Microtubule organization across cell types and states

Unveiling the role of cadaverine in mitigating salinity and/or Bisphenol A toxicity in tomato plants and reduced Bisphenol A accumulation in tomato roots

Mitigating the co-existence of environmental stresses on crop plants necessitates the development of integrated, eco-friendly, and sustainable approaches to alleviate plant stress responses. This study represents the first attempt to mitigate the toxic impact of prevalent pollutant (salinity) and an emergent plastic manufacturing pollutants (bisphenol A, BPA) using the polyamine (cadaverine).Tomato plants, treated with or without cadaverine, were subjected to NaCl salinity (120 mM), BPA (375 mg kg-1 soil), and their combinations compared to non-stressed control plants examining morphological, physiological, metabolic, and molecular responses. After 10 days of transplanting, tomato plants under combined stress were unable to survive without cadaverine application. However, cadaverine spraying mitigated the damaging effects of both single and combined stresses under short- and long-term exposure, enabling stressed plants to endure the conditions and complete their life cycles. Cadaverine efficiently restrained the reduction in chlorophylls, carotenoids, and cytosolutes under applied stresses compared to the stressed plants. Cadaverine also increased α-tocopherol content (by 171 and 53 %) and enhanced the activity of polyphenol oxidase (by 26 and 32 %), glutathione s-transferases (by 18 and 39 %), superoxide dismutase (by 23 and 46 %), and phenylalanine ammonia-lyase (by 9 and 25 %), under BPA and salinity stress, respectively. Thus, cadaverine ameliorated the oxidative and nitrosative burst induced by BPA or salinity, respectively by declining hydroxyl radical (by 28 % and 20 %), superoxide anion (by 73 % and 74 %), nitric oxide (by 60 and 65 %), lipid peroxidation (by 35 % and 54 %), and lipoxygenase activity (by 74 and 68 %). Moreover, cadaverine enhanced the expression of defence-related genes, including polyphenol oxidase, tubulin, and thaumatin-like protein, and reduced the uptake of BPA in the tomato's roots while promoting its metabolism in leaves and fruits. This ensured the safety of the harvested fruits. By mitigating stress, improving plant resilience, and limiting pollutant accumulation, cadaverine presents significant potential for sustainable agricultural practices and food safety. These findings offer valuable insights into the role of cadaverine in managing abiotic stress and safeguarding crop health in environmentally challenging conditions.

Nuclear Import Defects Drive Cell Cycle Dysregulation in Neurodegeneration

Neurodegenerative diseases (NDDs) and other age-related disorders have been classically defined by a set of key pathological hallmarks. Two of these hallmarks, cell cycle dysregulation (CCD) and nucleocytoplasmic transport (NCT) defects, have long been debated as being either causal or consequential in the pathology of accelerated aging. Specifically, aberrant cell cycle activation in post-mitotic neurons has been shown to trigger neuronal cell death pathways and cellular senescence. Additionally, NCT has been observed to be progressively dysregulated during aging and in neurodegeneration, where the increased subcellular redistribution of nuclear proteins, such as TAR DNA-Binding Protein-43 (TDP-43), to the cytoplasm is a primary driver of disease. However, the functional significance of NCT defects as either a causal mechanism or consequence of pathology, and how the redistribution of cell cycle machinery contributes to neurodegeneration, remains unclear. Here, we describe that pharmacological inhibition of importin-β nuclear import is capable of perturbing cell cycle machinery both in mitotic neuronal cell lines and post-mitotic primary neurons in vitro. Our NemfR86S mouse model of motor neuron disease, characterized by nuclear import defects, further recapitulates the hallmarks of CCD we observed in mitotic cell lines and in post-mitotic primary neurons in vitro, and in spinal motor neurons in vivo. The observed CCD is consistent with the transcriptional and phenotypical dysregulation commonly associated with neuronal cell death and senescence-like features in NDDs. Together, this evidence suggests that impairment of nuclear import pathways resulting in CCD may be a common driver of pathology in neurodegeneration.

Drosophila model systems reveal intestinal stem cells as key players in aging

The intestines play important roles in responding immediately and dynamically to food intake, environmental stress, and metabolic dysfunction, and they are involved in various human diseases and aging. A key part of their function is governed by intestinal stem cells (ISCs); therefore, understanding ISCs is vital. Dysregulation of ISC activity, which is influenced by various cell signaling pathways and environmental signals, can lead to inflammatory responses, tissue damage, and increased cancer susceptibility. Aging exacerbates these dynamics and affects ISC function and tissue elasticity. Additionally, proliferation and differentiation profoundly affect ISC behavior and gut health, highlighting the complex interplay between environmental factors and gut homeostasis. Drosophila models help us understand the complex regulatory networks in the gut, providing valuable insights into disease mechanisms and therapeutic strategies targeting human intestinal diseases.

Case Report: Proteomic analysis of cerebrospinal fluid in a retinoblastoma patient

This study focuses on the proteomic analysis of cerebrospinal fluid (CSF) in a patient with stage III retinoblastoma (RB) with the aim to identify molecular changes associated with central nervous system (CNS) relapse. The child received systemic chemotherapy and intrathecal topotecan as CNS prophylaxis, along with enucleation of the left eye. After two chemotherapy cycles, CNS relapse occurred, evidenced by positive CSF findings and magnetic resonance imaging (MRI) showing leptomeningeal involvement at the anterior skull base. The child's condition deteriorated, and two months later, he died due to progressive CNS disease. The aim of the study was to analyze serial CSF samples collected at different stages of treatment, as well as a control sample, to identify differences in CSF protein expression profiles during CNS RB relapse. Using mass spectrometry, a total of 1,029 proteins were identified across all CSF samples, samples were analyzed in duplicate ensuring technical replication. An unsupervised heatmap revealed 46 differentially expressed proteins. Over-regulated proteins in CSF-RB samples were primarily involved in inflammation, extracellular matrix remodeling, epithelial mesenchymal transition initiation, migration, invasion, and cellular metabolism (PON1, RNPEP, MCAM, NEGR1, NID1, SERPINA1, FAT2, RELN, NEGR1, and SEZ6). These processes are key drivers of cancer progression and metastasis. Proteomic analysis could be valuable in identifying proteins modulated in CSF during disease progression in RB patients, offering potential for new prognostic biomarkers.

Centrosomal and acentrosomal microtubule nucleation during neuronal development

Neurons rely on the microtubule cytoskeleton to create and maintain their sophisticated cellular architectures. Advances in cryogenic electron microscopy, expansion microscopy, live imaging, and gene editing have enabled novel insights into mechanisms of centrosomal and acentrosomal microtubule nucleation, the key process generating new microtubules. This has paved the way for the functional dissection of distinct microtubule networks that regulate various processes during neuronal development, including neuronal delamination, polarization, migration, maturation, and synapse function. We review recent progress in understanding the molecular concepts of microtubule nucleation, how these concepts underlie neurodevelopmental processes, and pinpoint the open questions. Since microtubules play a pivotal role in axon regeneration within the adult central nervous system, understanding the processes of microtubule nucleation could inform strategies to enhance the regenerative capabilities of neurons in the future.

Nuclear Import Defects Drive Cell Cycle Dysregulation in Neurodegeneration

Neurodegenerative diseases (NDDs) and other age-related disorders have been classically defined by a set of key pathological hallmarks. Two of these hallmarks, cell cycle dysregulation (CCD) and nucleocytoplasmic transport (NCT) defects, have long been debated as being either causal or consequential in the pathology of accelerated aging. Specifically, aberrant cell cycle activation in post-mitotic neurons has been shown to trigger neuronal cell death pathways and cellular senescence. Additionally, NCT has been observed to be progressively dysregulated during aging and in neurodegeneration, where the increased subcellular redistribution of nuclear proteins such as TAR DNA-Binding Protein-43 (TDP43) to the cytoplasm is a primary driver of many NDDs. However, the functional significance of NCT defects as either a primary driver or consequence of pathology, and how the redistribution of cell cycle machinery contributes to neurodegeneration, remains unclear. Here, we describe that pharmacological inhibition of importin-β nuclear import is capable of perturbing cell cycle machinery both in mitotic neuronal cell lines and post-mitotic primary neurons in vitro. Our Nemf R86S mouse model of motor neuron disease, characterized by nuclear import defects, further recapitulates the hallmarks of CCD in mitotic cell lines and in post-mitotic primary neurons in vitro, and in spinal motor neurons in vivo. The observed CCD is consistent with the transcriptional and phenotypical dysregulation observed in neuronal cell death and cellular senescence in NDDs. Together, this evidence suggests that impairment of nuclear import pathways resulting in CCD may be a common driver of pathology in neurodegeneration.

From the Cytoplasm into the Nucleus-Hepatitis B Virus Travel and Genome Repair

Hepatitis B virus (HBV) is a major global health concern, affecting millions of people worldwide. HBV is part of the hepadnaviridae family and one of the primary causes of acute and chronic liver infections, leading to conditions such as cirrhosis and hepatocellular carcinoma (HCC). Understanding the intracellular transport and genome repair mechanisms of HBV is crucial for developing new drugs, which-in combination with immune modulators-may contribute to potential cures. This review will explore the current knowledge of HBV intracytoplasmic and nuclear transport, as well as genome repair processes, while drawing comparisons to other viruses with nuclear replication.

Insights into medicinal attributes of imidazo[1,2-a]pyridine derivatives as anticancer agents

Cancer ranks among the most life-threatening diseases worldwide and is continuously affecting all age groups. Consequently, many research studies are being carried out to develop new cancer treatments, but many of them experience resistance and cause severe toxicity to the patients. Therefore, there is a continuous need to design novel anticancer agents that are target-based, have a higher potency, and have minimal toxicity. The imidazo[1,2-a]pyridine (IP) pharmacophore has been found to be a prominent moiety in the field of medicinal chemistry due to its vast biological properties. Also, it holds immense potential for combating cancer with minimal side effects, depending on the substitution patterns of the core structure. IPs exhibit significant capability in regulating various cellular pathways, offering possibilities for targeted anticancer effects. The present review summarizes the anticancer profile of numerous IP derivatives synthesized and developed by various researchers from 2016 till now, as inhibitors of phosphoinositide-3-kinase/mammalian target of rapamycin (PI3K/mTOR), protein kinase B/mammalian target of rapamycin (Akt/mTOR), aldehyde dehydrogenase (ALDH), and tubulin polymerization. This review provides a comprehensive analysis of the anticancer activity afforded by the discussed IP compounds, emphasizing the structure-activity-relationships (SARs). The aim is also to underscore the potential therapeutic future of the IP moiety as a potent partial structure for upcoming cancer drug development and to aid researchers in the field of rational drug design.

Adaptive rewiring: a general principle for neural network development

The nervous system, especially the human brain, is characterized by its highly complex network topology. The neurodevelopment of some of its features has been described in terms of dynamic optimization rules. We discuss the principle of adaptive rewiring, i.e., the dynamic reorganization of a network according to the intensity of internal signal communication as measured by synchronization or diffusion, and its recent generalization for applications in directed networks. These have extended the principle of adaptive rewiring from highly oversimplified networks to more neurally plausible ones. Adaptive rewiring captures all the key features of the complex brain topology: it transforms initially random or regular networks into networks with a modular small-world structure and a rich-club core. This effect is specific in the sense that it can be tailored to computational needs, robust in the sense that it does not depend on a critical regime, and flexible in the sense that parametric variation generates a range of variant network configurations. Extreme variant networks can be associated at macroscopic level with disorders such as schizophrenia, autism, and dyslexia, and suggest a relationship between dyslexia and creativity. Adaptive rewiring cooperates with network growth and interacts constructively with spatial organization principles in the formation of topographically distinct modules and structures such as ganglia and chains. At the mesoscopic level, adaptive rewiring enables the development of functional architectures, such as convergent-divergent units, and sheds light on the early development of divergence and convergence in, for example, the visual system. Finally, we discuss future prospects for the principle of adaptive rewiring.

Tunable intracellular transport on converging microtubule morphologies

A common type of cytoskeletal morphology involves multiple microtubules converging with their minus ends at the microtubule organizing center (MTOC). The cargo-motor complex will experience ballistic transport when bound to microtubules or diffusive transport when unbound. This machinery allows for sequestering and subsequent dispersal of dynein-transported cargo. The general principles governing dynamics, efficiency, and tunability of such transport in the MTOC vicinity are not fully understood. To address this, we develop a one-dimensional model that includes advective transport toward an attractor (such as the MTOC) and diffusive transport that allows particles to reach absorbing boundaries (such as cellular membranes). We calculated the mean first passage time (MFPT) for cargo to reach the boundaries as a measure of the effectiveness of sequestering (large MFPT) and diffusive dispersal (low MFPT). We show that the MFPT experiences a dramatic growth, transitioning from a low to high MFPT regime (dispersal to sequestering) over a window of cargo on-/off-rates that is close to in vivo values. Furthermore, increasing either the on-rate (attachment) or off-rate (detachment) can result in optimal dispersal when the attractor is placed asymmetrically. Finally, we also describe a regime of rare events where the MFPT scales exponentially with motor velocity and the escape location becomes exponentially sensitive to the attractor positioning. Our results suggest that structures such as the MTOC allow for the sensitive control of the spatial and temporal features of transport and corresponding function under physiological conditions.

Multivalent coiled-coil interactions enable full-scale centrosome assembly and strength

The outermost layer of centrosomes, called pericentriolar material (PCM), organizes microtubules for mitotic spindle assembly. The molecular interactions that enable PCM to assemble and resist external forces are poorly understood. Here, we use crosslinking mass spectrometry (XL-MS) to analyze PLK-1-potentiated multimerization of SPD-5, the main PCM scaffold protein in C. elegans. In the unassembled state, SPD-5 exhibits numerous intramolecular crosslinks that are eliminated after phosphorylation by PLK-1. Thus, phosphorylation induces a structural opening of SPD-5 that primes it for assembly. Multimerization of SPD-5 is driven by interactions between multiple dispersed coiled-coil domains. Structural analyses of a phosphorylated region (PReM) in SPD-5 revealed a helical hairpin that dimerizes to form a tetrameric coiled-coil. Mutations within this structure and other interacting regions cause PCM assembly defects that are partly rescued by eliminating microtubule-mediated forces, revealing that PCM assembly and strength are interdependent. We propose that PCM size and strength emerge from specific, multivalent coiled-coil interactions between SPD-5 proteins.

Multivalent coiled-coil interactions enable full-scale centrosome assembly and strength

During mitotic spindle assembly, microtubules generate tensile stresses on pericentriolar material (PCM), the outermost layer of centrosomes. The molecular interactions that enable PCM to assemble rapidly and resist external forces are unknown. Here we use cross-linking mass spectrometry to identify interactions underlying supramolecular assembly of SPD-5, the main PCM scaffold protein in C. elegans . Crosslinks map primarily to alpha helices within the phospho-regulated region (PReM), a long C-terminal coiled-coil, and a series of four N-terminal coiled-coils. PLK-1 phosphorylation of SPD-5 creates new homotypic contacts, including two between PReM and the CM2-like domain, and eliminates numerous contacts in disordered linker regions, thus favoring coiled-coil-specific interactions. Mutations within these interacting regions cause PCM assembly defects that are partly rescued by eliminating microtubule-mediated forces. Thus, PCM assembly and strength are interdependent. In vitro , self-assembly of SPD-5 scales with coiled-coil content, although there is a defined hierarchy of association. We propose that multivalent interactions among coiled-coil regions of SPD-5 build the PCM scaffold and contribute sufficient strength to resist microtubule-mediated forces.

The many faces of the bouquet centrosome MTOC in meiosis and germ cell development

Meiotic chromosomal pairing is facilitated by a conserved cytoskeletal organization. Telomeres associate with perinuclear microtubules via Sun/KASH complexes on the nuclear envelope (NE) and dynein. Telomere sliding on perinuclear microtubules contributes to chromosome homology searches and is essential for meiosis. Telomeres ultimately cluster on the NE, facing the centrosome, in a configuration called the chromosomal bouquet. Here, we discuss novel components and functions of the bouquet microtubule organizing center (MTOC) in meiosis, but also broadly in gamete development. The cellular mechanics of chromosome movements and the bouquet MTOC dynamics are striking. The newly identified zygotene cilium mechanically anchors the bouquet centrosome and completes the bouquet MTOC machinery in zebrafish and mice. We hypothesize that various centrosome anchoring strategies evolved in different species. Evidence suggests that the bouquet MTOC machinery is a cellular organizer, linking meiotic mechanisms with gamete development and morphogenesis. We highlight this cytoskeletal organization as a new platform for creating a holistic understanding of early gametogenesis, with direct implications to fertility and reproduction.

Microtubule nucleation and γTuRC centrosome localization in interphase cells require ch-TOG

Organization of microtubule arrays requires spatio-temporal regulation of the microtubule nucleator γ-tubulin ring complex (γTuRC) at microtubule organizing centers (MTOCs). MTOC-localized adapter proteins are thought to recruit and activate γTuRC, but the molecular underpinnings remain obscure. Here we show that at interphase centrosomes, rather than adapters, the microtubule polymerase ch-TOG (also named chTOG or CKAP5) ultimately controls γTuRC recruitment and activation. ch-TOG co-assembles with γTuRC to stimulate nucleation around centrioles. In the absence of ch-TOG, γTuRC fails to localize to these sites, but not the centriole lumen. However, whereas some ch-TOG is stably bound at subdistal appendages, it only transiently associates with PCM. ch-TOG's dynamic behavior requires its tubulin-binding TOG domains and a C-terminal region involved in localization. In addition, ch-TOG also promotes nucleation from the Golgi. Thus, at interphase centrosomes stimulation of nucleation and γTuRC attachment are mechanistically coupled through transient recruitment of ch-TOG, and ch-TOG's nucleation-promoting activity is not restricted to centrosomes.

A Systematic Review of Updated Mechanistic Insights Towards Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a degenerative neurological disorder that impairs memory, cognitive abilities, and the ability to do everyday activities. This neurodegenerative disease is growing increasingly common as the world's population ages. Here, we reviewed some of the key findings showing the function of Aβ peptide, oxidative stress, free radical damage Triggering Receptors Expressed cn Myeloid Cells 2 (TREM2), Nitric Oxide (NO) and gut microbiota in the aetiology of AD.

METHODS

The potentially relevant online medical databases, namely PubMed, Scopus, Google Scholar, Cochrane Library, and JSTOR, were exhaustively researched. In addition, the data reported in the present study were primarily intervened on the basis of the timeline selected from 1 January 2000 to 31 October 2021. The whole framework was designed substantially based on key terms and studies selected by virtue of their relevance to our investigations.

RESULTS

Findings suggested that channels of free radicals, such as transition metal accumulation and genetic factors, are mainly accountable for the redox imbalance that assist to understand better the pathogenesis of AD and incorporating new therapeutic approaches. Moreover, TREM2 might elicit a protective function for microglia in AD. NO causes an increase in oxidative stress and mitochondrial damage, compromising cellular integrity and viability. The study also explored that the gut and CNS communicate with one another and that regulating gut commensal flora might be a viable therapeutic for neurodegenerative illnesses like AD.

CONCLUSION

There are presently no viable therapies for Alzheimer's disease, but recent breakthroughs in our knowledge of the disease's pathophysiology may aid in the discovery of prospective therapeutic targets.

CTLs: Killers of intracellular bacteria

Many microbial pathogens have evolved a range of capabilities to evade host immune defense mechanisms and to survive and multiply in host cells. The presence of host intracellular bacteria makes it difficult for specific antibodies to function. After the intracellular bacteria escape the attack of the innate immune system, such as phagocytes, they survive in cells, and then adaptive immunity comes into play. Cytotoxic T lymphocytes (CTLs) play an important role in eliminating intracellular bacteria. The regulation of key transcription factors could promote CD4+/CD8+ T cells to acquire cytolytic ability. The TCR-CD3 complex transduces activation signals generated by TCR recognition of antigen and promotes CTLs to generate multiple pathways to kill intracellular bacteria. In this review, the mechanism of CD4/CD8 CTLs differentiation and how CD4/CD8 CTLs kill intracellular bacteria are introduced. In addition, their application and prospects in the treatment of bacterial infections are discussed.

Synthesis and Biological Activity Screening of Newly Synthesized Trimethoxyphenyl-Based Analogues as Potential Anticancer Agents

A group of novel trimethoxyphenyl (TMP)-based analogues were synthesized by varying the azalactone ring of 2-(3,4-dimethoxyphenyl)-4-(3,4,5-trimethoxybenzylidene)oxazolone 1 and characterized using NMR spectral data as well as elemental microanalyses. All synthesized compounds were screened for their cytotoxic activity utilizing the hepatocellular carcinoma (HepG2) cell line. Compounds 9, 10 and 11 exhibited good cytotoxic potency with IC₅₀ values ranging from 1.38 to 3.21 μM compared to podophyllotoxin (podo) as a reference compound. In addition, compounds 9, 10 and 11 exhibited potent inhibition of β-tubulin polymerization. DNA flow cytometry analysis of compound 9 shows cell cycle disturbance at the G2/M phase and a significant increase in Annexin-V-positive cells compared with the untreated control. Compound 9 was further studied regarding its apoptotic potential in HepG2 cells; it decreased the level of MMP and Bcl-2 as well as boosted the level of p53 and Bax compared with the control HepG2 cells.

Beyond the centrosome: The mystery of microtubule organising centres across mammalian preimplantation embryos

Mammalian preimplantation embryogenesis depends on the spatio-temporal dynamics of the microtubule cytoskeleton to enable exceptionally fast changes in cell number, function, architecture, and fate. Microtubule organising centres (MTOCs), which coordinate the remodelling of microtubules, are therefore of fundamental significance during the first days of a new life. Despite its indispensable role during early mammalian embryogenesis, the origin of microtubule growth remains poorly understood. In this review, we summarise the most recent discoveries on microtubule organisation and function during early human embryogenesis and compare these to innovative studies conducted in alternative mammalian models. We emphasise the differences and analogies of centriole inheritance and their role during the first cleavage. Furthermore, we highlight the significance of non-centrosomal MTOCs for embryo viability and discuss the potential of novel in vitro models and light-inducible approaches towards unravelling microtubule formation in research and assisted reproductive technologies.

Self-assembly of pericentriolar material in interphase cells lacking centrioles

The major microtubule-organizing center (MTOC) in animal cells, the centrosome, comprises a pair of centrioles surrounded by pericentriolar material (PCM), which nucleates and anchors microtubules. Centrosome assembly depends on PCM binding to centrioles, PCM self-association and dynein-mediated PCM transport, but the self-assembly properties of PCM components in interphase cells are poorly understood. Here, we used experiments and modeling to study centriole-independent features of interphase PCM assembly. We showed that when centrioles are lost due to PLK4 depletion or inhibition, dynein-based transport and self-clustering of PCM proteins are sufficient to form a single compact MTOC, which generates a dense radial microtubule array. Interphase self-assembly of PCM components depends on γ-tubulin, pericentrin, CDK5RAP2 and ninein, but not NEDD1, CEP152, or CEP192. Formation of a compact acentriolar MTOC is inhibited by AKAP450-dependent PCM recruitment to the Golgi or by randomly organized CAMSAP2-stabilized microtubules, which keep PCM mobile and prevent its coalescence. Linking of CAMSAP2 to a minus-end-directed motor leads to the formation of an MTOC, but MTOC compaction requires cooperation with pericentrin-containing self-clustering PCM. Our data reveal that interphase PCM contains a set of components that can self-assemble into a compact structure and organize microtubules, but PCM self-organization is sensitive to motor- and microtubule-based rearrangement.

Targeting Microtubules for the Treatment of Heart Disease

Heart disease remains the leading cause of morbidity and mortality worldwide. With the advancement of modern technology, the role(s) of microtubules in the pathogenesis of heart disease has become increasingly apparent, though currently there are limited treatments targeting microtubule-relevant mechanisms. Here, we review the functions of microtubules in the cardiovascular system and their specific adaptive and pathological phenotypes in cardiac disorders. We further explore the use of microtubule-targeting drugs and highlight promising druggable therapeutic targets for the future treatment of heart diseases.

Microtubule Anchoring: Attaching Dynamic Polymers to Cellular Structures

Microtubules are dynamic, filamentous polymers composed of α- and β-tubulin. Arrays of microtubules that have a specific polarity and distribution mediate essential processes such as intracellular transport and mitotic chromosome segregation. Microtubule arrays are generated with the help of microtubule organizing centers (MTOC). MTOCs typically combine two principal activities, the de novo formation of microtubules, termed nucleation, and the immobilization of one of the two ends of microtubules, termed anchoring. Nucleation is mediated by the γ-tubulin ring complex (γTuRC), which, in cooperation with its recruitment and activation factors, provides a template for α- and β-tubulin assembly, facilitating formation of microtubule polymer. In contrast, the molecules and mechanisms that anchor newly formed microtubules at MTOCs are less well characterized. Here we discuss the mechanistic challenges underlying microtubule anchoring, how this is linked with the molecular activities of known and proposed anchoring factors, and what consequences defective microtubule anchoring has at the cellular and organismal level.

Morphology and Transport in Eukaryotic Cells

Transport of intracellular components relies on a variety of active and passive mechanisms, ranging from the diffusive spreading of small molecules over short distances to motor-driven motion across long distances. The cell-scale behavior of these mechanisms is fundamentally dependent on the morphology of the underlying cellular structures. Diffusion-limited reaction times can be qualitatively altered by the presence of occluding barriers or by confinement in complex architectures, such as those of reticulated organelles. Motor-driven transport is modulated by the architecture of cytoskeletal filaments that serve as transport highways. In this review, we discuss the impact of geometry on intracellular transport processes that fulfill a broad range of functional objectives, including delivery, distribution, and sorting of cellular components. By unraveling the interplay between morphology and transport efficiency, we aim to elucidate key structure-function relationships that govern the architecture of transport systems at the cellular scale. Expected final online publication date for the Annual Review of Biophysics, Volume 51 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Coordination of Zika Virus Infection and Viroplasm Organization by Microtubules and Microtubule-Organizing Centers

Zika virus (ZIKV) became a global health concern in 2016 due to its links to congenital microcephaly and other birth defects. Flaviviruses, including ZIKV, reorganize the endoplasmic reticulum (ER) to form a viroplasm, a compartment where virus particles are assembled. Microtubules (MTs) and microtubule-organizing centers (MTOCs) coordinate structural and trafficking functions in the cell, and MTs also support replication of flaviviruses. Here we investigated the roles of MTs and the cell's MTOCs on ZIKV viroplasm organization and virus production. We show that a toroidal-shaped viroplasm forms upon ZIKV infection, and MTs are organized at the viroplasm core and surrounding the viroplasm. We show that MTs are necessary for viroplasm organization and impact infectious virus production. In addition, the centrosome and the Golgi MTOC are closely associated with the viroplasm, and the centrosome coordinates the organization of the ZIKV viroplasm toroidal structure. Surprisingly, viroplasm formation and virus production are not significantly impaired when infected cells have no centrosomes and impaired Golgi MTOC, and we show that MTs are anchored to the viroplasm surface in these cells. We propose that the viroplasm is a site of MT organization, and the MTs organized at the viroplasm are sufficient for efficient virus production.