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Developmental Cell Jul 2020Microtubules are non-covalent mesoscale polymers central to the eukaryotic cytoskeleton. Microtubule structure, dynamics, and mechanics are modulated by a cell's choice... (Review)
Review
Microtubules are non-covalent mesoscale polymers central to the eukaryotic cytoskeleton. Microtubule structure, dynamics, and mechanics are modulated by a cell's choice of tubulin isoforms and post-translational modifications, a "tubulin code," which is thought to support the diverse morphology and dynamics of microtubule arrays across various cell types, cell cycle, and developmental stages. We give a brief historical overview of research into tubulin diversity and highlight recent progress toward uncovering the mechanistic underpinnings of the tubulin code. As a large number of essential pathways converge upon the microtubule cytoskeleton, understanding how cells utilize tubulin diversity is crucial to understanding cellular physiology and disease.
Topics: Animals; Humans; Microtubule-Associated Proteins; Microtubules; Molecular Dynamics Simulation; Protein Processing, Post-Translational; Tubulin
PubMed: 32634400
DOI: 10.1016/j.devcel.2020.06.008 -
Science (New York, N.Y.) Jan 2020Tubulins play crucial roles in cell division, intracellular traffic, and cell shape. Tubulin concentration is autoregulated by feedback control of messenger RNA (mRNA)...
Tubulins play crucial roles in cell division, intracellular traffic, and cell shape. Tubulin concentration is autoregulated by feedback control of messenger RNA (mRNA) degradation via an unknown mechanism. We identified tetratricopeptide protein 5 (TTC5) as a tubulin-specific ribosome-associating factor that triggers cotranslational degradation of tubulin mRNAs in response to excess soluble tubulin. Structural analysis revealed that TTC5 binds near the ribosome exit tunnel and engages the amino terminus of nascent tubulins. TTC5 mutants incapable of ribosome or nascent tubulin interaction abolished tubulin autoregulation and showed chromosome segregation defects during mitosis. Our findings show how a subset of mRNAs can be targeted for coordinated degradation by a specificity factor that recognizes the nascent polypeptides they encode.
Topics: Feedback, Physiological; HEK293 Cells; Humans; Mutation; Protein Biosynthesis; RNA Stability; RNA, Messenger; Ribosomes; Transcription Factors; Tubulin
PubMed: 31727855
DOI: 10.1126/science.aaz4352 -
Cells Mar 2021Members of the tubulin superfamily are GTPases; the activities of GTPases are necessary for life. The members of the tubulin superfamily are the constituents of the... (Review)
Review
Members of the tubulin superfamily are GTPases; the activities of GTPases are necessary for life. The members of the tubulin superfamily are the constituents of the microtubules and the γ-tubulin meshwork. Mutations in members of the tubulin superfamily are involved in developmental brain disorders, and tubulin activities are the target for various chemotherapies. The intricate functions (game) of tubulins depend on the activities of the GTP-binding domain of α-, β-, and γ-tubulin. This review compares the GTP-binding domains of γ-tubulin, α-tubulin, and β-tubulin and, based on their similarities, recapitulates the known functions and the impact of the γ-tubulin GTP-binding domain in the regulation of the γ-tubulin meshwork and cellular homeostasis.
Topics: Amino Acid Sequence; Animals; Guanosine Triphosphate; Humans; Microtubules; Phosphorylation; Protein Domains; Tubulin
PubMed: 33800665
DOI: 10.3390/cells10040745 -
Cell Dec 2022The ATP-dependent ring-shaped chaperonin TRiC/CCT is essential for cellular proteostasis. To uncover why some eukaryotic proteins can only fold with TRiC assistance, we...
The ATP-dependent ring-shaped chaperonin TRiC/CCT is essential for cellular proteostasis. To uncover why some eukaryotic proteins can only fold with TRiC assistance, we reconstituted the folding of β-tubulin using human prefoldin and TRiC. We find unstructured β-tubulin is delivered by prefoldin to the open TRiC chamber followed by ATP-dependent chamber closure. Cryo-EM resolves four near-atomic-resolution structures containing progressively folded β-tubulin intermediates within the closed TRiC chamber, culminating in native tubulin. This substrate folding pathway appears closely guided by site-specific interactions with conserved regions in the TRiC chamber. Initial electrostatic interactions between the TRiC interior wall and both the folded tubulin N domain and its C-terminal E-hook tail establish the native substrate topology, thus enabling C-domain folding. Intrinsically disordered CCT C termini within the chamber promote subsequent folding of tubulin's core and middle domains and GTP-binding. Thus, TRiC's chamber provides chemical and topological directives that shape the folding landscape of its obligate substrates.
Topics: Humans; Chaperonin Containing TCP-1; Tubulin; Protein Folding; Proteostasis; Adenosine Triphosphate
PubMed: 36493755
DOI: 10.1016/j.cell.2022.11.014 -
WormBook : the Online Review of C.... Aug 2018The C. elegans tubulin family is composed of nine α-, six β-, and one γ-tubulin. Tubulins are highly conserved, functioning as α-β heterodimers that assemble into... (Review)
Review
The C. elegans tubulin family is composed of nine α-, six β-, and one γ-tubulin. Tubulins are highly conserved, functioning as α-β heterodimers that assemble into microtubules. These cylindrical and ubiquitous components of the cytoskeleton are critical for nearly all cellular and developmental processes. C. elegans has provided a model for the study of microtubules in multiple settings including separation of chromosomes, cellular polarity, and neuronal sensation. Tubulins and microtubules interact with a long list of other cellular proteins that regulate tubulin homeostasis, modify microtubule dynamics, and control incorporation into or disassociation of higher-order cellular structures such as spindles or ciliary axonemes. A collection of enzymes modifies tubulins, often at the variable carboxyl-terminal tail, adding another layer of regulation to microtubule structure and function. Genetic and cytological studies in C. elegans have revealed roles for tubulin and its associated proteins in numerous contexts from embryogenesis to adult behavior.
Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Microtubules; Tubulin
PubMed: 29381886
DOI: 10.1895/wormbook.1.182.1 -
Annual Review of Cell and Developmental... Oct 2023Microtubules are essential dynamic polymers composed of α/β-tubulin heterodimers. They support intracellular trafficking, cell division, cellular motility, and other... (Review)
Review
Microtubules are essential dynamic polymers composed of α/β-tubulin heterodimers. They support intracellular trafficking, cell division, cellular motility, and other essential cellular processes. In many species, both α-tubulin and β-tubulin are encoded by multiple genes with distinct expression profiles and functionality. Microtubules are further diversified through abundant posttranslational modifications, which are added and removed by a suite of enzymes to form complex, stereotyped cellular arrays. The genetic and chemical diversity of tubulin constitute a tubulin code that regulates intrinsic microtubule properties and is read by cellular effectors, such as molecular motors and microtubule-associated proteins, to provide spatial and temporal specificity to microtubules in cells. In this review, we synthesize the rapidly expanding tubulin code literature and highlight limitations and opportunities for the field. As complex microtubule arrays underlie essential physiological processes, a better understanding of how cells employ the tubulin code has important implications for human disease ranging from cancer to neurological disorders.
Topics: Humans; Tubulin; Microtubules; Microtubule-Associated Proteins; Protein Processing, Post-Translational; Cell Movement
PubMed: 37843925
DOI: 10.1146/annurev-cellbio-030123-032748 -
Current Opinion in Neurobiology Aug 2018Cells depend on the asymmetric distribution of their components for homeostasis, differentiation and movement. In no other cell type is this requirement more critical... (Review)
Review
Cells depend on the asymmetric distribution of their components for homeostasis, differentiation and movement. In no other cell type is this requirement more critical than in the neuron where complex structures are generated during process growth and elaboration and cargo is transported over distances several thousand times the cell body diameter. Microtubules act both as dynamic structural elements and as tracks for intracellular transport. Microtubules are mosaic polymers containing multiple tubulin isoforms functionalized with abundant posttranslational modifications that are asymmetrically distributed in neurons. An increasing body of evidence supports the hypothesis that the combinatorial information expressed through tubulin genetic and chemical diversity controls microtubule dynamics, mechanics and interactions with microtubule effectors and thus constitutes a 'tubulin code'. Here we give a brief overview of tubulin isoform usage and posttranslational modifications in the neuron, and highlight recent progress in understanding the molecular mechanisms of the tubulin code.
Topics: Animals; Cell Polarity; Neurons; Tubulin
PubMed: 29554585
DOI: 10.1016/j.conb.2018.03.001 -
Cells Mar 2019γ-Tubulin is a conserved member of the tubulin superfamily with a function in microtubule nucleation. Proteins of γ-tubulin complexes serve as nucleation templates as... (Review)
Review
γ-Tubulin is a conserved member of the tubulin superfamily with a function in microtubule nucleation. Proteins of γ-tubulin complexes serve as nucleation templates as well as a majority of other proteins contributing to centrosomal and non-centrosomal nucleation, conserved across eukaryotes. There is a growing amount of evidence of γ-tubulin functions besides microtubule nucleation in transcription, DNA damage response, chromatin remodeling, and on its interactions with tumor suppressors. However, the molecular mechanisms are not well understood. Furthermore, interactions with lamin and SUN proteins of the LINC complex suggest the role of γ-tubulin in the coupling of nuclear organization with cytoskeletons. γ-Tubulin that belongs to the clade of eukaryotic tubulins shows characteristics of both prokaryotic and eukaryotic tubulins. Both human and plant γ-tubulins preserve the ability of prokaryotic tubulins to assemble filaments and higher-order fibrillar networks. γ-Tubulin filaments, with bundling and aggregating capacity, are suggested to perform complex scaffolding and sequestration functions. In this review, we discuss a plethora of γ-tubulin molecular interactions and cellular functions, as well as recent advances in understanding the molecular mechanisms behind them.
Topics: Animals; Cell Cycle; Cell Nucleus; Humans; Microtubules; Nuclear Envelope; Nuclear Proteins; Tubulin
PubMed: 30893853
DOI: 10.3390/cells8030259 -
International Journal of Molecular... Jul 2019Platelets are anuclear cells with a short lifespan that play an essential role in many pathophysiological processes, including haemostasis, inflammation, infection,... (Review)
Review
Platelets are anuclear cells with a short lifespan that play an essential role in many pathophysiological processes, including haemostasis, inflammation, infection, vascular integrity, and metastasis. Billions of platelets are produced daily from megakaryocytes (platelet precursors). Despite this high production, the number of circulating platelets is stable and, under resting conditions, they maintain their typical discoid shape thanks to cytoskeleton proteins. The activation of platelets is associated with dynamic and rapid changes in the cytoskeleton. Two cytoskeletal polymer systems exist in megakaryocytes and platelets: actin filaments and microtubules, based on actin, and α- and β-tubulin heterodimers, respectively. Herein, we will focus on platelet-specific tubulins and their alterations and role of the microtubules skeleton in platelet formation (thrombopoiesis). During this process, microtubules mediate elongation of the megakaryocyte extensions (proplatelet) and granule trafficking from megakaryocytes to nascent platelets. In platelets, microtubules form a subcortical ring, the so-called marginal band, which confers the typical platelet discoid shape and is also responsible for changes in platelet morphology upon activation. Molecular alterations in the gene encoding β1 tubulin and microtubules post-translational modifications may result in quantitative or qualitative changes in tubulin, leading to altered cytoskeleton reorganization that may induce changes in the platelet number (thrombocytopenia), morphology or function. Consequently, β1-tubulin modifications may participate in pathological and physiological processes, such as development.
Topics: Animals; Blood Platelets; Genetic Variation; Humans; Protein Processing, Post-Translational; Tubulin
PubMed: 31315202
DOI: 10.3390/ijms20143484 -
Methods in Cell Biology 2010New analytical methods are needed for the successful outcome of experiments aimed at characterizing mechanisms of microtubule dynamics and at understanding the effects... (Review)
Review
New analytical methods are needed for the successful outcome of experiments aimed at characterizing mechanisms of microtubule dynamics and at understanding the effects of drugs on microtubules. The identification of tubulin isotypes and of regions of the microtubule involved in drug interactions has been advanced by proteomic methodologies. The diversity of tubulin sequences and posttranslational modifications (PTMs) can generate a complex mixture of heterodimers with unique molecular dynamics driving specific functions. Mass spectrometry (MS)-based approaches have been developed, and in combination with chromatographic and/or electrophoretic separation of tubulin polypeptides or peptides, they have contributed to our understanding of tubulin proteomics. We present protocols that we have used for the analysis of tubulin isotypes and PTMs present in tubulin isolated from cells in culture or tissues and for the identification of tubulin regions altered by microtubule-stabilizing agents. Tubulin proteomics complements structural and computer modeling information for a high-resolution view of microtubule dynamics and its alteration by drugs. These methodologies will help in providing insights into tubulin isotype-specific functions and in the design of drugs targeting either all tubulin heterodimers indiscriminately or only those containing specific isotypes.
Topics: Animals; Cells; Humans; Microtubule Proteins; Pharmaceutical Preparations; Protein Binding; Protein Isoforms; Protein Processing, Post-Translational; Proteomics; Tissue Extracts; Tubulin
PubMed: 20466132
DOI: 10.1016/S0091-679X(10)95007-3