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The Journal of Cell Biology Jun 2019Nearly all motile cilia have a "9+2" axoneme containing a central apparatus (CA), consisting of two central microtubules with projections, that is essential for...
Nearly all motile cilia have a "9+2" axoneme containing a central apparatus (CA), consisting of two central microtubules with projections, that is essential for motility. To date, only 22 proteins are known to be CA components. To identify new candidate CA proteins, we used mass spectrometry to compare axonemes of wild-type and a CA-less mutant. We identified 44 novel candidate CA proteins, of which 13 are conserved in humans. Five of the latter were studied more closely, and all five localized to the CA; therefore, most of the other candidates are likely to also be CA components. Our results reveal that the CA is far more compositionally complex than previously recognized and provide a greatly expanded knowledge base for studies to understand the architecture of the CA and how it functions. The discovery of the new conserved CA proteins will facilitate genetic screening to identify patients with a form of primary ciliary dyskinesia that has been difficult to diagnose.
Topics: Algal Proteins; Axoneme; Cell Movement; Chlamydomonas; Cilia; Flagella; Mass Spectrometry; Microtubule Proteins; Mutation; Proteome
PubMed: 31092556
DOI: 10.1083/jcb.201902017 -
EMBO Reports Jan 2024The primary cilium is a critical sensory organelle that is built of axonemal microtubules ensheathed by a ciliary membrane. In polarized epithelial cells, primary cilia...
The primary cilium is a critical sensory organelle that is built of axonemal microtubules ensheathed by a ciliary membrane. In polarized epithelial cells, primary cilia reside on the apical surface and must extend these microtubules directly into the extracellular space and remain a stable structure. However, the factors regulating cross-talk between ciliation and cell polarization, as well as axonemal microtubule growth and stabilization in polarized epithelia, are not fully understood. In this study, we find TTLL12, a previously uncharacterized member of the Tubulin Tyrosine Ligase-Like (TTLL) family, localizes to the base of primary cilia and is required for cilia formation in polarized renal epithelial cells. We also show that TTLL12 directly binds to the α/β-tubulin heterodimer in vitro and regulates microtubule dynamics, stability, and post-translational modifications (PTMs). While all other TTLLs catalyze the addition of glutamate or glycine to microtubule C-terminal tails, TTLL12 uniquely affects tubulin PTMs by promoting both microtubule lysine acetylation and arginine methylation. Together, this work identifies a novel microtubule regulator and provides insight into the requirements for apical extracellular axoneme formation.
Topics: Cilia; Tubulin; Axoneme; Microtubules; Epithelial Cells
PubMed: 38177908
DOI: 10.1038/s44319-023-00005-5 -
Cell Oct 2019The axoneme of motile cilia is the largest macromolecular machine of eukaryotic cells. In humans, impaired axoneme function causes a range of ciliopathies. Axoneme...
The axoneme of motile cilia is the largest macromolecular machine of eukaryotic cells. In humans, impaired axoneme function causes a range of ciliopathies. Axoneme assembly, structure, and motility require a radially arranged set of doublet microtubules, each decorated in repeating patterns with non-tubulin components. We use single-particle cryo-electron microscopy to visualize and build an atomic model of the repeating structure of a native axonemal doublet microtubule, which reveals the identities, positions, repeat lengths, and interactions of 38 associated proteins, including 33 microtubule inner proteins (MIPs). The structure demonstrates how these proteins establish the unique architecture of doublet microtubules, maintain coherent periodicities along the axoneme, and stabilize the microtubules against the repeated mechanical stress induced by ciliary motility. Our work elucidates the architectural principles that underpin the assembly of this large, repetitive eukaryotic structure and provides a molecular basis for understanding the etiology of human ciliopathies.
Topics: Axoneme; Cell Movement; Cilia; Ciliopathies; Cryoelectron Microscopy; Humans; Microtubule Proteins; Microtubules; Stress, Mechanical
PubMed: 31668805
DOI: 10.1016/j.cell.2019.09.030 -
Actas Urologicas Espanolas Feb 2010
Topics: Animals; Axoneme; Female; Fertilization; Humans; Invertebrates; Male; Mammals; Mitochondria; Oocytes; Sperm Injections, Intracytoplasmic
PubMed: 20403276
DOI: No ID Found -
Molecular Biology of the Cell Jul 2022The centriole is a minute cylindrical organelle present in a wide range of eukaryotic species. Most centrioles have a signature ninefold radial symmetry of microtubules...
The centriole is a minute cylindrical organelle present in a wide range of eukaryotic species. Most centrioles have a signature ninefold radial symmetry of microtubules that is imparted to the axonemes of the cilia and flagella they template, with nine centriolar microtubule doublets growing into nine axonemal microtubule doublets. There are exceptions to the ninefold symmetrical arrangement of axonemal microtubules in some species, with lower or higher fold symmetries. In the few cases where this has been examined, such alterations in axonemal symmetries are grounded in similar alterations in centriolar symmetries. Here, we examine the question of microtubule number continuity between centriole and axoneme in flagellated gametes of the gregarine , which have been reported to exhibit a sixfold radial symmetry of axonemal microtubules. We used time-lapse differential interference microscopy to identify the stage at which flagellated gametes are present. Thereafter, using electron microscopy and ultrastructure-expansion microscopy coupled to stimulated emission depletion superresolution imaging, we uncover that a six- or fivefold radial symmetry in the axoneme is accompanied by an eightfold radial symmetry in the centriole. We conclude that the transition between centriolar and axonemal microtubules can be characterized by unexpected plasticity.
Topics: Apicomplexa; Axoneme; Centrioles; Cilia; Flagella; Microtubules
PubMed: 35544302
DOI: 10.1091/mbc.E22-04-0123 -
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 -
Cold Spring Harbor Perspectives in... Nov 2016Axonemal dyneins form the inner and outer rows of arms associated with the doublet microtubules of motile cilia. These enzymes convert the chemical energy released from... (Review)
Review
Axonemal dyneins form the inner and outer rows of arms associated with the doublet microtubules of motile cilia. These enzymes convert the chemical energy released from adenosine triphosphate (ATP) hydrolysis into mechanical work by causing the doublets to slide with respect to each other. Dyneins form two major groups based on the number of heavy-chain motors within each complex. In addition, these enzymes contain other components that are required for assembly of the complete particles and/or for the regulation of motor function in response to phosphorylations status, ligands such as Ca, changes in cellular redox state and which also apparently monitor and respond to the mechanical state or curvature in which any given motor finds itself. It is this latter property, which is thought to result in waves of motor function propagating along the axoneme length. Here, I briefly describe our current understanding of axonemal dynein structure, assembly, and organization.
Topics: Axonemal Dyneins; Axoneme; Biological Transport; Cytoplasm
PubMed: 27527589
DOI: 10.1101/cshperspect.a028100 -
The Journal of Cell Biology Jan 2020Cells use motile cilia to generate force in the extracellular space. The structure of a cilium can be classified into three subdomains: the intracellular basal body (BB)...
Cells use motile cilia to generate force in the extracellular space. The structure of a cilium can be classified into three subdomains: the intracellular basal body (BB) that templates cilium formation, the extracellular axoneme that generates force, and the transition zone (TZ) that bridges them. While the BB is composed of triplet microtubules (TMTs), the axoneme is composed of doublet microtubules (DMTs), meaning the cilium must convert between different microtubule geometries. Here, we performed electron cryotomography to define this conversion, and our reconstructions reveal identifying structural features of the BB, TZ, and axoneme. Each region is distinct in terms of microtubule number and geometry, microtubule inner proteins, and microtubule linkers. TMT to DMT conversion occurs within the BB, and microtubule geometry changes to axonemal by the end of the TZ, followed by the addition of axoneme-specific components essential for cilium motility. Our results provide the highest-resolution images of the motile cilium to date and reveal how BBs template axonemes.
Topics: Animals; Axoneme; Basal Bodies; Cattle; Cilia; Cryoelectron Microscopy; Electron Microscope Tomography; Microtubule Proteins; Microtubules; Trachea
PubMed: 31874113
DOI: 10.1083/jcb.201907060 -
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 -
Journal of Cell Science Sep 2018Cilia perform essential signalling functions during development and tissue homeostasis. A key event in ciliogenesis occurs when the distal appendages of the mother...
Cilia perform essential signalling functions during development and tissue homeostasis. A key event in ciliogenesis occurs when the distal appendages of the mother centriole form a platform that docks ciliary vesicles and removes CP110-Cep97 inhibitory complexes. Here, we analysed the role of LRRC45 in appendage formation and ciliogenesis. We show that the core appendage proteins Cep83 and SCLT1 recruit LRRC45 to the mother centriole. Once there, LRRC45 recruits the keratin-binding protein FBF1. The association of LRRC45 with the basal body of primary and motile cilia in both differentiated and stem cells reveals a broad function in ciliogenesis. In contrast to the appendage components Cep164 and Cep123, LRRC45 was not essential for either docking of early ciliary vesicles or for removal of CP110. Rather, LRRC45 promotes cilia biogenesis in CP110-uncapped centrioles by organising centriolar satellites, establishing the transition zone and promoting the docking of Rab8 GTPase-positive vesicles. We propose that, instead of acting solely as a platform to recruit early vesicles, centriole appendages form discrete scaffolds of cooperating proteins that execute specific functions that promote the initial steps of ciliogenesis.
Topics: Axoneme; Carrier Proteins; Cilia; Humans; Membrane Proteins
PubMed: 30131441
DOI: 10.1242/jcs.223594