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Journal of Cell Biology
Journal Prestige (SJR): 6.479  Citation Impact (citeScore): 7 Number of Followers: 54  Subscription journalISSN (Print) 0021-9525 - ISSN (Online) 1540-8140 Published by Rockefeller University Press  [3 journals]
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- Expanded directly binds conserved regions of Fat to restrain growth via
the Hippo pathway-
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First page: e202204059
Abstract: The Hippo pathway is a conserved and critical regulator of tissue growth. The FERM protein Expanded is a key signaling hub that promotes activation of the Hippo pathway, thereby inhibiting the transcriptional co-activator Yorkie. Previous work identified the polarity determinant Crumbs as a primary regulator of Expanded. Here, we show that the giant cadherin Fat also regulates Expanded directly and independently of Crumbs. We show that direct binding between Expanded and a highly conserved region of the Fat cytoplasmic domain recruits Expanded to the apicolateral junctional zone and stabilizes Expanded. In vivo deletion of Expanded binding regions in Fat causes loss of apical Expanded and promotes tissue overgrowth. Unexpectedly, we find Fat can bind its ligand Dachsous via interactions of their cytoplasmic domains, in addition to the known extracellular interactions. Importantly, Expanded is stabilized by Fat independently of Dachsous binding. These data provide new mechanistic insights into how Fat regulates Expanded, and how Hippo signaling is regulated during organ growth.
PubDate: Tue, 18 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202204059
Issue No: Vol. 222, No. 5 (2023)
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- Correction: Yorkie controls tube length and apical barrier integrity
during airway development-
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First page: e201809121
Abstract: Vol. 218, No. 8 10.1083/jcb.201809121 July 17, 2019
PubDate: Thu, 13 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.20180912104072023c
Issue No: Vol. 222, No. 5 (2023)
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- Disagreement among the three musketeers of the unfolded protein response
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First page: e202304013
Abstract: Jipa and Juhász preview results from the lab of Tao Wang (2023. J. Cell Biol.https://doi.org/10.1083/jcb.202208147) which show a surprising antagonism between two branches of the unfolded protein response that dictates disease progression in a model of autosomal dominant retinitis pigmentosa.
PubDate: Thu, 13 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202304013
Issue No: Vol. 222, No. 5 (2023)
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- GPI anchors: Regulated as needed
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First page: e202303097
Abstract: GPI anchoring is an essential post-translational modification in eukaryotes that links proteins to the plasma membrane. In this issue, Liu et al. (2023. J. Cell Biol.https://doi.org/10.1083/jcb.202208159) suggest, for the first time, a regulation on demand of the GPI glycolipid precursor biosynthesis.
PubDate: Thu, 13 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202303097
Issue No: Vol. 222, No. 5 (2023)
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- Virus update for the M2 “mac-in-touch”
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First page: e202303016
Abstract: While HIV-1 infection of macrophages plays a major role in viral persistence and pathogenesis, how HIV-1 transfers from infected T cells to macrophages remains elusive. In this issue, Mascarau et al. (2023. J. Cell Biol.https://doi.org/10.1083/jcb.202205103) demonstrate how macrophage polarization drives their ability to fuse with HIV-1 infected T cells via the CD81/RhoA-ROCK/Myosin axis.
PubDate: Wed, 12 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202303016
Issue No: Vol. 222, No. 5 (2023)
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- A regulatory circuit comprising the CBP and SIRT7 regulates
FAM134B-mediated ER-phagy-
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First page: e202201068
Abstract: Macroautophagy (autophagy) utilizes a serial of receptors to specifically recognize and degrade autophagy cargoes, including damaged organelles, to maintain cellular homeostasis. Upstream signals spatiotemporally regulate the biological functions of selective autophagy receptors through protein post-translational modifications (PTM) such as phosphorylation. However, it is unclear how acetylation directly controls autophagy receptors in selective autophagy. Here, we report that an ER-phagy receptor FAM134B is acetylated by CBP acetyltransferase, eliciting intense ER-phagy. Furthermore, FAM134B acetylation promoted CAMKII-mediated phosphorylation to sustain a mode of milder ER-phagy. Conversely, SIRT7 deacetylated FAM134B to temper its activities in ER-phagy to avoid excessive ER degradation. Together, this work provides further mechanistic insights into how ER-phagy receptor perceives environmental signals for fine-tuning of ER homeostasis and demonstrates how nucleus-derived factors are programmed to control ER stress by modulating ER-phagy.
PubDate: Wed, 12 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202201068
Issue No: Vol. 222, No. 5 (2023)
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- RFWD3 promotes ZRANB3 recruitment to regulate the remodeling of stalled
replication forks-
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First page: e202106022
Abstract: Replication fork reversal is an important mechanism to protect the stability of stalled forks and thereby preserve genomic integrity. While multiple enzymes have been identified that can remodel forks, their regulation remains poorly understood. Here, we demonstrate that the ubiquitin ligase RFWD3, whose mutation causes Fanconi Anemia, promotes recruitment of the DNA translocase ZRANB3 to stalled replication forks and ubiquitinated sites of DNA damage. Using electron microscopy, we show that RFWD3 stimulates fork remodeling in a ZRANB3-epistatic manner. Fork reversal is known to promote nascent DNA degradation in BRCA2-deficient cells. Consistent with a role for RFWD3 in fork reversal, inactivation of RFWD3 in these cells rescues fork degradation and collapse, analogous to ZRANB3 inactivation. RFWD3 loss impairs ZRANB3 localization to spontaneous nuclear foci induced by inhibition of the PCNA deubiquitinase USP1. We demonstrate that RFWD3 promotes PCNA ubiquitination and interaction with ZRANB3, providing a mechanism for RFWD3-dependent recruitment of ZRANB3. Together, these results uncover a new role for RFWD3 in regulating ZRANB3-dependent fork remodeling.
PubDate: Mon, 10 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202106022
Issue No: Vol. 222, No. 5 (2023)
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- LC3B is a cofactor for LMX1B-mediated transcription of autophagy genes in
dopaminergic neurons-
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First page: e202303008
Abstract: It is becoming increasingly clear that the Atg8 family of autophagy proteins have roles not only in the cytoplasm, but also in the cell nucleus. In this issue, Jiménez-Moreno et al. (2023. J. Cell Biol.https://doi.org/10.1083/jcb.201910133) report that nuclear LC3B binds to the LIM homeodomain transcription factor LMX1B and acts as a cofactor for LMX1B-mediated transcription of autophagy genes, providing stress protection and ensuring survival of midbrain dopaminergic neurons.
PubDate: Mon, 10 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202303008
Issue No: Vol. 222, No. 5 (2023)
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- PERK prevents rhodopsin degradation during retinitis pigmentosa by
inhibiting IRE1-induced autophagy-
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First page: e202208147
Abstract: Chronic endoplasmic reticulum (ER) stress is the underlying cause of many degenerative diseases, including autosomal dominant retinitis pigmentosa (adRP). In adRP, mutant rhodopsins accumulate and cause ER stress. This destabilizes wild-type rhodopsin and triggers photoreceptor cell degeneration. To reveal the mechanisms by which these mutant rhodopsins exert their dominant-negative effects, we established an in vivo fluorescence reporter system to monitor mutant and wild-type rhodopsin in Drosophila. By performing a genome-wide genetic screen, we found that PERK signaling plays a key role in maintaining rhodopsin homeostasis by attenuating IRE1 activities. Degradation of wild-type rhodopsin is mediated by selective autophagy of ER, which is induced by uncontrolled IRE1/XBP1 signaling and insufficient proteasome activities. Moreover, upregulation of PERK signaling prevents autophagy and suppresses retinal degeneration in the adRP model. These findings establish a pathological role for autophagy in this neurodegenerative condition and indicate that promoting PERK activity could be used to treat ER stress-related neuropathies, including adRP.
PubDate: Thu, 06 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202208147
Issue No: Vol. 222, No. 5 (2023)
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- Double-checking chromosome segregation
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First page: e202301106
Abstract: Enduring chromosome segregation errors represent potential threats to genomic stability due to eventual chromosome copy number alterations (aneuploidy) and formation of micronuclei—key intermediates of a rapid mutational process known as chromothripsis that is found in cancer and congenital disorders. The spindle assembly checkpoint (SAC) has been viewed as the sole surveillance mechanism that prevents chromosome segregation errors during mitosis and meiosis. However, different types of chromosome segregation errors stemming from incorrect kinetochore–microtubule attachments satisfy the SAC and are more frequent than previously anticipated. Remarkably, recent works have unveiled that most of these errors are corrected during anaphase and only rarely result in aneuploidy or formation of micronuclei. Here, we discuss recent progress in our understanding of the origin and fate of chromosome segregation errors that satisfy the SAC and shed light on the surveillance, correction, and clearance mechanisms that prevent their transmission, to preserve genomic stability.
PubDate: Wed, 05 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.202301106
Issue No: Vol. 222, No. 5 (2023)
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- ATG8-dependent LMX1B-autophagy crosstalk shapes human midbrain
dopaminergic neuronal resilience-
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First page: e201910133
Abstract: The LIM homeodomain transcription factors LMX1A and LMX1B are essential mediators of midbrain dopaminergic neuronal (mDAN) differentiation and survival. Here we show that LMX1A and LMX1B are autophagy transcription factors that provide cellular stress protection. Their suppression dampens the autophagy response, lowers mitochondrial respiration, and elevates mitochondrial ROS, and their inducible overexpression protects against rotenone toxicity in human iPSC-derived mDANs in vitro. Significantly, we show that LMX1A and LMX1B stability is in part regulated by autophagy, and that these transcription factors bind to multiple ATG8 proteins. Binding is dependent on subcellular localization and nutrient status, with LMX1B interacting with LC3B in the nucleus under basal conditions and associating with both cytosolic and nuclear LC3B during nutrient starvation. Crucially, ATG8 binding stimulates LMX1B-mediated transcription for efficient autophagy and cell stress protection, thereby establishing a novel LMX1B-autophagy regulatory axis that contributes to mDAN maintenance and survival in the adult brain.
PubDate: Tue, 04 Apr 2023 00:00:00 GMT
DOI: 10.1083/jcb.201910133
Issue No: Vol. 222, No. 5 (2023)
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- Endothelial depletion of Atg7 triggers astrocyte–microvascular
disassociation at blood–brain barrier-
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First page: e202103098
Abstract: Microvascular basement membrane (BM) plays a pivotal role in the interactions of astrocyte with endothelium to maintain the blood–brain barrier (BBB) homeostasis; however, the significance and precise regulation of the endothelial cell–derived BM component in the BBB remain incompletely understood. Here, we report that conditional knockout of Atg7 in endothelial cells (Atg7-ECKO) leads to astrocyte–microvascular disassociation in the brain. Our results reveal astrocytic endfeet detachment from microvessels and BBB leakage in Atg7-ECKO mice. Furthermore, we find that the absence of endothelial Atg7 downregulates the expression of fibronectin, a major BM component of the BBB, causing significantly reduced coverage of astrocytes along cerebral microvessels. We reveal Atg7 triggers the expression of endothelial fibronectin via regulating PKA activity to affect the phosphorylation of cAMP-responsive element-binding protein. These results suggest that Atg7-regulated endothelial fibronectin production is required for astrocytes adhesion to microvascular wall for maintaining the BBB homeostasis. Thus, endothelial Atg7 plays an essential role in astrocyte–endothelium interactions to maintain the BBB integrity.
PubDate: Thu, 30 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202103098
Issue No: Vol. 222, No. 5 (2023)
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- Productive HIV-1 infection of tissue macrophages by fusion with infected
CD4 + T cells-
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First page: e202205103
Abstract: Macrophages are essential for HIV-1 pathogenesis and represent major viral reservoirs. Therefore, it is critical to understand macrophage infection, especially in tissue macrophages, which are widely infected in vivo, but poorly permissive to cell-free infection. Although cell-to-cell transmission of HIV-1 is a determinant mode of macrophage infection in vivo, how HIV-1 transfers toward macrophages remains elusive. Here, we demonstrate that fusion of infected CD4+ T lymphocytes with human macrophages leads to their efficient and productive infection. Importantly, several tissue macrophage populations undergo this heterotypic cell fusion, including synovial, placental, lung alveolar, and tonsil macrophages. We also find that this mode of infection is modulated by the macrophage polarization state. This fusion process engages a specific short-lived adhesion structure and is controlled by the CD81 tetraspanin, which activates RhoA/ROCK-dependent actomyosin contractility in macrophages. Our study provides important insights into the mechanisms underlying infection of tissue-resident macrophages, and establishment of persistent cellular reservoirs in patients.
PubDate: Wed, 29 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202205103
Issue No: Vol. 222, No. 5 (2023)
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- The meiotic LINC complex component KASH5 is an activating adaptor for
cytoplasmic dynein-
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First page: e202204042
Abstract: Cytoplasmic dynein-driven movement of chromosomes during prophase I of mammalian meiosis is essential for synapsis and genetic exchange. Dynein connects to chromosome telomeres via KASH5 and SUN1 or SUN2, which together span the nuclear envelope. Here, we show that KASH5 promotes dynein motility in vitro, and cytosolic KASH5 inhibits dynein’s interphase functions. KASH5 interacts with a dynein light intermediate chain (DYNC1LI1 or DYNC1LI2) via a conserved helix in the LIC C-terminal, and this region is also needed for dynein’s recruitment to other cellular membranes. KASH5’s N-terminal EF-hands are essential as the interaction with dynein is disrupted by mutation of key calcium-binding residues, although it is not regulated by cellular calcium levels. Dynein can be recruited to KASH5 at the nuclear envelope independently of dynactin, while LIS1 is essential for dynactin incorporation into the KASH5–dynein complex. Altogether, we show that the transmembrane protein KASH5 is an activating adaptor for dynein and shed light on the hierarchy of assembly of KASH5–dynein–dynactin complexes.
PubDate: Wed, 22 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202204042
Issue No: Vol. 222, No. 5 (2023)
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- ADAD2 interacts with RNF17 in P-bodies to repress the Ping-pong cycle in
pachytene piRNA biogenesis-
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First page: e202206067
Abstract: Pachytene piRNA biogenesis is a hallmark of the germline, distinct from another wave of pre-pachytene piRNA biogenesis with regard to the lack of a secondary amplification process known as the Ping-pong cycle. However, the underlying molecular mechanism and the venue for the suppression of the Ping-pong cycle remain elusive. Here, we showed that a testis-specific protein, ADAD2, interacts with a TDRD family member protein RNF17 and is associated with P-bodies. Importantly, ADAD2 directs RNF17 to repress Ping-pong activity in pachytene piRNA biogenesis. The P-body localization of RNF17 requires the intrinsically disordered domain of ADAD2. Deletion of Adad2 or Rnf17 causes the mislocalization of each other and subsequent Ping-pong activity derepression, secondary piRNAs overproduced, and disruption of P-body integrity at the meiotic stage, thereby leading to spermatogenesis arrested at the round spermatid stage. Collectively, by identifying the ADAD2-dependent mechanism, our study reveals a novel function of P-bodies in suppressing Ping-pong activity in pachytene piRNA biogenesis.
PubDate: Fri, 17 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202206067
Issue No: Vol. 222, No. 5 (2023)
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- The exocyst complex is an essential component of the mammalian
constitutive secretory pathway-
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First page: e202205137
Abstract: Secreted proteins fulfill a vast array of functions, including immunity, signaling, and extracellular matrix remodeling. In the trans-Golgi network, proteins destined for constitutive secretion are sorted into post-Golgi carriers which fuse with the plasma membrane. The molecular machinery involved is poorly understood. Here, we have used kinetic trafficking assays and transient CRISPR-KO to study biosynthetic sorting from the Golgi to the plasma membrane. Depletion of all canonical exocyst subunits causes cargo accumulation in post-Golgi carriers. Exocyst subunits are recruited to and co-localize with carriers. Exocyst abrogation followed by kinetic trafficking assays of soluble cargoes results in intracellular cargo accumulation. Unbiased secretomics reveals impairment of soluble protein secretion after exocyst subunit knockout. Importantly, in specialized cell types, the loss of exocyst prevents constitutive secretion of antibodies in lymphocytes and of leptin in adipocytes. These data identify exocyst as the functional tether of secretory post-Golgi carriers at the plasma membrane and an essential component of the mammalian constitutive secretory pathway.
PubDate: Wed, 15 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202205137
Issue No: Vol. 222, No. 5 (2023)
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- Yeast Svf1 binds ceramides and contributes to sphingolipid metabolism at
the ER cis-Golgi interface-
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First page: e202109162
Abstract: Ceramides are essential precursors of complex sphingolipids and act as potent signaling molecules. Ceramides are synthesized in the endoplasmic reticulum (ER) and receive their head-groups in the Golgi apparatus, yielding complex sphingolipids (SPs). Transport of ceramides between the ER and the Golgi is executed by the essential ceramide transport protein (CERT) in mammalian cells. However, yeast cells lack a CERT homolog, and the mechanism of ER to Golgi ceramide transport remains largely elusive. Here, we identified a role for yeast Svf1 in ceramide transport between the ER and the Golgi. Svf1 is dynamically targeted to membranes via an N-terminal amphipathic helix (AH). Svf1 binds ceramide via a hydrophobic binding pocket that is located in between two lipocalin domains. We showed that Svf1 membrane-targeting is important to maintain flux of ceramides into complex SPs. Together, our results show that Svf1 is a ceramide binding protein that contributes to sphingolipid metabolism at Golgi compartments.
PubDate: Fri, 10 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202109162
Issue No: Vol. 222, No. 5 (2023)
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- PP6 regulation of Aurora A–TPX2 limits NDC80 phosphorylation and
mitotic spindle size-
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First page: e202205117
Abstract: Amplification of the mitotic kinase Aurora A or loss of its regulator protein phosphatase 6 (PP6) have emerged as drivers of genome instability. Cells lacking PPP6C, the catalytic subunit of PP6, have amplified Aurora A activity, and as we show here, enlarged mitotic spindles which fail to hold chromosomes tightly together in anaphase, causing defective nuclear structure. Using functional genomics to shed light on the processes underpinning these changes, we discover synthetic lethality between PPP6C and the kinetochore protein NDC80. We find that NDC80 is phosphorylated on multiple N-terminal sites during spindle formation by Aurora A–TPX2, exclusively at checkpoint-silenced, microtubule-attached kinetochores. NDC80 phosphorylation persists until spindle disassembly in telophase, is increased in PPP6C knockout cells, and is Aurora B-independent. An Aurora-phosphorylation-deficient NDC80-9A mutant reduces spindle size and suppresses defective nuclear structure in PPP6C knockout cells. In regulating NDC80 phosphorylation by Aurora A–TPX2, PP6 plays an important role in mitotic spindle formation and size control and thus the fidelity of cell division.
PubDate: Fri, 10 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202205117
Issue No: Vol. 222, No. 5 (2023)
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- TLN1 contains a cancer-associated cassette exon that alters talin-1
mechanosensitivity-
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First page: e202209010
Abstract: Talin-1 is the core mechanosensitive adapter protein linking integrins to the cytoskeleton. The TLN1 gene is comprised of 57 exons that encode the 2,541 amino acid TLN1 protein. TLN1 was previously considered to be expressed as a single isoform. However, through differential pre-mRNA splicing analysis, we discovered a cancer-enriched, non-annotated 51-nucleotide exon in TLN1 between exons 17 and 18, which we refer to as exon 17b. TLN1 is comprised of an N-terminal FERM domain, linked to 13 force-dependent switch domains, R1-R13. Inclusion of exon 17b introduces an in-frame insertion of 17 amino acids immediately after Gln665 in the region between R1 and R2 which lowers the force required to open the R1-R2 switches potentially altering downstream mechanotransduction. Biochemical analysis of this isoform revealed enhanced vinculin binding, and cells expressing this variant show altered adhesion dynamics and motility. Finally, we showed that the TGF-β/SMAD3 signaling pathway regulates this isoform switch. Future studies will need to consider the balance of these two TLN1 isoforms.
PubDate: Mon, 06 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202209010
Issue No: Vol. 222, No. 5 (2023)
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- A live-cell marker to visualize the dynamics of stable microtubules
throughout the cell cycle-
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First page: e202106105
Abstract: The microtubule (MT) cytoskeleton underlies processes such as intracellular transport and cell division. Immunolabeling for posttranslational modifications of tubulin has revealed the presence of different MT subsets, which are believed to differ in stability and function. Whereas dynamic MTs can readily be studied using live-cell plus-end markers, the dynamics of stable MTs have remained obscure due to a lack of tools to directly visualize these MTs in living cells. Here, we present StableMARK (Stable Microtubule-Associated Rigor-Kinesin), a live-cell marker to visualize stable MTs with high spatiotemporal resolution. We demonstrate that a rigor mutant of Kinesin-1 selectively binds to stable MTs without affecting MT organization and organelle transport. These MTs are long-lived, undergo continuous remodeling, and often do not depolymerize upon laser-based severing. Using this marker, we could visualize the spatiotemporal regulation of MT stability before, during, and after cell division. Thus, this live-cell marker enables the exploration of different MT subsets and how they contribute to cellular organization and transport.
PubDate: Thu, 02 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202106105
Issue No: Vol. 222, No. 5 (2023)
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- Deep learning techniques and mathematical modeling allow 3D analysis of
mitotic spindle dynamics-
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First page: e202111094
Abstract: Time-lapse microscopy movies have transformed the study of subcellular dynamics. However, manual analysis of movies can introduce bias and variability, obscuring important insights. While automation can overcome such limitations, spatial and temporal discontinuities in time-lapse movies render methods such as 3D object segmentation and tracking difficult. Here, we present SpinX, a framework for reconstructing gaps between successive image frames by combining deep learning and mathematical object modeling. By incorporating expert feedback through selective annotations, SpinX identifies subcellular structures, despite confounding neighbor-cell information, non-uniform illumination, and variable fluorophore marker intensities. The automation and continuity introduced here allows the precise 3D tracking and analysis of spindle movements with respect to the cell cortex for the first time. We demonstrate the utility of SpinX using distinct spindle markers, cell lines, microscopes, and drug treatments. In summary, SpinX provides an exciting opportunity to study spindle dynamics in a sophisticated way, creating a framework for step changes in studies using time-lapse microscopy.
PubDate: Thu, 02 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202111094
Issue No: Vol. 222, No. 5 (2023)
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- ExTrack characterizes transition kinetics and diffusion in noisy
single-particle tracks-
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First page: e202208059
Abstract: Single-particle tracking microscopy is a powerful technique to investigate how proteins dynamically interact with their environment in live cells. However, the analysis of tracks is confounded by noisy molecule localization, short tracks, and rapid transitions between different motion states, notably between immobile and diffusive states. Here, we propose a probabilistic method termed ExTrack that uses the full spatio-temporal information of tracks to extract global model parameters, to calculate state probabilities at every time point, to reveal distributions of state durations, and to refine the positions of bound molecules. ExTrack works for a wide range of diffusion coefficients and transition rates, even if experimental data deviate from model assumptions. We demonstrate its capacity by applying it to slowly diffusing and rapidly transitioning bacterial envelope proteins. ExTrack greatly increases the regime of computationally analyzable noisy single-particle tracks. The ExTrack package is available in ImageJ and Python.
PubDate: Wed, 01 Mar 2023 00:00:00 GMT
DOI: 10.1083/jcb.202208059
Issue No: Vol. 222, No. 5 (2023)
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- Accumulated precursors of specific GPI-anchored proteins upregulate GPI
biosynthesis with ARV1-
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First page: e202208159
Abstract: We previously reported that glycosylphosphatidylinositol (GPI) biosynthesis is upregulated when endoplasmic reticulum–associated degradation (ERAD) is defective; however, the underlying mechanistic basis remains unclear. Based on a genome-wide CRISPR–Cas9 screen, we show that a widely expressed GPI-anchored protein CD55 precursor and ER-resident ARV1 are involved in upregulation of GPI biosynthesis under ERAD-deficient conditions. In cells defective in GPI transamidase, GPI-anchored protein precursors fail to obtain GPI, with the remaining uncleaved GPI-attachment signal at the C-termini. We show that ERAD deficiency causes accumulation of the CD55 precursor, which in turn upregulates GPI biosynthesis, where the GPI-attachment signal peptide is the active element. Among the 31 GPI-anchored proteins tested, only the GPI-attachment signal peptides of CD55, CD48, and PLET1 enhance GPI biosynthesis. ARV1 is prerequisite for the GPI upregulation by CD55 precursor. Our data indicate that GPI biosynthesis is balanced to need by ARV1 and precursors of specific GPI-anchored proteins.
PubDate: Fri, 24 Feb 2023 00:00:00 GMT
DOI: 10.1083/jcb.202208159
Issue No: Vol. 222, No. 5 (2023)
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- EVL and MIM/MTSS1 regulate actin cytoskeletal remodeling to promote
dendritic filopodia in neurons-
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First page: e202106081
Abstract: Dendritic spines are the postsynaptic compartment of a neuronal synapse and are critical for synaptic connectivity and plasticity. A developmental precursor to dendritic spines, dendritic filopodia (DF), facilitate synapse formation by sampling the environment for suitable axon partners during neurodevelopment and learning. Despite the significance of the actin cytoskeleton in driving these dynamic protrusions, the actin elongation factors involved are not well characterized. We identified the Ena/VASP protein EVL as uniquely required for the morphogenesis and dynamics of DF. Using a combination of genetic and optogenetic manipulations, we demonstrated that EVL promotes protrusive motility through membrane-direct actin polymerization at DF tips. EVL forms a complex at nascent protrusions and DF tips with MIM/MTSS1, an I-BAR protein important for the initiation of DF. We proposed a model in which EVL cooperates with MIM to coalesce and elongate branched actin filaments, establishing the dynamic lamellipodia-like architecture of DF.
PubDate: Fri, 24 Feb 2023 00:00:00 GMT
DOI: 10.1083/jcb.202106081
Issue No: Vol. 222, No. 5 (2023)
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