pathway of Nuclear and Cytoplasmic Spatial PQC is coordinated at Nuclear Vacuolar Junctions

Effective Protein Quality Control (PQC), essential for cellular health, relies on spatial sequestration of misfolded proteins into defined inclusions. Here we elucidate the coordination of nuclear and cytoplasmic spatial PQC. While cytoplasmic misfolded proteins concentrate in a cytoplasmic, perinuclear Juxta Nuclear Quality control compartment (JUNQ), nuclear misfolded proteins sequester into a perinucleolar IntraNuclear Quality control compartment (INQ). Particle tracking reveals the INQ and JUNQ converge to face each other across the nuclear envelope at a site proximal to the Nuclear-Vacuolar Junction (NVJ) marked by perinuclear ESCRT-II/-III protein Chm7. Strikingly, this ESCRT-dependent convergence facilitates VPS4-dependent vacuolar clearance of misfolded cytoplasmic and nuclear proteins, the latter entailing extrusion of nuclear INQ into the vacuole. We propose perinuclear ESCRT coordinates spatial PQC at nuclear-vacuolar contacts to facilitate vacuolar clearance of nuclear and cytoplasmic misfolded proteins.

biochemistry↗

bioRxiv2020

Multi-Scale 3D Cryo-Correlative Microscopy for Vitrified Cells

Three-dimensional (3D) visualization of vitrified cells can uncover structures of subcellular complexes without chemical fixation or staining. Here, we present a pipeline integrating three imaging modalities to visualize the same specimen at cryogenic temperature at different scales: cryo-fluorescence confocal microscopy, volume cryo-focused ion beam scanning electron microscopy, and transmission cryo-electron tomography. Our proof-of-concept benchmark revealed the 3D distribution of organelles and subcellular structures in whole heat-shocked yeast cells, including the ultrastructure of protein inclusions that recruit fluorescently-labelled chaperone Hsp104. Since our workflow efficiently integrates imaging at three different scales and can be applied to other types of cells, it could be used for large-scale phenotypic studies of frozen-hydrated specimens in a variety of healthy and diseased conditions with and without treatments.

cell biology↗