Issues

Like other organelles, the heterogeneity of lysosomes within a single cell has been challenging to capture and study in detail. In this issue, Chen and Gutierrez discuss new work that tackles this question using DNA-PAINT imaging from Lakadamyali and colleagues.

Cozma and Westermann highlight work from Larson and colleagues which shows that kinetochores display directional asymmetry in side attachments, gripping more strongly when pulled toward plus-ends.

Duronio and colleagues highlight work from Xu et al. that reveals how the nuclear import adaptor KPNA3 controls histone locus body formation and prevents aberrant condensation of NPAT in the cytoplasm.

Kane discusses work from Huda et al. showing that in S. cerevisiae transient cell cycle–dependent asymmetry in PI(3,5)P₂ levels promotes vacuolar acidification in daughter cells.

de Jager et al. show that compacted and expanded microtubule lattice spacings coexist within cells and that microtubules recognized by a marker for stable microtubules are predominantly expanded. This adds another potential regulatory layer to the organization of microtubule networks and the establishment of specialized subsets.

This study reveals that the signaling lipid PI(3,5)P₂ accumulates on the daughter vacuole while it disappears from the mother vacuole during yeast mitosis. Asymmetric PI(3,5)P₂ synthesis is crucial for vacuolar-pH asymmetry and provides insights into how the mother cell ages while the daughter cell is rejuvenated.

PtdIns(4,5)P₂ plays essential roles in plasmalemmal functions, but its two-dimensional distribution has been unclear due to technical challenges. This paper shows that the freeze-fracture replica labeling method can address this problem, revealing that PtdIns(4,5)P₂ is enriched in yeast eisosome/MCC but not clustered in PC12 cells.

It was unclear how the H2A-H2B chaperone Nap1 cooperates with the importin Kap114 to transport and process H2A-H2B. Fung et al. explain how they co-chaperone H2A-H2B, and how Ran^GTP and Nap1, within the quaternary Nap1₂/H2A-H2B/Kap114/Ran^GTP complex, coordinate the transfer of H2A-H2B from Kap114 to assembling nucleosomes.

Larson et al. show that kinetochores grip the sides of microtubules much more strongly when they are pulled toward plus ends. This striking mechanical asymmetry correlates with molecular rearrangements inside the kinetochores and might promote biorientation during early mitosis by stabilizing attachments specifically when sister kinetochores have captured opposing microtubules.

Xu et al. reveal the roles of the nuclear import adaptor KPNA3 in regulating histone locus body formation by importing NPAT into nuclei. Moreover, KPNA3 modulates the self-association of NPAT via a steric hindrance strategy to prevent aberrant NPAT condensation in the cytoplasm.

The neuromuscular junction (NMJ) is a well characterized synapse, yet, the postsynaptic contributions that allow for synapse function are not well understood. von Saucken et al. use the Drosophila larval NMJ to define synaptic muscle (myo)nuclei and their properties and determine how BMP signaling regulates these myonuclear properties.

Guo et al. reveal that the SARS-CoV-2 nucleocapsid (N) protein inhibits NF-κB activation by disrupting the TAK1–TAB2/3 complex, a mechanism that differs from the SARS-CoV N protein. They identify key residues in the SARS-CoV-2 N protein, shedding light on differences in viral pathogenicity.

Tey et al. characterize the role of ubiquitin in the rapid turnover kinetics of the immune checkpoint protein CTLA4. A complex architecture of associated ubiquitin chains is revealed by a comprehensive ubiquitin chain restriction analysis in the absence of the deubiquitylase USP8.

Excessive lipids and oxidative stress are strong risk factors for cardiovascular complications. Feng et al. report that saturated fatty acids cause mitochondrial damage and ROS elevation in human endothelial cells. Activation of lysosome biogenesis using TRPML1 agonists is sufficient to mitigate SFA-induced mitochondria damage.

Courjaret et al. map the distribution of Ca²⁺ signaling effectors that support the tunneling of Ca²⁺ entering the cell to distal effectors. They further engineer a specific Ca²⁺ tunneling inhibitor (CaTAr) to show the importance of Ca²⁺ tunneling for chloride extrusion and sweating.

Traffic of soluble secretory proteins from the endoplasmic reticulum by the export receptor, SURF4, is remarkably complex. Different cargoes use distinct mechanisms of engagement with the COPII cargo adaptor, SEC24, and in some cases bind co-translationally with SURF4 to “fast-track” out of the ER.

Lehmann et al. characterize two new populations of neurons that undergo remodeling during Drosophila metamorphosis. Beat-Va_M neurons undergo extensive neurite pruning, which is largely independent of neuronal ecdysone signaling, and instead, primarily driven by astrocytes. Beat-Va_L neurons undergo Abd-B–mediated, caspase-driven cell death in a segmentally restricted manner.

Han et al. use primary hippocampal cultures to demonstrate that neurons with axon-carrying–dendrite (AcD) morphology can develop independent of an in vivo environment. They found that the axon initial segment (AIS) of AcD neurons maintains cytoskeletal integrity but lacks homeostatic plasticity and receives fewer inhibitory inputs.

Liu et al. developed an optimized method to study transcriptional dynamics in living C. elegans. They inserted MS2 loops in the intron of mCherry and tagged endogenous genes with this modified mCherry, which allowed monitoring transcription upon stress and avoided interfering with endogenous gene expression.

Ishikawa et al. establish a comprehensive resource of strains and plasmids to suppress genes required for fission yeast viability. Strains and plasmids are individually stored, and they enable complicated phenotypical analyses, facilitating functional investigations of essential genes that are evolutionary conserved among eukaryotes.

Fahim and Marcus et al. developed live-cell microscopy approaches to address whether co-localized enzyme factors are forming biochemically relevant interactions within RNA–protein condensates. These tools enable rigorous tracking of protein–protein interactions within biomolecular condensates, such as stress granules and mRNA processing bodies.

This study developed a multiplexed and quantitative DNA-PAINT super-resolution imaging pipeline to investigate the distribution of late endosomal/lysosomal (LEL) proteins across individual LELs, revealing cell-type-specific LEL subpopulations with unique protein compositions, offering insights into organelle heterogeneity at single-organelle resolution.

Khosrozadeh et al. developed CryoVesNet, which enables accurate segmentation of synaptic vesicles in cryo-electron tomograms. This automated tool analyzes synaptic ultrastructure and vesicle pools efficiently across diverse synapses, advancing our understanding of synaptic function and synaptic vesicle pool dynamics.