{"title":"How condensed are mitotic chromosomes?","authors":"Hide A Konishi, Hironori Funabiki","doi":"10.1083/jcb.202409044","DOIUrl":"https://doi.org/10.1083/jcb.202409044","url":null,"abstract":"<p><p>Chromosomes undergo dramatic compaction during mitosis, but accurately measuring their volume has been challenging. Employing serial block face scanning electron microscopy, Cisneros-Soberanis et al. (https://doi.org/10.1083/jcb.202403165) report that mitotic chromosomes compact to a nucleosome concentration of ∼760 µM.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11473595/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142466349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zachary N Wilson, Sai Sangeetha Balasubramaniam, Sara Wong, Max-Hinderk Schuler, Mitchell J Wopat, Adam L Hughes
{"title":"Mitochondrial-derived compartments remove surplus proteins from the outer mitochondrial membrane.","authors":"Zachary N Wilson, Sai Sangeetha Balasubramaniam, Sara Wong, Max-Hinderk Schuler, Mitchell J Wopat, Adam L Hughes","doi":"10.1083/jcb.202307036","DOIUrl":"10.1083/jcb.202307036","url":null,"abstract":"<p><p>The outer mitochondrial membrane (OMM) creates a boundary that imports most of the mitochondrial proteome while removing extraneous or damaged proteins. How the OMM senses aberrant proteins and remodels to maintain OMM integrity remains unresolved. Previously, we identified a mitochondrial remodeling mechanism called the mitochondrial-derived compartment (MDC) that removes a subset of the mitochondrial proteome. Here, we show that MDCs specifically sequester proteins localized only at the OMM, providing an explanation for how select mitochondrial proteins are incorporated into MDCs. Remarkably, selective sorting into MDCs also occurs within the OMM, as subunits of the translocase of the outer membrane (TOM) complex are excluded from MDCs unless assembly of the TOM complex is impaired. Considering that overloading the OMM with mitochondrial membrane proteins or mistargeted tail-anchored membrane proteins induces MDCs to form and sequester these proteins, we propose that one functional role of MDCs is to create an OMM-enriched trap that segregates and sequesters excess proteins from the mitochondrial surface.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11320589/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141971160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Giel Korsten, Miriam Osinga, Robin A Pelle, Albert K Serweta, Baukje Hoogenberg, Harm H Kampinga, Lukas C Kapitein
{"title":"Nuclear poly-glutamine aggregates rupture the nuclear envelope and hinder its repair.","authors":"Giel Korsten, Miriam Osinga, Robin A Pelle, Albert K Serweta, Baukje Hoogenberg, Harm H Kampinga, Lukas C Kapitein","doi":"10.1083/jcb.202307142","DOIUrl":"10.1083/jcb.202307142","url":null,"abstract":"<p><p>Huntington's disease (HD) is caused by a polyglutamine expansion of the huntingtin protein, resulting in the formation of polyglutamine aggregates. The mechanisms of toxicity that result in the complex HD pathology remain only partially understood. Here, we show that nuclear polyglutamine aggregates induce nuclear envelope (NE) blebbing and ruptures that are often repaired incompletely. These ruptures coincide with disruptions of the nuclear lamina and lead to lamina scar formation. Expansion microscopy enabled resolving the ultrastructure of nuclear aggregates and revealed polyglutamine fibrils sticking into the cytosol at rupture sites, suggesting a mechanism for incomplete repair. Furthermore, we found that NE repair factors often accumulated near nuclear aggregates, consistent with stalled repair. These findings implicate nuclear polyQ aggregate-induced loss of NE integrity as a potential contributing factor to Huntington's disease and other polyglutamine diseases.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11329780/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141988073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Distinct roles of Kif6 and Kif9 in mammalian ciliary trafficking and motility.","authors":"Chuyu Fang, Xinwen Pan, Di Li, Wei Chen, Ying Huang, Yawen Chen, Luan Li, Qi Gao, Xin Liang, Dong Li, Xueliang Zhu, Xiumin Yan","doi":"10.1083/jcb.202312060","DOIUrl":"10.1083/jcb.202312060","url":null,"abstract":"<p><p>Ciliary beat and intraflagellar transport depend on dynein and kinesin motors. The kinesin-9 family members Kif6 and Kif9 are implicated in motile cilia motilities across protists and mammals. How they function and whether they act redundantly, however, remain unclear. Here, we show that Kif6 and Kif9 play distinct roles in mammals. Kif6 forms puncta that move bidirectionally along axonemes, whereas Kif9 appears to oscillate regionally on the ciliary central apparatus. Consistently, only Kif6 displays microtubule-based motor activity in vitro, and its ciliary localization requires its ATPase activity. Kif6 deficiency in mice disrupts coordinated ciliary beat across ependymal tissues and impairs cerebrospinal fluid flow, resulting in severe hydrocephalus and high mortality. Kif9 deficiency causes mild hydrocephalus without obviously affecting the ciliary beat or the lifespan. Kif6-/- and Kif9-/- males are infertile but exhibit oligozoospermia with poor sperm motility and defective forward motion of sperms, respectively. These results suggest Kif6 as a motor for cargo transport and Kif9 as a central apparatus regulator.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11334332/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142000013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Daniel Ballmer, Hua Jane Lou, Midori Ishii, Benjamin E Turk, Bungo Akiyoshi
{"title":"Aurora B controls anaphase onset and error-free chromosome segregation in trypanosomes.","authors":"Daniel Ballmer, Hua Jane Lou, Midori Ishii, Benjamin E Turk, Bungo Akiyoshi","doi":"10.1083/jcb.202401169","DOIUrl":"10.1083/jcb.202401169","url":null,"abstract":"<p><p>Kinetochores form the interface between chromosomes and spindle microtubules and are thus under tight control by a complex regulatory circuitry. The Aurora B kinase plays a central role within this circuitry by destabilizing improper kinetochore-microtubule attachments and relaying the attachment status to the spindle assembly checkpoint. Intriguingly, Aurora B is conserved even in kinetoplastids, a group of early-branching eukaryotes which possess a unique set of kinetochore proteins. It remains unclear how their kinetochores are regulated to ensure faithful chromosome segregation. Here, we show in Trypanosoma brucei that Aurora B activity controls the metaphase-to-anaphase transition through phosphorylation of the divergent Bub1-like protein KKT14. Depletion of KKT14 overrides the metaphase arrest resulting from Aurora B inhibition, while expression of non-phosphorylatable KKT14 delays anaphase onset. Finally, we demonstrate that re-targeting Aurora B to the outer kinetochore suffices to promote mitotic exit but causes extensive chromosome missegregation in anaphase. Our results indicate that Aurora B and KKT14 are involved in an unconventional circuitry controlling cell cycle progression in trypanosomes.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11354203/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142080364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Lactylation stabilizes TFEB to elevate autophagy and lysosomal activity.","authors":"Yewei Huang, Gan Luo, Kesong Peng, Yue Song, Yusha Wang, Hongtao Zhang, Jin Li, Xiangmin Qiu, Maomao Pu, Xinchang Liu, Chao Peng, Dante Neculai, Qiming Sun, Tianhua Zhou, Pintong Huang, Wei Liu","doi":"10.1083/jcb.202308099","DOIUrl":"10.1083/jcb.202308099","url":null,"abstract":"<p><p>The transcription factor TFEB is a major regulator of lysosomal biogenesis and autophagy. There is growing evidence that posttranslational modifications play a crucial role in regulating TFEB activity. Here, we show that lactate molecules can covalently modify TFEB, leading to its lactylation and stabilization. Mechanically, lactylation at K91 prevents TFEB from interacting with E3 ubiquitin ligase WWP2, thereby inhibiting TFEB ubiquitination and proteasome degradation, resulting in increased TFEB activity and autophagy flux. Using a specific antibody against lactylated K91, enhanced TFEB lactylation was observed in clinical human pancreatic cancer samples. Our results suggest that lactylation is a novel mode of TFEB regulation and that lactylation of TFEB may be associated with high levels of autophagy in rapidly proliferating cells, such as cancer cells.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11354204/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142080365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Amit Chougule, Chunbin Zhang, Nickolas Vinokurov, Devin Mendez, Elizabeth Vojtisek, Chenjun Shi, Jitao Zhang, Joseph Gardinier
{"title":"Purinergic signaling through the P2Y2 receptor regulates osteocytes' mechanosensitivity.","authors":"Amit Chougule, Chunbin Zhang, Nickolas Vinokurov, Devin Mendez, Elizabeth Vojtisek, Chenjun Shi, Jitao Zhang, Joseph Gardinier","doi":"10.1083/jcb.202403005","DOIUrl":"10.1083/jcb.202403005","url":null,"abstract":"<p><p>Osteocytes' response to dynamic loading plays a crucial role in regulating the bone mass but quickly becomes saturated such that downstream induction of bone formation plateaus. The underlying mechanisms that downregulate osteocytes' sensitivity and overall response to loading remain unknown. In other cell types, purinergic signaling through the P2Y2 receptor has the potential to downregulate the sensitivity to loading by modifying cell stiffness through actin polymerization and cytoskeleton organization. Herein, we examined the role of P2Y2 activation in regulating osteocytes' mechanotransduction using a P2Y2 knockout cell line alongside conditional knockout mice. Our findings demonstrate that the absence of P2Y2 expression in MLO-Y4 cells prevents actin polymerization while increasing the sensitivity to fluid flow-induced shear stress. Deleting osteocytes' P2Y2 expression in conditional-knockout mice enabled bone formation to increase when increasing the duration of exercise. Overall, P2Y2 activation under loading produces a negative feedback loop, limiting osteocytes' response to continuous loading by shifting the sensitivity to mechanical strain through actin stress fiber formation.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11363863/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142107803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
David K Dansu, Ipek Selcen, Sami Sauma, Emily Prentice, Dennis Huang, Meng Li, Sarah Moyon, Patrizia Casaccia
{"title":"Histone H4 acetylation differentially modulates proliferation in adult oligodendrocyte progenitors.","authors":"David K Dansu, Ipek Selcen, Sami Sauma, Emily Prentice, Dennis Huang, Meng Li, Sarah Moyon, Patrizia Casaccia","doi":"10.1083/jcb.202308064","DOIUrl":"10.1083/jcb.202308064","url":null,"abstract":"<p><p>Adult oligodendrocyte progenitors (aOPCs) generate myelinating oligodendrocytes like neonatal progenitors (nOPCs), and they also display unique functional features. Here, using unbiased histone proteomics analysis and ChIP sequencing analysis of PDGFRα+ OPCs sorted from neonatal and adult Pdgfra-H2B-EGFP reporter mice, we identify the activating H4K8ac histone mark as enriched in the aOPCs. We detect increased occupancy of the H4K8ac activating mark at chromatin locations corresponding to genes related to the progenitor state (e.g., Hes5, Gpr17), metabolic processes (e.g., Txnip, Ptdgs), and myelin components (e.g., Cnp, Mog). aOPCs showed higher levels of transcripts related to lipid metabolism and myelin, and lower levels of transcripts related to cell cycle and proliferation compared with nOPCs. In addition, pharmacological inhibition of histone acetylation decreased the expression of the H4K8ac target genes in aOPCs and decreased their proliferation. Overall, this study identifies acetylation of the histone H4K8 as a regulator of the proliferative capacity of aOPCs.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11318668/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141916810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marco Heydecker, Akiko Shitara, Desu Chen, Duy T Tran, Andrius Masedunskas, Muhibullah S Tora, Seham Ebrahim, Mark A Appaduray, Jorge Luis Galeano Niño, Abhishek Bhardwaj, Kedar Narayan, Edna C Hardeman, Peter W Gunning, Roberto Weigert
{"title":"Coordination of force-generating actin-based modules stabilizes and remodels membranes in vivo.","authors":"Marco Heydecker, Akiko Shitara, Desu Chen, Duy T Tran, Andrius Masedunskas, Muhibullah S Tora, Seham Ebrahim, Mark A Appaduray, Jorge Luis Galeano Niño, Abhishek Bhardwaj, Kedar Narayan, Edna C Hardeman, Peter W Gunning, Roberto Weigert","doi":"10.1083/jcb.202401091","DOIUrl":"10.1083/jcb.202401091","url":null,"abstract":"<p><p>Membrane remodeling drives a broad spectrum of cellular functions, and it is regulated through mechanical forces exerted on the membrane by cytoplasmic complexes. Here, we investigate how actin filaments dynamically tune their structure to control the active transfer of membranes between cellular compartments with distinct compositions and biophysical properties. Using intravital subcellular microscopy in live rodents we show that a lattice composed of linear filaments stabilizes the granule membrane after fusion with the plasma membrane and a network of branched filaments linked to the membranes by Ezrin, a regulator of membrane tension, initiates and drives to completion the integration step. Our results highlight how the actin cytoskeleton tunes its structure to adapt to dynamic changes in the biophysical properties of membranes.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11344176/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142017579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sriraksha Srinivasan, Daniel Álvarez, Arun T John Peter, Stefano Vanni
{"title":"Unbiased MD simulations identify lipid binding sites in lipid transfer proteins.","authors":"Sriraksha Srinivasan, Daniel Álvarez, Arun T John Peter, Stefano Vanni","doi":"10.1083/jcb.202312055","DOIUrl":"10.1083/jcb.202312055","url":null,"abstract":"<p><p>The characterization of lipid binding to lipid transfer proteins (LTPs) is fundamental to understand their molecular mechanism. However, several structures of LTPs, and notably those proposed to act as bridges between membranes, do not provide the precise location of their endogenous lipid ligands. To address this limitation, computational approaches are a powerful alternative methodology, but they are often limited by the high flexibility of lipid substrates. Here, we develop a protocol based on unbiased coarse-grain molecular dynamics simulations in which lipids placed away from the protein can spontaneously bind to LTPs. This approach accurately determines binding pockets in LTPs and provides a working hypothesis for the lipid entry pathway. We apply this approach to characterize lipid binding to bridge LTPs of the Vps13-Atg2 family, for which the lipid localization inside the protein is currently unknown. Overall, our work paves the way to determine binding pockets and entry pathways for several LTPs in an inexpensive, fast, and accurate manner.</p>","PeriodicalId":15211,"journal":{"name":"Journal of Cell Biology","volume":"223 11","pages":""},"PeriodicalIF":7.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11303870/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141893508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}