The role of GCP8 in microtubule nucleation and cell cicle progression
[eng] Microtubules (MTs) mediate a range of essential cellular processes including cell division, intracellular transport and organelle positioning, by forming specifically adapted arrays. Assembly, maintenance and remodelling of these arrays crucially depend on the de novo formation of MTs, termed...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2019 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/137438 |
| Acceso en línea: | https://hdl.handle.net/2445/137438 http://hdl.handle.net/10803/667234 |
| Access Level: | acceso abierto |
| Palabra clave: | Microtúbuls Proliferació cel·lular Proteïnes Microtubules Cell proliferation Proteins |
| Sumario: | [eng] Microtubules (MTs) mediate a range of essential cellular processes including cell division, intracellular transport and organelle positioning, by forming specifically adapted arrays. Assembly, maintenance and remodelling of these arrays crucially depend on the de novo formation of MTs, termed nucleation, and its regulation in space and time. This process is mediated by the γ-‐tubulin ring complex (γTuRC), and impairment of the function of this complex is typically associated with mitotic defects. However, while the depletion of most γTuRC subunits compromises mitotic progression, the main role of GCP8/MZT2 seems to be the regulation of MT nucleation at the centrosome during interphase, although the molecular details are still unclear. Therefore, the main goal of this project was to elucidate the mechanism by which GCP8 regulates interphase MT organization. I found that GCP8 regulates MT nucleation by direct binding to a small segment at the N-‐terminal end of the GCP2 subunit of the γTuRC. Interestingly, using immunoprecipitation coupled to mass spectrometry, I have identified the MT depolymerase KIF2A as an interactor of GCP8. GCP8 recruits KIF2A to inhibit γTuRC-‐ dependent nucleation at the centrosome and the Golgi apparatus. Moreover, I have observed that the depletion of GCP8 or KIF2A also results in loss of Golgi integrity. Compared to control cells, where the Golgi is typically organized as a ribbon on one side of the centrosome, Golgi membranes in knockdown cells appear more condensed and cluster tightly around the centrosome. Curiously, these defects promote cell cycle exit in non-‐transformed RPE-‐1 cells. Cell cycle exit is p53-‐ independent and thus is unlikely to be caused by problems during mitotic progression. Strikingly, depletion of GCP8 or KIF2A impairs mTOR activation which may explain the cell cycle progression defect. In summary, by analysing the contribution of GCP8 in the regulation of interphase MT nucleation, I have described an unexpected mechanism that links MT-‐dependent organization of the centrosome-‐Golgi axis to G1/S progression and involves regulation of mTOR. |
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