Biology subjects

Yang, Y.-M.

Publications and source records attributed to Yang, Y.-M..

7 recordsLinked to original sources

bioRxiv2026

Calcium-dependent facilitation of P/Q-type calcium channels governs the polarity and magnitude of short-term synaptic plasticity

P/Q-type calcium channel (Cav2.1) is the major channel that mediates Ca2+ influx during action potentials (APs) and evokes neurotransmitter release from presynaptic terminals. Repetitive activity induces its Ca2+-dependent facilitation (CDF) via binding of calmodulin (CaM) superfamily proteins to the IQ-like motif, specifically isoleucine (I) and methionine (M) sites, on the cytoplasmic c-terminus of Cav2.1. However, whether and how CDF contributes to short-term synaptic plasticity remains elusive. By recordings from the calyx of Held terminal in IQ-like motif point mutation knock-in mice (Cav2.1 IM-AA KI), we found that activity-dependent CDF is completely abolished, resulting in lower quantal output and shorter release time course as well as profound reductions in the magnitute of short-term facilitation and depression (STF and STD) in different Ca2+ concentrations. Prolonging deactivation of Ca2+ channels by broadening spike width normalizes quantal output and release time course in Cav2.1 IM-AA synapses, but does not fully rescue STF/STD. These results indicate that CDF of Cav2.1 channels governs the polarity and magnitude of short-term synaptic plasticity in fast-spiking central synapses.

neuroscience↗

bioRxiv2024

The ubiquitin-proteasome system regulates the formation of specialized ribosomes during high salt stress in yeast

Rps26-deficient ribosomes are a physiologically relevant ribosome population which arises during osmotic stress to support the translation of mRNAs involved in the response to high salt in yeast. They are formed by binding of the chaperone Tsr2 to fully assembled ribosomes to release Rps26 when intracellular Na+ concentrations rise. Tsr2-mediated Rps26 release is reversible, enabling a rapid response that conserves ribosomes. However, because the concentration of Tsr2 relative to ribosomes is low, how the released Rps26*Tsr2 complex is managed to allow for accumulation of Rps26-deficient ribosomes to nearly 50% of all ribosomes remains unclear. Here we show that released Rps26 is degraded via the Pro/N-degron pathway, enabling the accumulation of Rps26-deficient ribosomes. Substitution of the N-terminal proline of Rps26 to serine increases the stability of free Rps26, limits the accumulation of Rps26-deficient ribosomes and renders yeast sensitive to high salt. The GID-complex, an E3 ubiquitin ligase, and its adaptor Gid4, mediate polyubiquitination of Rps26 at Lys66 and Lys70. Moreover, this ubiquitination event is required for Rps26 degradation, the accumulation of Rps26-deficient ribosomes and the high salt stress resistance. Together, the data show that targeted degradation of released Rps26 from the Rps26*Tsr2 complex allows Tsr2 to be recycled, thus facilitating multiple rounds of Rps26 release.

biochemistry↗

bioRxiv2023

Unstructured Domains in Assembly Factors Promote the Hierarchy of Ribosome Maturation via Their Structural Plasticity.

Ribosomes are assembled with the help of a large machinery of assembly factors (AFs), whose roles remain incompletely characterized. Recent structural studies of assembly intermediates have provided tremendous context for such studies and helped reveal novel roles, including as RNA chaperones. These structures have also revealed that a subset of the AFs have entirely non-globular structures, or large non-globular extensions, which extend across the assembling ribosomal subdomains, contacting many rRNA regions, ribosomal proteins (RPs) and other AFs. How these unusual structures could help promote assembly has remained unclear although it has been suggested that their potential for making multiple interactions helps constrain early assembly steps. By studying the roles of the AF Ltv1, an entirely non-globular protein, during late maturation steps of the 40S subunits head, we show here how the structural plasticity that derives from the non-globular structure is used to communicate maturation steps across the nascent subunit, thereby establishing the previously described hierarchy in head assembly. Our data indicate that while this structural plasticity enables integration of distinct folding and assembly steps, it also creates the potential for mutations that allow for bypass of these QC steps. These mutations are pathogenic in humans, further demonstrating the importance of proper 40S subunit assembly for protein homeostasis.

biochemistry↗

bioRxiv2023

Limited Expression of Nrf2 in Neurons Across the Central Nervous System

Nrf2 is a broadly expressed transcription factor that regulates gene expression in response to reactive oxygen species (ROS) and oxidative stress. It is commonly referred to as a ubiquitous pathway, but this generalization overlooks work indicating that Nrf2 is essentially unexpressed in some neuronal populations. To explore whether this pattern extends throughout the central nervous system (CNS), we quantified Nrf2 expression and chromatin accessibility at the Nrf2 locus across multiple single cell datasets. In both the mouse and human CNS, Nrf2 was repressed in almost all mature neurons, but highly expressed in non-neuronal support cells, and this pattern was robust across multiple human CNS diseases. A subset of key Nrf2 target genes, like Slc7a11, also remained low in neurons. Thus, these data suggest that while most cells express Nrf2, with activity determined by ROS levels, neurons actively avoid Nrf2 activity by keeping Nrf2 expression low.

neuroscience↗

bioRxiv2022

Chaperone-Directed Ribosome Repair after Oxidative Damage

Reactive oxygen species are ubiquitous in cells, where they damage RNA and protein. While relief mechanisms, including effects on translation, have been described, whether ribosomes are functionally compromised by oxidation, and how this damage is mitigated, remains unknown. Here we show that cysteines in ribosomal proteins, including Rps26, are readily oxidized and rendered non-functional, which is exacerbated when yeast are exposed to H2O2. Oxidized Rps26 is released from ribosomes by its chaperone Tsr2, which allows for repair of the damaged ribosomes with newly made Rps26. Ribosomes containing damaged Rpl10 or Rpl23 are similarly repaired by their chaperones, Sqt1 and Bcp1. Ablation of this pathway impairs growth, which is exacerbated under oxidative stress. These findings reveal a novel mechanism for chaperone-mediated ribosome repair with implications for aging and health. One-Sentence SummaryChaperones repair thiol-oxidized ribosomes by release of damaged components and incorporation of newly made ribosomal proteins.

molecular biology↗

bioRxiv2021

The chaperone Tsr2 regulates Rps26 release and reincorporation from mature ribosomes to enable a reversible, ribosome-mediated response to stress

Although ribosome assembly is quality controlled to maintain protein homeostasis, different ribosome populations have been described. How these form, especially under stress conditions that impact energy levels and stop the energy-intensive production of ribosomes, remains unknown. Here we demonstrate how a physiologically relevant ribosome population arises during high Na+ and pH stress via dissociation of Rps26 from fully assembled ribosomes to enable a translational response to these stresses. The chaperone Tsr2 releases Rps26 in the presence of high Na or pH in vitro and is required for Rps26 release in vivo. Moreover, Tsr2 stores free Rps26 and promotes re-incorporation of the protein, thereby repairing the subunit after the stress subsides. Our data implicate a residue in Rps26 involved in Diamond Blackfan Anemia in mediating the effects of Na+. These data demonstrate how different ribosome populations can arise rapidly, without major energy input, and without bypass of quality control mechanisms. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/438496v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@151e234org.highwire.dtl.DTLVardef@d9d3fcorg.highwire.dtl.DTLVardef@ec628corg.highwire.dtl.DTLVardef@13a0917_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LITsr2 releases Rps26 from mature ribosomes to remodel ribosome populations C_LIO_LITsr2 stores released Rps26 and allows for ribosome repair after stress C_LIO_LIRps26 exploits a Mg binding site linked to Diamond Blackfan Anemia (DBA) C_LIO_LIChaperone-mediated ribosome remodeling might be common for chaperoned RPs C_LI

molecular biology↗

bioRxiv2019

Human antiviral protein MxA forms novel metastable membrane-less cytoplasmic condensates exhibiting rapid reversible \"crowding\"-driven phase transitions

Phase-separated biomolecular condensates of proteins and nucleic acids form functional membrane-less organelles in the mammalian cell cytoplasm and nucleus. We report that the interferon (IFN)-inducible human \"myxovirus resistance protein A\" (MxA) forms membrane-less metastable condensates in the cytoplasm. Light and electron microscopy studies revealed that transient expression of HA- or GFP-tagged MxA in Huh7, HEK293T or Cos7 cells, or exposure of Huh7 cells to IFN-2a led to the appearance of MxA in the cytoplasm in membrane-less variably-sized spherical or irregular bodies, in filaments and even a reticulum. 1,6-Hexanediol treatment led to rapid disassembly of these condensates; however, FRAP revealed a relative rigidity with a mobile fraction of only 0.24{+/-}0.02 within condensates. In vesicular stomatitis virus (VSV)-infected Huh7 cells, the nucleocapsid (N) protein, which participates in forming phase-separated viral structures, associated with GFP-MxA condensates. Remarkably, the cytoplasmic GFP-MxA condensates disassembled within 1-3 min of exposure of cells to hypotonic medium (40-50 milliosmolar) and reassembled within 0.5-2 min of re-exposure of cells to isotonic medium (310-325 milliosmolar) through multiple cycles. Mechanistically, the extent of cytoplasmic \"crowding\" regulated this phase-separation process. GFP-MxA condensates also included the DNA sensor protein cyclic GMP-AMP synthase (cGAS), another protein known to be associated with liquid-like condensates. Functionally, GFP-MxA expression inhibited DNA/cGAS-responsive ISG54-luciferase activity but enhanced relative inducibility of ISG54-luc by IFN-, revealing a physical separation between condensate- and cytosol-based signaling pathways in the cytoplasm. Taken together, the data reveal a new aspect of the cell biology of MxA in the cell cytoplasm.\n\nImportanceThe human interferon-inducible \"myxovirus resistance protein A\" (MxA), which displays antiviral activity against several RNA and DNA viruses, exists in the cytoplasm in phase-separated membrane-less metastable condensates of variably-sized spherical or irregular bodies, in filaments and even in a reticulum. MxA condensate formation appeared necessary but not sufficient for antiviral activity. Remarkably, MxA condensates showed the unique property of rapid (within 1-3 min) reversible disassembly and reassembly in intact cells exposed sequentially to hypotonic and isotonic conditions Mechanistically, these phase transitions were regulated by the extent of cytoplasmic \"crowding.\" Moreover, GFP-MxA condensates included the DNA sensor protein cyclic GMP-AMP synthase (cGAS). Functionally, GFP-MxA expression inhibited DNA/cGAS-responsive ISG54-luciferase activity but enhanced inducibility of ISG54-luc by IFN-, revealing a biological distinction between condensate- and cytosol-based signaling pathways. Since intracellular edema and ionic changes are hallmarks of cytopathic viral effects, the rapid hypotonicity-driven disassembly of MxA condensates may modulate MxA.function during virus infection.

cell biology↗