Biology subjects

Rice, L. J.

Publications and source records attributed to Rice, L. J..

3 recordsLinked to original sources

bioRxiv2026

The folding, dimerization and allosteric landscapes of the ALS protein SOD1: a comprehensive mutational atlas

Mutations in superoxide dismutase 1 (SOD1) can disturb monomer folding and dimerization, ultimately leading to the development of amyotrophic lateral sclerosis (ALS). Genotype-phenotype knowledge of SOD1 monomer folding and dimerization is largely incomplete, impeding our ability to treat and understand SOD1-ALS. To address this issue, we performed multidimensional deep mutational scanning of [~]6,000 SOD1 variants (amino acid substitutions, insertions, deletions), quantifying folded monomer abundance, and measuring wild-type-variant heterodimerization. Importantly, both abundance and heterodimerization capture pathogenicity, with heterodimerization being a slightly better classifier of pathogenic variants. Notably, [~]80% of pathogenic variants and [~]70% of variants of uncertain significance in SOD1 perturb both monomer abundance and heterodimerization, pointing to protein destabilization as a major driver of SOD1-ALS. Orthogonal validation in mammalian cells shows that protein abundance strongly correlates with other disease-relevant phenotypes, including protein aggregation and toxicity. Although monomer abundance and heterodimerization are strongly coupled, residual effects identify variants that perturb the heterodimer beyond their impact on monomer folding. Mapping residual effects uncovers potential allosteric sites that modulate dimer stability independently of monomer folding, revealing mechanistic insights and potential therapeutic entry points to stabilize SOD1 as a dimer. Together, these results demonstrate that multidimensional phenotype variant mapping improves mechanistic understanding of SOD1 variants and clinical variant interpretation, while uncovering structural targets for SOD1-ALS treatment.

biophysics↗

bioRxiv2025

Small heat shock proteins HspB1 and HspB5 differentially alter the condensation and aggregation of the TDP-43 low complexity domain

TAR DNA-binding protein 43 (TDP-43) is a nucleic acid-binding protein that regulates processes of mRNA metabolism, during which it undergoes condensation mediated by its C-terminal low complexity domain (TDP-43LCD). TDP-43 aggregation and condensation are associated with neurodegenerative disease. However, the proteostasis mechanisms that regulate these processes remain elusive. Some evidence has shown that the molecular chaperone small heat shock protein HspB1 binds to and regulates the cytoplasmic phase separation of TDP-43, indicating that other small heat shock proteins may have similar effects. Here, we demonstrate divergent behaviours for HspB1 and its homolog HspB5 on TDP-43LCD condensation and aggregation. In addition to inhibiting TDP-43LCD aggregation, HspB1 partitions into TDP-43LCD condensates and increases the dynamic exchange of TDP-43LCD within condensates and with the surrounding solution. These effects of HspB1 are enhanced by mutations that mimic phosphorylation. HspB5 inhibits TDP-43LCD aggregation more effectively than HspB1 and partitions into TDP-43LCD condensates, where it delays pathological transition of the condensate to a gel/solid. We localise the chaperone effects of HspB1 and HspB5 to the N- and C-terminal regions of the protein, emphasising the role of sequence diversity in these regions in defining small heat shock protein function. These findings demonstrate that HspB1 and HspB5 are regulators of TDP-43 phase separation and aggregation and may be potential therapeutic targets in mitigating toxic TDP-43 aggregation in neurodegenerative disease. StatementThis work describes how two small heat shock proteins (proteins that bind to misfolded proteins) impact the condensation and aggregation of TDP-43, a protein implicated in most cases of amyotrophic lateral sclerosis. In doing so, it highlights their divergent behaviours and therapeutic potential.

biochemistry↗

bioRxiv2024

Single-molecule observations of human small heat shock proteins in complex with aggregation-prone client proteins

Small heat shock proteins (sHsps) are molecular chaperones that act to prevent the aberrant aggregation of misfolded proteins. Whilst it is widely suggested that sHsps prevent aggregation by binding to misfolded client proteins, the dynamic and heterogeneous nature of sHsps has hindered attempts to establish the mechanistic details of how sHsp-client protein complexes form. Single-molecule approaches have emerged as a powerful tool to investigate dynamic and heterogeneous interactions such as those that can occur between sHsps and their client proteins. Here, we use total internal reflection fluorescence microscopy to observe and characterise the complexes formed between model aggregation-prone client proteins [firefly luciferase (FLUC), rhodanese, and chloride intracellular channel 1 protein (CLIC)], and the human sHsps B-crystallin (B-c; HSPB1) and Hsp27 (HSPB5). We show that small (monomeric or dimeric) forms of both B-c and Hsp27 bind to misfolded or oligomeric forms of the client proteins at early stages of aggregation, resulting in the formation of soluble sHsp-client complexes. Stoichiometric analysis of these complexes revealed that additional B-c subunits accumulate onto pre-existing sHsp-client complexes to form larger species - this does not occur to the same extent for Hsp27. Instead, Hsp27-client interactions tend to be more transient than those of B-c. Elucidating these mechanisms of sHsp function is crucial to our understanding of how these molecular chaperones act to inhibit protein aggregation and maintain cellular proteostasis.

molecular biology↗