title: 3D electron tomography of brain tissue unveils distinct Golgi structures that sequester cytoplasmic contents in neurons.
abstract: Macroautophagy is morphologically characterized by autophagosome formation. Autophagosomes are double-membraned vesicles that sequester cytoplasmic components for further degradation in the lysosome. Basal autophagy is paramount for intracellular quality control in post-mitotic cells but, surprisingly, the number of autophagosomes in post-mitotic neurons is very low, suggesting that alternative degradative structures could exist in neurons. To explore this possibility, we have examined neuronal subcellular architecture by performing three-dimensional (3D) electron tomography analysis of mouse brain tissue that had been preserved through high-pressure freezing. Here, we report that sequestration of neuronal cytoplasmic contents occurs at the Golgi complex in distinct and dynamic structures that coexist with autophagosomes in the brain. These structures are composed of several concentric double-membraned layers that appear to be formed simultaneously by the direct bending and sealing of discrete Golgi stacks. These structures are labelled for proteolytic enzymes, and lysosomes and late endosomes are found in contact with them, leading to the possibility that the sequestered material could be degraded inside them. Our findings highlight the key role that 3D electron tomography, together with tissue rapid-freezing techniques, will have in gaining new knowledge about subcellular architecture.
authors: Macromolecular Structures Department, Centro Nacional de Biotecnología-CSIC, Darwin, 3, Cantoblanco, Madrid 28049, Spain mrfernandez@cnb.csic.es jj.fernandez@cnb.csic.es.
authors: Maria Rosario
authors: MR
authors: Fernandez-Fernandez
authors: Macromolecular Structures Department, Centro Nacional de Biotecnología-CSIC, Darwin, 3, Cantoblanco, Madrid 28049, Spain.
authors: Desire
authors: D
authors: Ruiz-Garcia
authors: Macromolecular Structures Department, Centro Nacional de Biotecnología-CSIC, Darwin, 3, Cantoblanco, Madrid 28049, Spain.
authors: Eva
authors: E
authors: Martin-Solana
authors: Macromolecular Structures Department, Centro Nacional de Biotecnología-CSIC, Darwin, 3, Cantoblanco, Madrid 28049, Spain.
authors: Francisco Javier
authors: FJ
authors: Chichon
authors: Macromolecular Structures Department, Centro Nacional de Biotecnología-CSIC, Darwin, 3, Cantoblanco, Madrid 28049, Spain.
authors: Jose L
authors: JL
authors: Carrascosa
authors: Macromolecular Structures Department, Centro Nacional de Biotecnología-CSIC, Darwin, 3, Cantoblanco, Madrid 28049, Spain mrfernandez@cnb.csic.es jj.fernandez@cnb.csic.es.
authors: Jose-Jesus
authors: 0000-0003-2222-3355
authors: JJ
authors: Fernandez
mesh_terms: D000818:Animals; D001921:Brain / Q000648:ultrastructure*; D015925:Cryopreservation; D055032:Electron Microscope Tomography / Q000379:methods*; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure*; D021621:Imaging, Three-Dimensional; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure*
keywords: Brain tissue; Electron tomography; Golgi complex; High-pressure freezing; Neuron