RESUMO
During development of the mammalian brain, neural stem cells divide and give rise to adult stem cells, glia and neurons, which migrate to their final locations. Nuclear migration is an important feature of neural stem cell (radial glia progenitor) proliferation and subsequent postmitotic neuronal migration. Defects in nuclear migration contribute to severe neurodevelopmental disorders such as microcephaly and lissencephaly. In this review, we address the cellular and molecular mechanisms responsible for nuclear migration during the radial glia cell cycle and postmitotic neuronal migration, with a particular focus on the role of molecular motors and cytoskeleton dynamics in regulating nuclear behavior.
Assuntos
Encéfalo/crescimento & desenvolvimento , Núcleo Celular/metabolismo , Animais , Movimento Celular , HumanosRESUMO
Cenp-F is a multifaceted protein implicated in cancer and developmental pathologies. The Cenp-F C-terminal region contains overlapping binding sites for numerous proteins that contribute to its functions throughout the cell cycle. Here, we focus on the nuclear pore protein Nup133 that interacts with Cenp-F both at nuclear pores in prophase and at kinetochores in mitosis, and on the kinase Bub1, known to contribute to Cenp-F targeting to kinetochores. By combining in silico structural modeling and yeast two-hybrid assays, we generate an interaction model between a conserved helix within the Nup133 ß-propeller and a short leucine zipper-containing dimeric segment of Cenp-F. We thereby create mutants affecting the Nup133/Cenp-F interface and show that they prevent Cenp-F localization to the nuclear envelope, but not to kinetochores. Conversely, a point mutation within an adjacent leucine zipper affecting the kinetochore targeting of Cenp-F KT-core domain impairs its interaction with Bub1, but not with Nup133, identifying Bub1 as the direct KT-core binding partner of Cenp-F. Finally, we show that Cenp-E redundantly contributes together with Bub1 to the recruitment of Cenp-F to kinetochores.
Assuntos
Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , Cinetocoros/metabolismo , Proteínas dos Microfilamentos/genética , Proteínas dos Microfilamentos/metabolismo , Antígenos de Histocompatibilidade Menor/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Poro Nuclear/metabolismo , Proteínas de Ciclo Celular/metabolismo , Células HeLa , Humanos , Antígenos de Histocompatibilidade Menor/genética , Mitose , Membrana Nuclear/metabolismo , Poro Nuclear/genética , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Ligação Proteica , Proteínas Serina-Treonina Quinases/genéticaRESUMO
Selective autophagy is the mechanism by which large cargos are specifically sequestered for degradation. The structural details of cargo and receptor assembly giving rise to autophagic vesicles remain to be elucidated. We utilize the yeast cytoplasm-to-vacuole targeting (Cvt) pathway, a prototype of selective autophagy, together with a multi-scale analysis approach to study the molecular structure of Cvt vesicles. We report the oligomeric nature of the major Cvt cargo Ape1 with a combined 2.8 Å X-ray and negative stain EM structure, as well as the secondary cargo Ams1 with a 6.3 Å cryo-EM structure. We show that the major dodecameric cargo prApe1 exhibits a tendency to form higher-order chain structures that are broken upon interaction with the receptor Atg19 in vitro The stoichiometry of these cargo-receptor complexes is key to maintaining the size of the Cvt aggregate in vivo Using correlative light and electron microscopy, we further visualize key stages of Cvt vesicle biogenesis. Our findings suggest that Atg19 interaction limits Ape1 aggregate size while serving as a vehicle for vacuolar delivery of tetrameric Ams1.