1
|
Taheri A, Wang Z, Singal B, Guo F, Al-Bassam J. Cryo-EM structures of the tubulin cofactors reveal the molecular basis for the biogenesis of alpha/beta-tubulin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.29.577855. [PMID: 38405852 PMCID: PMC10889022 DOI: 10.1101/2024.01.29.577855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Microtubule polarity and dynamic polymerization originate from the self-association properties of the a-tubulin heterodimer. For decades, it has remained poorly understood how the tubulin cofactors, TBCD, TBCE, TBCC, and the Arl2 GTPase mediate a-tubulin biogenesis from α- and β-tubulins. Here, we use cryogenic electron microscopy to determine structures of tubulin cofactors bound to αβ-tubulin. These structures show that TBCD, TBCE, and Arl2 form a heterotrimeric cage-like TBC-DEG assembly around the a-tubulin heterodimer. TBCD wraps around Arl2 and almost entirely encircles -tubulin, while TBCE forms a lever arm that anchors along the other end of TBCD and rotates α-tubulin. Structures of the TBC-DEG-αβ-tubulin assemblies bound to TBCC reveal the clockwise rotation of the TBCE lever that twists a-tubulin by pulling its C-terminal tail while TBCD holds -tubulin in place. Altogether, these structures uncover transition states in αβ-tubulin biogenesis, suggesting a vise-like mechanism for the GTP-hydrolysis dependent a-tubulin biogenesis mediated by TBC-DEG and TBCC. These structures provide the first evidence of the critical functions of the tubulin cofactors as enzymes that regulate the invariant organization of αβ-tubulin, by catalyzing α- and β-tubulin assembly, disassembly, and subunit exchange which are crucial for regulating the polymerization capacities of αβ-tubulins into microtubules.
Collapse
|
2
|
Caputo M, Martinelli I, Fini N, Gianferrari G, Simonini C, Trovato R, Santorelli FM, Tessa A, Mandrioli J, Zucchi E. A Variant in TBCD Associated with Motoneuronopathy and Corpus Callosum Hypoplasia: A Case Report. Int J Mol Sci 2023; 24:12386. [PMID: 37569761 PMCID: PMC10418765 DOI: 10.3390/ijms241512386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/26/2023] [Accepted: 08/01/2023] [Indexed: 08/13/2023] Open
Abstract
Mutations in the tubulin-specific chaperon D (TBCD) gene, involved in the assembly and disassembly of the α/β-tubulin heterodimers, have been reported in early-onset progressive neurodevelopment regression, with epilepsy and mental retardation. We describe a rare homozygous variant in TBCD, namely c.881G>A/p.Arg294Gln, in a young woman with a phenotype dominated by distal motorneuronopathy and mild mental retardation, with neuroimaging evidence of corpus callosum hypoplasia. The peculiar phenotype is discussed in light of the molecular interpretation, enriching the literature data on tubulinopathies generated from TBCD mutations.
Collapse
Affiliation(s)
- Maria Caputo
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; (M.C.); (G.G.); (C.S.)
| | - Ilaria Martinelli
- Department of Neurosciences, Azienda Ospedaliero-Universitaria Di Modena, Viale Giardini, 1355, 41126 Modena, Italy; (I.M.); (N.F.); (E.Z.)
- Clinical and Experimental PhD Program, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Nicola Fini
- Department of Neurosciences, Azienda Ospedaliero-Universitaria Di Modena, Viale Giardini, 1355, 41126 Modena, Italy; (I.M.); (N.F.); (E.Z.)
| | - Giulia Gianferrari
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; (M.C.); (G.G.); (C.S.)
| | - Cecilia Simonini
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; (M.C.); (G.G.); (C.S.)
| | - Rosanna Trovato
- Molecular Medicine, IRCCS Fondazione Stella Maris, 56128 Pisa, Italy; (R.T.); (F.M.S.); (A.T.)
| | | | - Alessandra Tessa
- Molecular Medicine, IRCCS Fondazione Stella Maris, 56128 Pisa, Italy; (R.T.); (F.M.S.); (A.T.)
| | - Jessica Mandrioli
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; (M.C.); (G.G.); (C.S.)
- Department of Neurosciences, Azienda Ospedaliero-Universitaria Di Modena, Viale Giardini, 1355, 41126 Modena, Italy; (I.M.); (N.F.); (E.Z.)
| | - Elisabetta Zucchi
- Department of Neurosciences, Azienda Ospedaliero-Universitaria Di Modena, Viale Giardini, 1355, 41126 Modena, Italy; (I.M.); (N.F.); (E.Z.)
- Neuroscience PhD Program, University of Modena and Reggio Emilia, 41125 Modena, Italy
| |
Collapse
|
3
|
Pinho-Correia LM, Prokop A. Maintaining essential microtubule bundles in meter-long axons: a role for local tubulin biogenesis? Brain Res Bull 2023; 193:131-145. [PMID: 36535305 DOI: 10.1016/j.brainresbull.2022.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
Axons are the narrow, up-to-meter long cellular processes of neurons that form the biological cables wiring our nervous system. Most axons must survive for an organism's lifetime, i.e. up to a century in humans. Axonal maintenance depends on loose bundles of microtubules that run without interruption all along axons. The continued turn-over and the extension of microtubule bundles during developmental, regenerative or plastic growth requires the availability of α/β-tubulin heterodimers up to a meter away from the cell body. The underlying regulation in axons is poorly understood and hardly features in past and contemporary research. Here we discuss potential mechanisms, particularly focussing on the possibility of local tubulin biogenesis in axons. Current knowledge might suggest that local translation of tubulin takes place in axons, but far less is known about the post-translational machinery of tubulin biogenesis involving three chaperone complexes: prefoldin, CCT and TBC. We discuss functional understanding of these chaperones from a range of model organisms including yeast, plants, flies and mice, and explain what is known from human diseases. Microtubules across species depend on these chaperones, and they are clearly required in the nervous system. However, most chaperones display a high degree of functional pleiotropy, partly through independent functions of individual subunits outside their complexes, thus posing a challenge to experimental studies. Notably, we found hardly any studies that investigate their presence and function particularly in axons, thus highlighting an important gap in our understanding of axon biology and pathology.
Collapse
Affiliation(s)
- Liliana Maria Pinho-Correia
- The University of Manchester, Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, School of Biology, Manchester, UK
| | - Andreas Prokop
- The University of Manchester, Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, School of Biology, Manchester, UK.
| |
Collapse
|