bims-protra Biomed News
on Proteostasis and translation
Issue of 2025–06–22
five papers selected by
Marius d’Hervé, McGill University



  1. J Biosci. 2025 ;pii: 48. [Epub ahead of print]50
      The molecular chaperone Hsp70 is a pivotal player in cellular protein quality control due to its wide range of substrates ranging from unfolded, native, to misfolded proteins. Increasing evidence suggests that Hsp70 decides the fate of proteins; however, the inherent rules that govern the decision-making capacity of Hsp70 are not clear. In this review, we have articulated the functions of Hsp70 with respect to proteostasis and established a link between its co-chaperones in deciding the fate of the substrate. The substrate binding of Hsp70 is mediated by its catalytic cycle where Hsp70 achieves high- and low-substrate-affinity ADP- and ATP-bound forms, respectively. This catalytic cycle of Hsp70 is maintained by co-chaperones J-domain proteins (JDPs), and nucleotide exchange factors (NEFs). JDPs bind to the ATP-bound form of Hsp70 and hydrolyze ATP that enhances substrate binding, whereas NEFs exchange ADP with ATP and facilitate substrate release. During evolution, several isoforms of Hsp70 and its co-chaperones have emerged which may have functional significance. Apart from facilitating the catalytic cycle of Hsp70, co-chaperones often mediate collaboration between Hsp70 and downstream protein quality-control pathways such as the ubiquitin proteasome system, autophagy, or disaggregase machinery. Therefore, co-chaperones have a significant role in Hsp70's triage decision of whether to fold, hold, or degrade.
  2. Nucleic Acids Res. 2025 Jun 06. pii: gkaf496. [Epub ahead of print]53(11):
      HiBiT is an engineered luciferase's 11-amino-acid component that can be introduced as a tag at either terminus of a protein of interest. When the LgBiT component and a substrate are present, HiBiT and LgBiT dimerize forming a functional luciferase. The HiBiT technology has been extensively used for high-throughput protein turnover studies in cells. Here, we have adapted the use of the HiBiT technology to quantify messenger RNA (mRNA) translation temporally in vitro in the rabbit reticulocyte system and in cellulo in HEK293 cells constitutively expressing LgBiT. The assay system can uniquely detect differences in cap, 5'UTR, modified nucleotide composition, coding sequence optimization and poly(A) length, and their effects on mRNA translation over time. Importantly, using these assays we established the optimal mRNA composition varied depending on the encoded protein of interest, highlighting the importance of screening methods tailored to the protein of interest, and not reliant on reporter proteins. Our findings demonstrated that HiBiT can be easily and readily adapted to monitor real-time mRNA translation in live cells and offers a novel and highly favourable method for the development of mRNA-based therapeutics.
    DOI:  https://doi.org/10.1093/nar/gkaf496
  3. Nucleic Acids Res. 2025 Jun 06. pii: gkaf528. [Epub ahead of print]53(11):
      Concentrations of RNAs and proteins provide important determinants of cell fate. Robust gene circuit design requires an understanding of how the combined actions of individual genetic components influence both messenger RNA (mRNA) and protein levels. Here, we simultaneously measure mRNA and protein levels in single cells using hybridization chain reaction Flow-FISH (HCR Flow-FISH) for a set of commonly used synthetic promoters. We find that promoters generate differences in both the mRNA abundance and the effective translation rate of these transcripts. Stronger promoters not only transcribe more RNA but also show higher effective translation rates. While the strength of the promoter is largely preserved upon genome integration with identical elements, the choice of polyadenylation signal and coding sequence can generate large differences in the profiles of the mRNAs and proteins. We used long-read direct RNA sequencing to define the transcription start and splice sites of common synthetic promoters and independently vary the defined promoter and 5' UTR sequences in HCR Flow-FISH. Together, our high-resolution profiling of transgenic mRNAs and proteins offers insight into the impact of common synthetic genetic components on transcriptional and translational mechanisms. By developing a novel framework for quantifying expression profiles of transgenes, we have established a system for building more robust transgenic systems.
    DOI:  https://doi.org/10.1093/nar/gkaf528
  4. Nat Neurosci. 2025 Jun 18.
      The nervous system is primarily composed of neurons and glia, and the communication between them has profound roles in regulating the development and function of the brain. Neuron-glia signal transduction is known to be mediated by secreted signals through ligand-receptor interactions on the cell membrane. Here we show a new mechanism for neuron-glia signal transduction, wherein neurons transmit proteins to glia through extracellular vesicles, activating glial signaling pathways. We find that in the amphid sensory organ of Caenorhabditis elegans, different sensory neurons exhibit varying aging rates. This discrepancy in aging is governed by the cross-talk between neurons and glia. We demonstrate that early aged neurons can transmit heat shock proteins to glia via extracellular vesicles. These neuronal heat shock proteins activate the glial IRE1-XBP1 pathway, leading to the transcriptional regulation of chondroitin synthases to protect glia-embedded neurons from aging-associated functional decline. Therefore, our studies unveil a new mechanism for neuron-glia communication in the nervous system and provide new insights into our understanding of brain aging.
    DOI:  https://doi.org/10.1038/s41593-025-01989-0
  5. Cell Rep. 2025 Jun 19. pii: S2211-1247(25)00648-5. [Epub ahead of print]44(7): 115877
      Deciphering RNA molecules' function and regulation requires an in-depth understanding of the myriad interactions these RNAs form within their cellular environment. In this review, we present a comprehensive overview of recent technological advances that collectively form a molecular toolkit for mapping the molecular environment of RNA. We discuss innovative RNA-centric methods designed to overcome long-standing challenges in capturing direct RNA-protein interactions in living cells. Additionally, we explore transformative proximity-labeling techniques that leverage engineered enzymes and chemical catalysts to spatially resolve the composition of RNA-associated microenvironments. By critically evaluating the strengths and limitations of these emerging methodologies, we highlight how they are reshaping our understanding of RNA function, from local binding events to the dynamic organization of RNA-scaffolded compartments. These advancements not only promise to elucidate the molecular grammar underlying RNA regulatory networks in unprecedented details but also pave the way for an integrative, system-level understanding of complex RNA-mediated cellular processes.
    Keywords:  CP: Molecular biology; RNA localization; RNA-binding proteins; biotechnology development; microenvironment mapping
    DOI:  https://doi.org/10.1016/j.celrep.2025.115877