Caroline Q Connors, Michael S Mauro, J Tristian Wiles, Andrew D Countryman, Sophia L Martin, Benjamin Lacroix, Mimi Shirasu-Hiza, Julien Dumont, Karen E Kasza, Timothy R Davies, Julie C Canman
{"title":"Germ fate determinants protect germ precursor cell division by reducing septin and anillin levels at the cell division plane.","authors":"Caroline Q Connors, Michael S Mauro, J Tristian Wiles, Andrew D Countryman, Sophia L Martin, Benjamin Lacroix, Mimi Shirasu-Hiza, Julien Dumont, Karen E Kasza, Timothy R Davies, Julie C Canman","doi":"10.1091/mbc.E24-02-0096-T","DOIUrl":"10.1091/mbc.E24-02-0096-T","url":null,"abstract":"<p><p>Animal cell cytokinesis, or the physical division of one cell into two, is thought to be driven by constriction of an actomyosin contractile ring at the division plane. The mechanisms underlying cell type-specific differences in cytokinesis remain unknown. Germ cells are totipotent cells that pass genetic information to the next generation. Previously, using <i>formin<sup>cyk-1</sup>(ts)</i> mutant <i>Caenorhabditis elegans</i> 4-cell embryos, we found that the P2 germ precursor cell is protected from cytokinesis failure and can divide with greatly reduced F-actin levels at the cell division plane. Here, we identified two canonical germ fate determinants required for P2-specific cytokinetic protection: PIE-1 and POS-1. Neither has been implicated previously in cytokinesis. These germ fate determinants protect P2 cytokinesis by reducing the accumulation of septin<sup>UNC-59</sup> and anillin<sup>ANI-1</sup> at the division plane, which here act as negative regulators of cytokinesis. These findings may provide insight into the regulation of cytokinesis in other cell types, especially in stem cells with high potency.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244169/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140861931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Russell J R Barkley, Jack C Crowley, Andrew J Brodrick, Warren R Zipfel, John S L Parker
{"title":"Fluorescent protein tags affect the condensation properties of a phase-separating viral protein.","authors":"Russell J R Barkley, Jack C Crowley, Andrew J Brodrick, Warren R Zipfel, John S L Parker","doi":"10.1091/mbc.E24-01-0013","DOIUrl":"10.1091/mbc.E24-01-0013","url":null,"abstract":"<p><p>Fluorescent protein (FP) tags are extensively used to visualize and characterize the properties of biomolecular condensates despite a lack of investigation into the effects of these tags on phase separation. Here, we characterized the dynamic properties of µNS, a viral protein hypothesized to undergo phase separation and the main component of mammalian orthoreovirus viral factories. Our interest in the sequence determinants and nucleation process of µNS phase separation led us to compare the size and density of condensates formed by FP::µNS to the untagged protein. We found an FP-dependent increase in droplet size and density, which suggests that FP tags can promote µNS condensation. To further assess the effect of FP tags on µNS droplet formation, we fused FP tags to µNS mutants to show that the tags could variably induce phase separation of otherwise noncondensing proteins. By comparing fluorescent constructs with untagged µNS, we identified mNeonGreen as the least artifactual FP tag that minimally perturbed µNS condensation. These results show that FP tags can promote phase separation and that some tags are more suitable for visualizing and characterizing biomolecular condensates with minimal experimental artifacts.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244164/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141161979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stephen M King, Miho Sakato-Antoku, Ramila S Patel-King, Jeremy L Balsbaugh
{"title":"The methylome of motile cilia.","authors":"Stephen M King, Miho Sakato-Antoku, Ramila S Patel-King, Jeremy L Balsbaugh","doi":"10.1091/mbc.E24-03-0130","DOIUrl":"10.1091/mbc.E24-03-0130","url":null,"abstract":"<p><p>Cilia are highly complex motile, sensory, and secretory organelles that contain perhaps 1000 or more distinct protein components, many of which are subject to various posttranslational modifications such as phosphorylation, N-terminal acetylation, and proteolytic processing. Another common modification is the addition of one or more methyl groups to the side chains of arginine and lysine residues. These tunable additions delocalize the side-chain charge, decrease hydrogen bond capacity, and increase both bulk and hydrophobicity. Methylation is usually mediated by S-adenosylmethionine (SAM)-dependent methyltransferases and reversed by demethylases. Previous studies have identified several ciliary proteins that are subject to methylation including axonemal dynein heavy chains that are modified by a cytosolic methyltransferase. Here, we have performed an extensive proteomic analysis of multiple independently derived cilia samples to assess the potential for SAM metabolism and the extent of methylation in these organelles. We find that cilia contain all the enzymes needed for generation of the SAM methyl donor and recycling of the S-adenosylhomocysteine and tetrahydrofolate byproducts. In addition, we find that at least 155 distinct ciliary proteins are methylated, in some cases at multiple sites. These data provide a comprehensive resource for studying the consequences of methyl marks on ciliary biology.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244166/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140867686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Joseph Yoniles, Jacob A Summers, Kara A Zielinski, Cali Antolini, Mayura Panjalingam, Stella Lisova, Frank R Moss, Maximus Aldo Di Perna, Christopher Kupitz, Mark S Hunter, Lois Pollack, Soichi Wakatsuki, Peter D Dahlberg
{"title":"Time-resolved cryogenic electron tomography for the study of transient cellular processes.","authors":"Joseph Yoniles, Jacob A Summers, Kara A Zielinski, Cali Antolini, Mayura Panjalingam, Stella Lisova, Frank R Moss, Maximus Aldo Di Perna, Christopher Kupitz, Mark S Hunter, Lois Pollack, Soichi Wakatsuki, Peter D Dahlberg","doi":"10.1091/mbc.E24-01-0042","DOIUrl":"10.1091/mbc.E24-01-0042","url":null,"abstract":"<p><p>Cryogenic electron tomography (cryo-ET) is the highest resolution imaging technique applicable to the life sciences, enabling subnanometer visualization of specimens preserved in their near native states. The rapid plunge freezing process used to prepare samples lends itself to time-resolved studies, which researchers have pursued for in vitro samples for decades. Here, we focus on developing a freezing apparatus for time-resolved studies in situ. The device mixes cellular samples with solution-phase stimulants before spraying them directly onto an electron microscopy grid that is transiting into cryogenic liquid ethane. By varying the flow rates of cell and stimulant solutions within the device, we can control the reaction time from tens of milliseconds to over a second before freezing. In a proof-of-principle demonstration, the freezing method is applied to a model bacterium, <i>Caulobacter crescentus,</i> mixed with an acidic buffer. Through cryo-ET we resolved structural changes throughout the cell, including surface-layer protein dissolution, outer membrane deformation, and cytosolic rearrangement, all within 1.5 s of reaction time. This new approach, Time-Resolved cryo-ET (TR-cryo-ET), enhances the capabilities of cryo-ET by incorporating a subsecond temporal axis and enables the visualization of induced structural changes at the molecular, organelle, or cellular level.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244162/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140876785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Tubulin glycylation controls ciliary motility through modulation of outer-arm dyneins.","authors":"Tomohiro Kubo, Rinka Sasaki, Toshiyuki Oda","doi":"10.1091/mbc.E24-04-0154","DOIUrl":"10.1091/mbc.E24-04-0154","url":null,"abstract":"<p><p>Tubulins undergo several kinds of posttranslational modifications (PTMs) including glutamylation and glycylation. The contribution of these PTMs to the motilities of cilia and flagella is still unclear. Here, we investigated the role of tubulin glycylation by examining a novel <i>Chlamydomonas</i> mutant lacking TTLL3, an enzyme responsible for initiating glycylation. Immunostaining of cells and flagella revealed that glycylation is only restricted to the axonemal tubulin composing the outer-doublet but not the central-pair microtubules. Furthermore, the flagellar localization of TTLL3 was found to be dependent on intraflagellar transport. The mutant, <i>ttll3(ex5)</i>, completely lacks glycylation and consequently exhibits slower swimming velocity compared with the wild-type strain. By combining the <i>ttll3(ex5)</i> mutation with multiple axonemal dynein-deficient mutants, we found that the lack of glycylation does not affect the motility of the outer-arm dynein lacking mutations. Sliding disintegration assay using isolated axonemes revealed that the lack of glycylation decreases microtubule sliding velocity in the normal axoneme but not in the axoneme lacking the outerarm dyneins. Based on our recent study that glycylation occurs exclusively on β-tubulin in <i>Chlamydomonas</i>, these findings suggest that tubulin glycylation controls flagellar motility through modulating outer-arm dyneins, presumably by neutralizing the negative charges of glutamate residues at the C-terminus region of β-tubulin.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244163/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140957975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A novel noncanonical function for IRF6 in the recycling of E-cadherin.","authors":"Angelo Antiguas, Martine Dunnwald","doi":"10.1091/mbc.E23-11-0430","DOIUrl":"10.1091/mbc.E23-11-0430","url":null,"abstract":"<p><p>Interferon Regulatory Factor 6 (IRF6) is a transcription factor essential for keratinocyte cell-cell adhesions. Previously, we found that recycling of E-cadherin was defective in the absence of IRF6, yet total E-cadherin levels were not altered, suggesting a previously unknown, nontranscriptional function for IRF6. IRF6 protein contains a DNA binding domain (DBD) and a protein binding domain (PBD). The transcriptional function of IRF6 depends on its DBD and PBD, however, whether the PBD is necessary for the interaction with cytoplasmic proteins has yet to be demonstrated. Here, we show that an intact PBD is required for recruitment of cell-cell adhesion proteins at the plasma membrane, including the recycling of E-cadherin. Colocalizations and coimmunoprecipitations reveal that IRF6 forms a complex in recycling endosomes with Rab11, Myosin Vb, and E-cadherin, and that the PBD is required for this interaction. These data indicate that IRF6 is a novel effector of the endosomal recycling of E-cadherin and demonstrate a non-transcriptional function for IRF6 in regulating cell-cell adhesions.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244161/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141161976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jordan M Barrows, Barbara K Talavera-Figueroa, Isaac P Payne, Erika L Smith, Erin D Goley
{"title":"GTPase activity regulates FtsZ ring positioning in <i>Caulobacter crescentus</i>.","authors":"Jordan M Barrows, Barbara K Talavera-Figueroa, Isaac P Payne, Erika L Smith, Erin D Goley","doi":"10.1091/mbc.E23-09-0365","DOIUrl":"10.1091/mbc.E23-09-0365","url":null,"abstract":"<p><p>Bacterial cell division is crucial for replication and requires careful coordination via proteins collectively called the divisome. The tubulin-like GTPase FtsZ is the master regulator of this process and serves to recruit downstream divisome proteins and regulate their activities. Upon assembling at mid-cell, FtsZ exhibits treadmilling motion driven by GTP binding and hydrolysis. Treadmilling is proposed to play roles in Z-ring condensation and in distribution and regulation of peptidoglycan (PG) cell wall enzymes. FtsZ polymer superstructure and dynamics are central to its function, yet their regulation is incompletely understood. We addressed these gaps in knowledge by evaluating the contribution of GTPase activity to FtsZ's function in vitro and in <i>Caulobacter crescentus</i> cells. We observed that a lethal mutation that abrogates FtsZ GTP hydrolysis impacts FtsZ dynamics and Z-ring positioning, but not constriction. Aberrant Z-ring positioning was due to insensitivity to the FtsZ regulator MipZ when GTPase activity is reduced. Z-ring mislocalization resulted in DNA damage, likely due to constriction over the nucleoid. Collectively, our results indicate that GTP hydrolysis serves primarily to position the Z-ring at mid-cell in <i>Caulobacter</i>. Proper Z-ring localization is required for effective coordination with chromosome segregation to prevent DNA damage and ensure successful cell division.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244171/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140957787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Sur7 mediates a novel pathway for PI<sub>4,5</sub>P<sub>2</sub> regulation in <i>C. albicans</i> that promotes stress resistance and cell wall morphogenesis.","authors":"Carla E Lanze, James B Konopka","doi":"10.1091/mbc.E23-08-0324","DOIUrl":"10.1091/mbc.E23-08-0324","url":null,"abstract":"<p><p>The human fungal pathogen <i>Candida albicans</i> can cause lethal systemic infections due to its ability to resist stress from the host and to undergo invasive hyphal growth. Previous studies showed that plasma membrane MCC/eisosome domains were important for virulence by promoting the ability of Sur7 to mediate normal cell wall morphogenesis and stress resistance. The <i>sur7Δ</i> mutant displayed abnormal clusters of PI<sub>4,5</sub>P<sub>2</sub>, suggesting that misregulation of this lipid underlies the <i>sur7Δ</i> phenotype. To test this, we increased PI<sub>4,5</sub>P<sub>2</sub> levels by deleting combinations of the three PI<sub>4,5</sub>P<sub>2</sub> 5' phosphatase genes (<i>INP51</i>, <i>INP52</i>, and <i>INP54</i>) and found that some combinations, such as <i>inp51Δ inp52Δ</i>, gave phenotypes similar the <i>sur7Δ</i> mutant. In contrast, deleting one copy of <i>MSS4</i>, the gene that encodes the 5' kinase needed to create PI<sub>4,5</sub>P<sub>2</sub>, reduced the abnormal PI<sub>4,5</sub>P<sub>2</sub> clusters and also decreased the abnormal cell wall and stress sensitive phenotypes of the <i>sur7Δ</i> mutant. Additional studies support a model that the abnormal PI<sub>4,5</sub>P<sub>2</sub> patches recruit septin proteins, which in turn promote aberrant cell wall growth. These results identify Sur7 as a novel regulator of PI<sub>4,5</sub>P<sub>2</sub> and highlight the critical role of PI<sub>4,5</sub>P<sub>2</sub> in the regulation of <i>C. albicans</i> virulence properties.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244165/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141076253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Piyush Daga, Basil Thurakkal, Simran Rawal, Tamal Das
{"title":"Matrix stiffening promotes perinuclear clustering of mitochondria.","authors":"Piyush Daga, Basil Thurakkal, Simran Rawal, Tamal Das","doi":"10.1091/mbc.E23-04-0139","DOIUrl":"10.1091/mbc.E23-04-0139","url":null,"abstract":"<p><p>Mechanical cues from the tissue microenvironment, such as the stiffness of the extracellular matrix, modulate cellular forms and functions. As numerous studies have shown, this modulation depends on the stiffness-dependent remodeling of cytoskeletal elements. In contrast, very little is known about how the intracellular organelles such as mitochondria respond to matrix stiffness and whether their form, function, and localization change accordingly. Here, we performed an extensive quantitative characterization of mitochondrial morphology, subcellular localization, dynamics, and membrane tension on soft and stiff matrices. This characterization revealed that while matrix stiffness affected all these aspects, matrix stiffening most distinctively led to an increased perinuclear clustering of mitochondria. Subsequently, we could identify the matrix stiffness-sensitive perinuclear localization of filamin as the key factor dictating this perinuclear clustering. The perinuclear and peripheral mitochondrial populations differed in their motility on soft matrix but surprisingly they did not show any difference on stiff matrix. Finally, perinuclear mitochondrial clustering appeared to be crucial for the nuclear localization of RUNX2 and hence for priming human mesenchymal stem cells towards osteogenesis on a stiff matrix. Taken together, we elucidate a dependence of mitochondrial localization on matrix stiffness, which possibly enables a cell to adapt to its microenvironment.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244172/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140957789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Courtney J Matheny, Hiroshi Qadota, Aaron O Bailey, Silvana Valdebenito-Silva, Andres F Oberhauser, Guy M Benian
{"title":"The myosin chaperone UNC-45 has an important role in maintaining the structure and function of muscle sarcomeres during adult aging.","authors":"Courtney J Matheny, Hiroshi Qadota, Aaron O Bailey, Silvana Valdebenito-Silva, Andres F Oberhauser, Guy M Benian","doi":"10.1091/mbc.E23-12-0488","DOIUrl":"10.1091/mbc.E23-12-0488","url":null,"abstract":"<p><p><i>C. elegans</i> undergo age-dependent declines in muscle organization and function, similar to human sarcopenia. The chaperone UNC-45 is required to fold myosin heads after translation and is likely used for refolding after thermally- or chemically-induced unfolding. UNC-45's TPR region binds HSP-90 and its UCS domain binds myosin heads. We observe early onset sarcopenia when UNC-45 is reduced at the beginning of adulthood. There is sequential decline of HSP-90, UNC-45, and MHC B myosin. A mutation in <i>age-1</i> delays sarcopenia and loss of HSP-90, UNC-45, and myosin. UNC-45 undergoes age-dependent phosphorylation, and mass spectrometry reveals phosphorylation of six serines and two threonines, seven of which occur in the UCS domain. Additional expression of UNC-45 results in maintenance of MHC B myosin and suppression of A-band disorganization in old animals. Our results suggest that increased expression or activity of UNC-45 might be a strategy for prevention or treatment of sarcopenia.</p>","PeriodicalId":18735,"journal":{"name":"Molecular Biology of the Cell","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11244168/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141161939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}