ON THE COVER
Artistic representation of dynein-2 molecular motors (red) powering retrograde intraflagellar transport (IFT) on axonemal microtubules (green). This retrograde IFT machinery advances toward the ciliary transition zone barrier (dark grey at the end of the microtubule tracks), which they need to cross in order to exit the cilium. Image © Maria J.G. De-Castro et al. https://doi.org/10.1083/jcb.202010178
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People & Ideas
Rushika M. Perera: Lysosomes unveil what cancer cells hide
Rushika M. Perera studies how pancreatic cancer cells utilize autophagy and the lysosome to adapt to stress.
Stressed-out yeast do not pass GO
Coller highlights work from Argüello-Miranda et al. that reveals that yeast devoid of nutrients can enter into quiescence outside of the G1/GO phase in the cell cycle.
Thank ORP9 for FFAT: With endosomal ORP10, it’s fission accomplished!
Wong et al. discuss recent work from Kawasaki et al. describing a role for lipid countertransport at ER–endosome contact sites in endosomal fission.
The ides of MARCH5: The E3 ligase essential for peroxisome degradation by pexophagy
Platta and Erdmann highlight work from Zheng et al. that shows that MARCH5 is recruited to peroxisomes and plays a role in pexophagy regulation.
IFT trains overcome an NPHP module barrier at the transition zone
Park and Leroux introduce work from the Dantas laboratory that reveals that the NPHP module of the ciliary transition zone functions as a barrier for retrograde IFT trains.
Cell cycle–independent integration of stress signals by Xbp1 promotes Non-G1/G0 quiescence entry
Argüello-Miranda et al. use machine learning and spectral imaging to show how the stress-activated transcriptional repressor Xbp1 can drive cellular quiescence—a reversible arrest of proliferation crucial for stress survival and development—even outside the G1 cell cycle stage.
Pcp1/pericentrin controls the SPB number in fission yeast meiosis and ploidy homeostasis
Zhu et al. show that the dynamic localization of Pcp1 on the spindle pole body (SPB) regulates SPB fusion during sexual reproduction of Schizosaccharomyces pombe. Polyploid zygotes lose the dynamics of Pcp1, resulting in blockage of SPB fusion and dysregulation of meiosis and mitosis.
Astral microtubule cross-linking safeguards uniform nuclear distribution in the Drosophila syncytium
Deshpande et al. use a single-embryo explant assay, RNAi, and micromanipulation to show that antiparallel microtubule cross-linking by Fascetto (Feo) and the kinesin-4, Klp3A, is required for regular nuclear distribution in the Drosophila melanogaster syncytial embryo.
LUBAC regulates ciliogenesis by promoting CP110 removal from the mother centriole
Shen et al. identify the linear ubiquitin ligase complex LUBAC as a novel regulator of ciliogenesis and further mechanistically explain that LUBAC regulates ciliogenesis by promoting the removal of CP110 on the mother centriole. Their findings provide insights into ciliary functions and ciliopathies during development.
CEP97 phosphorylation by Dyrk1a is critical for centriole separation during multiciliogenesis
Lee et al. identify Dyrk1a as a new interaction partner that phosphorylates CEP97, which in turn promotes recruitment of Plk1. The complex of CEP97–Dyrk1a–Plk1 plays a substantive role in the maturation and location of centrioles/basal bodies and proper ciliogenesis in multiciliated cells.
PI4P/PS countertransport by ORP10 at ER–endosome membrane contact sites regulates endosome fission
ORP10 localizes in a PI4P-dependent manner at ER–endosome membrane contact sites tethered by ORP9 and VAP, where it mediates countertransport of PI4P and PS. This in turn supplies endosomes with PS, thereby promoting EHD1 recruitment and endosome fission.
Clathrin adaptors mediate two sequential pathways of intra-Golgi recycling
Casler et al. show that in the yeast Golgi, the AP-1 and Ent5 adaptors act downstream of COPI to recycle transmembrane proteins. Various resident Golgi proteins partition between two sequential AP-1/Ent5–dependent pathways. The timing of recycling pathways can explain the polarized composition of the Golgi.
Ubiquitin ligase MARCH5 localizes to peroxisomes to regulate pexophagy
Zheng et al. report that mitochondrial ubiquitin ligase MARCH5 is a dual-organelle locating protein that interacts with several peroxisomal proteins. Peroxisomal MARCH5 is required for mTOR inhibition–induced pexophagy by binding and ubiquitinating PMP70.
pVHL-mediated SMAD3 degradation suppresses TGF-β signaling
R-SMAD stability is essential for TGF-β signaling. In this study, Zhou and Dabiri et al. describe a new role of the tumor suppressor pVHL as an E3 ligase for R-SMAD ubiquitination, implicating the potential interaction between oxygen sensing and TGF-β signaling in human cells and Drosophila tissue development.
CHMP2B regulates TDP-43 phosphorylation and cytotoxicity independent of autophagy via CK1
In this study, Deng et al. reveal a previously unknown function of the ESCRT protein CHMP2B in regulating TDP-43 toxicity and phosphorylation, which is independent of autophagy, by modulating ubiquitination and the turnover of CK1 via the proteasome-mediated pathway.
WDR60-mediated dynein-2 loading into cilia powers retrograde IFT and transition zone crossing
Using CRISPR/Cas9-mediated genome editing and live imaging of endogenous dynein-2, De-Castro et al. show for the first time that WDR-60 loss impairs dynein-2 loading onto anterograde IFT trains, reducing the motor availability to drive retrograde IFT trains out of cilia through the transition zone barrier.
Micron-scale supramolecular myosin arrays help mediate cytoskeletal assembly at mature adherens junctions
Yu-Kemp et al. explore mechanisms that epithelial cells use to assemble supramolecular actomyosin structures at E-Cadherin–based cell–cell junctions. They find that individual actin assembly pathways are not essential. Instead, microscopy and pharmacologic inhibition suggest that micron-scale supramolecular myosin arrays help bundle actin at mature junctions.
Volumetric morphometry reveals spindle width as the best predictor of mammalian spindle scaling
Kletter et al. introduce Spindle3D, an open-source image analysis tool that allows for consistent and automated morphometric quantification of the mitotic spindle and chromatin in confocal images. They analyze various cell types via Spindle3D and find that mitotic spindle width is a robust predictor of mammalian spindle scaling.
Quantitative correlative microscopy reveals the ultrastructural distribution of endogenous endosomal proteins
Van der Beek et al. introduce a quantitative CLEM method using fluorescence to label electron microscopy images by overlay. By comparing the ultrastructural distributions of the endosomal regulators Rab5, Rab7, EEA1, APPL1, and PI(3)P, they reveal distinct endosomal subpopulations and an unexpected localization of EEA1 to late endosomes.
Shared and specific functions of Arfs 1–5 at the Golgi revealed by systematic knockouts
The small GTPases Arf1–5 are important regulators of membrane traffic and Golgi functions. Pennauer et al. analyze viability and phenotypes of individual and combined CRISPR/Cas9 Arf knockout cell lines. Deletion of Arf1 or Arf4 produces specific phenotypes, while Arf4 alone is sufficient for cell viability.