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Annual Review of Biophysics May 2021Dyneins make up a family of AAA+ motors that move toward the minus end of microtubules. Cytoplasmic dynein is responsible for transporting intracellular cargos in... (Review)
Review
Dyneins make up a family of AAA+ motors that move toward the minus end of microtubules. Cytoplasmic dynein is responsible for transporting intracellular cargos in interphase cells and mediating spindle assembly and chromosome positioning during cell division. Other dynein isoforms transport cargos in cilia and power ciliary beating. Dyneins were the least studied of the cytoskeletal motors due to challenges in the reconstitution of active dynein complexes in vitro and the scarcity of high-resolution methods for in-depth structural and biophysical characterization of these motors. These challenges have been recently addressed, and there have been major advances in our understanding of the activation, mechanism, and regulation of dyneins. This review synthesizes the results of structural and biophysical studies for each class of dynein motors. We highlight several outstanding questions about the regulation of bidirectional transport along microtubules and the mechanisms that sustain self-coordinated oscillations within motile cilia.
Topics: Animals; Biological Transport; Cilia; Dyneins; Humans; Intracellular Space; Microtubules
PubMed: 33957056
DOI: 10.1146/annurev-biophys-111020-101511 -
International Journal of Molecular... Sep 2021Primary cilia are non-motile, cell cycle-associated organelles that can be found on most vertebrate cell types. Comprised of microtubule bundles organised into an... (Review)
Review
Primary cilia are non-motile, cell cycle-associated organelles that can be found on most vertebrate cell types. Comprised of microtubule bundles organised into an axoneme and anchored by a mature centriole or basal body, primary cilia are dynamic signalling platforms that are intimately involved in cellular responses to their extracellular milieu. Defects in ciliogenesis or dysfunction in cilia signalling underlie a host of developmental disorders collectively referred to as ciliopathies, reinforcing important roles for cilia in human health. Whilst primary cilia have long been recognised to be present in striated muscle, their role in muscle is not well understood. However, recent studies indicate important contributions, particularly in skeletal muscle, that have to date remained underappreciated. Here, we explore recent revelations that the sensory and signalling functions of cilia on muscle progenitors regulate cell cycle progression, trigger differentiation and maintain a commitment to myogenesis. Cilia disassembly is initiated during myoblast fusion. However, the remnants of primary cilia persist in multi-nucleated myotubes, and we discuss their potential role in late-stage differentiation and myofiber formation. Reciprocal interactions between cilia and the extracellular matrix (ECM) microenvironment described for other tissues may also inform on parallel interactions in skeletal muscle. We also discuss emerging evidence that cilia on fibroblasts/fibro-adipogenic progenitors and myofibroblasts may influence cell fate in both a cell autonomous and non-autonomous manner with critical consequences for skeletal muscle ageing and repair in response to injury and disease. This review addresses the enigmatic but emerging role of primary cilia in satellite cells in myoblasts and myofibers during myogenesis, as well as the wider tissue microenvironment required for skeletal muscle formation and homeostasis.
Topics: Animals; Axoneme; Cell Cycle; Cell Differentiation; Centrosome; Cilia; Cytoskeleton; Extracellular Matrix; Humans; Muscle Development; Muscle Fibers, Skeletal; Muscle, Skeletal; Myoblasts; Organelles; Signal Transduction
PubMed: 34502512
DOI: 10.3390/ijms22179605 -
Nature Communications Oct 2021TRIP6, a member of the ZYXIN-family of LIM domain proteins, is a focal adhesion component. Trip6 deletion in the mouse, reported here, reveals a function in the brain:...
TRIP6, a member of the ZYXIN-family of LIM domain proteins, is a focal adhesion component. Trip6 deletion in the mouse, reported here, reveals a function in the brain: ependymal and choroid plexus epithelial cells are carrying, unexpectedly, fewer and shorter cilia, are poorly differentiated, and the mice develop hydrocephalus. TRIP6 carries numerous protein interaction domains and its functions require homodimerization. Indeed, TRIP6 disruption in vitro (in a choroid plexus epithelial cell line), via RNAi or inhibition of its homodimerization, confirms its function in ciliogenesis. Using super-resolution microscopy, we demonstrate TRIP6 localization at the pericentriolar material and along the ciliary axoneme. The requirement for homodimerization which doubles its interaction sites, its punctate localization along the axoneme, and its co-localization with other cilia components suggest a scaffold/co-transporter function for TRIP6 in cilia. Thus, this work uncovers an essential role of a LIM-domain protein assembly factor in mammalian ciliogenesis.
Topics: Adaptor Proteins, Signal Transducing; Animals; Brain; Ependyma; Focal Adhesions; Gene Expression Regulation; LIM Domain Proteins; Mice; Mice, Knockout; RNA Interference; Transcription Factors; Transcriptome
PubMed: 34620853
DOI: 10.1038/s41467-021-26057-6 -
Frontiers in Physiology 2021In artery tree, endothelial function correlates with the distribution of shear stress, a dragging force generated by flowing blood. In laminar shear stress areas,... (Review)
Review
In artery tree, endothelial function correlates with the distribution of shear stress, a dragging force generated by flowing blood. In laminar shear stress areas, endothelial cells (ECs) are available to prevent atherosclerosis, however, ECs in disturbed shear stress sites are featured with proinflammation and atherogenesis. Basic studies in the shear stress field that focused on the mechanosensors of ECs have attracted the interest of researchers. Among all the known mechanosensors, the primary cilium is distinctive because it is enriched in disturbed shear stress regions and sparse in laminar shear stress areas. The primary cilium, a rod liked micro-organelle, can transmit extracellular mechanical and chemical stimuli into intracellular space. In the cardiovascular system, primary cilia are enriched in disturbed shear stress regions, where blood flow is slow and oscillatory, such as the atrium, downstream of the aortic valve, branches, bifurcations, and inner curves of the artery. However, in the atrioventricular canal and straight vessels, blood flow is laminar, and primary cilia can barely be detected. Primary cilia in the heart cavity prevent ECs from mesenchymal transition and calcification by suppressing transforming growth factor (TGF) signaling. Besides, primary cilia in the vascular endothelium protected ECs against disturbed shear stress-induced cellular damage by triggering Ca influx as well as nitric oxide (NO) release. Moreover, primary cilia inhibit the process of atherosclerosis. In the current review, we discussed ciliogenesis, ciliary structure, as well as ciliary distribution, function and the coordinate signal transduction with shear stress in the cardiovascular system.
PubMed: 33633590
DOI: 10.3389/fphys.2021.640774 -
Seminars in Cell & Developmental Biology Feb 2021Cilia and centrosomes of eukaryotic cells play important roles in cell movement, fluid transport, extracellular sensing, and chromosome division. The physiological... (Review)
Review
Cilia and centrosomes of eukaryotic cells play important roles in cell movement, fluid transport, extracellular sensing, and chromosome division. The physiological functions of cilia and centrosomes are generated by their dynamics, motions, and forces controlled by the physical, chemical, and biological environments. How an individual cilium achieves its beat pattern and induces fluid flow is governed by its ultrastructure as well as the coordination of associated molecular motors. Thus, a bottom-up understanding of the physiological functions of cilia and centrosomes from the molecular to tissue levels is required. Correlations between the structure and motion can be understood in terms of mechanics. This review first focuses on cilia and centrosomes at the molecular level, introducing their ultrastructure. We then shift to the organelle level and introduce the kinematics and mechanics of cilia and centrosomes. Next, at the tissue level, we introduce nodal ciliary dynamics and nodal flow, which play crucial roles in the organogenetic process of left-right asymmetry. We also introduce respiratory ciliary dynamics and mucous flow, which are critical for protecting the epithelium from drying and exposure to harmful particles and viruses, i.e., respiratory clearance function. Finally, we discuss the future research directions in this field.
Topics: Axonemal Dyneins; Axoneme; Basal Bodies; Biological Transport; Biomechanical Phenomena; Centrosome; Chromosome Segregation; Cilia; Epithelial Cells; Gene Expression; Humans; Microtubules; Movement; Organogenesis; Respiration; Rheology
PubMed: 32307225
DOI: 10.1016/j.semcdb.2020.03.007 -
Cells Sep 2022Cilia are eukaryotic organelles essential for movement, signaling or sensing. Primary cilia act as antennae to sense a cell's environment and are involved in a wide... (Review)
Review
Cilia are eukaryotic organelles essential for movement, signaling or sensing. Primary cilia act as antennae to sense a cell's environment and are involved in a wide range of signaling pathways essential for development. Motile cilia drive cell locomotion or liquid flow around the cell. Proper functioning of both types of cilia requires a highly orchestrated bi-directional transport system, intraflagellar transport (IFT), which is driven by motor proteins, kinesin-2 and IFT dynein. In this review, we explore how IFT is regulated in cilia, focusing from three different perspectives on the issue. First, we reflect on how the motor track, the microtubule-based axoneme, affects IFT. Second, we focus on the motor proteins, considering the role motor action, cooperation and motor-train interaction plays in the regulation of IFT. Third, we discuss the role of kinases in the regulation of the motor proteins. Our goal is to provide mechanistic insights in IFT regulation in cilia and to suggest directions of future research.
Topics: Axoneme; Biological Transport; Cilia; Dyneins; Kinesins
PubMed: 36078145
DOI: 10.3390/cells11172737 -
Methods in Molecular Biology (Clifton,... 2020Eukaryotic flagella are conserved multifunctional organelles with roles in motility, intercellular interactions, and signal transduction. Leishmania possess a single...
Eukaryotic flagella are conserved multifunctional organelles with roles in motility, intercellular interactions, and signal transduction. Leishmania possess a single flagellum at all stages of their life cycle. Flagella of promastigote forms in the fly are long and motile, with a canonical 9 + 2 microtubule axoneme and an extra-axonemal paraflagellar rod (PFR). This protocol describes a simple method for the isolation of Leishmania mexicana promastigote flagella, optimized to yield intact flagella that retain both the cytoskeletal elements (9 + 2 axoneme and PFR) and the surrounding membrane. The isolated flagella and deflagellated cell bodies are suitable for analysis by electron microscopy, protein mass spectrometry, and lipidomics.
Topics: Cell Fractionation; Centrifugation, Density Gradient; Cytoskeleton; Flagella; Leishmania mexicana; Life Cycle Stages; Lipidomics; Mass Spectrometry; Microscopy, Electron; Protozoan Proteins
PubMed: 32221938
DOI: 10.1007/978-1-0716-0294-2_29 -
Cells Jul 2021Although ubiquitously present, the relevance of cilia for vertebrate development and health has long been underrated. However, the aberration or dysfunction of ciliary... (Review)
Review
Although ubiquitously present, the relevance of cilia for vertebrate development and health has long been underrated. However, the aberration or dysfunction of ciliary structures or components results in a large heterogeneous group of disorders in mammals, termed ciliopathies. The majority of human ciliopathy cases are caused by malfunction of the ciliary dynein motor activity, powering retrograde intraflagellar transport (enabled by the cytoplasmic dynein-2 complex) or axonemal movement (axonemal dynein complexes). Despite a partially shared evolutionary developmental path and shared ciliary localization, the cytoplasmic dynein-2 and axonemal dynein functions are markedly different: while cytoplasmic dynein-2 complex dysfunction results in an ultra-rare syndromal skeleto-renal phenotype with a high lethality, axonemal dynein dysfunction is associated with a motile cilia dysfunction disorder, primary ciliary dyskinesia (PCD) or Kartagener syndrome, causing recurrent airway infection, degenerative lung disease, laterality defects, and infertility. In this review, we provide an overview of ciliary dynein complex compositions, their functions, clinical disease hallmarks of ciliary dynein disorders, presumed underlying pathomechanisms, and novel developments in the field.
Topics: Animals; Axonemal Dyneins; Cilia; Ciliopathies; Cytoplasmic Dyneins; Humans; Kartagener Syndrome; Polymorphism, Genetic; Short Rib-Polydactyly Syndrome
PubMed: 34440654
DOI: 10.3390/cells10081885 -
European Respiratory Review : An... Dec 2023Cilia are organelles emanating from the cell surface, consisting of an axoneme of microtubules that extends from a basal body derived from the centrioles. They are... (Review)
Review
Cilia are organelles emanating from the cell surface, consisting of an axoneme of microtubules that extends from a basal body derived from the centrioles. They are either isolated and nonmotile (primary cilia), or grouped and motile (motile cilia). Cilia are at the centre of fundamental sensory processes and are involved in a wide range of human disorders. Pulmonary cilia include motile cilia lining the epithelial cells of the conductive airways to orchestrate mucociliary clearance, and primary cilia found on nondifferentiated epithelial and mesenchymal cells acting as sensors and cell cycle keepers. Whereas cilia are essential along the airways, their regulatory molecular mechanisms remain poorly understood, resulting in a lack of therapeutic strategies targeting their structure or functions. This review summarises the current knowledge on cilia in the context of lung homeostasis and COPD to provide a comprehensive overview of the (patho)biology of cilia in respiratory medicine with a particular emphasis on COPD.
Topics: Humans; Lung; Mucociliary Clearance; Axoneme; Cilia; Epithelial Cells; Homeostasis; Pulmonary Disease, Chronic Obstructive
PubMed: 38056888
DOI: 10.1183/16000617.0106-2023 -
Proceedings of the National Academy of... May 2023Human islet primary cilia are vital glucose-regulating organelles whose structure remains uncharacterized. Scanning electron microscopy (SEM) is a useful technique for...
Human islet primary cilia are vital glucose-regulating organelles whose structure remains uncharacterized. Scanning electron microscopy (SEM) is a useful technique for studying the surface morphology of membrane projections like cilia, but conventional sample preparation does not reveal the submembrane axonemal structure, which holds key implications for ciliary function. To overcome this challenge, we combined SEM with membrane-extraction techniques to examine primary cilia in native human islets. Our data show well-preserved cilia subdomains which demonstrate both expected and unexpected ultrastructural motifs. Morphometric features were quantified when possible, including axonemal length and diameter, microtubule conformations, and chirality. We further describe a ciliary ring, a structure that may be a specialization in human islets. Key findings are correlated with fluorescence microscopy and interpreted in the context of cilia function as a cellular sensor and communications locus in pancreatic islets.
Topics: Humans; Microscopy, Electron, Scanning; Cilia; Microscopy, Fluorescence; Islets of Langerhans; Microtubules
PubMed: 37205712
DOI: 10.1073/pnas.2302624120