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Development (Cambridge, England) Jan 2024Cilia are microtubule (MT)-based organelles present on the surface of nearly all vertebrate cells. MTs are polymers of α- and β-tubulins that are each encoded by...
Cilia are microtubule (MT)-based organelles present on the surface of nearly all vertebrate cells. MTs are polymers of α- and β-tubulins that are each encoded by multiple, individual isotype genes. Tubulin isotype composition is thought to influence MT behaviors. Ciliary MTs differ from other MTs in the cell in terms of organization, stability and post-translational modifications. However, little is known about the tubulin isotypes that build ciliary MTs and the functional requirements for tubulin isotypes in cilia have not been examined in vertebrates. Here, we have tested the role of the β-tubulin isotype genes in the mouse that harbor a conserved amino acid motif associated with ciliated organisms. We found that Tubb4b localizes to cilia in multi-ciliated cells (MCCs) specifically. In respiratory and oviduct MCCs, Tubb4b is asymmetrically localized within multi-cilia, indicating that the tubulin isotype composition changes along the length of the ciliary axonemal MTs. Deletion of Tubb4b resulted in striking structural defects within the axonemes of multi-cilia, without affecting primary cilia. These studies show that Tubb4b is essential for the formation of a specific MT-based subcellular organelle and sheds light on the requirements of tubulin isotypes in cilia.
Topics: Animals; Mice; Axoneme; Cilia; Microtubules; Protein Processing, Post-Translational; Tubulin
PubMed: 38031972
DOI: 10.1242/dev.201819 -
Chest Sep 2018Primary ciliary dyskinesia is a rare genetic disease of the motile cilia and is one of a rapidly expanding collection of disorders known as ciliopathies. Patients with... (Review)
Review
Primary ciliary dyskinesia is a rare genetic disease of the motile cilia and is one of a rapidly expanding collection of disorders known as ciliopathies. Patients with primary ciliary dyskinesia have diverse clinical manifestations, including chronic upper and lower respiratory tract disease, left-right laterality defects, and infertility. In recent years, our understanding of the genetics of primary ciliary dyskinesia has rapidly advanced. A growing number of disease-associated genes and pathogenic mutations have been identified, which encode axonemal, cytoplasmic, and regulatory proteins involved in the assembly, structure, and function of motile cilia. Our knowledge of cilia genetics and the function of the proteins encoded has led to a greater understanding of the clinical manifestations of motile ciliopathies. These advances have changed our approach toward diagnostic testing for primary ciliary dyskinesia. In this review, we will describe how new insights into genetics have allowed us to define the clinical features of primary ciliary dyskinesia, revolutionize diagnostics, and reveal previously unrecognized genotype-phenotype relationships in primary ciliary dyskinesia.
Topics: Genetic Testing; Genotype; Humans; Kartagener Syndrome; Phenotype
PubMed: 29800551
DOI: 10.1016/j.chest.2018.05.007 -
Journal of Medical Genetics Jan 2015Primary ciliary dyskinesia (PCD) is a rare genetically heterogeneous disorder caused by the abnormal structure and/or function of motile cilia. The PCD diagnosis is... (Review)
Review
Primary ciliary dyskinesia (PCD) is a rare genetically heterogeneous disorder caused by the abnormal structure and/or function of motile cilia. The PCD diagnosis is challenging and requires a well-described clinical phenotype combined with the identification of abnormalities in ciliary ultrastructure and/or beating pattern as well as the recognition of genetic cause of the disease. Regarding the pace of identification of PCD-related genes, a rapid acceleration during the last 2-3 years is notable. This is the result of new technologies, such as whole-exome sequencing, that have been recently applied in genetic research. To date, PCD-causative mutations in 29 genes are known and the number of causative genes is bound to rise. Even though the genetic causes of approximately one-third of PCD cases still remain to be found, the current knowledge can already be used to create new, accurate genetic tests for PCD that can accelerate the correct diagnosis and reduce the proportion of unexplained cases. This review aims to present the latest data on the relations between ciliary structure aberrations and their genetic basis.
Topics: Axonemal Dyneins; Axoneme; Cilia; Genetic Testing; Humans; Kartagener Syndrome; Microscopy, Electron, Transmission
PubMed: 25351953
DOI: 10.1136/jmedgenet-2014-102755 -
Biomolecules Jul 2022Hsp90 is a ubiquitous molecular chaperone involved in many cell signaling pathways, and its interactions with specific chaperones and cochaperones determines which... (Review)
Review
Hsp90 is a ubiquitous molecular chaperone involved in many cell signaling pathways, and its interactions with specific chaperones and cochaperones determines which client proteins to fold. Hsp90 has been shown to be involved in the promotion and maintenance of proper protein complex assembly either alone or in association with other chaperones such as the R2TP chaperone complex. Hsp90-R2TP acts through several mechanisms, such as by controlling the transcription of protein complex subunits, stabilizing protein subcomplexes before their incorporation into the entire complex, and by recruiting adaptors that facilitate complex assembly. Despite its many roles in protein complex assembly, detailed mechanisms of how Hsp90-R2TP assembles protein complexes have yet to be determined, with most findings restricted to proteomic analyses and in vitro interactions. This review will discuss our current understanding of the function of Hsp90-R2TP in the assembly, stabilization, and activity of the following seven classes of protein complexes: L7Ae snoRNPs, spliceosome snRNPs, RNA polymerases, PIKKs, MRN, TSC, and axonemal dynein arms.
Topics: Axonemal Dyneins; HSP90 Heat-Shock Proteins; Humans; Molecular Chaperones; Protein Binding; Proteomics
PubMed: 36008939
DOI: 10.3390/biom12081045 -
Cytoskeleton (Hoboken, N.J.) Aug 2018Ciliary and flagellar motility is caused by the ensemble action of inner and outer dynein arm motors acting on axonemal doublet microtubules. The switch point or...
Ciliary and flagellar motility is caused by the ensemble action of inner and outer dynein arm motors acting on axonemal doublet microtubules. The switch point or switching hypothesis, for which much experimental and computational evidence exists, requires that dyneins on only one side of the axoneme are actively working during bending, and that this active motor region propagate along the axonemal length. Generation of a reverse bend results from switching active sliding to the opposite side of the axoneme. However, the mechanochemical states of individual dynein arms within both straight and curved regions and how these change during beating has until now eluded experimental observation. Recently, Lin and Nicastro used high-resolution cryo-electron tomography to determine the power stroke state of dyneins along flagella of sea urchin sperm that were rapidly frozen while actively beating. The results reveal that axonemal dyneins are generally in a pre-power stroke conformation that is thought to yield a force-balanced state in straight regions; inhibition of this conformational state and microtubule release on specific doublets may then lead to a force imbalance across the axoneme allowing for microtubule sliding and consequently the initiation and formation of a ciliary bend. Propagation of this inhibitory signal from base-to-tip and switching the microtubule doublet subsets that are inhibited is proposed to result in oscillatory motion.
Topics: Animals; Axonemal Dyneins; Axoneme; Cilia; Dyneins; Flagella; Male; Microtubules
PubMed: 30176122
DOI: 10.1002/cm.21483 -
Microbial Cell (Graz, Austria) Sep 2020Cilia and flagella are slender projections found on most eukaryotic cells including unicellular organisms such as and where they serve motility and signaling... (Review)
Review
Cilia and flagella are slender projections found on most eukaryotic cells including unicellular organisms such as and where they serve motility and signaling functions. The cilium is a large molecular machine consisting of hundreds of different proteins that are trafficked into the organelle to organize a repetitive microtubule-based axoneme. Several recent studies took advantage of improved cryo-EM methodology to unravel the high-resolution structures of ciliary complexes. These include the recently reported purification and structure determination of axonemal doublet microtubules from the green algae , which allows for the modeling of more than 30 associated protein factors to provide deep molecular insight into the architecture and repetitive nature of doublet microtubules. In addition, we will review several recent contributions that dissect the structure and function of ciliary trafficking complexes that ferry structural and signaling components between the cell body and the cilium organelle.
PubMed: 33150161
DOI: 10.15698/mic2020.11.734 -
Cell Death and Differentiation Jan 2018The p53 family of transcription factors (p53, p63 and p73) covers a wide range of functions critical for development, homeostasis and health of mammals across their... (Review)
Review
The p53 family of transcription factors (p53, p63 and p73) covers a wide range of functions critical for development, homeostasis and health of mammals across their lifespan. Beside the well-established tumor suppressor role, recent evidence has highlighted novel non-oncogenic functions exerted by p73. In particular, p73 is required for multiciliated cell (MCC) differentiation; MCCs have critical roles in brain and airways to move fluids across epithelial surfaces and to transport germ cells in the reproductive tract. This novel function of p73 provides a unifying cellular mechanism for the disparate inflammatory and immunological phenotypes of p73-deficient mice. Indeed, mice with Trp73 deficiency suffer from hydrocephalus, sterility and chronic respiratory tract infections due to profound defects in ciliogenesis and complete loss of mucociliary clearance since MCCs are essential for cleaning airways from inhaled pollutants, pathogens and allergens. Cross-species genomic analyses and functional rescue experiments identify TAp73 as the master transcriptional integrator of ciliogenesis, upstream of previously known central nodes. In addition, TAp73 shows a significant ability to regulate cellular metabolism and energy production through direct transcriptional regulation of several metabolic enzymes, such as glutaminase-2 and glucose-6 phosphate dehydrogenase. This recently uncovered role of TAp73 in the regulation of cellular metabolism strongly affects oxidative balance, thus potentially influencing all the biological aspects associated with p73 function, including development, homeostasis and cancer. Although through different mechanisms, p63 isoforms also contribute to regulation of cellular metabolism, thus indicating a common route used by all family members to control cell fate. At the structural level, the complexity of p73's function is further enhanced by its ability to form heterotetramers with some p63 isoforms, thus indicating the existence of an intrafamily crosstalk that determines the global outcome of p53 family function. In this review, we have tried to summarize all the recent evidence that have emerged on the novel non-oncogenic roles of p73, in an attempt to provide a unified view of the complex function of this gene within its family.
Topics: Amino Acids; Animals; Axoneme; Cilia; Epidermis; Humans; Metabolism; Mice; Oxidative Stress; Respiratory System; Transcription Factors; Transcription, Genetic; Tumor Protein p73
PubMed: 29077094
DOI: 10.1038/cdd.2017.178 -
Cytoskeleton (Hoboken, N.J.) Mar 2021Motile cilia (also interchangeably called "flagella") are conserved organelles extending from the surface of many animal cells and play essential functions in... (Review)
Review
Motile cilia (also interchangeably called "flagella") are conserved organelles extending from the surface of many animal cells and play essential functions in eukaryotes, including cell motility and environmental sensing. Large motor complexes, the ciliary dyneins, are present on ciliary outer-doublet microtubules and drive movement of cilia. Ciliary dyneins are classified into two general types: the outer dynein arms (ODAs) and the inner dynein arms (IDAs). While ODAs are important for generation of force and regulation of ciliary beat frequency, IDAs are essential for control of the size and shape of the bend, features collectively referred to as waveform. Also, recent studies have revealed unexpected links between IDA components and human diseases. In spite of their importance, studies on IDAs have been difficult since they are very complex and composed for several types of IDA motors, each unique in composition and location in the axoneme. Thanks in part to genetic, biochemical, and structural analysis of Chlamydomonas reinhardtii, we are beginning to understand the organization and function of the ciliary IDAs. In this review, we summarize the composition of Chlamydomonas IDAs particularly focusing on each subunit, and discuss the assembly, conservation, and functional role(s) of these IDA subunits. Furthermore, we raise several additional questions/challenges regarding IDAs, and discuss future perspectives of IDA studies.
Topics: Animals; Axoneme; Chlamydomonas; Chlamydomonas reinhardtii; Cilia; Dyneins; Flagella; Humans; Mutation
PubMed: 33876572
DOI: 10.1002/cm.21662 -
Cells Feb 2024Dynein, an ancient microtubule-based motor protein, performs diverse cellular functions in nearly all eukaryotic cells, with the exception of land plants. It has evolved... (Review)
Review
Dynein, an ancient microtubule-based motor protein, performs diverse cellular functions in nearly all eukaryotic cells, with the exception of land plants. It has evolved into three subfamilies-cytoplasmic dynein-1, cytoplasmic dynein-2, and axonemal dyneins-each differentiated by their cellular functions. These megadalton complexes consist of multiple subunits, with the heavy chain being the largest subunit that generates motion and force along microtubules by converting the chemical energy of ATP hydrolysis into mechanical work. Beyond this catalytic core, the functionality of dynein is significantly enhanced by numerous non-catalytic subunits. These subunits are integral to the complex, contributing to its stability, regulating its enzymatic activities, targeting it to specific cellular locations, and mediating its interactions with other cofactors. The diversity of non-catalytic subunits expands dynein's cellular roles, enabling it to perform critical tasks despite the conservation of its heavy chains. In this review, we discuss recent findings and insights regarding these non-catalytic subunits.
Topics: Cytoplasmic Dyneins; Catalytic Domain; Dyneins
PubMed: 38391943
DOI: 10.3390/cells13040330 -
Biophysical Reviews Apr 2018Dynein motors are biologically important bio-nanomachines, and many atomic resolution structures of cytoplasmic dynein components from different organisms have been... (Review)
Review
Dynein motors are biologically important bio-nanomachines, and many atomic resolution structures of cytoplasmic dynein components from different organisms have been analyzed by X-ray crystallography, cryo-EM, and NMR spectroscopy. This review provides a historical perspective of structural studies of cytoplasmic and axonemal dynein including accessory proteins. We describe representative structural studies of every component of dynein and summarize them as a structural atlas that classifies the cytoplasmic and axonemal dyneins. Based on our review of all dynein structures in the Protein Data Bank, we raise two important points for understanding the two types of dynein motor and discuss the potential prospects of future structural studies.
PubMed: 29478092
DOI: 10.1007/s12551-018-0402-y